JP2001195769A - Optical pickup device, recording/reproducing device, provided with the optical pickup device optical element, information recording/reproducing method, optical system, lens, diffraction optical system for optical disk, reproducing device and objective lens for optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device correcting aberration with simple constitution, a recording/reproducing device provided with the optical pickup device, an optical element, an information recording/reproducing method, an optical system, a lens, a diffraction optical system for an optical disk, a reproducing device and an objective lens for the optical pickup device. SOLUTION: In this optical pickup device containing an optical surface provided with a diffraction zonal lens on the refraction surface of the objective lens 1, and actions of a diffraction surface and a refraction surface are canceled for three wavelengths light sources 11, 12, 13 different from each other, and a spherical aberration is corrected. Further, related to the beams from three wavelengths light sources 11, 12, 13 by using 1st order diffraction beams as the diffraction beams, a loss of a light quantity is reduced. Further, the objective lens is provided with a diffraction pattern on at least one surface, and when luminous flux from the light sources of different wavelengths are converged on an information recording surface, the 1st order diffraction beams from the diffraction pattern are used together in the reproduction of plural recording media. By the condition of the recording media, the used diffraction beams are +1st order diffraction beams together or -1st order diffraction beam together.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device, a recording / reproducing device provided with the optical pickup device, an optical element, an information recording / reproducing method, an optical system, a lens, a diffractive optical system for an optical disk, a reproducing device, and an optical device. Objective lens for pickup device, sound and / or optical pickup device
Alternatively, the present invention relates to an image recording and / or reproducing apparatus and an objective lens used in an optical pickup device.

[0002]

2. Description of the Related Art In recent years, along with the practical use of a short-wavelength red laser, a DVD, which is a high-density optical information recording medium (also called an optical disk) of the same size as a CD (compact disk) and having a large capacity, has been developed. It has been commercialized. In a DVD recording / reproducing apparatus, when a 650 nm semiconductor laser is used, the numerical aperture NA of the objective lens on the optical disk side is set to 0.6 to 0.6.
It is set to 0.65. DVD has a track pitch of 0.74
μm, the shortest bit length is 0.4 μm, and the density is reduced to half or less of the CD track pitch of 1.6 μm and the shortest pit length of 0.83 μm. In the case of a DVD, the thickness of the transparent substrate is 0.6 mm, which is half the thickness of the transparent substrate of a CD, in order to suppress coma aberration generated when the optical disk is tilted with respect to the optical axis.

In addition to the above-mentioned CDs and DVDs, optical disks of various standards such as different light source wavelengths and transparent substrate thicknesses, such as CD-R, RW (write-once compact disk), VD (video disk), MD (Mini-disc), MO (magneto-optical disc), and the like have also been commercialized and spread. In addition, the wavelength of semiconductor lasers has been shortened, and blue lasers having a short wavelength of about 400 nm have been commercialized. When the wavelength is shortened, even if the same numerical aperture as that of the DVD is used, it is possible to further increase the capacity of the optical information recording medium.

[0004] Also, a CD which is as large as a CD which is a conventional optical information recording medium as described above and which can be recorded and reproduced is used.
-R and the development of a plurality of optical information recording media having different thicknesses of the transparent substrate on the recording surface and the wavelength of the recording / reproducing laser beam, such as a DVD having a higher recording density, have been developed. It is required to enable recording and reproduction with the same optical pickup. For this reason, various optical pickups that converge laser light with a required numerical aperture on a recording surface with the same objective lens while providing a plurality of laser light sources corresponding to the wavelengths used have been proposed (for example, Japanese Patent Application Laid-Open No. H8-5536).
No. 3, No. 10-92010).

Among these, Japanese Patent Application Laid-Open No. 9-54973 discloses that 635 nm is transmitted light (0th-order diffracted light), 785 nm
Discloses an optical system using a hologram optical element using -1st order diffracted light, an optical system using hologram optical element using 635 nm for + 1st order diffracted light, and 785 nm for transmitted light (0th order diffracted light). Also, JP-A-10-28
Japanese Patent No. 3668 discloses an optical system that transmits 100% through a hologram-type ring lens at 650 nm and performs first-order diffraction by a hologram-type ring lens at 780 nm.

However, in these hologram elements and hologram type ring lenses, if the diffraction efficiency of the 0th-order light at one wavelength is almost 100%, the + 1st-order diffraction light or the -1st-order diffraction light at the other wavelength is inevitable. There is a limit to the diffraction efficiency of the folded light, and a desired high diffraction efficiency cannot be obtained, and there is a problem that a light amount loss occurs and the light amount use efficiency deteriorates. When a loss of light quantity occurs, a laser with a higher power is required, especially at the time of recording information.

Further, in the hologram element and the hologram type ring lens, the diffraction efficiency of the 0th-order light at one wavelength is set to almost 100%, and at the other wavelength, the 0th-order light is not transmitted as much as possible, and the + 1st-order diffraction light or −1 When increasing the diffraction efficiency of the second-order diffracted light, the depth of the hologram is 3.8
５5.18 μm. For this reason,
In particular, when the function of the hologram optical element or the hologram type ring lens is integrated with the objective lens, there is also a problem that machining and molding of the mold are extremely difficult.

[0008]

SUMMARY OF THE INVENTION The present inventors have previously made up a plurality of concentrically divided annular zones, each of which includes a plurality of light sources having different wavelengths and / or a thickness of a recording surface. Aberration corrected almost to the diffraction limit for different transparent substrates,
An objective lens capable of forming an optical pickup with a simplified configuration has been proposed (Japanese Patent Application No. 9-286954). The objective lens has a function of automatically obtaining a necessary aperture according to the wavelength used and / or the thickness of the transparent substrate. However, when a laser / detector integrated unit in which a laser light source and a photodetector are integrated is used, there is a problem that accurate detection cannot be performed due to flare light incident on the photodetector. This is particularly remarkable in a laser / detector integrated unit that uses a hologram to deflect a light beam and guide it to a photodetector. In addition, DVD recordable discs (DVD-RAM, DVD-R,
When performing high-speed recording on DVD-RW, DVD + RW, etc.) or CD-type recordable discs (CD-R, CD-RW, etc.), some light has flare compared to an optical system using a dedicated lens. Therefore, the use efficiency of the light amount is poor, and it is necessary to increase the power of the laser light source.

An object of the present invention is to provide an optical pickup device capable of recording and / or reproducing information of different types of optical information recording media by using one optical pickup device, each using light of at least two different wavelengths. An object of the present invention is to provide a recording / reproducing device, an optical element, and a recording / reproducing method.

Further, even when using light of at least two different wavelengths and applying to different types of optical information recording media, different optical information recording media can be used without generating large spherical aberration and chromatic aberration. For
An object of the present invention is to enable recording and / or reproduction of information with one pickup device. Moreover, it is another object to provide an optical pickup device having a simple configuration. In particular, when different types of optical information recording media having different thicknesses of transparent substrates are used, the problem of spherical aberration becomes more serious, but even in such a case, large spherical aberration and chromatic aberration occur. It is another object of the present invention to be able to record and / or reproduce information on and from different optical information recording media with a single optical pickup device without causing the optical information recording media to be different.

Further, even in a pickup device using an integrated unit of a plurality of lasers and a plurality of detectors, flare light which may adversely affect the detection is not irradiated onto the photodetector, and the light detector is not illuminated. The object of the present invention is to make it possible to perform good light detection, and to make the S-characteristic in the detection good. Further, it is another object of the present invention to provide an optical pickup device, a recording / reproducing device, an optical element, and a recording / reproducing method, in which a loss of the light amount is small and the utilization efficiency of the light amount is excellent.

DV having different wavelengths and transparent substrate thicknesses
Various compatible optical systems have been proposed for recording and / or reproducing information using a single objective lens without generating large spherical aberration or chromatic aberration for both D and CD. However, in practical use, the divergent light beam from the light source is reduced in its divergence by a coupling lens, or is made into a parallel light beam or a weak convergent light beam, and the objective lens and the transparent substrate of the optical information recording medium are connected. The light beam is converged on the information recording surface via the optical recording medium, and requires two lenses, a coupling lens and an objective lens. Therefore, there is a problem that it is difficult to reduce the size and thickness of the optical pickup device, and the cost is increased.

On the other hand, as described above, various optical disks other than CDs and DVDs have become widespread, and an optical system which is compatible with these optical disks and has a simple structure, and an optical pickup provided with the optical system. A device is needed. It is also an object of the present invention to provide such an optical system, a lens, a diffractive optical system for an optical disc, a reproducing device, and an objective lens for an optical pickup device.

[0014]

In order to achieve the above object, an optical pickup device according to claim 1 reproduces information from an optical information recording medium or records information on an optical information recording medium. A first light source that emits a first light beam having a first wavelength;
A second light source that emits a second light beam having a second wavelength different from the wavelength of the second light source; and a condensing optical system having an optical axis, a diffraction unit, and a photodetector, wherein the first light beam is By passing through the diffractive portion, at least one order diffracted light in which the n-th order diffracted light amount of the first light beam is larger than any other order diffracted light amount of the first light beam is generated. 2
Passes through the diffraction section, thereby generating at least one order of diffracted light in which the n-th order diffracted light amount of the second light beam is larger than any other order diffracted light amount of the second light beam. It is characterized by that. Here, n is an integer other than 0.

The optical element according to claim 77 is an optical element used in an optical pickup device for reproducing information from an optical information recording medium or recording information on the optical information recording medium, An axis, and a diffractive portion, wherein the first light beam passes through the diffractive portion, and
A diffracted light of at least one order in which the n-th order diffracted light amount of the light beam is larger than any other order diffracted light amount of the first light beam is generated, and the wavelength difference from the first light beam is 80 nm.
When the second light flux of about 400 nm passes through the diffraction section, the n-th order diffracted light amount of the second light flux is reduced to the second light flux.
And a diffracted light beam of at least one order larger than the diffracted light amount of any other order of the light beam is generated. Here, n is an integer other than 0.

The information recording / reproducing method according to claim 136 is a recording / reproducing method for reproducing / recording information on at least two kinds of optical information recording media by an optical pickup device, wherein the optical pickup device comprises: Comprises a first light source, a second light source, and a condensing optical system having an optical axis and a diffractive portion, and a first light flux from the first light source or a second light source from the second light source. A second light beam different from the wavelength of the first light beam
And emitting the first light beam or the second light beam through the diffractive portion and diffracting light of at least one order of the first light beam or at least one of the second light beams. Generating a diffracted light of the order (where the n-th order diffracted light of the at least one order diffracted light of the first light flux is larger than the diffracted light of any other order of the first light flux) And the second
Of the diffracted light of at least one order of the first light beam is larger than the diffracted light amount of any other order of the second light beam), and the first light beam is condensed by the condensing optical system. The n-order diffracted light of the second optical information recording medium on the first information recording surface of the first optical information recording medium or the n-order diffracted light of the second light flux on the second information recording surface of the second optical information recording medium. An optical pickup device for condensing the information to record information on or reproduce information from the first optical information recording medium or the second optical information recording medium; and Detecting a first reflected light of the emitted n-order diffracted light from the first information recording surface or a second reflected light of the collected n-order diffracted light from the second information recording surface; And step. Here, n is an integer other than 0.

An optical pickup device capable of reproducing or recording information on an optical information recording medium according to the present invention comprises: a first light source for emitting a first light beam having a first wavelength; A second light source that emits a second light beam having a second wavelength different from the first wavelength, a condensing optical system having an optical axis and a diffraction unit, and a photodetector are provided.

The first light beam passes through the diffracting portion, so that the n-th order diffracted light amount of the first light beam is larger than the diffracted light amount of any other order of the first light beam. Two orders of diffracted light are generated, and the second light beam passes through the diffracting portion, so that the n-th order diffracted light amount of the second light beam is larger than any other order diffracted light amount of the second light beam. At least one order of diffracted light is also generated. Here, n is an integer other than 0.

Further, the optical element of the present invention is an optical element having a diffractive portion which enables the above-described embodiment. An apparatus for reproducing information from an optical information recording medium or recording information on an optical information recording medium according to the present invention includes the above-described optical pickup device.

It is noted that the n-th order diffracted light amount is larger than any other order diffracted light amount with respect to light of a predetermined wavelength.
This means that the diffraction efficiency of the nth-order diffracted light is higher than the diffraction efficiency of each diffracted light of other orders than the nth order.
In addition, n of the n-th order includes a sign, and in the first light beam that has passed through the diffractive portion of the present invention, the + 1st-order diffracted light is generated more than the diffracted lights of other orders. Is
In order to generate more + 1st-order diffracted light than diffracted light of other orders also in the second light flux that has passed through the diffractive portion, the second light flux that has passed through the diffractive portion has a value of -1. It does not include generating the next diffracted light more than diffracted lights of other orders.

Further, the optical pickup device of the present invention enables recording and / or reproduction of different types of optical information recording media using light of at least two different wavelengths with one pickup device. . That is, the optical pickup device of the present invention is used for recording / reproducing on different information recording media such as a first optical information recording medium and a second optical information recording medium. The first light beam of the first light source of the optical pickup device of the present invention is used for reproducing information from the first optical information recording medium or for the first light beam.
The second light flux of the second light source is used for reproducing information from the second optical information recording medium or the second optical information recording medium. Used to record information in In general, an optical information recording medium has a transparent substrate on an information recording surface.

Expressing the function of the present invention in another way, the condensing optical system converts the n-th order diffracted light of the first light beam generated in the diffraction portion by the first light beam reaching the diffraction portion into the first light beam. To reproduce the information recorded on the optical information recording medium of
In order to record information on the first information recording medium, the light can be condensed on the first information recording surface of the first optical information recording medium via the first transparent substrate. The n-th order diffracted light of the second light beam generated in the diffraction unit by the second light beam that has reached the second light beam is used to reproduce information recorded on the second optical information recording medium or to record information on the second information recording medium. In order to achieve this, the light can be focused on the second information recording surface of the second optical information recording medium via the second transparent substrate, and the photodetector is provided with the first information recording surface or the second information. This means that the light beam reflected from the recording surface can be received.

More preferred embodiments are described below. The condensing optical system converts the nth-order diffracted light of the first light beam that has passed through the diffractive portion into a predetermined aperture in the first light beam on the image side of the objective lens on the first information recording surface of the first optical information recording medium. The number can be collected in a state of 0.07λrms or less, that is, a state in which the light beam in the aperture for practical use is at or below the diffraction limit performance at the best image point. The nth-order diffracted light of the second light beam passing through the second optical information recording medium is applied to the second information recording surface of the second optical information recording medium at a predetermined numerical aperture of the second light beam on the image side of the objective lens.
The light can be converged in a state of not more than 07λrms, that is, in a state where the light flux in the aperture for practical use has the diffraction limit performance or less at the best image point.

Further, even if a wavelength shift of about ± 10 nm or less occurs due to a temperature change or a current change in the first light source or the second light source, the image of the objective lens is not formed on each information recording surface. It is preferable that the n-th order diffracted light be condensed within 0.07λrms or less within a predetermined numerical aperture on the side. In particular, the first beam or
The second light beam has a wavelength of 600 nm or less (for example, 350 n
m to 480 nm), and even if a wavelength shift of about ± 10 nm or less occurs, the n-th order diffracted light is collected within a predetermined numerical aperture on the image side of the objective lens at 0.07 λrms or less. Lighting is particularly preferred.

It is preferable that the n-th order diffracted light be the first-order diffracted light or the -1st-order diffracted light because the loss of the light amount is smaller than in the case of using the diffracted light of the order higher than ± 1 order.

Further, the diffraction efficiency of the n-th order diffracted light of the first light beam in the diffracting portion is defined as A%, and the diffracted light of another order (preferably the order having the highest diffraction efficiency among orders other than n) is given. When the diffraction efficiency is B%, it is preferable that AB ≧ 10, the diffraction efficiency of the n-th order diffracted light of the second light flux in the diffracting unit is A ′%, and the diffraction efficiency of the diffracted light of some other order is Is preferably B ′%, it is preferable that A′−B ′ ≧ 10. Further, AB ≧ 30, A′−B ′ ≧ 3
More preferably 0, AB ≧ 50, A′-
B ′ ≧ 50 is more preferable, and AB ≧ 7
More preferably, 0, A′−B ′ ≧ 70.

When both the first light beam and the second light beam are used for recording information on the optical information recording medium, the diffraction efficiency of the n-th order diffracted light in the diffractive portion is equal to the wavelength of the first light beam and the second light beam. It is preferable to make the maximum at a wavelength between the wavelength of the light flux.

When only one of the first light beam and the second light beam is used for recording information on the optical information recording medium, and the other light beam is used only for reproduction, the diffraction of the n-th order diffracted light in the diffractive portion is performed. Preferably, the efficiency is minimized at a wavelength between the wavelength of the first light flux and the wavelength of the second light flux. More preferably, the diffraction efficiency of the n-th order diffracted light in the diffracting portion is maximized in the one used for recording information, whether the wavelength of the first light beam or the wavelength of the second light beam.

The optical element provided with the diffractive portion is not particularly limited, and examples thereof include a lens having a refracting surface, a flat element, and the like provided in the condensing optical system.

When a lens having a refractive surface is used as the optical element provided with the diffractive portion, specific examples of the optical element include:
Examples include an objective lens, a collimator lens, and a coupling lens. A diffractive portion can be provided on a refracting surface of these lenses or the like. Further, a plate-shaped or lens-shaped optical element for the purpose of only providing the diffraction section may be added to the light-collecting optical system.

When the diffractive portion is provided on the refracting surface of the objective lens, the outer diameter of the objective lens (the outer diameter including the flange if the objective lens has a flange) is 0.4 mm or more smaller than the aperture diameter.
It is preferably 2 mm larger.

The diffractive portion may be provided on the optical surface on the light source side of the optical element, may be provided on the image side (optical information recording medium side), or may be provided on both surfaces. Further, the diffractive portion may be provided on a convex surface or may be provided on a concave surface.

It is more preferable to provide the objective lens with a diffractive portion, because it leads to a reduction in the number of components and also reduces an assembly error in manufacturing the optical pickup device. In that case, the objective lens is preferably a single ball,
It may be a single ball. Although a plastic lens is preferred, a glass lens may be used. Further, a resin layer having a diffraction portion formed on the surface of the glass lens may be provided. Further, it is preferable that the objective lens provided with the diffractive portion has a flange portion having a surface extending in a direction perpendicular to the optical axis on the outer periphery. As a result, highly accurate attachment to the pickup device can be easily performed, and stable performance can be obtained even when the environmental temperature changes. Further, it is preferable that the refraction surface of the objective lens is an aspherical surface, and the diffraction portion is provided on the aspherical surface. Of course, the diffraction section may be provided on one side of the objective lens, or may be provided on both sides.

It is preferable that the optical element provided with the diffraction portion is made of a material having an Abbe number νd of 50 or more and 100 or less. Further, it may be plastic or glass. In the case of a plastic lens, the material preferably has a refractive index of 1.4 to 1.75, more preferably 1.48 to 1.6, and more preferably 1.5 to 1.56. Is more preferable.

When the diffractive portion is provided on a lens (preferably a plastic lens), it is preferable to satisfy the following conditional expression in order to obtain an optical pickup device and an optical element that are stable against temperature changes. . -0.0002 / ° C <Δn / ΔT <-0.00005 ° C ΔT: Temperature change. Δn: the amount of change in the refractive index of the lens.

Further, it is preferable that the following conditional expression is satisfied. 0.05 nm / ° C <Δλ1 / ΔT <0.5 nm / ° C Δλ1 (nm): change in wavelength of the first light source when there is a temperature change ΔT

The diffraction section may be an amplitude type diffraction section, but is preferably a phase type diffraction section from the viewpoint of light use efficiency. Further, the diffraction pattern of the diffraction section is preferably rotationally symmetric with respect to the optical axis. Also, the diffraction part
When viewed from the direction of the optical axis, it is preferable to have a plurality of orbicular zones, and the plurality of orbicular zones are formed substantially concentrically around the optical axis or a point near the optical axis. A circle is preferred, but an ellipse may be used. Particularly, a blazed ring zone diffraction surface having a step is preferable. Further, an annular diffraction surface formed in a step shape may be used. Also, as you move away from the optical axis,
An annular diffractive surface formed in a step-like manner as an annular zone that discretely shifts in a direction of increasing the lens thickness may be used. The diffractive portion is preferably in the shape of an annular zone, but may be a one-dimensional diffraction grating.

When the diffractive portion has a concentric annular shape, the pitch of the diffractive annular zone is defined by using a phase difference function or an optical path difference function. In this case, it is preferable that the phase difference function represented by a power series indicating each position of the plurality of orbicular zones has a coefficient other than 0 in at least one term other than the square term. With this configuration, it is possible to correct spherical aberration of chromatic aberration caused by light of different wavelengths.

It is preferable that the phase difference function represented by a power series indicating each position of the plurality of orbicular zones of the diffraction section have a coefficient other than 0 in the square term, because paraxial chromatic aberration can be corrected. However, when it is important not to make the pitch of the diffraction zones too small, even if the phase difference function represented by a power series indicating each position of the plurality of zones of the diffraction section does not include the square term. Good.

The number of steps of the diffraction ring zone of the diffraction section is
It is preferably from 2 to 45. More preferably, it is 40 or less. More preferably, it is 15 or less. In order to count the number of steps, the number of steps of the annular zone may be counted.

It is preferable that the depth of the step of the diffraction ring zone of the diffraction portion in the optical axis direction is 2 μm or less. With this configuration, the optical element can be easily manufactured, and the n-th order diffracted light can be easily converted into the first order or −1 order diffracted light.

When a diffractive portion is provided on the surface of the optical element on the light source side, it is preferable that the depth of the step increases as the distance from the optical axis increases.

With respect to the function of the diffractive surface for deflecting the light beam, in the present invention, the case where the light beam is further deflected toward the optical axis is called a positive action, and the case where it is deflected away from the optical axis is called a negative action.

The pitch of the ring-shaped diffraction surface may be provided in inverse proportion to the height from the optical axis. Also, the way the pitch is provided is not inversely proportional to the height from the optical axis,
That is, a pitch in which the optical path difference function has a higher-order term may be provided.

In particular, when a pitch having a higher-order term of the optical path difference function is provided, that is, when the pitch is not provided in inverse proportion to the height from the optical axis, the optical path difference function has:
It may have an inflection point, but preferably has no inflection point.

The diffractive action added by the diffractive portion may be positive on the entire surface of the diffractive portion or negative on the entire surface of the diffractive portion. Further, the sign of the diffraction effect added by the diffraction unit may be switched at least once in a direction away from the optical axis perpendicular to the optical axis. For example, as shown in FIG. 47C, there is a type that changes from negative to positive in a direction away from the optical axis perpendicular to the optical axis. In other words, a plurality of orbicular zones of the diffractive portion are blazed, and in a diffractive orbicular zone closer to the optical axis, the step is located on a side farther from the optical axis,
It can also be said that the step portion is located closer to the optical axis in the diffraction ring zone away from the optical axis. Further, a type that changes from positive to negative in a direction away from the optical axis perpendicular to the optical axis as shown in FIG. To put this differently, the multiple zones of the diffraction section
Blazed, the step portion is located on the side closer to the optical axis in the diffraction zone near the optical axis, and the step portion is located in the diffraction zone near the optical axis away from the optical axis. It can be said that it is located on the side distant from.

In FIG. 134, the pitch of the diffraction zones refers to the distance p between the steps of the zones perpendicular to the optical axis and the steps of the zones, and the depth of the steps refers to the depth in the direction of the optical axis. It refers to the length d of the step.

When the pitch is fine, the degree of convergence and divergence of the part increases, and when the pitch increases, the degree of convergence and divergence of the part weakens.

Further, in an optical element having a diffraction portion,
A diffractive portion may be provided on the entire surface through which the light beam passes. In other words, it can be said that all the light beams having a size smaller than the maximum numerical aperture on the image side of the objective lens may pass through the diffractive portion. A diffractive portion may be simply provided on the entire optical surface of the optical element, and 70% or more (preferably 80% or more, more preferably 90% or more) of one optical surface of the optical element is diffracted. It may be a unit.

Further, the diffraction portion may be provided only on a part of the surface of the optical element through which the light beam passes, and the other part may be a refraction surface or a transmission surface. In other words, of the luminous flux corresponding to the maximum numerical aperture on the image side of the objective lens, the luminous flux in a part of the area perpendicular to the optical axis passes through the diffraction part, and the luminous flux in the other part of the area. Can pass through a refraction surface or a transmission surface without passing through the diffraction portion. When the diffraction portion is provided only on a part of the surface through which the light beam passes, the diffraction portion may be provided only near the optical axis including the optical axis, or the diffraction portion is not provided near the optical axis, and the diffraction portion is provided in an annular shape. You may. For example, 10% or more and less than 90% of one optical surface of the optical element may be the diffraction portion. Alternatively, 10% or more and less than 50% may be the diffraction portion.

When the diffractive portion is provided only on a part of the surface of the optical element through which the light beam passes, when NA1> NA2,
NA1> NAH1, NAH1 ≧ NA2, NA2 ≧ NAL
It is preferable that 1 ≧ 0. If NA2> NA1, NA2> NAH2, NAH2 ≧ NA1, NA1
It is preferable that ≧ NAL2 ≧ 0. NA1,
NA2 is a predetermined numerical aperture on the image side of the objective lens when using the first light beam and the second light beam, respectively. NAH
1, NAH2 is the numerical aperture on the image side of the objective lens of the first light beam and the second light beam that have passed through the outermost part of the diffraction unit.
NAL1 and NAL2 are numerical apertures on the image side of the objective lens of the first light beam and the second light beam that have passed through the innermost part of the diffraction unit.

In the case where the diffractive portion is provided only on a part of the surface of the optical element through which the light beam passes, when NA1> NA2, of the first light beam, the light beam passing through the diffractive portion at NA1 or less and the diffracting portion It is preferable that the light condensing positions of the light passing through other refracting surfaces be substantially equal. If NA2> NA1, the second
Of the luminous flux of the above, the luminous flux that has passed through the diffraction portion at NA2 or less,
It is preferable that the light condensing positions of the light that has passed through the refraction surface other than the diffractive portion are substantially equal.

Further, the diffraction section includes a first diffraction pattern,
It may have a second diffraction pattern, in which the second diffraction pattern is farther from the optical axis than the first diffraction pattern. Further, the diffractive portion and the refraction surface without the diffractive portion may be combined on the same surface.

In the case of having two types of diffraction patterns,
In the first light flux that has passed through the first diffraction pattern of the diffraction portion, more n-order diffracted light is generated than the other order diffracted light, and can be focused on the first information recording surface. In the second light flux that has passed through the first diffraction pattern of the diffraction section, n-order diffracted light is generated more than diffracted light of other orders, and collected on the second information recording surface. In the first light beam that is light-capable and has passed through the second diffraction pattern of the diffraction unit,
The n-th order diffracted light is generated more than the other order diffracted light, and can be focused on the first information recording surface, and the second order diffracted light passes through the second diffraction pattern of the diffractive portion. In a light beam, the 0th-order light, which is transmitted light, may be generated more than diffracted light of other orders. In this case, the n-th order is preferably the first order.

Further, as another aspect, in the first light beam that has passed through the first diffraction pattern of the diffraction portion, the n-th order diffracted light is generated more than the other order diffracted light, and The n-th order diffracted light can be condensed on the first information recording surface, and the n-th order diffracted light in the second light flux passing through the first diffractive pattern of the diffractive portion is larger than the other order diffracted lights. In the first light flux generated and condensed on the second information recording surface and having passed through the second diffraction pattern of the diffraction section, the n-th order diffracted light is compared with the diffracted lights of the other orders. In the second luminous flux that can be condensed on the first information recording surface and has passed through the second diffraction pattern of the diffraction section, diffracted light of a negative order other than the nth order is generated. Are generated more than the diffracted light of the first order. In this case, the n-th order is preferably the first order, and the negative order is preferably the -1 order.

In the case of an optical pickup device or an optical element used for a plurality of optical information recording media having different thicknesses of the transparent substrate, it is particularly preferable that the pitch of the annular zone of the diffraction portion satisfies the following conditional expression. 0.4 ≦ | (Ph / Pf) −2 | ≦ 25

More preferably, 0.8 ≦ | (Ph / P
f) −2 | ≦ 6, more preferably 1.2 ≦ |
(Ph / Pf) -2 | ≦.

The pitch of the ring zone of the diffractive portion corresponding to the maximum numerical aperture on the image side of the objective lens is Pf, and is 1 / the maximum numerical aperture.
The pitch of the ring zone of the diffraction section corresponding to No. 2 is Ph. The maximum numerical aperture refers to the maximum numerical aperture among the predetermined numerical apertures of several types of optical information recording media on which information is read / recorded in the optical pickup device. Note that the predetermined numerical aperture is a numerical aperture that enables reading / recording of information on an optical information recording medium by a light beam of a predetermined wavelength in the optical pickup device, and is defined by a standard of a certain optical information recording medium. The numerical aperture may be a given numerical aperture. In addition, the pitch of the ring zone of the diffraction unit corresponding to the maximum numerical aperture on the image side of the objective lens, when the maximum numerical aperture,
In the diffraction section, it means the pitch of the orbicular zone located at the outermost periphery of the light beam passing therethrough. Also, the pitch of the orbicular zone of the diffraction portion corresponding to 1/2 of the maximum numerical aperture is 1 / the maximum numerical aperture.
In the case of the numerical aperture of 2, it means the pitch of the orbicular zone located at the outermost periphery of the light beam passing through the diffractive portion.

An optical pickup device may be used in which one of the light beams of the two light sources has no aberration up to the aperture in actual use, and the outer portion has flare in the aberration.

In other words, it can be expressed as follows. When the first light beam is used, the first light beam within the predetermined numerical aperture on the image side of the objective lens is placed on the first information recording surface of the first optical information recording medium in a state of 0.07 λrms or less. When the first light flux is used, the first light flux that has passed outside the predetermined numerical aperture on the image side of the objective lens when using the first light flux is
On the first information recording surface, the state becomes larger than 0.07 λrms, and when the second light flux is used, the second light flux that has passed through a predetermined numerical aperture on the image side of the objective lens is also larger than the predetermined numerical aperture. The second light flux that has passed outside is also focused on the second information recording surface of the second optical information recording medium in a state of 0.07 λrms or less. In this case, NA1 <NA2, and when performing recording / reproduction on the first optical information recording medium, N1
The luminous flux between A1 and NA2 is to be flare.

Alternatively, when the second light beam is used, the second light beam within the predetermined numerical aperture on the image side of the objective lens is the second light beam.
0.07λ on the second information recording surface of the optical information recording medium
rms or less, and the second light flux passing outside the predetermined numerical aperture on the image side of the objective lens when using the second light flux is 0.07λr on the second information recording surface.
ms when the first light flux is used.
Both the first light beam that has passed within the predetermined numerical aperture on the image side of the objective lens and the first light beam that has passed outside the predetermined numerical aperture are the first light beams.
0.07λ on the first information recording surface of the optical information recording medium
Light is collected in a state of rms or less. In this case, NA1> N
A2, which means that the luminous flux between NA2 and NA1 is flare when recording / reproducing on / from the second optical information recording medium.

These embodiments are based on the design of the diffraction section.
Can be set arbitrarily. For example, while providing a diffractive portion on the entire surface of the optical element, the design of the diffractive portion may cause flare at or above a predetermined numerical aperture, or a diffractive portion may be provided on a part of the surface of the optical element. A refracting surface may be used, and flare may be generated by the refracting surface or the diffractive portion.

In the above-described embodiment for generating the flare,
The aperture limiting means that blocks or diffracts the first light beam outside the predetermined numerical aperture on the image side of the objective lens when using the first light beam and transmits the second light beam is also used when the second light beam is used. Preferably, there is no aperture limiting means for blocking or diffracting the second light beam outside the predetermined numerical aperture on the image side of the objective lens and transmitting the first light beam. That is, it is preferable to provide only a normal stop without providing a dichroic filter or a hologram filter. As long as the diffractive portion is designed so as to satisfy the above function, it is preferable to provide only a normal aperture, so that the mechanism is simplified and preferable.

However, flare may be generated using a filter such as a hologram filter. When a filter such as a hologram filter is provided,
A separate filter may be provided in the condensing optical system, or a filter may be provided on the objective lens.

In addition, when a light beam having a smaller numerical aperture is condensed, a flare may be provided under or over the position where the minimum spot is formed. You may. Preferably, it is better to provide over.

When the flare is generated as described above, the flare may be generated continuously or discontinuously in the spherical aberration diagram.

As another embodiment, there is an embodiment of an optical pickup device which does not generate flare. The following are mentioned.

In other words, it can be expressed as follows. When the first light beam is used, the first light beam within the predetermined numerical aperture on the image side of the objective lens is placed on the first information recording surface of the first optical information recording medium in a state of 0.07 λrms or less. When the first light flux is used, the first light flux that has passed outside the predetermined numerical aperture on the image side of the objective lens when using the first light flux is
On the first information recording surface, the light is condensed or shielded in a state of 0.07 λrms or less, and does not reach the first information recording surface, and when the second light beam is used, Neither the second light flux that has passed through the predetermined numerical aperture on the image side of the objective lens nor the second light flux that has passed outside the predetermined numerical aperture,
On the second information recording surface of the second optical information recording medium, 0.0
Light is collected in a state of 7λrms or less. In this case, NA1
<NA2, when recording / reproducing on the first optical information recording medium, whether the light flux between NA1 and NA2 is also collected,
Or it means shielding.

Alternatively, when the second light beam is used, the second light beam within the predetermined numerical aperture on the image side of the objective lens is the second light beam.
0.07λ on the second information recording surface of the optical information recording medium
The second light flux condensed in a state of not more than rms and passing outside the predetermined numerical aperture on the image side of the objective lens when the second light flux is used is 0.07λ on the second information recording surface.
When the first light flux is used, the light is converged or shielded in a state of not more than rms and does not reach the second information recording surface. Both the first light beam that has passed and the first light beam that has passed outside the predetermined numerical aperture are condensed on the first information recording surface of the first optical information recording medium in a state of 0.07λrms or less. You. In this case, NA1> NA2, and when recording / reproducing on / from the second optical information recording medium, the light flux between NA2 and NA1 is also collected or shielded.

In these embodiments, depending on the design of the diffraction section,
Can be set arbitrarily.

Without generating the above-mentioned flare, NA1 and NA2
In the mode of blocking the light beam between NA2 and NA1, the first light beam outside the predetermined numerical aperture on the image side of the objective lens when using the first light beam is shielded or diffracted, and The second light beam is transmitted through the aperture limiting means, or blocks or diffracts the second light beam outside the predetermined numerical aperture on the image side of the objective lens when the second light beam is used, and the first light beam is transmitted. It is preferable to provide an opening limiting means. Alternatively, it is preferable to provide an aperture restricting means so that each light beam has a predetermined numerical aperture.

That is, in one of the first light beam and the second light beam, the light beam is preferably shielded by a ring filter such as a dichroic filter or a hologram filter as aperture limiting means at a predetermined numerical aperture or more. . When a filter such as a dichroic filter or a hologram filter is provided, a separate filter may be provided in the condensing optical system, or a filter may be provided on the objective lens.

However, even in the case where flare is not generated, only a normal aperture is provided without providing a dichroic filter or a hologram filter, and all light beams within the maximum numerical aperture are focused on the information recording surface. It may be. In other words, within the maximum numerical aperture on the image side of the objective lens, both the first light beam and the second light beam are condensed on the information recording surface in a state of 0.07λrms or less. Is also good.

Also, even when NA1 = NA2, it is preferable that no flare be generated in the above-described manner.

It should be noted that the different information recording media, ie, the first optical information recording medium and the second optical information recording medium, are information recording media that use different wavelengths of light for recording / reproduction. I do. The thickness and refractive index of the transparent substrate may be the same or different. Further, the value of the predetermined numerical aperture may be the same or different. of course,
The information recording densities may be the same or different. Paraxial chromatic aberration and spherical aberration caused by the difference in the wavelength of light used for recording / reproduction of each of the different information recording media are corrected by the diffraction unit of the present invention. It is most preferable to correct both the spherical aberration and the paraxial chromatic aberration, and it is most preferable to correct only the spherical aberration and not to correct the paraxial chromatic aberration, but it is preferable to correct only the paraxial chromatic aberration and not correct the spherical aberration. It may be.

Further, even when the thickness of the transparent substrate is different in different information recording media, and the spherical aberration is generated based on the thickness of the transparent substrate, the spherical aberration is changed by the diffractive portion of the present invention. Will be corrected. In the case where the thicknesses of the transparent substrates in the first optical information recording medium and the second optical information recording medium are different from each other, the generated spherical aberration becomes larger, and the effect of the present invention becomes more remarkable, which is preferable.

It is preferable that the difference between the wavelength of the first light beam and the wavelength of the second light beam is 80 nm or more and 400 nm or less. More preferably, 100 nm or more, 20
0 nm or less. More preferably, it is 120 nm or more and 200 nm or less. A first light source and a second light source;
Are, for example, 760-820 nm, 630
Any one of two light sources that emit light having a wavelength of from 670 nm to 670 nm and from 350 nm to 480 nm can be preferably used in combination. Of course, three or four light sources may be used. In the case where there is a third light source that emits the third light beam or a fourth light source that emits the fourth light beam, the n-th order diffracted light is also different in the third light beam and the fourth light beam that have passed through the diffraction unit. It is preferable to generate more than the diffracted light of the following order.

When the wavelength of the second light beam is longer than the wavelength of the first light beam, the axial chromatic aberration in the second light beam and the first light beam satisfies the following conditional expression. Is preferred. −λ2 / ｛2 × (NA2) ² ｝ ≦ Z ≦ λ2 / ｛2 × (N
A2) ² ｝ λ2: wavelength of the second light beam NA2: a predetermined numerical aperture on the image side of the objective lens with respect to the second light beam.

It is preferable that the following conditional expression is satisfied when t2> t1 and λ2> λ1 using optical information recording media having different thicknesses of the transparent substrate. 0.2 × 10-6 / ℃ <ΔWSA3 ・ λ1 / ｛f ・ (NA1) ⁴・ ΔT｝ <2.2 × 1
0-6 / ° C NA1: Numerical aperture of the objective lens on the image side required when reproducing or recording on the optical information recording medium using the first light flux. λ1: wavelength of the first light beam f: focal length of the objective lens with respect to the first light beam ΔT: change in environmental temperature. ΔWSA3 (λ1rms): the amount of change in the third-order spherical aberration component of the wavefront aberration of the light beam focused on the optical information recording surface when reproducing or recording on the optical information recording medium using the first light beam

When the first light beam is used,
In a case where a first light beam, which is a non-parallel light beam such as divergent light or convergent light, is incident on an objective lens and a second light beam is used,
A second light beam, which is a non-parallel light beam such as divergent light or convergent light, may be incident on the objective lens.

Alternatively, when the first light beam is used, the first light beam which is a parallel light beam is made incident on the objective lens, and when the second light beam is used, the first light beam is a non-parallel light beam such as divergent light or convergent light. The second light beam may be made incident on the objective lens. Alternatively, when the first light beam is used, the first light beam that is a non-parallel light beam such as divergent light or convergent light is made incident on the objective lens, and when the second light beam is used, the second light beam that is the parallel light beam is used. The light beam may be made incident on the objective lens.

When either the first light beam, the second light beam, or both light beams use a non-parallel light beam, the magnification m1 with respect to the objective lens when using the first light beam, and the second It is preferable that the absolute value of the difference from the magnification m2 with respect to the objective lens when a light beam is used is 0 to 1/15. More preferably, it is 0 to 1/18.
When λ2> λ1 and t2> t1, m1 is preferably larger. In particular, the above range is preferable when the second light beam is used for a CD and the first light beam is used for a DVD. Note that the wavelength of the first light source is λ1, the wavelength of the second light source is λ2, the thickness of the first transparent substrate is t1, and the thickness of the second transparent substrate is t2.

Alternatively, the parallel light beam may be made incident on the objective lens both when using the first light beam and when using the second light beam. In this case, the diffractive portion may have a form as shown in FIGS. 47 (b) and (c), but the forms shown in FIGS. 47 (a) and (d) are more preferable.

Further, the optical pickup device is provided with divergence changing means (hereinafter also referred to as "divergence correction means") for correcting the divergence of the light beam incident on the objective lens, and the first light beam and the second light beam are provided. In, the divergence of the light beam incident on the objective lens may be changed.

When the divergent light is incident on the objective lens, it is preferable that the objective lens is a glass lens.

The first information recording medium or the second information recording medium
When reproduction / recording can be performed on only one of the information recording media and only reproduction is performed on the other of the information recording media, the imaging magnification of the entire optical pickup device with respect to the first light flux is determined by the optical pickup device. It is preferable that the entire imaging magnification of the optical pickup device for the two light beams is different.
In this case, the imaging magnification of the objective lens for the first light flux and the imaging magnification of the objective lens for the second light flux may be the same or different.

Also, λ1 <λ2, t1 <t2, and
When reproduction / recording can be performed only on the first information recording medium and only reproduction is performed on the second information recording medium, the imaging magnification of the entire optical pickup device with respect to the first light beam is set to the second magnification. Is preferably smaller than the overall imaging magnification of the optical pickup device with respect to the light flux. Further, when the above condition is satisfied and 0.61 <NA1 <0.66, a coupling lens for changing magnification is provided between the first light source and the collimator lens in the condensing optical system. In the optical optical system, it is preferable that a first light beam collimator lens and a second light beam collimator lens are separately provided. It is preferable that both the imaging magnification of the objective lens for the first light flux and the imaging magnification of the objective lens for the second light flux are 0. The wavelength of the first light source is λ1, the wavelength of the second light source is λ2, the thickness of the first transparent substrate is t1, the thickness of the second transparent substrate is t2, The predetermined numerical aperture on the image side of the objective lens required for recording or reproduction on the first optical information recording medium is NA1.

Also, λ1 <λ2, t1 <t2, and
When reproduction / recording can be performed only on the second information recording medium and only reproduction is performed on the first information recording medium, the imaging magnification of the entire optical pickup device with respect to the first light flux is set to the second magnification. Is preferably larger than the overall imaging magnification of the optical pickup device with respect to the light flux. It is preferable that both the imaging magnification of the objective lens for the first light flux and the imaging magnification of the objective lens for the second light flux are 0.

In the case where reproduction / recording can be performed on both the first information recording medium and the second information recording medium, or when only reproduction is performed on both, the optical pickup device includes: It is preferable that the imaging magnification of the entire optical pickup device with respect to the first light flux is substantially equal to the overall imaging magnification of the optical pickup device with respect to the second light flux. In this case, the imaging magnification of the objective lens for the first light flux and the imaging magnification of the objective lens for the second light flux may be the same or different.

The photodetector may be common to the first light beam and the second light beam. Alternatively, a second light detector may be provided, and the light detector may be used for the first light beam, and the second light detector may be used for the second light beam.

Further, the photodetector and the first light source or the second light source may be unitized. Alternatively, the photodetector and the first light source and the second light source may be unitized. Alternatively, the photodetector, the second photodetector, the first light source, and the second light beam may all be integrally unitized. Further, only the first light source and the second light source may be unitized.

In particular, when the first light source and the second light source are unitized and provided on the same surface, when NA1> NA2, the first light source is connected to the objective lens. Preferably provided on the optical axis, NA1 <NA2
In this case, it is preferable to provide the second light source on the optical axis of the objective lens. The predetermined numerical aperture on the image side of the objective lens required for recording or reproduction on the first optical information recording medium is N.
A1, and a predetermined numerical aperture on the image side of the objective lens required for recording or reproduction of the second optical information recording medium is NA2.

The working distance when recording / reproducing on the first optical information recording medium is WD1, and the working distance when recording / reproducing on the second optical information recording medium is WD2. | WD1-WD2
| ≦ 0.29 mm is preferable. In this case, it is more preferable that the magnification at the time of recording / reproducing on the first optical information recording medium is equal to the magnification at the time of recording / reproducing on the second optical information recording medium. More preferably, the magnification is 0. When t1 <t2 and λ1 <λ2, it is preferable that WD1 ≧ WD2. These conditions regarding the working distance are particularly preferable when the first optical information recording medium is a DVD and the second optical information recording medium is a CD. When the working distance is satisfied, the diffractive portion may have a form as shown in FIGS. 47 (a) and (d), but the forms shown in FIGS. 47 (b) and 47 (c) are more preferable.

An optical element such as a condensing optical system or an objective lens forms a spot on an information recording surface of an optical information recording medium so as to converge a light beam and record and reproduce information. Is what you do. In particular, NA1> NA2, λ1 <
In the case of λ2, and for the second light beam, the light beam outside the NA2 is flare on the second information recording surface of the second optical information recording medium (on the image forming surface). When the wavefront aberration is greater than 0.07λ2 rms), it is preferable that the spot satisfy the following conditions. 0.66 × λ2 / NA2 ≦ w ≦ 1.15 × λ2 / NA2 w> 0.83 × λ2 / NA1 λ1: wavelength of first light flux λ2: wavelength of second light flux NA1: predetermined for first light flux Numerical aperture NA2: predetermined numerical aperture for the second light flux w: beam diameter of 13.5% intensity of the second light flux on the image plane

When the spot is not a perfect circle, it is preferable that the beam diameter in the direction in which the beam diameter is most narrowed be the above-mentioned beam diameter (w).

Further, it is preferable to satisfy the following conditions. 0.74 × λ2 / NA2 ≦ w ≦ 0.98 × λ2 / NA2

Further, the spot shape is such that a spot used for recording / reproducing with high light intensity exists at the center, and a flare whose light intensity is low enough to have no adverse effect on detection exists around the spot. The shape may be such that a spot used for recording / reproducing with high light intensity is present at the center, and a donut-shaped flare is present around the spot.

It is preferable that the spot has a good S-shaped characteristic. Specifically, the overshoot is 0 to
Preferably it is 20%.

The wavelength of the first light source is λ1, the wavelength of the second light source is λ2, the thickness of the first transparent substrate is t1,
The thickness of the second transparent substrate is t2, the predetermined numerical aperture on the image side of the objective lens required for recording or reproduction of the first optical information recording medium with the light of wavelength λ1 is NA1, and the light of wavelength λ2 is used. Assuming that the predetermined numerical aperture on the image side of the objective lens required for recording or reproduction of the second optical information recording medium is NA2, a preferable example is the following conditional expression. In this case, the n-order diffracted light is preferably a first-order diffracted light. Of course, the preferred embodiment is not limited to the following conditional expressions. λ1 <λ2 t1 <t2 NA1> NA2 (preferably NA1>NA2> 0.5 ×
NA1)

When the above conditional expression is satisfied, the objective lens of the condensing optical system has a diffractive portion, and the recording / recording of the second optical information recording medium
FIG. 112 shows a case where the condensing optical system converges the n-th order diffracted light of the second light flux that has passed through the diffractive portion on the second information recording surface of the second optical information recording medium in order to perform reproduction. As described above, the spherical aberration may have at least one discontinuous portion.

When a discontinuous portion is provided, it is preferable that the spherical aberration has a discontinuous portion near NA2. For example, when the numerical aperture (NA) is 0.45, the spherical aberration has a discontinuous portion, and when the numerical aperture (NA) is 0.5, the spherical aberration has a discontinuous portion.

When the spherical aberration has a discontinuity,
The condensing optical system converts the nth-order diffracted light having a numerical aperture of NA1 or less in the first light beam that has passed through the diffractive portion onto the first information recording surface of the first optical information recording medium so that the wavefront aberration at the best image point is zero. 0.07λrms.
The nth-order diffracted light having a numerical aperture equal to or smaller than the numerical aperture serving as a discontinuous portion in the second light flux passing through the diffractive portion is converted into a 0.07λ wavefront aberration at the best image point on the second information recording surface of the second optical information recording medium.
It is preferable to condense light so as to have rms.

When the above-mentioned conditional expression is satisfied, the objective lens of the condensing optical system has a diffractive portion, and the condensing optical system passes through the diffractive portion in order to perform recording / reproduction on the second optical information recording medium. When the n-th order diffracted light of the second light flux is condensed on the second information recording surface of the second optical information recording medium, as shown in FIG. 27, the spherical aberration is continuous and has a discontinuous portion. It may not be done.

When the spherical aberration is continuous and has no discontinuity, it is preferable that the spherical aberration is 20 μm or more at NA1 and 10 μm or less at NA2. More preferably, at NA1, the spherical aberration is 50
μm or more, and spherical aberration is 2 μm or less at NA2

Under the above conditions, for example, a specific preferred example in the case of using one kind of DVD as the first optical information recording medium and one kind of CD as the second optical information recording medium is as follows. The following embodiments are exemplified, but not limited thereto. 0.55 mm <t1 <0.65 mm 1.1 mm <t2 <1.3 mm 630 nm <λ1 <670 nm 760 nm <λ2 <820 nm 0.55 <NA1 <0.68 0.40 <NA2 <0.55

In the above range, when the diffracting portion performs ring diffraction, the number of diffracting portions corresponding to NA2 or less is preferably 19 or less or 21 or more. In addition, it is preferable that the total number of the diffractive portions is equal to or greater than 35 orbs.

When the above range is satisfied, the spot diameter preferably satisfies the following mode.

The objective lens of the focusing optical system has a diffraction part,
λ1 = 650 nm, t1 = 0.6 mm, NA1 = 0.6
Wherein a first light flux, which is a parallel light having a uniform intensity distribution, is incident on the objective lens, and is passed through a first transparent substrate.
When condensed on the first information recording surface, the spot diameter at the best focus is preferably 0.88 to 0.91 μm.

Or λ1 = 650 nm, t1 = 0.6
mm, NA1 = 0.65, and the objective lens
When a first light flux, which is a parallel light having a uniform intensity distribution, is incident and focused on the first information recording surface via the first transparent substrate, the spot diameter at the best focus is 0.8.
It is preferably from 1 to 0.84 μm.

Further, when the above range is satisfied and the diffraction portion is provided on the objective lens, the pitch of the diffraction portion is 10 to 7 when the numerical aperture (NA) is 0.4.
It is preferably 0 μm. More preferably, 20
５０50 μm.

Further, among the above conditions, one specific preferred example is as follows.
However, it is not limited to this. In particular, when recording is also performed on a CD as the second optical information recording medium, NA2
Is preferably set to 0.5. Furthermore, when recording is also performed on a DVD as the first optical information recording medium, NA1 is preferably set to 0.65. t1 = 0.6 mm t2 = 1.2 mm λ1 = 650 nm λ2 = 780 nm NA1 = 0.6 NA2 = 0.45

The following embodiment may be adopted.
In the case of the following embodiments, the n-order diffracted light is preferably -1st-order light. λ1 <λ2 t1> t2

Further, as a specific example of an optical information recording medium recording or reproducing apparatus having the optical pickup device of the present invention for reproducing information from an optical information recording medium or recording information on the optical information recording medium, DVD / CD Playback device, DVD / CD / CD-R
Recording / playback device, DVD-RAM / DVD / CD-R / CD recording / playback device, DVD / CD / CD-RW recording / playback device, DVD / LD playback device, DV
D / blue laser (350-480nm etc., especially 400n
m) using an optical information recording medium recording / reproducing device, CD /
Optical information recording medium recording / reproducing device using blue laser,
And the like, but are not limited thereto. Further, these optical information recording medium recording or reproducing devices have a power supply, a spindle motor, and the like in addition to the optical pickup device.

Further, the objective lens according to the present invention has a variation in spherical aberration of the marginal ray of ΔSA with respect to a minute change in at least one of the wavelength of the first light source and the wavelength of the second light source. When the amount of change of the upper chromatic aberration is ΔCA, it is preferable to satisfy the following conditional expression. -1 <△ SA / △ CA <−0.2

The optical system according to claim 137 includes one or more optical elements. In an optical system used for at least one of recording and reproducing information on and from an information recording medium, at least one of the optical elements is preferably used. One optical element has a diffractive surface that selectively generates diffracted light of the same order with respect to light of at least two different wavelengths.

According to claim 137, since the optical element has the diffractive surface, it is possible to correct spherical aberration with respect to light of at least two different wavelengths and also correct axial chromatic aberration. can do. That is, it is possible to correct spherical aberration and axial chromatic aberration with a simple configuration in which many optical elements such as an objective lens are commonly used, and it is possible to reduce the size, weight, and cost of the optical system. Also, at least two optical elements different from each other
Since it has a diffractive surface that selectively generates diffracted light of the same order with respect to light of two wavelengths, loss of light quantity can be reduced. A sufficient amount of light can be obtained by using the objective lens.

Further, the optical system according to claim 138 includes at least one optical element. In the optical system used for at least one of recording and reproducing of information on the information recording medium, at least two different wavelengths are used. A diffractive surface for selectively generating a diffracted light of a specific order with respect to each of the above-mentioned lights is formed on almost the entirety of at least one optical surface of at least one of the optical elements.

According to the 138th aspect, since the diffraction surface is formed on the optical element, the spherical aberration and the axial chromatic aberration are corrected for at least two wavelengths different from each other as in the 1st aspect. Can be. Further, since the diffraction surface is formed on almost the entire optical surface of at least one of the optical elements, the correction can be performed more efficiently.

In the present specification, each term is as defined below. First, the optical element in the present invention refers to each of all optical elements that can be applied to an optical system for recording information on an information recording medium and / or reproducing information on the information recording medium. , A coupling lens, an objective lens, a polarizing beam splitter, a quarter-wave plate, and a beam splitter for synthesizing light from two or more light sources, but are not limited thereto. Further, an optical element provided with only the diffractive portion of the present invention and having no other role may be used.

The optical system according to the present invention is a set of one or more of the above optical elements capable of recording or reproducing a CD and a DVD, for example, and is used for recording and / or recording information on an information recording medium. Alternatively, it may mean not only the entire optical system for enabling information on the information recording medium to be reproduced, but also a part of the optical system, and includes at least one optical element as described above.

The information recording medium of the present invention includes, for example, various CDs such as CD, CD-R, CD-RW, CD-Video, and CD-ROM.
D, DVD, DVD-ROM, DVD-RAM, DVD-R, DVD-RW, etc.
Disc-shaped information recording media such as VD, MD, LD, and MO can be used. Generally, a transparent substrate exists on an information recording surface of an information recording medium. Of course, the present invention is not limited to these, and includes an optical information recording medium using a blue laser, which is not currently on the market.

In the present invention, recording and reproducing information on and from the information recording medium means recording information on the information recording surface of the information recording medium and reproducing the information recorded on the information recording surface. That means. The pickup device / optical system of the present invention may be used for performing only recording or reproduction, or may be used for performing both recording and reproduction. Further, it may be used for recording on one information recording medium and reproducing on another information recording medium, or may be used for recording or reproducing on a certain information recording medium. It may be used for reproducing and for recording and reproducing on another information recording medium. In addition,
The reproduction here includes simply reading information.

The pickup device and the optical system used for at least one of recording and reproduction of information on the information recording medium can be applied to the pickup device and the optical system. It also includes a pickup device and an optical system intended to be used for such purposes.

In the present invention, the light of at least two different wavelengths is, for example, 78 light used for CD.
0nm wavelength light and 635nm used for DVD
Alternatively, it may be light having two different wavelengths from light having a wavelength of 650 nm, and further includes light having a wavelength of, for example, 400 nm for recording and / or reproducing a large-capacity information recording medium recorded at high density. However, light of three different wavelengths may be used. Of course, light of four or more different wavelengths may be used. Further, even if the optical system actually uses light of three or more different wavelengths or an optical system intended for the same, it naturally means light of at least two different wavelengths. Of course, a combination of 400 nm and 780 nm or a combination of 400 nm and 650 nm may be used.

In the present invention, light of different wavelengths refers to light of a plurality of wavelengths having a sufficient wavelength difference and used according to the type of information recording medium and the difference in recording density as exemplified above. And does not refer to light of a different wavelength due to a temporary shift within about ± 10 nm caused by a temperature change or output change of one light source that outputs one wavelength of light. The factors that cause light of different wavelengths to be used include, in addition to the above-mentioned differences in the type and recording density of the information recording medium, for example, differences in the thickness of the transparent substrate of the information recording medium and differences in recording and reproduction And the like.

The diffractive surface is a surface provided with a relief on the surface of an optical element, for example, the surface of a lens, so as to condense or diverge a light beam by diffraction. If there is a region where diffraction occurs and a region where diffraction does not occur, it refers to a region where diffraction occurs. As the shape of the relief, for example, on the surface of the optical element, it is formed as a concentric annular zone centered on the optical axis, and if the cross section is viewed on a plane including the optical axis, each annular zone has a saw-like shape. It is known, but includes such shapes.

Generally, from the diffraction surface, the 0th order light, ± 1st order light, ± 1st order light
Innumerable orders of diffracted light are generated as secondary light... For example, in the case of a diffractive surface having a sawtooth-shaped relief as described above, the diffraction efficiency of a specific order is reduced by the diffraction of other orders. The shape of the relief can be set so as to be higher than the efficiency or, in some cases, to make the diffraction efficiency of one specific order (for example, + 1st order light) almost 100%. In the present invention, to selectively generate the diffracted light of a specific order means that the diffraction efficiency of the diffracted light of a specific order for light of a predetermined wavelength is the diffraction efficiency of the diffracted light of each order other than the specific order Higher than that of at least two wavelengths different from each other. Select that diffracted light of the same order that the specific order of the diffracted light of a specific order that is selectively generated is the same order. It happens. Here, that the order of the diffracted light is the same means that the order of the diffracted light is the same including the sign.

The diffraction efficiency is obtained by simulating the ratio of the amount of the diffracted light of each order to the total diffracted light based on the shape of the diffraction surface (relief shape), and setting the wavelength of the irradiated light to a predetermined wavelength. It is calculated by the following.
Examples of the predetermined wavelength include wavelengths of 780 nm and 650 nm.

The fact that the diffraction surface is formed on almost the entire surface of at least one of the optical surfaces of the optical element means that the diffraction structure (relief) is provided in almost all of the range through which the light beam passes on the optical surface. However, this means that the optical element is not an optical element in which a diffraction structure is provided only on a part of the optical surface, for example, only on the periphery. At this time, the range in which the light flux from the light source passes to the information recording medium is determined by the aperture stop used in the optical system or the optical pickup device. When viewed as an optical element with a diffractive surface alone, the area where the diffractive surface is formed covers almost the entire optical surface, but the peripheral surface where the light beam does not pass should be formed with some margin. Therefore, when this part is considered as a region usable as an optical surface and included in the optical surface, it is preferable that the area ratio of the diffractive surface in the optical surface as an optical element alone is at least half or more, and almost 100% Is more preferable.

The optical system according to claim 139 is characterized in that the specific orders of the diffracted lights selectively generated with respect to the respective lights of at least two different wavelengths are the same. is there.

According to claim 139, since the diffractive surface maximizes the diffraction efficiency of the diffracted light of the same order with respect to each light of at least two wavelengths, the diffractive surface maximizes the diffraction efficiency of the diffracted light of the different order. The loss of light amount is smaller than in the case of

Further, the optical system according to claim 140 is characterized in that the diffracted light of the same order is a first-order diffracted light. The first order diffracted light may be a plus first order diffracted light or a minus first order diffracted light.

According to the 140th aspect, since the diffracted light of the same order is the first-order diffracted light, the diffracted light of the same order is 1st-order.
The loss of light quantity is smaller than in the case of diffracted light of a higher order than the next.

The optical system according to claim 141 is characterized in that at least one of the optical elements having the diffractive surface is a lens having a refractive power. The optical system according to claim 141 may be one in which a fine structure (relief) for diffraction is further formed on the surface of a lens having refractive power. At this time, the envelope surface of the fine structure for diffraction becomes the refractive surface shape of the lens. For example, on at least one surface of an aspheric single lens objective lens,
It may be a lens provided with a so-called blaze-type diffractive surface, and a lens provided with an annular zone having a sawtooth meridional section on the entire surface.

According to claim 141, since the optical element having the diffraction surface is a lens having a refractive power,
Both spherical aberration and chromatic aberration can be corrected, and the number of parts can be reduced.

An optical system according to claim 142 is characterized in that the refractive surface of the lens is aspheric.

143. The optical system according to claim 143, wherein the lens has a diffraction efficiency of diffracted light with respect to light having a certain wavelength which is a wavelength between a maximum wavelength and a minimum wavelength of the at least two different wavelengths. Is larger than the diffraction efficiency of the diffracted light with respect to the light having the maximum wavelength and the light having the minimum wavelength.

The optical system according to claim 144, wherein the lens has a diffraction efficiency of diffracted light with respect to the light of the maximum wavelength or the minimum wavelength of the at least two different wavelengths, and the maximum wavelength of the light of the at least two different wavelengths. The diffraction efficiency is higher than the diffraction efficiency of diffracted light with respect to light having a wavelength between the minimum wavelength and the minimum wavelength.

Further, in the optical system according to the present invention, the sign of the diffraction effect (hereinafter also referred to as “diffraction power”) added on the diffraction surface of the lens is perpendicular to the optical axis from the optical axis. It is characterized in that switching is performed at least once in a direction in which the user moves away.

According to claim 145, the sign of the diffractive power added on the diffractive surface of the lens is switched at least once in a direction perpendicular to the optical axis and away from the optical axis, thereby reducing the wavelength variation of the spherical aberration. Can be suppressed.

The optical system according to claim 146 is characterized in that the diffraction power applied on the diffraction surface of the lens switches once from negative to positive in a direction perpendicular to the optical axis and away from the optical axis. Things.

According to claim 146, the diffraction power applied on the diffraction surface of the lens is switched once from negative to positive in a direction perpendicular to the optical axis and away from the optical axis, so that, for example, both the CD system and the DVD system When a parallel light beam is incident on the objective lens, the influence on the spherical aberration due to the difference in the thickness of the transparent substrate of the information recording medium can be efficiently corrected without making the annular zone pitch of the diffraction surface too small.

Regarding the diffraction power, in particular, in the case of an optical element having an optical surface having a refracting action and an optical element having a diffractive surface provided on an optical surface having a refracting action, The function of converging or diverging the light beam is added to the refraction function of the base refraction surface. At this time, not only in the paraxial region but also when a function of converging is added to a light beam of an actual finite height, in the present invention, it is assumed that a predetermined position on the diffraction surface has a positive diffraction power, and When the effect of adding
It has a negative diffraction power.

Further, in the optical system according to the present invention, the diffractive surface is composed of a plurality of annular zones as viewed in the optical axis direction, and the plurality of annular zones are substantially concentric with respect to the optical axis or a point near the optical axis. It is characterized by being formed in a shape. That is, the diffractive surface of claim 147 is described in, for example,
As described in Japanese Patent Application Laid-Open No. 2373, it is formed in a stepwise manner as an annular zone that discretely shifts in a direction in which the lens thickness increases as the distance from the optical axis increases.

Further, in the optical system according to the present invention, the phase difference function represented by a power series indicating each position of the plurality of annular zones is:
At least one term other than the square term has a coefficient other than zero.

According to claim 148, spherical aberration between two different wavelengths can be controlled. Here, being controllable means that the difference in spherical aberration between the two wavelengths can be made extremely small, and that the difference required in optical specifications can be provided.

The optical system according to claim 149, wherein a phase difference function represented by a power series indicating each position of the plurality of orbicular zones is:
The square term has a coefficient other than zero.

According to claim 149, it is possible to effectively correct chromatic aberration in the paraxial region.

The optical system according to claim 150, wherein a phase difference function represented by a power series indicating each position of the plurality of orbicular zones is:
It is characterized by not including a square term.

According to claim 150, since the phase difference function does not include the square term, the paraxial power of the diffractive surface becomes 0 and only the fourth-order and higher-order terms are used. Instead, the spherical aberration can be controlled.

The optical system according to claim 151 includes an objective lens in said one or more optical elements, and forms an image with respect to each of said at least two different wavelengths of light (wavelength λ). The wavefront aberration on the surface is not more than 0.07λrms within a predetermined numerical aperture on the image side of the objective lens.

According to claim 151, since the wavefront aberration is equal to or less than the Marechal tolerance of 0.07λrms within a predetermined numerical aperture on the image side of the objective lens, excellent optical characteristics with sufficiently small spherical aberration can be obtained. it can.

The optical system according to claim 152 is characterized in that one of the at least two different wavelengths has one wavelength λ _1.
Is varied within the range of ± 10 nm, the wavefront aberration on the image plane is not larger than 0.1 within a predetermined numerical aperture on the image side of the objective lens.
07λ ₁ rms or less.

According to claim 152, the wavelength λ ₁ is ± 10
Even if it fluctuates within the range of nm, excellent optical characteristics with sufficiently small spherical aberration can be obtained.

The optical system according to claim 153, wherein, of the at least two different wavelengths, the light having a wavelength λ ₂ and the predetermined numerical aperture on the image side of the objective lens have the wavelength λ ₂
With respect to light of another wavelength that is larger than a predetermined numerical aperture of light of the same wavelength, the wavefront aberration of the light of wavelength λ ₂ on the image forming surface is 0.07 λ ₂ rms within the predetermined numerical aperture of the light of another wavelength.
It is characterized by being larger.

[0156] wherein according to claim 153, 0.07λ ₂ within the wavelength lambda ₂ of the prescribed numerical aperture wavefront aberration related to the light of different wavelengths of light (greater than a predetermined numerical aperture with respect to wavelength lambda ₂ of light)
Since it is as large as rms or more, an appropriate spot diameter can be obtained for the light of wavelength λ ₂ . In other words, a desired effect can be obtained by making almost no aberration up to the numerical aperture in practical use, and making the outer portion flare the aberration.

An optical system according to claim 154, wherein the wavefront aberration of the light of the wavelength λ ₂ on the imaging surface is 0.10λ ₂ rms or more within a predetermined numerical aperture for the light of the different wavelength. It is a feature.

[0158] wherein according to claim 154, 0.10λ ₂ within the wavelength lambda ₂ of the prescribed numerical aperture wavefront aberration related to the light of different wavelengths of light (greater than a predetermined numerical aperture with respect to wavelength lambda ₂ of light)
Since it is as large as rms or more, a more appropriate spot diameter can be obtained for the light of wavelength λ ₂ .

The optical system according to claim 155, wherein the predetermined numerical aperture for the light of the different wavelength is NA1, and the wavelength λ ₂
Assuming that the predetermined numerical aperture for the light of NA is NA2, NA1>
NA2> 0.5 × NA1 is satisfied.

Further, in the optical system according to the present invention, a parallel light beam is incident on the objective lens with respect to at least one of the at least two different wavelengths, and another one of the other wavelengths. A non-parallel light beam is incident on the light.

According to claim 156, a parallel light beam is incident on at least one of the at least two wavelengths of the at least two different wavelengths to the objective lens, and a non-parallel light beam is incident on the at least another one of the wavelengths. Is incident, the wavelength 1 of each light of at least two wavelengths
For a change of about 0 nm, it becomes possible to suppress the spherical aberration fluctuation to an extremely small value.

An optical system according to claim 157, wherein a parallel light beam is incident on the objective lens with respect to light of at least two wavelengths among the at least two different wavelengths. It is.

The optical system according to claim 158 is characterized in that a non-parallel light beam is incident on the objective lens with respect to at least two wavelengths of the at least two different wavelengths. Things.

The optical system according to claim 159, wherein the longer wavelength of any two of the at least two different wavelengths is λ _3, and the objective lens of the objective lens for the light of the wavelength λ ₃ Assuming that the predetermined numerical aperture on the image side is NA, the axial chromatic aberration between the wavelength λ ₃ and the shorter wavelength is −λ ₃
/ (2NA ² ) or more and + λ ₃ / (2NA ² ) or less.

According to claim 159, since the focus hardly changes when the wavelength is switched, it becomes possible to eliminate the need for focus servo and to narrow the range of movement by focus servo.

The optical system according to claim 160 is characterized in that the light having at least two different wavelengths is used for information recording media having different thicknesses of transparent substrates.

The optical system according to claim 161 is characterized in that the at least two different wavelengths are three different wavelengths.

The optical system according to claim 162, wherein the three different wavelengths of light are respectively λ1, λ2, λ3
(Λ1 <λ2 <λ3) and when the predetermined numerical aperture on the image side of the objective lens for each of these three different wavelengths is NA1, NA2, NA3, respectively, 0.60 ≦ NA1, 0. 60 ≦ NA2, 0.40 ≦
NA3 ≦ 0.50 is satisfied.

The optical system according to claim 163 is provided with a filter capable of blocking at least a part of light incident on the objective lens outside the smallest predetermined numerical aperture among the predetermined numerical apertures. It is characterized by having.

Further, the optical system according to claims 164 and 165 is characterized in that the optical element having the diffraction surface is an objective lens.

The optical system according to claim 166 is characterized in that the objective lens comprises a single lens.

An optical system according to claim 167 is characterized in that the diffraction surfaces are provided on both surfaces of the objective lens.

The optical system according to claim 168 is characterized in that the Abbe number νd of the material of the objective lens is larger than 50.

According to claim 168, when axial chromatic aberration is corrected for light sources of different two wavelengths, the secondary spectrum can be reduced.

The optical system according to claim 169 is characterized in that the objective lens is made of plastic. According to claim 169, an inexpensive and lightweight optical system can be obtained. An optical system according to claim 170 is characterized in that the objective lens is made of glass. According to claims 169 and 170, it is possible to obtain an optical system that is extremely resistant to temperature changes.

An optical system according to a seventeenth aspect is characterized in that the objective lens has a resin layer on which the diffraction surface is formed on a glass lens surface. Claim 1
According to 71, since a resin layer that easily forms a diffractive structure is provided on a glass lens, an optical system that is extremely resistant to temperature changes and that is advantageous in terms of cost can be obtained.

The optical system according to claim 172, wherein the wavelength difference between the at least two different wavelengths is 80n.
m or more.

The optical system according to claim 173, wherein the wavelength difference between the at least two different wavelengths is 400
nm or less.

The optical system according to claim 174, wherein the wavelength difference between the at least two different wavelengths is 100%.
nm or more and 200 nm or less.

The optical system according to claim 175, wherein the diffractive efficiency of the selectively generated diffracted light of the specific order is different from the light of the at least two different wavelengths. The diffraction efficiency is 10% or more higher than the diffraction efficiency of each order diffracted light.

The optical system according to claim 176, wherein the diffraction efficiency of the selectively generated diffracted light of the specific order with respect to each of the lights of at least two different wavelengths is different from that of the specific order. The diffraction efficiency is 30% or more higher than the diffraction efficiency of each order diffraction light.

In the optical system according to the present invention, the diffraction efficiency of the selectively generated diffracted light of a specific order is at least 50% with respect to each of the at least two different wavelengths. It is characterized by.

The optical system according to claim 178, wherein the diffractive efficiency of the selectively generated diffracted light of a specific order is 70% or more with respect to each of the at least two different wavelengths. It is characterized by.

In the optical system according to claim 179, the presence of the diffractive surface allows at least two different optical systems.
When the selectively generated specific order diffracted light of two wavelengths is focused, spherical aberration is improved as compared with the case where the diffractive surface is not provided.

In the optical system according to the present invention, the diffracted light of a specific order, which is selectively generated with respect to each of the at least two different wavelengths (wavelength λ), is formed on the image plane. The wavefront aberration is not more than 0.07λrms.

[0186] Further, the present invention provides an optical pickup device having the above-mentioned optical systems.

The optical pickup device according to claim 182 includes at least two light sources for outputting lights of different wavelengths, and one or more optical elements for condensing the light from the light sources on an information recording medium. In an optical pickup device including an optical system and a photodetector that detects transmitted light or reflected light from the information recording medium, at least one of the optical elements is output from the at least two light sources. It has a diffractive surface that selectively generates diffracted light of the same order for light of two different wavelengths.

The optical pickup device according to claim 183 includes at least two light sources for outputting lights of different wavelengths, and one or more optical elements for condensing the light from the light sources on an information recording medium. In an optical pickup device including an optical system and a photodetector that detects transmitted light or reflected light from the information recording medium, the optical pickup device includes a light detector that outputs light of two different wavelengths output from the at least two light sources. A diffractive surface for selectively generating diffracted light of a specific order is formed on almost the entire optical surface of at least one of the at least one optical element.

[0189] Further, the optical pickup device according to claim 184 is characterized in that at least one of the optical elements having a diffractive surface according to claim 46 or 47 is a lens having a refractive power.

An optical pickup device according to claim 185, wherein the lens has a certain wavelength which is a wavelength between a maximum wavelength and a minimum wavelength of two different wavelengths output from the at least two light sources. The diffraction efficiency of the diffracted light with respect to the light is set to be greater than the diffraction efficiency of the diffracted light with respect to the light having the maximum wavelength and the light having the minimum wavelength.

186. The optical pickup device according to claim 186, wherein the lens has different diffraction efficiencies of diffracted light with respect to light of maximum wavelength or minimum wavelength of two different wavelengths output from the at least two light sources. The diffraction efficiency of the diffracted light with respect to light having a wavelength between the maximum wavelength and the minimum wavelength of at least two wavelengths is made larger.

The optical pickup device according to claim 187 is characterized in that the lens has a flange on the outer periphery. An optical pickup device according to claim 188,
The flange portion has a surface extending substantially perpendicular to the optical axis of the lens. The lens portion can be easily attached to the optical pickup device by the flange portion, and when a surface extending in a direction substantially perpendicular to the optical axis is provided on the flange portion, attachment with higher precision can be easily performed.

An optical pickup device according to claim 189, further comprising an objective lens in the one or more optical elements, wherein two or more different light sources output from the at least two light sources are provided.
The wavefront aberration on the image plane for each of the light of the two wavelengths (wavelength λ) is 0.07λrms or less within a predetermined numerical aperture on the image side of the objective lens.

An optical pickup device according to claim 190, wherein the one or more optical elements include an objective lens, and the two or more different light sources output from the at least two light sources.
The wavefront aberration on the image plane is 0.07λrms or less within the maximum numerical aperture on the image side of the objective lens with respect to each of the light beams having two wavelengths (wavelength λ).

The optical pickup device according to claim 191 is characterized in that two different light sources output from the at least two light sources are provided.
One of even one wavelength lambda ₁ of the wavelength varies within the range of ± 10 nm, the wave front aberration on the image plane, 0.07λ ₁ rms or less within the predetermined numerical aperture on the image side of the objective lens It is characterized by being.

Further, in the optical pickup device according to claim 192, two different light sources output from the at least two light sources are provided.
Of the two wavelengths, the light of the wavelength λ _{2 and} the light of the other wavelength whose predetermined numerical aperture on the image side of the objective lens is larger than the predetermined numerical aperture of the light of the wavelength λ ₂ are light of the different wavelength. about within a predetermined numerical aperture, wherein the wave front aberration on the image plane of the wavelength lambda ₂ of light is larger than 0.07λ ₂ rms.

[0197] Further, it is an optical pickup apparatus of claim 193, within a predetermined numerical aperture related to the light of the specific wavelength wavefront aberration on the imaging plane of the wavelength lambda ₂ of light is 0.10λ ₂ rms or more It is characterized by.

The optical pickup device according to claim 194, wherein the predetermined numerical aperture for the light of the different wavelength is NA1.
When the NA2 a prescribed numerical aperture for said wavelength lambda ₂ of light, and satisfies the NA1>NA2> 0.5 × NA1.

Further, in the optical pickup device according to the present invention, a parallel light beam is incident on the objective lens with respect to at least one of two different wavelengths output from the at least two light sources. , A non-parallel light beam is incident on light of another at least one wavelength.

[0200] Further, in the optical pickup device according to the present invention, a parallel light beam is incident on the objective lens with respect to lights of two different wavelengths output from the at least two light sources.

Further, in the optical pickup device of the present invention, a non-parallel light beam is incident on the objective lens with respect to light beams of two different wavelengths output from the at least two light sources. .

Further, in the optical pickup device according to claim 198, two different light sources output from the at least two light sources are provided.
The longer wavelength for one wavelength is λ ₃ , and the wavelength λ ₃
The predetermined numerical aperture on the image side of the objective lens with respect to the
Where the axial chromatic aberration between the wavelength λ ₃ and the shorter wavelength is not less than −λ ₃ / (2NA ² ) and not more than + λ ₃ / (2NA ² ).

The optical pickup device according to claim 199 is characterized in that two different light sources output from the at least two light sources are provided.
Light of two wavelengths is used for information recording media having different thicknesses of the transparent substrate.

Further, in the optical pickup device of claim 200, the diffractive surface is formed of a plurality of annular zones as viewed from the optical axis direction, and the plurality of annular zones are substantially centered on the optical axis or a point near the optical axis. A pitch Pf of the orbicular zone formed concentrically and corresponding to the maximum numerical aperture on the image side of the objective lens.
And a pitch Ph of the annular zone corresponding to a half of the maximum numerical aperture, the following relationship is established. 0.4 ≦ | (Ph / Pf) −2 | ≦ 25

According to the 200th aspect, when the value is equal to or more than the lower limit of the above relational expression, the effect of diffraction for correcting higher-order spherical aberration does not weaken. The difference in spherical aberration between the two wavelengths can be corrected by the effect of diffraction. In addition, when the value is equal to or less than the upper limit, a portion where the pitch of the diffraction ring zone is too small is less likely to occur, and a lens having high diffraction efficiency can be manufactured. In the above relational expression, 0.8 ≦ | (Ph / Pf) −2 | ≦ 6.0 is preferable, and 1.2 ≦ | (Ph / Pf) −2 | ≦ 2.0 is more preferable.

Further, the optical pickup device according to claim 201 is characterized in that the at least two light sources are three light sources.

In the optical pickup device of the present invention, lights of three different wavelengths output from the three light sources are respectively set to λ1, λ2, λ3 (λ1 <λ2 <λ3), and these three different light sources are used. The predetermined numerical aperture on the image side of the objective lens for each of the
1, NA2, NA3, 0.60 ≦ NA1, 0.60 ≦ NA2, 0.40 ≦
NA3 ≦ 0.50 is satisfied.

The optical pickup device according to claim 203 is provided with a filter capable of blocking at least a part of light incident on the objective lens outside the smallest predetermined numerical aperture among the predetermined numerical apertures. It is characterized by having.

[0209] Further, the optical pickup device of the present invention is characterized in that the optical pickup device has an aperture limiting means for providing the predetermined numerical aperture for each of the two different wavelengths of light.

[0210] Further, the optical pickup device of the present invention is characterized in that there is no aperture limitation for one of the two different wavelengths to be the predetermined numerical aperture.
For example, specifically, the maximum numerical aperture has an aperture limit, and no aperture limit is set for a predetermined numerical aperture smaller than the maximum numerical aperture. As a result, an aperture limiting means such as a filter having wavelength selectivity can be dispensed with, and it is possible to reduce the size and cost.

[0211] In the optical pickup device according to claim 206, the one or more optical elements include an objective lens, and the objective lens collects the lights having different wavelengths on the information recording medium. It is characterized by being commonly used when emitting light.

[0212] Also, in the optical pickup device according to claim 207, the unit in which the at least two light sources and the objective lens are integrated is driven at least in parallel with the main surface of the information recording medium. Features.

[0213] The optical pickup device according to the present invention is characterized in that the unit is driven perpendicular to the main surface of the information recording medium.

[0214] Further, the present invention provides a recording / reproducing apparatus which is equipped with the above-mentioned optical pickup device and is capable of recording or reproducing at least one of audio and video.

A lens according to claim 210 is used for at least one of recording and reproduction of information on an information recording medium, and has a refractive power and a diffractive surface on at least one optical surface. The sign of the diffraction power applied on the surface is switched at least once in a direction perpendicular to the optical axis and away from the optical axis.

The lens according to claim 211 is the lens according to claim 74, wherein the diffraction surface has a plurality of blazed diffraction zones, and the diffraction zone near the optical axis has a stepped portion. 212. A structure according to claim 212, wherein the portion is located on a side distant from the optical axis, and in the diffraction ring zone on a side distant from the optical axis, the step portion is located on a side close to the optical axis.
In the lens, the diffraction surface has a plurality of blazed diffraction zones, and in the diffraction zone near the optical axis, the step portion is located on the side near the optical axis, and the step away from the optical axis. Is characterized in that the step is located on the side away from the optical axis.

The present invention also provides an optical element applicable to an optical system for recording and / or reproducing information on an information recording medium, wherein light of at least two different wavelengths is used. When used in an optical system for recording and / or reproducing information on an information recording medium, it has a diffraction surface that selectively generates diffracted light of the same order with respect to the light of at least two different wavelengths. An optical element characterized in that:

The present invention also provides a lens applicable as an objective lens in an optical system for recording and / or reproducing information on an information recording medium, wherein light of at least two different wavelengths is used. When used as an objective lens in an optical system for recording and / or reproducing information on the information recording medium, the diffraction efficiency of diffracted light of the same order with respect to the light of at least two different wavelengths is improved. A lens having a diffractive surface that is selectively generated.

The present invention also provides an optical element applicable to an optical system for recording and / or reproducing information on an information recording medium, wherein light of at least two different wavelengths is used. When used in an optical system for recording and / or reproducing information on an information recording medium, a diffractive surface that selectively generates a specific order of diffracted light with respect to the light of at least two different wavelengths, An optical element formed substantially over at least one of the optical surfaces.

[0220] Further, in a lens applicable to an objective lens in an optical system for recording and / or reproducing information on an information recording medium, light of at least two different wavelengths is used. When used as an objective lens in an optical system for recording and / or reproducing information on an information recording medium, diffraction that selectively generates a specific order diffracted light with respect to the at least two different wavelengths of light. The lens is characterized in that the surface is formed on almost the entire surface of at least one of the optical surfaces.

The diffraction optical system for an optical disk according to claim 217 is a recording / reproducing optical system having two light sources having different wavelengths and performing recording / reproducing by the same optical system, wherein the optical system is provided on a refracting surface. Including an optical surface provided with a diffractive orbicular lens, the aberration generated on the refracting surface due to the difference in wavelength and the aberration produced by the diffractive orbicular lens cancel each other out, and the diffracted light used for the cancellation is different for two light source wavelengths. The diffracted light is of the same order.

As described above, this diffractive optical system includes an optical surface having a diffractive orbicular lens provided on a refracting surface, and a diffracted light beam of the same order for each of two different light sources having different wavelengths. The present invention is characterized in that the spherical aberration caused by the refraction surface is canceled out, so that the aberration is corrected to be almost the same as the diffraction limit. The diffracted light of the same order is preferably a first-order diffracted light.

In the method of making the diffracted lights of the same order correspond to the respective wavelengths of the two light sources as in the present invention, the loss of the light amount is smaller as compared with the case of making the diffracted lights of different orders correspond. It has the advantage that. For example, 780n
When two wavelengths, m and 635 nm, are used, the use of first-order diffracted light for both wavelengths is more comprehensive than the use of first-order diffracted light for either wavelength and the 0th-order diffracted light for the other wavelength. Low loss. Further, when diffracted light of the same order is used for both wavelengths, the loss of light amount is smaller when the first-order diffracted light is used than when higher-order diffracted light is used.

In the diffraction optical system for an optical disk according to the present invention, the canceling aberration is spherical aberration and / or chromatic aberration.

In the diffraction optical system for an optical disk according to claim 219, the diffracted light of the same order is a first-order diffracted light.

Further, the diffractive optical system for an optical disk of claim 220 is characterized in that the light sources of two different wavelengths correspond to optical disks having different transparent substrate thicknesses.

Further, the diffraction optical system for an optical disk according to claim 221 is characterized in that, of the two light sources having different wavelengths, the shorter light source wavelength is 700 nm or less.

Further, the diffraction optical system for an optical disk according to claim 222 is characterized in that, of the two light sources having different wavelengths, the longer light source wavelength is 600 nm or more.

In the diffraction optical system for an optical disk according to claim 223, the diffractive orbicular zone lens is characterized in that the phase function representing the position of the orbicular zone includes a coefficient of a term other than the square of a power series.

Further, the diffraction optical system for an optical disk according to the present invention is characterized in that the optical refraction surface is aspherical.

Further, the diffraction optical system for an optical disk according to claim 225 is characterized in that the diffraction efficiency of diffracted light is maximized at a substantially intermediate wavelength between two light sources having different wavelengths.

The diffraction optical system for an optical disk according to claim 226 is characterized in that, for two light sources having different wavelengths, the diffraction efficiency of the diffracted light is maximum at one of the light source wavelengths.

The diffraction optical system for optical disks according to claim 227, wherein the diffractive orbicular zone lens on the optical surface corrects the spherical aberration to under, and the aspherical surface of the optical surface corrects the spherical aberration to over. And

In the diffractive optical system for an optical disk according to claim 227, for example, a CD system (for example, a wavelength of 780 nm and a substrate thickness of 1.2 mm) and a DVD system (for example, a wavelength of 650 nm)
m and substrate thickness of 0.6 mm) when using an objective lens with parallel light incidence, the spherical aberration of the CD system is larger than that of the DVD system because the substrate is thicker. The spherical aberration of the diffractive lens is set to be under in order to correct for the wavelength difference. At this time, the CD
At a long wavelength of the system, the spherical aberration of the diffractive lens becomes largely under, and the influence of the difference in substrate thickness is corrected. For aspheric surfaces, instead of compensating for the effects of differences in substrate thickness, CD
The spherical aberration is almost the same for both DVD and DVD systems. The above utilizes the fact that the wave fluctuation of the spherical aberration can be largely controlled when a higher-order term of diffraction is used.

In the diffraction optical system for an optical disk according to claim 228, the difference between the wavelengths of the two light sources having different wavelengths is 80 nm or more.

In the diffraction optical system for optical disks according to claim 229, in the objective lens optical system of the optical disk, a diffractive orbicular lens is provided on the optical surface so that each of the two different light sources having different wavelengths can be used. It is characterized in that axial chromatic aberration of two diffracted lights of the same order is corrected.

The diffractive optical system for optical disks according to claim 230 is characterized in that the wavelength difference between the two different light sources is 80 nm or more, and that the optical system has a single lens objective lens satisfying the following conditions. νd> 50, where νd: Abbe number of the glass material of the objective lens

In the diffractive optical system for an optical disk according to claim 231, one of the lens performances for two different wavelengths has no aberration up to the aperture in practical use, and the outer portion has flare. It is characterized by having done.

The diffraction optical system for an optical disk according to claim 232 is one of the lens performances for the two different wavelengths.
NA1 is the numerical aperture for the wavelength that has no aberration at all apertures.
When the numerical aperture of the other wavelength in practical use is NA2, the following condition is satisfied. NA1>NA2> 0.5 × NA1

Further, the diffraction optical system for an optical disk according to claim 233 is characterized in that the optical disk thickness for the two different wavelengths is different.

Further, the optical pickup device of claim 234 has at least two or more light sources having different wavelengths, and divergent light fluxes from the respective light sources are put on the information recording surface of the optical information recording medium by the same objective lens. In a recording / reproducing optical system that records information via a transparent substrate and / or reproduces information on the information recording surface, the objective lens includes at least an optical surface having an annular diffraction surface provided on a refraction surface, and For one light source, the luminous flux transmitted through the objective lens and the transparent substrate has diffraction-limited performance at the best image point.

Here, the diffraction-limited performance refers to the measurement of the wavefront aberration of a light beam, and the root mean square (r) of the wavefront aberration of the entire light beam.
ms value) is equal to or less than 0.07 times the wavelength that is Marechal's allowable value. The aperture in actual use refers to the numerical aperture specified in the standard of each optical information recording medium, and is a spot necessary for recording or reproducing information on each optical information recording medium. This corresponds to the numerical aperture of an objective lens having diffraction-limited performance capable of obtaining a diameter.

As described above, in the present invention, the numerical aperture in actual use is defined for the optical information recording medium, so that the actual numerical aperture of the light beam passing through the optical system of the pickup device on the optical information recording medium side is reduced. It may be larger than the numerical aperture in use.

In the present invention, the maximum numerical aperture preferably means the maximum numerical aperture among practically used numerical apertures. That is, in the case of a pickup device used interchangeably with a plurality of optical information recording media, a plurality of numerical apertures in actual use are defined, and the largest one is preferably the maximum numerical aperture. Further, the predetermined numerical aperture and the required numerical aperture have the same meaning as the numerical aperture in actual use.

When recording or reproducing information on or from the optical information recording medium, when a light source having a wavelength different from the light source specified by the standard is used in an actual optical pickup device, the specified wavelength is used. The actual numerical aperture is set such that the ratio between the actual numerical aperture and the actual numerical aperture is constant. As an example, for a CD, the numerical aperture is 0.45 when a light source with a wavelength of 780 nm is used in the standard, but the numerical aperture is 0.38 when a light source with a wavelength of 650 nm is used.

Further, the optical pickup device of claim 235 has at least two or more light sources having different wavelengths, and diverges light beams from each light source on the information recording surface of the optical information recording medium by the same objective lens. In a recording / reproducing optical system that records information via a transparent substrate and / or reproduces information on an information recording surface, the objective lens includes an optical surface having a ring-shaped diffraction surface provided on a refraction surface, and For one light source, the luminous flux transmitted through the objective lens and the transparent substrate has diffraction-limited performance at the best image point, and for at least one light source, the luminous flux transmitted through the objective lens and the transparent substrate Of these, the luminous flux up to the aperture in actual use has diffraction-limited performance at its best image point, and the outer part is provided with the above annular zone-like diffraction surface so as to be flare. And it features.

The optical pickup device according to claim 236 is characterized in that the above device has at least three light sources having different wavelengths.

An optical pickup device according to claim 237 is characterized in that in the above-mentioned device, there is provided an optical surface provided with at least two or more annular diffraction surfaces.

In the optical pickup device according to the present invention, the optical pickup device may further include a ring-shaped filter that shields a part of the light beam incident on the objective lens from a practically used opening. It is characterized by.

An optical pickup device according to claim 239 is characterized in that, in the above device, a unit including the light source and the objective lens is driven at least in parallel to the optical information recording medium.

In the optical pickup device according to the present invention, the unit including the light source and the objective lens is further driven vertically to the optical information recording medium.

[0252] The invention according to claim 241 is an audio and / or image recording and / or audio and / or image reproducing apparatus equipped with the above-mentioned optical pickup device.

The objective lens according to claim 242 has at least two or more light sources having different wavelengths, and the divergent light flux from each light source is transparent on the information recording surface of the optical information recording medium by the same objective lens. An objective lens used for a recording / reproducing optical system for recording information via a substrate and / or reproducing information on an information recording surface, wherein the objective lens has a ring-shaped diffraction surface provided on a refraction surface. For at least one light source, the luminous flux transmitted through the objective lens and the transparent substrate has diffraction-limited performance at the best image point.

The objective lens according to claim 243 has at least two or more light sources having different wavelengths, and the divergent light flux from each light source is transparent on the information recording surface of the optical information recording medium by the same objective lens. An objective lens used for a recording / reproducing optical system for recording information via a substrate and / or reproducing information on an information recording surface, wherein the objective lens has a ring-shaped diffraction surface provided on a refraction surface. For at least one light source, the luminous flux transmitted through the objective lens and the transparent substrate is diffraction-limited at the best image point, and for at least one light source, Of the luminous flux transmitted through the transparent substrate, the luminous flux up to the aperture in practical use has the diffraction-limited performance at the best image point, and the outer part of the luminous flux forms the above-mentioned annular band so as to flare. Characterized in that a surface.

In the optical pickup device of the invention, a light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system including an objective lens. A first light source of wavelength λ1 for recording / reproducing a first optical information recording medium, a second light source of wavelength λ2 for recording / reproducing a second optical information recording medium, and recording / reproducing of a third optical information recording medium. A third light source of wavelength λ3,
In an optical pickup device for recording / reproducing an optical information recording medium, at least one surface of the objective lens has a spherical aberration substantially equal to or less than a diffraction limit by diffracted light of the same order for each optical information recording medium. Is characterized in that a diffraction surface in which is corrected is formed.

In the optical pickup device according to the invention, a light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system including an objective lens, and the wavelengths of the light beams are mutually determined. A first light source of wavelength λ1 for recording / reproducing a first optical information recording medium, a second light source of wavelength λ2 for recording / reproducing a second optical information recording medium, and recording / reproducing of a third optical information recording medium. A third light source of wavelength λ3,
In an optical pickup device for recording / reproducing an optical information recording medium, at least one surface of the objective lens uses diffracted light of the same order for each optical information recording medium, and at least one optical information recording medium is used. Therefore, the aperture up to the practical use is almost equal to or less than the diffraction limit,
It is characterized in that the aberration is flared for the portion outside the opening.

[0257] In the optical pickup device according to claim 245, which performs recording and / or reproduction of an optical information recording medium, the objective lens having the diffractive surface uses diffracted light of the same order for each optical information recording medium. For at least one optical information recording medium, the area up to the aperture in practical use was almost equal to or less than the diffraction limit, and the aberration outside the aperture was flare.

As described in the claims below, it is preferable that the diffractive surface is formed on both surfaces of the objective lens, and the diffracted light is a first-order diffracted light. The diffractive surface is formed in an annular shape around the optical axis of the objective lens, and the phase function representing the position of the annular zone includes a coefficient of a term other than the square of a power series. It may or may not include coefficients for the series squared term. Further, it is preferable that the diffractive surface has the maximum diffraction efficiency of diffracted light at the wavelengths at both ends or an intermediate band with respect to each of the first light source, the second light source, and the third light source. Further, the objective lens has at least one aspherical surface, and the above-mentioned performance can be provided by correcting spherical aberration to be under on a diffractive surface and over-correcting spherical aberration by an aspheric surface.

In the optical pickup device of the present invention, the diffraction surface is formed on both surfaces of the objective lens.

[0260] In the optical pickup device of the present invention, the diffracted light of the same order is a first-order diffracted light.

In the optical pickup device of the invention, the diffractive surface is formed in an annular shape centered on the optical axis of the objective lens, and the phase function representing the position of the annular zone is other than the square of the power series. Is characterized by including the coefficient of the term.

Further, in the optical pickup device according to claim 249, the diffraction surface is formed in an annular shape centered on the optical axis of the objective lens, and a phase function representing a position of the annular zone is a power series square. It is characterized by including the coefficient of the term.

In the optical pickup device of claim 250, the diffractive surface is formed in an annular shape around the optical axis of the objective lens, and the phase function representing the position of the annular zone is a power series square. It does not include the coefficient of the term.

An optical pickup device according to claim 251 is characterized in that the first light source, the second light source, and the third light source each have a maximum diffraction efficiency of the diffracted light at the wavelengths at both ends or an intermediate band. Features.

[0265] In the optical pickup device according to claim 252, at least one of the objective lenses is aspheric.
The spherical aberration is corrected to be under on the diffraction surface, and the spherical aberration is corrected to be over on the aspherical surface.

In the invention according to claim 253, there are provided the first light source, the second light source and the third light source.
52. An apparatus for recording audio and / or images and / or reproducing audio and / or images, comprising the optical pickup device according to any one of 52.

In the objective lens of the invention, the light beam emitted from the light source is condensed on the information recording surface via the transparent substrate of the optical information recording medium by the condensing optical system, and the first light beams having different wavelengths from each other. A first light source having a wavelength λ1 for recording / reproducing an information recording medium, and a wavelength λ2 for recording / reproducing a second optical information recording medium.
An objective lens used in an optical pickup device for recording / reproducing an optical information recording medium, comprising: a second light source having a wavelength λ3 for recording / reproducing a third optical information recording medium. On at least one surface of the objective lens, a diffractive surface whose spherical aberration is corrected to approximately the same as or less than the diffraction limit by diffracted light of the same order for each optical information recording medium is formed.

In the objective lens of the invention, the light beam emitted from the light source is condensed on the information recording surface via the transparent substrate of the optical information recording medium by the condensing optical system, and the first light beams having different wavelengths from each other. A first light source having a wavelength λ1 for recording / reproducing an information recording medium, and a wavelength λ2 for recording / reproducing a second optical information recording medium.
And a third light source having a wavelength λ3 for recording / reproducing the third optical information recording medium, and an objective lens used in an optical pickup device for recording / reproducing the optical information recording medium. For at least one surface of the lens, diffracted light of the same order for each optical information recording medium is used. In the following, the spherical aberration is corrected, and the portion outside the spherical aberration is flared.

In the optical pickup device according to claim 256, the light beam emitted from the light source is condensed on the information recording surface via the transparent substrate of the optical information recording medium by the condensing optical system, and the first light beams having different wavelengths from each other. A first light source having a wavelength λ1 for recording / reproducing an optical information recording medium, a second light source having a wavelength λ2 for recording / reproducing a second optical information recording medium, and a third light source having a wavelength λ3 for recording / reproducing a third optical information recording medium. In an optical pickup device having a light source and performing recording / reproducing of an optical information recording medium, at least one surface of a condensing optical system is almost the same as a diffraction limit by diffracted light of the same order for each optical information recording medium. It is characterized in that a diffractive surface whose spherical aberration is corrected to a degree or less is formed.

In the optical pickup device of claim 257, the light beam emitted from the light source is condensed on the information recording surface via the transparent substrate of the optical information recording medium by the condensing optical system, and the first light beams having different wavelengths from each other. A first light source having a wavelength λ1 for recording / reproducing an optical information recording medium, a second light source having a wavelength λ2 for recording / reproducing a second optical information recording medium, and a third light source having a wavelength λ3 for recording / reproducing a third optical information recording medium. An optical pickup device having a light source and used for an optical pickup device for recording / reproducing an optical information recording medium, wherein at least one surface of a condensing optical system has a diffraction of the same order for each optical information recording medium. Using light, at least one optical information recording medium is provided with a diffraction surface with a flare of aberration on the outer part of the optical information recording medium up to the aperture in practical use, which is almost equal to or less than the diffraction limit, and the outer part thereof is provided. thing And it features.

The optical pickup device of claim 258 further comprises a first light source having a wavelength λ1 and a wavelength λ2 (λ2 ≠ λ1).
A second light source, an objective lens having a diffraction pattern on at least one surface, and condensing a light flux from each light source on the information recording surface of the optical information recording medium via a transparent substrate;
A photodetector that receives reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium,
By using at least the m-th order diffracted light (where m is an integer other than 0) of the light beam from the first light source from the diffraction pattern of the objective lens, the first light having a thickness of the transparent substrate of t1 is used. By recording and / or reproducing the information recording medium and utilizing at least the n-th order diffracted light (where n = m) of the light beam from the second light source from the diffraction pattern of the objective lens, the thickness of the transparent substrate Records the second optical information recording medium of t2 (where t2 ≠ t1) and / or
Or to play.

The optical pickup device according to claim 259, wherein the wavelengths λ1, λ2 of the first and second light sources are λ1
<Λ2, and the thicknesses t1 and t2 of the transparent substrate are t1 <
An optical pickup device used in the relationship of t2,
The m-order and n-order diffracted lights are both + 1st-order diffracted lights.

In the optical pickup device of claim 260, the wavelengths λ1 and λ2 of the first and second light sources are λ1 and λ2.
<Λ2, and the thicknesses t1 and t2 of the transparent substrate are t1>
An optical pickup device used in the relationship of t2,
The m-order and n-order diffracted lights are both -1st-order diffracted lights.

An optical pickup device according to claim 261 is the device according to claim 258, wherein the thickness of the transparent substrate is t.
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproducing the first optical information recording medium with the first light source of wavelength λ1 is NA1, and the thickness of the transparent substrate is t2. (Where t2> t1) a second optical information recording medium having a wavelength λ2 (where λ2> λ1), which is necessary for recording and / or reproducing information on and from the optical information recording medium side of the objective lens. Set the required numerical aperture to NA2 (however, NA
When 2 <NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the light beam from the first light source has the most diffraction pattern of the objective lens. +1 from the circumference away from the optical axis
The next-order diffracted light is converted into a luminous flux having a numerical aperture on the optical information recording medium side of NAH1, and the + 1st-order diffracted light from the circumference closest to the optical axis of the diffraction pattern of the objective lens of the luminous flux from the first light source is: The numerical aperture on the optical information recording medium side is converted into a light beam of NAL1, and the condition NAH1 <NA10 ≦ NAL1 ≦ NA2 is satisfied.

The optical pickup device of claim 262 is the device of claim 258, wherein the thickness of the transparent substrate is t.
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproducing the first optical information recording medium with the first light source of wavelength λ1 is NA1, and the thickness of the transparent substrate is t2. (Where t2> t1) a second optical information recording medium having a wavelength λ2 (where λ2> λ1), which is necessary for recording and / or reproducing information on and from the optical information recording medium side of the objective lens. Set the required numerical aperture to NA2 (however, NA
2> NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the light beam from the first light source has the most diffraction pattern of the objective lens. +1 from the circumference away from the optical axis
The next-order diffracted light is converted into a luminous flux having a numerical aperture on the optical information recording medium side of NAH1, and the + 1st-order diffracted light from the circumference closest to the optical axis of the diffraction pattern of the objective lens of the luminous flux from the first light source is: The numerical aperture on the side of the optical information recording medium is converted into a light flux of NAL1, and the condition NAH1 <NA20 ≦ NAL1 ≦ NA1 is satisfied.

The optical pickup device of claim 263 is the device of claim 258, wherein the thickness of the transparent substrate is t.
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproducing the first optical information recording medium with the first light source of wavelength λ1 is NA1, and the thickness of the transparent substrate is t2. (Where t2 <t1) the objective lens necessary for recording and / or reproducing the second optical information recording medium with a second light source having a wavelength λ2 (where λ2> λ1) on the optical information recording medium side. Set the required numerical aperture to NA2 (however, NA
When 2 <NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the light beam from the first light source has the most diffraction pattern of the objective lens. -1 from the circumference away from the optical axis
The next-order diffracted light is converted into a light flux having a numerical aperture of NAH1 on the optical information recording medium side, and a -1st-order diffracted light of the light flux from the first light source from the circumference closest to the optical axis of the diffraction pattern of the objective lens is The numerical aperture on the optical information recording medium side is converted to a light flux of NAL1, and the condition NAH1 <NA10 ≦ NAL1 ≦ NA2 is satisfied.

An optical pickup device according to claim 265 is the device according to claim 258, wherein the thickness of the transparent substrate is t.
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproducing the first optical information recording medium with the first light source of wavelength λ1 is A1, and the thickness of the transparent substrate is t2. (Where t2 <t1) the objective lens necessary for recording and / or reproducing the second optical information recording medium with a second light source having a wavelength λ2 (where λ2> λ1) on the optical information recording medium side. The required numerical aperture is NA2 (NA2
> NA1), at least one of the objective lenses
The diffraction patterns provided on the two surfaces are rotationally symmetric with respect to the optical axis, and the -1st-order diffracted light of the light beam from the first light source from the circumference farthest from the optical axis of the diffraction pattern of the objective lens is , The numerical aperture on the optical information recording medium side is converted to a light flux of NAH1, and the -1st-order diffracted light of the light flux from the first light source from the circumference closest to the optical axis of the diffraction pattern of the objective lens is optical information. The numerical aperture on the recording medium side is converted into a luminous flux of NAL1, and satisfies the condition of NAH1 <NA20 ≦ NAL1 ≦ NA1.

An optical pickup device according to claim 265 is the device according to claim 261, wherein the numerical aperture of the light beam from the first light source when passing through the objective lens is equal to or smaller than NA1 and passes through the diffraction pattern. It is characterized in that the condensing position of the non-existent light beam and the condensing position of the light beam passing through the diffraction pattern are substantially equal.

[0279] The optical pickup device according to claim 266 is the device according to claim 262, wherein the numerical aperture of the light beam from the second light source when passing through the objective lens is equal to or less than NA2 and passes through the diffraction pattern. It is characterized in that the condensing position of the non-existent light beam and the condensing position of the light beam passing through the diffraction pattern are substantially equal.

[0280] In the optical pickup device according to the invention, the numerical aperture of the light beam from the first light source when passing through the objective lens is equal to or smaller than NA1 and passes through the diffraction pattern. It is characterized in that the condensing position of the non-existent light beam and the condensing position of the light beam passing through the diffraction pattern are substantially equal.

In the optical pickup device of the invention, the numerical aperture of the light beam from the second light source when passing through the objective lens is equal to or smaller than NA2 and passes through the diffraction pattern. It is characterized in that the condensing position of the non-existent light beam and the condensing position of the light beam passing through the diffraction pattern are substantially equal.

The optical pickup device according to claim 269 is the device according to claim 265, wherein the luminous flux from the second light source is a + 1st-order diffracted light from the circumference farthest from the optical axis of the diffraction pattern of the objective lens. Is converted into a luminous flux whose numerical aperture on the optical information recording medium side is NAH2, and the + 1st-order diffracted light of the luminous flux from the second light source from the circumference closest to the optical axis of the diffraction pattern of the objective lens is the optical information The numerical aperture on the recording medium side is converted into a light flux of NAL2, and the numerical aperture of the light flux from the first light source when passing through the objective lens is NA1.
The following light flux is used to record and / or record on the first optical information recording medium.
Alternatively, a spot capable of reproducing is focused on the information recording surface of the optical information recording medium, and the numerical aperture of the light flux from the second light source when passing through the objective lens is NAH2.
The following light flux is used to record on the second optical information recording medium and / or
Alternatively, the spherical aberration of the light beam passing through the objective lens is set so that a spot enabling reproduction can be focused on the information recording surface of the optical information recording medium.

The optical pickup device according to claim 270 is the device according to claim 266, wherein the luminous flux from the second light source is a + 1st-order diffracted light from the circumference farthest from the optical axis of the diffraction pattern of the diffraction pattern of the objective lens. Is converted into a luminous flux whose numerical aperture on the optical information recording medium side is NAH2, and the + 1st-order diffracted light of the luminous flux from the second light source from the circumference closest to the optical axis of the diffraction pattern of the objective lens is the optical information The numerical aperture on the recording medium side is converted into a light flux of NAL2, and the numerical aperture of the light flux from the first light source when passing through the objective lens is NAH.
A spot that enables recording and / or reproduction of the first optical information recording medium using the light flux of 1 or less is condensed on the information recording surface of the optical information recording medium, and the light flux from the second light source is Of which, the numerical aperture through the objective lens is NA2
The following light flux is used to record on the second optical information recording medium and / or
Alternatively, the spherical aberration of the light beam passing through the objective lens is set so that a spot enabling reproduction can be focused on the information recording surface of the optical information recording medium.

[0284] In the optical pickup apparatus according to the twenty-seventh aspect, in the apparatus according to the twenty-sixth aspect, the light beam from the second light source is -1st time from the circumference farthest from the optical axis of the diffraction pattern of the diffraction pattern of the objective lens. The folded light is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH2, and the -1st-order diffracted light from the circumference closest to the optical axis of the diffraction pattern of the objective lens of the light flux from the second light source is: The numerical aperture on the optical information recording medium side is converted into a light flux of NAL2, and the numerical aperture of the light flux from the first light source when passing through the objective lens is NA1.
The following light flux is used to record and / or record on the first optical information recording medium.
Alternatively, a spot capable of reproducing is focused on the information recording surface of the optical information recording medium, and the numerical aperture of the light flux from the second light source when passing through the objective lens is NAH2.
The following light flux is used to record on the second optical information recording medium and / or
Alternatively, the spherical aberration of the light beam passing through the objective lens is set so that a spot enabling reproduction can be focused on the information recording surface of the optical information recording medium.

[0285] In the optical pickup apparatus of the present invention, in the apparatus of the present invention, the light beam from the second light source is -1st time from the circumference farthest from the optical axis of the diffraction pattern of the diffraction pattern of the objective lens. The folded light is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH2, and the -1st-order diffracted light from the circumference closest to the optical axis of the diffraction pattern of the objective lens of the light flux from the second light source is: The numerical aperture on the optical information recording medium side is converted into a light flux of NAL2, and the numerical aperture of the light flux from the first light source when passing through the objective lens is NAH.
A spot that enables recording and / or reproduction of the first optical information recording medium using the light flux of 1 or less is condensed on the information recording surface of the optical information recording medium, and the light flux from the second light source is Of which, the numerical aperture through the objective lens is NA2
The following light flux is used to record on the second optical information recording medium and / or
Alternatively, the spherical aberration of the light beam passing through the objective lens is set so that a spot enabling reproduction can be focused on the information recording surface of the optical information recording medium.

[0286] In the optical pickup device of the present invention, the numerical aperture of the light beam from the first light source when passing through the objective lens is NA.
When the light flux of 1 or less has a wavefront aberration of 0.07 λrms or less at the best image point via the transparent substrate of the first optical information recording medium, and when the light flux from the second light source passes through the objective lens, A light beam having a numerical aperture of NAH2 or less has a wavefront aberration of 0.07 λrms or less at the best image point via the transparent substrate of the second optical information recording medium.

[0287] Also, in the optical pickup device of the present invention, the numerical aperture of the light beam from the first light source when passing through an objective lens is NA.
When the light flux of H1 or less has a wavefront aberration of 0.07 λrms or less at the best image point through the transparent substrate of the first optical information recording medium, and when the light flux from the second light source passes through the objective lens, A light beam having a numerical aperture of 2 or less has a wavefront aberration of 0.07 λrms or less at the best image point via the transparent substrate of the second optical information recording medium.

[0288] In the optical pickup device of the present invention, the numerical aperture of the light beam from the first light source when passing through an objective lens is NA.
When the light flux of 1 or less has a wavefront aberration of 0.07 λrms or less at the best image point via the transparent substrate of the first optical information recording medium, and when the light flux from the second light source passes through the objective lens, A light beam having a numerical aperture of NAH2 or less has a wavefront aberration of 0.07 λrms or less at the best image point via the transparent substrate of the second optical information recording medium.

[0289] In the optical pickup device of the invention, the numerical aperture of the light beam from the first light source when passing through an objective lens may be NA.
When the light flux of H1 or less has a wavefront aberration of 0.07 λrms or less at the best image point through the transparent substrate of the first optical information recording medium, and when the light flux from the second light source passes through the objective lens, A light beam having a numerical aperture of 2 or less has a wavefront aberration of 0.07 λrms or less at the best image point via the transparent substrate of the second optical information recording medium.

An optical pickup device according to claim 277 is the device according to any one of claims 258 to 276, wherein at least one optical pickup device is provided between the first light source and the objective lens and between the second light source and the objective lens. And a luminous flux incident on the objective lens from the first light source and a luminous flux incident on the objective lens from the second light source are parallel lights.

The optical pickup device according to claim 278 is the device according to claim 277, wherein the paraxial focal position of the objective lens with respect to the light beam from the first light source and the objective lens with respect to the light beam from the second light source. It is characterized in that paraxial focal positions substantially coincide.

[0292] Also, in the optical pickup device according to claim 279, in the device according to claim 265, 269 or 273, a second diffraction pattern is provided outside the diffraction pattern, and a light beam from the first light source is provided. On the other hand, the + 1st-order diffracted light of the second diffraction pattern is condensed at the condensing position,
The second diffraction pattern is set so that the light beam from the second light source is not diffracted by the second diffraction pattern.

[0293] In the optical pickup device according to claim 280, in the device according to claim 266, 270 or 274, a second diffraction pattern is provided outside the diffraction pattern, and a light beam from the first light source is provided. , The second diffraction pattern is mainly + 1st-order diffraction light, and the second diffraction pattern is set so that the light flux from the second light source passes through the second diffraction pattern and is condensed at the light condensing position. It is characterized by having done.

[0294] In the optical pickup device of the present invention, a second diffraction pattern is provided outside the diffraction pattern in the device of the 267, 271 or 275, so that the light beam from the first light source is On the other hand, the -1st-order diffracted light of the second diffraction pattern is condensed at the condensing position,
The second diffraction pattern is set so that the light beam from the second light source is not diffracted by the second diffraction pattern.

[0295] Further, in the optical pickup apparatus according to claim 282, in the apparatus according to claim 268, 272 or 276, a second diffraction pattern is provided outside the diffraction pattern, and the light beam from the first light source is In the second diffraction pattern, the second diffraction pattern is mainly set to -1st order diffracted light, and the light flux from the second light source is transmitted through the second diffraction pattern and condensed at the condensing position. It is characterized by having done.

In the optical pickup device according to the present invention, a second diffraction pattern is provided outside the diffraction pattern in order to prevent a light beam from the first light source from being transmitted. The transmitted light of all the second diffraction patterns is condensed at the condensing position, and the second
It is characterized in that the second diffraction pattern is set so that the light beam from the light source mainly becomes -1st-order diffracted light in the second diffraction pattern.

[0297] Further, in the optical pickup device according to claim 284, in the device according to claim 266, 270 or 274, a second diffraction pattern is provided outside the diffraction pattern, and a light beam from the first light source is provided. The second diffraction pattern is set so that it passes through a second diffraction pattern, and the luminous flux from the second light source becomes -1st-order light in the second diffraction pattern and is condensed at the condensing position. It is characterized by.

[0298] Also, in the optical pickup device according to claim 285, in the device according to claim 267, 271 or 275, a second diffraction pattern is provided outside the diffraction pattern, and a light beam from the first light source is provided. The transmitted light of all the second diffraction patterns is condensed at the condensing position, and the second
The second diffraction pattern is characterized in that the light beam from the light source is mainly + 1st-order diffracted light in the second diffraction pattern.

In the optical pickup device of claim 286, in the device of claim 268, 272 or 276, a second diffraction pattern is provided outside the diffraction pattern, and the light flux from the first light source is The second diffraction pattern is set so that it passes through the second diffraction pattern, the luminous flux from the second light source becomes + 1st-order light in the second diffraction pattern, and is collected at the light collection position. Features.

The optical pickup device according to claim 287 is the optical pickup device according to claim 265, 267, 269, 271, 273 or 275, wherein the light beam emitted from the first light source and the light beam emitted from the second light source are emitted. An optical multiplexing means capable of multiplexing a light beam, wherein a light beam from the first light source is transmitted between the multiplexing means and the optical information recording medium;
It is characterized by having aperture limiting means that does not transmit a light beam that passes through a region of the light beam from the light source that is opposite to the optical axis of the diffraction pattern.

The optical pickup device according to claim 288 is the same as the optical pickup device according to claim 266, 268, 270, 274 or 27.
6. The device according to 6, wherein the light flux emitted from the first light source is:
An optical multiplexing unit capable of multiplexing the emitted light beam from the second light source; a light beam from the second light source is transmitted between the multiplexing unit and the optical information recording medium; It is characterized by having aperture limiting means that does not transmit a light beam that passes through a region of the light beam from the light source that is opposite to the optical axis of the diffraction pattern.

289. The optical pickup device of claim 287, wherein in the device of claim 287, the aperture limiting means transmits the light beam from the first light source and the light of the diffraction pattern out of the light beam of the second light source. It is an annular filter that reflects or absorbs a light beam passing through a region opposite to the axis.

In the optical pickup device of the present invention, the light beam from the second light source is transmitted, and the light beam of the first light source on the side opposite to the optical axis of the diffraction pattern. It is an annular filter that reflects or absorbs a light beam passing through the region.

The optical pickup device according to claim 291 is the device according to claim 287, wherein the aperture limiting means transmits the light beam from the first light source and the light of the diffraction pattern among the light beams of the second light source. It is an annular filter for diffracting a light beam passing through a region opposite to the axis.

In the optical pickup device of the present invention, the aperture limiting means transmits the light beam from the second light source, and the light beam of the diffraction pattern among the light beams of the first light source. It is an annular filter for diffracting a light beam passing through a region opposite to the axis.

An optical pickup device according to claim 293 is the device according to any one of claims 258 to 292, wherein the photodetector is common to the first light source and the second light source. Features.

The optical pickup device according to claim 294 is the device according to any one of claims 258 to 292, wherein the photodetectors are a first photodetector for a first light source and a second photodetector.
And a second photodetector for the light source are separately provided, and are located at spatially separated positions.

In the optical pickup apparatus according to the present invention, at least one of the first light source and the first light detector or the pair of the second light source and the second light detector is a unit. It is characterized by having been made.

In the optical pickup device according to the present invention, the first light source, the second light source and a common light detector (single light detector) are unitized. It is characterized by having been done.

The optical pickup device according to claim 297 is the device according to claim 294, wherein the photodetector is a first photodetector for a first light source and a second photodetector for a second light source. The first light source, the second light source, the first light detector, and the second light detector are unitized.

[0311] Further, the optical pickup device of the present invention is characterized in that, in the device of any one of claims 258 to 297, a photodetector for detecting transmitted light from an optical disk is further provided.

The optical pickup device according to claim 299 is characterized in that the first light source having the wavelength λ1 and the wavelength λ2 (where λ1
≠ λ2) a second light source, multiplexing means capable of multiplexing the light beam emitted from the first light source and the light beam emitted from the second light source, and a diffraction pattern on at least one surface. And an objective lens for condensing a light beam from each light source on the information recording surface of the optical information recording medium via a transparent substrate, and a diffractive optical element having a light beam emitted from the first light source and the second light source. A photodetector that receives reflected light from the optical information recording medium, and m-th order diffracted light (where m
Is at least one integer other than 0), thereby recording and / or reproducing the first optical information recording medium having the transparent substrate having a thickness of t1, and transmitting the light flux from the second light source to the objective lens. Recording and / or reproducing a second optical information recording medium having a transparent substrate having a thickness of t2 (where t2 ≠ t1) by utilizing at least an nth-order diffracted light (where n = m) from a diffraction pattern. It is characterized by.

The optical pickup device according to claim 300 is the device according to claim 299, wherein the first and second optical pickup devices are different from each other.
Wherein the wavelengths λ1 and λ2 of the light source are λ1 <λ2, and the thicknesses t1 and t2 of the transparent substrate are used in a relationship of t1 <t2. It is a second-order diffracted light.

The optical pickup device according to claim 301 is the device according to claim 299, wherein the first and second optical pickup devices are different from each other.
Wherein the wavelengths λ1, λ2 of the light source are λ1 <λ2, and the thicknesses t1, t2 of the transparent substrate are used in a relationship of t1> t2, wherein the m-order and n-order diffracted lights are both − It is a first-order diffracted light.

[0315] Further, the optical pickup device of the present invention is characterized in that, in the optical pickup device of the present invention, the diffractive optical element and the objective lens are driven integrally.

The optical pickup device according to claim 303 is the device according to claims 258 to 302, wherein the depth of the first diffraction pattern in the optical axis direction is 2 μm or less.

Further, the objective lens for an optical pickup device according to claim 304 has a diffraction pattern on at least one surface, and when a light beam of wavelength λ1 enters, at least an m-th order diffracted light from the diffraction pattern (however, , M is one integer other than 0) is collected at the first collection position, and the wavelength λ2
When a light beam of (λ2 ≠ λ1) is incident, at least the n-th order diffracted light (where n
= M) is collected at a second light collection position different from the first light collection position.

305. The objective lens for an optical pickup device according to claim 305, wherein the wavelengths λ1 and λ2 are λ1 <λ2, and the first light-condensing position is a first optical information recording medium having a thickness t1 of a transparent substrate. And the second light condensing position is a light condensing position on the second optical information recording medium having a thickness t2 of the transparent substrate, and the thicknesses t1 and t2 of the transparent substrate are t2 and t3.
When 1 <t2, the m-order and n-order diffracted lights are both + 1st-order diffracted lights.

The object lens for an optical pickup device according to claim 306, wherein said wavelengths λ1 and λ2 are λ1 <λ2, and said first light condensing position is a first optical information recording medium having a thickness t1 of a transparent substrate. And the second light condensing position is a light condensing position on the second optical information recording medium having a thickness t2 of the transparent substrate, and the thicknesses t1 and t2 of the transparent substrate are t2 and t3.
When 1> t2, the m-order and n-order diffracted lights are both -1st-order diffracted lights.

The objective lens for an optical pickup device according to claim 307 has a diffraction pattern on at least one surface, and when a light beam of wavelength λ1 is incident, at least an m-th order diffracted light from the diffraction pattern (however, , M is one integer other than 0) has a light-condensing position used for recording and / or reproducing the first optical information recording medium having the thickness t1 of the transparent substrate, and has a wavelength λ2 (where λ2 ≠). When the light beam of λ1) is incident, at least the nth-order diffracted light (where n = m) from the diffraction pattern has a thickness t2 of the transparent substrate.
(Where t2 ≠ t1) is characterized by having a condensing position used for recording and / or reproducing the second optical information recording medium.

The objective lens for an optical pickup device according to claim 308 is the object lens according to claim 307, wherein
When the wavelengths λ1 and λ2 satisfy λ1 <λ2 and the thicknesses t1 and t2 of the transparent substrate satisfy the relationship of t1 <t2, the m-order and n-order diffracted lights are both + 1st-order diffracted lights. .

Alternatively, in the objective lens for an optical pickup device according to claim 309, in the objective lens of claim 307, the wavelengths λ1 and λ2 are λ1 <λ2, and the thicknesses t1 and t2 of the transparent substrate are t1> t2. When the relationship is
The m-order and n-order diffracted lights are both -1st-order diffracted lights.

The objective lens for an optical pickup device according to claim 310 is the object lens according to claim 308, wherein
The first optical information recording medium having a transparent substrate having a thickness of t1 has a wavelength of λ1
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the first light source is N
A1, a second optical information recording medium having a transparent substrate having a thickness of t2 (where t2> t1) has a wavelength of λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the second light source is N
When A2 (where NA2 <NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the light flux from the first light source is reflected by the objective lens. The + 1st-order diffracted light from the circumference of the diffraction pattern that is farthest from the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the diffraction pattern of the diffraction pattern of the objective lens of the light flux from the first light source is obtained. The + 1st-order diffracted light from the circumference closest to the optical axis is converted into a light flux having a numerical aperture on the optical information recording medium side of NAL1, and satisfies the condition of NAH1 <NA10 ≦ NAL1 ≦ NA2.

The objective lens for an optical pickup device according to claim 311 is the object lens according to claim 308, wherein
The first optical information recording medium having a transparent substrate having a thickness of t1 has a wavelength of λ1
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the first light source is N
A1, a second optical information recording medium having a transparent substrate having a thickness of t2 (where t2> t1) has a wavelength of λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the second light source is N
When A2 (where NA2> NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the light flux from the first light source is reflected by the objective lens. The + 1st-order diffracted light from the circumference of the diffraction pattern that is farthest from the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the diffraction pattern of the diffraction pattern of the objective lens of the light flux from the first light source is obtained. The + 1st-order diffracted light from the circumference closest to the optical axis is converted into a light flux having a numerical aperture on the optical information recording medium side of NAL1 and satisfies the condition of NAH1 <NA20 ≦ NAL1 ≦ NA1.

The objective lens for an optical pickup device according to claim 312 is the object lens according to claim 309, wherein
The first optical information recording medium having a transparent substrate having a thickness of t1 has a wavelength of λ1
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the first light source is N
A1, a second optical information recording medium with a transparent substrate having a thickness of t2 (where t2 <t1) has a wavelength of λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the second light source is N
When A2 (where NA2 <NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the light flux from the first light source is reflected by the objective lens. The -1st-order diffracted light from the circumference of the diffraction pattern that is the most distant from the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the diffraction pattern of the light flux from the first light source is reflected by the objective lens. Is converted into a luminous flux having a numerical aperture on the optical information recording medium side of NAL1 and satisfies the condition of NAH1 <NA10.ltoreq.NAL1.ltoreq.NA2. .

The objective lens for an optical pickup device according to claim 313 is the object lens according to claim 309, wherein
The first optical information recording medium having a transparent substrate having a thickness of t1 has a wavelength of λ1
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the first light source is N
A1, a second optical information recording medium with a transparent substrate having a thickness of t2 (where t2 <t1) has a wavelength of λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the second light source is N
When A2 (where NA2> NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the light flux from the first light source is reflected by the objective lens. The -1st-order diffracted light from the circumference of the diffraction pattern that is the most distant from the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the diffraction pattern of the light flux from the first light source is reflected by the objective lens. -1st order diffracted light from the circumference closest to the optical axis is converted into a light flux having a numerical aperture on the optical information recording medium side of NAL1, and satisfies the condition of NAH1 <NA2O ≦ NAL1 ≦ NA1. .

The objective lens for an optical pickup device according to claim 314 is the objective lens according to any one of claims 304 to 313, wherein the optical surface includes a diffraction pattern portion and a refraction portion, and the diffraction portion and the refraction portion. Is characterized by including a step of 5 μm or more.

In the objective lens for an optical pickup device according to the present invention, the average depth of the diffraction pattern of the diffraction portion closest to the optical axis is 2 μm or less. There is a feature.

The objective lens for an optical pickup device according to claim 316 is the object lens according to claim 315, wherein
The average depth of the diffraction pattern of the diffraction part closest to the optical axis is 2 μm
The average depth of the diffraction pattern of the diffraction portion farthest from the optical axis is 2 μm or more.

The objective lens for an optical pickup device according to claim 317 is characterized in that, in the objective lens according to any one of claims 304 to 316, the diffraction pattern on the optical surface includes an optical axis portion.

The objective lens for an optical pickup device according to claim 318 is the objective lens according to any one of claims 304 to 316, wherein the optical axis portion of the optical surface is a refraction surface without providing a diffraction pattern. It is characterized by.

The objective lens for an optical pickup device according to claim 319 is the one according to claims 304, 305, 307, 30.
For an 8 or 310 objective lens, a light source wavelength of 650
When an image is formed at a predetermined imaging magnification on an information recording surface through a transparent substrate having a thickness of 0.6 mm in nm, it has diffraction-limited performance at least up to a numerical aperture of 0.6, and a light source wavelength of 780 nm. When an image is formed at a predetermined imaging magnification through a 2 mm transparent substrate, it has a diffraction-limited performance up to at least a numerical aperture of 0.45.

The objective lens for an optical pickup device of claim 320 is the object lens of claim 319, wherein
The number of steps of the diffraction pattern is 15 or less.

The objective lens for an optical pickup device according to claim 321 is the objective lens according to any one of claims 304 to 320, wherein the optical surface on which the diffraction pattern is provided is:
It is characterized by being convex.

The objective lens for an optical pickup device according to claim 322 is the object lens according to claim 321, wherein
The refraction portion of the optical surface provided with the diffraction pattern is aspheric.

The objective lens for an optical pickup device according to claim 323 is the object lens according to claim 322, wherein
The diffraction pattern includes at least one aspheric refraction part.

The objective lens for an optical pickup device according to the present invention is characterized in that, in the objective lens according to any one of claims 304 to 323, the objective lens is a single lens.

The objective lens for an optical pickup device according to claim 325 is the object lens according to claim 324, wherein
The diffraction pattern is provided only on one optical surface of the single lens.

The objective lens for an optical pickup device according to claim 326 is the object lens according to claim 324, wherein
The diffraction pattern is provided on one optical surface of the single lens, and the other optical surface is aspheric.

The objective lens as described above is designed such that a parallel light beam having no aberration is incident from the first light source and converges without aberration through the transparent substrate (thickness t1) of the first optical information recording medium. Using a special objective lens, a case where parallel light having no aberration is incident on the objective lens from the second light source and passes through a transparent substrate (thickness t2, where t2> t1) of the second optical information recording medium consider.

With respect to the incident parallel light, when there is no substrate, the back focus at the wavelength λ1 is fB1, and the back focus at the wavelength λ2 (where λ2> λ1) is fB2.

At this time, if the paraxial chromatic aberration ΔfB is defined by ΔfB = fB2−fB1 (1), ΔfB> 0 when the objective lens is a refractive aspheric single lens.

In addition, the spherical aberration based on the paraxial focal position when the light converges via the transparent substrate of the second optical information recording medium at the wavelength λ2 does not become zero due to the following factors. Spherical aberration caused by the wavelength dependence of the refractive index of the objective lens when the wavelength changes from λ1 to λ2. Spherical aberration caused by the difference between the transparent substrate thickness t1 of the first optical information recording medium and the transparent substrate thickness t2 of the second optical information recording medium. The refractive index of the transparent substrate of the first optical information recording medium nd1 (λ
1) and the refractive index nd2 of the transparent substrate of the second optical information recording medium
Spherical aberration caused by the difference of (λ2).

In the case where the objective lens is a refraction type aspherical single lens, the spherical aberration caused by the factor becomes excessive. The spherical aberration due to the above factor is also over. Also, nd2 <n
d11, and the spherical aberration due to the factor is also over.

Most of the excessive spherical aberration caused by the factor (1) is caused by the factor (2), followed by that. Can be almost ignored.

The above premise is, for example, that the first optical information recording medium is a DVD, the first light source has a wavelength λ1 of 650 nm, the second optical information recording medium is a CD, and the second light source has a wavelength λ2 of 7.
This corresponds to the case where the thickness is set to 80 nm, and the DVD (thickness t1 = 0.
6 mm) and a CD (t2 = 1.2 mm), the material of the transparent substrate is the same, but the thickness is different.

Next, looking at the + 1st-order diffracted light having a diffraction pattern rotationally symmetric with respect to the optical axis, as shown in FIG. 113 (a), the + 1st-order light has a larger diffraction angle as the wavelength becomes longer, and The light is diffracted toward the optical axis, and the light is bent further to the under side. That is, the + 1st-order diffracted light is a case where a stigmatic parallel light beam from the second light source having a wavelength of λ2 is incident as compared with a case where a stigmatic parallel light beam from a first light source having a wavelength of λ1 is incident. Has the effect of reducing paraxial chromatic aberration and spherical aberration. Utilizing this effect, the spherical aberration when passing through the transparent substrate of the second optical information recording medium at the wavelength λ2 and the spherical aberration when passing through the transparent substrate of the first optical information recording medium at the wavelength λ1 are used. The difference can be reduced by introducing a rotationally symmetric diffraction pattern and utilizing its + 1st order diffracted light.

When the thickness t1 of the substrate of the first optical information recording medium is larger than the thickness t2 of the transparent substrate of the second optical information recording medium, the spherical aberration due to the above-mentioned factors becomes under, and
As shown in FIG. 3B, the aberration can be reduced by using the −1st-order diffracted light having the effect of overcoming the paraxial chromatic aberration and spherical aberration that occur.

In the present invention, when the + 1st-order diffracted light is used, the refractive index of the objective lens material when the wavelength is λ1 is n
(Λ1), when the refractive index of the objective lens material when the wavelength is λ2 is n (λ2), the depth of the diffraction pattern is λ1 /
{N (λ1) -1} or λ2 / {n (λ2) -1}, which is 2 μm or less even when a plastic material having a relatively small refractive index is used. It is easier to manufacture an objective lens with an integrated diffraction pattern than a mold ring lens.

In the optical pickup device according to the present invention, the first light source having the wavelength λ1 and the wavelength λ2 (λ1 ≠ λ2)
A second light source, an objective lens having a diffraction pattern on at least one surface, and condensing a light flux from each light source on the information recording surface of the optical information recording medium via a transparent substrate;
A light detector for receiving reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium, wherein the light flux from the first light source is reflected from a diffraction pattern of the objective lens. m-th order diffracted light (where m is one integer except 0)
At least, the thickness of the transparent substrate becomes t
(1) performing at least one of recording and reproduction of information on the first optical information recording medium, and n-th order light (where n = m) of a light beam from the second light source from a diffraction pattern of the objective lens; An optical pickup device that performs at least one of recording and reproduction of information on and from a second optical information recording medium having a transparent substrate with a thickness of t2 (t2 に よ り t1) by utilizing at least Is made of a plastic material, and the plastic material has a change in refractive index when a temperature change ΔT (° C.) occurs, where Δn is −0.0002 / ° C. <Δn / ΔT <−0.00005 /
° C, and the first light source has a temperature change ΔT
(° C.), the change amount of the oscillation wavelength is Δλ1 (n
m), the relationship of 0.05 nm / ° C <Δλ1 / ΔT <0.5 nm / ° C is satisfied.

According to claim 327, the characteristic fluctuation of the optical pickup device due to the temperature change of the refractive index of the plastic objective lens and the characteristic fluctuation of the optical pickup device due to the temperature change of the wavelength at the light source act in such a direction as to cancel each other, A compensation effect can be obtained, and an optical pickup device extremely resistant to temperature fluctuation can be obtained.

The optical pickup device of claim 328 is characterized in that the first light source having the wavelength λ1 and the wavelength λ2 (λ1 ≠ λ2)
A second light source, an objective lens having a diffraction pattern on at least one surface, and condensing a light flux from each light source on the information recording surface of the optical information recording medium via a transparent substrate;
A light detector for receiving reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium, wherein the light flux from the first light source is reflected from a diffraction pattern of the objective lens. m-th order diffracted light (where m is one integer except 0)
At least, the thickness of the transparent substrate becomes t
(1) performing at least one of recording and reproduction of information on the first optical information recording medium, and n-th order light (where n = m) of a light beam from the second light source from a diffraction pattern of the objective lens; An optical pickup device that performs at least one of recording and reproduction of information on and from a second optical information recording medium having a transparent substrate with a thickness of t2 (t2 ≠ t1) by utilizing at least
1, λ2 and the thicknesses t1, t2 of the transparent substrate are in a relation of λ2> λ1 t2> t1, and are necessary for recording and / or reproducing the first optical information recording medium with the first light source. The required numerical aperture of the objective lens on the optical information recording medium side is NA1,
The focal length of the objective lens at the wavelength λ1 (mm) is f1 (mm), and when the environmental temperature change is ΔT (° C.), the light is focused on the information recording surface of the first information recording medium. The amount of change of the third-order spherical aberration component of the wavefront aberration of the light beam is represented by ΔWS
When A3 (λ1 rms), 0.2 × 10 ⁻⁶ / ° C <ΔWSA3 · λ1 / ｛f · (NA
1) It is characterized by satisfying a relationship of ⁴ · ΔT｝ <2.2 × 10 ⁻⁶ / ° C.

According to claim 328, if the above relational expression is not more than the upper limit, it is easy to maintain the characteristics as an optical pickup device even if the environmental temperature changes.
In addition, when the value is equal to or more than the lower limit, it is easy to maintain the characteristics as the optical pickup device even when the wavelength is changed.

In the optical pickup device according to the present invention, at least one collimator is provided between the first light source and the objective lens and between the second light source and the objective lens. A light beam incident on the objective lens from the first light source and a light beam incident on the objective lens from the second light source,
Each is characterized by substantially parallel light.

In the optical pickup device of claim 330, in claim 327, 328 or 329, the t1 is 0.55 mm to 0.65 mm, and the t2 is 1.05 mm.
1 mm to 1.3 mm, λ1 is 630 nm to 670 nm, and λ2 is 760 nm to 820 nm.
nm.

In the optical pickup device according to claim 331, the first light source having the wavelength λ1 and the wavelength λ2 (λ2 ≠ λ1)
A second light source, an objective lens having a diffraction pattern on at least one surface, and condensing a light beam from each light source on the information recording surface of the optical information recording medium via a transparent substrate;
A photodetector that receives reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium,
By utilizing at least the m-th order diffracted light (where m is an integer other than 0) of the light beam from the first light source from the diffraction pattern of the objective lens, the first transparent substrate has a thickness of t1. At least one of recording and reproduction of information on an optical information recording medium is performed, and at least n-th order diffracted light (where n = m) of a light beam from the second light source from a diffraction pattern of the objective lens is used. As a result, the second thickness of the transparent substrate is t2 (where t2 ≠ t1).
An optical pickup device that performs at least one of recording and reproduction of information on the optical information recording medium,
The image processing apparatus further includes a correction unit configured to correct a divergence of a light beam incident on the objective lens from at least one of the first and second light sources.

According to claim 331, by correcting the divergence of the light beam incident on the objective lens, the third-order spherical aberration of the entire optical system including the objective lens can be corrected as designed.

[0358] Further, the optical pickup device of claim 332 includes at least one collimator between the first light source and the objective lens and between the second light source and the objective lens in claim 331. Claim 33
The optical pickup device according to claim 3, wherein the correction of the divergence by the correction unit is performed by changing a distance between the first and / or second light source and the at least one collimator. Is corrected by changing the distance between the first and / or second light source and the at least one collimator. By changing the distance between the light source and the collimator, the divergence of the speed of light incident on the objective lens from the at least one light source can be corrected.

The optical pickup device according to claim 334, further comprising: a first light source having a wavelength λ1 and a wavelength λ2 (λ1 ≠ λ2).
A second light source, an objective lens having a diffraction pattern on at least one surface, and condensing a light flux from each light source on the information recording surface of the optical information recording medium via a transparent substrate;
A light detector for receiving reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium, wherein the light flux from the first light source is reflected from a diffraction pattern of the objective lens. m-th order diffracted light (where m is one integer except 0)
At least, the thickness of the transparent substrate becomes t
(1) performing at least one of recording and reproduction of information on the first optical information recording medium, and n-th order light (where n = m) of a light beam from the second light source from a diffraction pattern of the objective lens; An optical pickup device that performs at least one of recording and reproduction of information on a second optical information recording medium having a transparent substrate with a thickness of t2 (t2１t1) by utilizing at least For each of two different wavelengths (λ) of light output from the light source and the second light source, the wavefront aberration on the image plane is within 0.1 mm within the maximum numerical aperture on the image side of the objective lens. 07
λrms or less.

According to claim 334, in the recording and / or reproduction of the first and second information recording media, there is no flare on each information recording surface and the photodetector, and the characteristics of the optical pickup device are excellent. Become.

The optical pickup device according to claim 335 is the same as any one of claims 258 to 292, 334,
The first light source and the second light source are unitized,
The light detector is common to the first light source and the second light source.

[0362]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention, particularly, Claim 13 will be described.
Preferred embodiments according to 7 to 335 will be described with reference to the drawings.

The optical system according to the first embodiment of the present invention is basically a single lens having two aspheric surfaces, and a diffractive orbicular zone (annular diffractive surface) is provided on one aspherical surface. It is. Generally, when spherical aberration is corrected for a certain main wavelength light on an aspheric refraction surface, the spherical aberration is under (undercorrection) for light having a shorter wavelength than the main wavelength light. Conversely, in a diffractive lens having a diffractive surface, when spherical aberration is corrected with a certain main wavelength light, the spherical aberration can be over-corrected at a wavelength shorter than the main wavelength light. is there. Therefore, the aspheric coefficient of the aspheric lens due to refraction,
By appropriately selecting the coefficient of the phase difference function of the diffractive lens and combining the refracting power and the diffractive power, it is possible to satisfactorily correct the spherical aberration for both different two-wavelength lights.

In general, the pitch of a diffraction ring zone is defined by using a phase difference function or an optical path difference function which will be described in detail in the embodiments described later. Specifically, the phase difference function ΦB is expressed by the following [Equation 1] with the unit being radian, and the optical path difference function ΦB
b is represented by [Equation 2] in mm.

[0365]

(Equation 1)

(Equation 2) Although these two expression methods have different units, they are equivalent in terms of expressing the pitch of the diffraction ring zone. That is, the main wavelength λ
(Unit mm), the coefficient B of the phase difference function is λ / 2π
Can be converted to the coefficient b of the optical path difference function, and conversely, the coefficient b of the optical path difference function can be converted to the coefficient B of the phase difference function by multiplying by 2π / λ.

Now, for the sake of simplicity, a diffractive lens using first-order diffracted light will be described. In the case of an optical path difference function, an annular zone is engraved every time the function value exceeds an integral multiple of the principal wavelength λ. In the case of a phase difference function, a ring zone is carved every time the function value exceeds an integral multiple of 2π.

For example, assuming a lens in which a diffractive annular zone is engraved on the object side surface of both cylindrical surfaces having no refracting power, the principal wavelength is 0.5 μ = 0.0005 mm, and the quadratic coefficient (square) Term) is -0.05 (-628.3 when converted to a second order coefficient of the phase difference function), and all the coefficients of the other orders are set to zero, the radius of the first annular zone is h = 0.1 mm, The radius of the second annular zone is h = 0.141 mm. Also,
Regarding the focal length f of this diffractive lens, f = −1 / (2 ·
It is known that b2) = 10 mm.

Now, based on the above definition, it is possible to correct chromatic aberration in the so-called paraxial region close to the optical axis by setting the secondary coefficient of the phase difference function or the optical path difference function to a non-zero value. Can be. Further, by setting non-zero coefficients other than the second-order coefficients of the phase difference function or the optical path difference function, for example, the fourth-order coefficient, the sixth-order coefficient, the eighth-order coefficient, and the tenth-order coefficient, to spherical aberration between two wavelengths. Can be controlled.
Here, controlling means that the difference in spherical aberration between the two wavelengths can be made extremely small, and that a difference required for optical specifications can be provided.

As a specific application of the above, when collimated light (parallel light) from two light sources having different wavelengths is simultaneously made incident on the objective lens to form an image on an optical disk, first, a phase difference function or an optical path difference is used. The paraxial axial chromatic aberration is corrected using the quadratic coefficient of the function, and the spherical aberration is calculated using the fourth and subsequent coefficients of the phase difference function or the optical path difference function.
Preferably, the difference between the wavelengths is made small so as to be within an allowable range.

As another example, light from two light sources having different wavelengths is used by one objective lens, and light of one wavelength is applied to a disk having a thickness of t1 (the thickness of the transparent substrate). Consider a case where the aberration is corrected, and the aberration is corrected for a disk having a thickness of t2 for light of the other wavelength. In this case, the difference between the two wavelengths of the spherical aberration is provided mainly by using the fourth or higher order coefficient of the phase difference function or the optical path difference function, and for each thickness, the spherical aberration is reduced at each wavelength. It can be made to be corrected. Further, in any case, it is easier to correct aberrations between two wavelengths if the refracting surface is an aspheric surface than a spherical surface.

The aspheric refracting surface has different refractive powers and different light converging points for different wavelengths, so that each light converging point can correspond to an optical disc having a different substrate thickness. In this case, the shorter light source wavelength is 700 nm or less, and the longer light source wavelength is 600 nm.
m or more, and the wavelength difference is preferably 80 nm or more. Further, the wavelength difference is more preferably 400 nm or less, and further preferably, the wavelength difference is 10 nm or less.
0 nm or more and 200 nm or less, and the diffraction surface is:
For two different wavelengths of light, it is desirable that the diffraction efficiency is maximized at a wavelength substantially between the two wavelengths. However, the light having the maximum diffraction efficiency at one of the wavelengths may be used.

By utilizing the same action as the above-described correction of spherical aberration, a diffractive orbicular zone lens is provided on the optical surface, and each of two different light sources having different wavelengths is subjected to one axis of diffracted light of the same order. The upper chromatic aberration can be corrected. That is, the axial chromatic aberration with respect to the light of the two different wavelength light sources is ± λ.
/ (2NA2). Here, λ is the longer wavelength of the two wavelengths, and NA is the image-side numerical aperture corresponding to the longer wavelength.

The wavelength difference between the two different wavelength light sources is 80 nm or more, and the Abbe number of the glass material of the objective lens is ν.
When d is satisfied, it is desirable to satisfy νd> 50 (1). The above condition (1) is satisfied when axial chromatic aberration is corrected for light sources of two different wavelengths.
This is a condition for reducing the next spectrum.

Next, when a diffractive surface is provided on one surface of a thin single lens, the entire single lens is considered as a combination of a diffractive surface serving as a base with the diffractive relief removed and a diffractive surface. Consider the chromatic aberration of this synthetic lens. The achromatic condition at a certain wavelength λx and wavelength λy (λx <λy) is as follows.

FR · νR + fD · νD = 0 where fR and fD are the refractive lenses and the focal lengths of the diffractive surfaces νR and νD are the Abbe numbers of the refractive lens and the diffractive surface, respectively, and are determined by the following equations. νR = (n0−1) / (nx−ny) νD = λ0 / (λx−λy)

Where n0: refractive index at the reference wavelength, λ0:
Reference wavelength

At this time, the chromatic aberration δ for a certain wavelength λz
f is given by the following equation. .delta.f = f (.theta.R-.theta.D) / (. nu.R-.nu.D) (2) where .theta.R and .theta.D are respectively determined by the following formulas based on the partial dispersion ratio of the refractive lens and the diffractive surface.

ΘR = (nx−nz) / (nx−ny)

ΘD = (λx−λz) / (λx−λy) where nz: refractive index at wavelength λz

As an example, λ0 = λx = 635 nm, λy
= 780 nm and λz = 650 nm, and the glass material of the base refractive lens is BSC7 of Hoya (νd = 64.2).
ΝR = 134.5, νD = -4.38,
θR = 0.128, θD = 0.103, and δf =
0.18.times.10@-3 f.

Further, when the glass material of the base refractive lens is changed to Hoya E-FD1 (νd = 29.5),
νR = 70.5, θR = 0.136, and δf =
0.44 × 10 ⁻³ f.

As described above, in the equation (2), the denominator on the right side (νR−νD) is such that | νD | is sufficiently smaller than | νR |. Is dominant in the change of Abbe number νR. On the other hand, .theta.R and .theta.D are determined only by the wavelength, and the right side numerator (.theta.R -.theta.D) has a smaller contribution than the right side denominator (.nu.R -.nu.D).

From the above, it can be seen that in a lens having a diffractive surface, it is effective to select a material having a large Abbe number νR as the material of the refractive lens in order to keep the secondary spectrum δf small. Conditional expression (1) indicates an effective limit for suppressing the secondary spectrum so as to cope with a change in the wavelength of the light source.

When achromatism is performed by bonding two types of refractive lenses without using a diffractive surface, for each material, θR = a + b · νR + △ θR
When (a and b are constants), △ θR is small, and if there is no anomalous dispersion, the secondary spectrum δf does not depend on the Abbe numbers νR of the two refractive lenses. Therefore, it is understood that the equation (1) is a condition unique to the diffractive optical system.

In order to easily manufacture the diffractive lens of the present embodiment, it is desirable that the objective lens is made of a plastic material. As the plastic material satisfying the conditional expression (1), an acryl-based or polyolefin-based material is used, and a polyolefin-based material is preferable from the viewpoint of moisture resistance, heat resistance and the like.

Next, the configuration of the objective lens according to the second embodiment of the present invention and the configuration of an optical pickup device having the objective lens will be described in detail.

FIG. 48 is a schematic configuration diagram of an optical pickup device according to the present embodiment. An optical disc 20 which is an optical information recording medium for recording and / or reproducing information by an optical pickup device includes a first optical disc (for example, DVD) and a second optical disc (for example, next-generation high-density optical disc using a blue laser) having a thickness t1 of a transparent substrate. And a third optical disc (for example, C2) having a transparent substrate thickness t2 different from t1.
The following description is based on the three types D). Here, the thickness t1 of the transparent substrate is 0.6 mm, and t2 is 1.2 mm.

The illustrated optical pickup device has a first semiconductor laser 11 (wavelength λ ₁ = 61) as a first light source.
0 nm to 670 nm) and a blue laser 1 as a second light source.
2 (wavelength λ ₂ = 400 nm to 440 nm) and a second semiconductor laser 13 (wavelength λ ₃ = 740 nm to
870 nm) and the objective lens 1 as a part of the optical system. The first light source, the second light source, and the third light source are selectively used according to an optical disc on which information is recorded and / or reproduced.

The divergent light beam emitted from the first semiconductor laser 11, the blue laser 12, or the second semiconductor laser 13 passes through the transparent substrate 21 of the optical disk 20 via the beam splitter 19 and the stop 3, and is transmitted by the objective lens 1. The light is condensed on each information recording surface 22 to form a spot.

[0390] Incident light from each laser is applied to the information recording surface 22.
The reflected light is modulated by the above information pits, enters the common photodetector 30 via the beam splitter 18 and the toric lens 29, and uses the output signal to read a signal for reading information recorded on the optical disc 20; A focus detection signal and a track detection signal are obtained.

The stop 3 provided in the optical path is
In this example, the diaphragm has a fixed numerical aperture (NA 0.65), and does not require an extra mechanism, and can realize cost reduction. The numerical aperture of the stop 3 may be variable so that unnecessary light (NA 0.45 or more) can be removed during recording and / or reproduction of the third optical disc.

By forming an annular filter integrally on the optical surface of the objective lens 1 so as to block a part of the light beam outside the actually used aperture, the flare light outside the actually used aperture can be reduced inexpensively. It can also be easily removed.

When a finite conjugate type optical system is used as in this embodiment, it is necessary to maintain a constant relationship between the light source and the condensing optical system in order to maintain the light condensing performance. It is desirable that the movement for tracking be performed with the light sources 11, 12, and 13 and the objective lens 1 as one unit.

Next, the configuration of the objective lens and the optical pickup device including the same according to the third embodiment of the present invention will be described in detail.

FIG. 49 shows a schematic configuration diagram of an optical pickup device of the present embodiment. The optical pickup device of FIG. 49 is an example using a laser / detector integrated unit 40 in which a laser, a photodetector, and a hologram are unitized.
The same components as those in FIG. 48 are denoted by the same reference numerals. In this optical pickup device, the first semiconductor laser 11, the blue laser 12, the first light detecting means 31, and the second light detecting means 3
2. The hologram beam splitter 23 is unitized as a laser / detector integrated unit 40.

When reproducing the first optical disk, the light beam emitted from the first semiconductor laser 11 passes through the hologram beam splitter 23, is stopped down by the stop 3, and passes through the transparent substrate 21 of the first optical disk 20 by the objective lens 1. The light is condensed on the information recording surface 22 via the optical disc. The light flux modulated and reflected by the information pits on the information recording surface 22 is diffracted again by the disk-side surface of the hologram beam splitter 23 via the objective lens 1 and the stop 3, and the second light beam corresponding to the first semiconductor laser 11. The light enters the first photodetector 31.
Then, using the output signal of the first photodetector 31, the first
A read signal, a focus detection signal, and a track detection signal of information recorded on the optical disc 20 are obtained.

When reproducing the second optical disc, the light beam emitted from the blue laser 12 is diffracted by the laser-side surface of the hologram beam splitter 23 and follows the same light path as the light beam from the first semiconductor laser 11. That is, the surface of the hologram beam splitter 23 on the semiconductor laser side functions as a light combining unit. Further, the light is condensed on the information recording surface 22 via the aperture 3 and the objective lens 1 via the transparent substrate 21 of the second optical disc 20. And
The light beam modulated and reflected by the information pits on the information recording surface 22 is again diffracted by the disk-side surface of the hologram beam splitter 23 through the objective lens 1 and the aperture 3 and the second light detection corresponding to the blue laser 12 is performed. Incident on the vessel 32. Then, using the output signal of the second photodetector 32,
A signal for reading information recorded on the second optical disc 20,
A focus detection signal and a track detection signal are obtained.

Further, when reproducing the third optical disk,
A laser / detector integrated unit 41 in which the second semiconductor laser 13, the third light detecting means 33, and the hologram beam splitter 24 are unitized is used. The light beam emitted from the second semiconductor laser 13 passes through the hologram beam splitter 24, is reflected by the beam splitter 19, which is a combining means of the emitted light, is stopped down by the stop 3, and is transmitted by the objective lens 1 to the transparent substrate 21 of the optical disc 20. Is focused on the information recording surface 22 via the. And the information recording surface 2
The light flux modulated and reflected by the information pit in 2 is diffracted again by the hologram beam splitter 24 via the objective lens 1, the aperture 3 and the beam splitter 19, and enters the third photodetector 33. Then, the third photodetector 33
The read signal, the focus detection signal and the track detection signal of the information recorded on the third optical disc 20 are obtained by using the output signal of the third optical disk 20.

In the optical pickup devices of the second and third embodiments, an aspherical refracting surface of the objective lens 1 is provided with an annular diffraction surface concentric with the optical axis 4. In general, when an objective lens is composed of only an aspherical refracting surface, a certain wavelength λ
When the spherical aberration is corrected for a, the spherical aberration is under for the wavelength λb shorter than λa. On the other hand, when the diffraction surface is used, when the spherical aberration is corrected for a certain wavelength λa, the spherical aberration becomes excessive for a wavelength λb shorter than λa. Therefore, it is possible to correct the spherical aberration between different wavelengths by combining the refracting power and the diffractive power by appropriately selecting the coefficient of the phase difference function of the diffractive surface and the aspherical optical design using the refracting surface. Become. In the aspherical refraction surface, when the wavelength is different, the refracting power is changed, and the light condensing position is also different. Therefore, by appropriately designing the aspherical refraction surface, it is possible to converge even the different wavelengths on the information recording surface 22 of each transparent substrate 21.

In the objective lenses 1 of the second and third embodiments, by appropriately designing the phase difference function between the aspherical refraction surface and the orbicular diffraction surface, the first semiconductor laser 11,
For each light beam emitted from the blue laser 12 or the second semiconductor laser 13, the spherical aberration generated due to the difference in the thickness of the transparent substrate 21 of the optical disk 20 is corrected. Further, when the phase difference function representing the position of the orbicular zone in the orbicular diffractive surface uses the coefficient of the fourth or higher power series term, the chromatic aberration of spherical aberration can be corrected. For the third optical disc (CD), the aperture in practical use is NA 0.4.
In the third optical disc, the spherical aberration is corrected within the NA of 0.45, and the spherical aberration in the area outside the NA of 0.45 is regarded as flare. As a result of these corrections, the aberration of the condensed spot on the information recording surface 22 of each optical disc 20 is substantially equal to or less than the diffraction limit (0.07 λrms).

The optical pickup devices of the second and third embodiments as described above include, for example, CDs, CD-Rs, and CDs.
-RW, CD-Video, CD-ROM, DVD, D
VD-ROM, DVD-RAM, DVD-R, DVD-
A player or drive compatible with any two or more different optical information recording media such as RW and MD, or an A incorporating the same.
It can be installed in a device for recording audio and / or images and / or reproducing audio and / or images in V equipment, personal computers, other information terminals, and the like.

Next, the structure of an objective lens and an optical pickup device including the same according to a fourth embodiment of the present invention will be described in detail.

FIG. 67 is a schematic configuration diagram of the optical pickup device 10 of the present embodiment. In FIG. 67, the same reference numerals may be used for members common to the second and third embodiments. In FIG. 67, an optical pickup device 10 includes a plurality of optical discs 20 as optical information recording media.
Is recorded / reproduced. Hereinafter, the plurality of optical disks 20 will be referred to as a first optical disk (D) having a transparent substrate thickness t1.
VD) and the second optical disk (next-generation high-density optical disk using a blue laser) and a thickness t of a transparent substrate different from t1
2 as a third optical disk (CD). Here, the thickness of the transparent substrate t1 = 0.6 mm, t2 = 1.
2 mm.

The optical pickup device 10 includes a first semiconductor laser 11 (wavelength λ ₁ = 610) as a first light source.
nm to 670 nm) and a blue laser 12 as a second light source.
(Wavelength λ ₂ = 400 nm to 440 nm) and the second semiconductor laser 13 (wavelength λ ₃ = 740 nm to 8
70 nm). The first light source, the second light source, and the third light source are exclusively used depending on an optical disc on which recording / reproduction is performed.

The condensing optical system 5 includes a first semiconductor laser 11,
This is a means for converging a light beam emitted from the blue laser 12 or the second semiconductor laser 13 on the respective information recording surfaces 22 via the transparent substrate 21 of the optical disk 20 to form spots. In the present embodiment, a collimator lens 2 that converts a light beam emitted from a light source into parallel light (which may be substantially parallel) and a light beam that has been converted into parallel light by the collimator lens 2 are condensed as a light collection optical system 5. And an objective lens 1.

[0406] On both surfaces of the objective lens 1, an annular diffraction surface concentric with the optical axis 4 is formed. In general, when the condensing optical system 5 is configured only with the aspherical refraction surface, when the spherical aberration is corrected for a certain wavelength λa, the spherical aberration is under for a wavelength λb shorter than λa. On the other hand, when the diffraction surface is used, when the spherical aberration is corrected for a certain wavelength λa, the spherical aberration becomes excessive for a wavelength λb shorter than λa. Therefore, aspherical optical design with a refractive surface,
By appropriately selecting the coefficient of the phase function of the diffractive surface and combining the refractive power and the diffractive power, it becomes possible to correct spherical aberration between different wavelengths. On the aspherical refraction surface, if the wavelength is different, the refracting power changes and the light condensing position is also different. Therefore, by appropriately designing the aspheric refraction surface, the information recording surface 22 of each transparent substrate can be used even for different wavelengths.
Can be collected.

On the above annular diffraction surface, the first semiconductor laser 11, the blue laser 12, or the second semiconductor laser 13
The aberration correction is performed on each light beam emitted from the lens using the first-order diffracted light. Corresponding to the diffracted light of the same order, the loss of the light amount is smaller than in the case of responding to the diffracted light of a different order, and moreover, it is 1 more than corresponding to the diffracted light of the higher order.
When the second-order diffracted light is used, the loss of light quantity is small. Therefore, the objective lens 1 of the present embodiment is effective in an optical pickup device that records information on an optical disc that records high-density information, such as a DVD-RAM. The diffraction surface is
For three different wavelengths of light, it is desirable that the diffraction efficiency is maximum at the intermediate wavelength, but it may be that having the maximum diffraction efficiency at the wavelengths at both ends.

Also, by appropriately designing the phase difference function between the aspherical refracting surface and the orbicular diffraction surface, the first semiconductor laser 1
1. For each light beam emitted from the blue laser 12 or the second semiconductor laser 13, the transparent substrate 2 of the optical disk 20
1. The spherical aberration generated due to the difference in thickness is corrected.
Further, in the phase difference function indicating the position of the orbicular zone formed in the objective lens 1, the chromatic aberration of the spherical aberration can be corrected by using the coefficient of the fourth or higher term of the power series. In the third optical disc (CD), the aperture in practical use is NA 0.45, and the spherical aberration is corrected within NA 0.45, and the spherical aberration in a region outside NA 0.45 is defined as flare. A light beam passing through an area within NA 0.45 forms a light spot on the information recording surface, and a flare light passing outside NA 0.45 is separated from the light spot on the information recording surface so as not to have an adverse effect. Pass through. With these corrections, the information recording surface 2
2 is the diffraction limit (0.07λrm)
s) is almost the same or lower.

In this embodiment, the stop 3 provided in the optical path has a fixed numerical aperture (NA 0.65), does not require an extra mechanism, and can realize low cost. . Note that the numerical aperture of the stop 3 may be variable so that unnecessary light (NA 0.45 or more) can be removed during recording / reproduction of the third optical disc. Also, the beam splitter 6,
Numeral 7 is for adjusting the optical axis of each laser beam.
As is well known, a photodetector (not shown) may be provided for each light source, and one light detector may be used for three light sources 1.
The reflected light corresponding to 1, 12, and 13 may be received.

Next, an objective lens according to a fifth embodiment of the present invention will be described.

[0411] In the present embodiment, only the point that the phase difference function indicating the position of the orbicular zone uses the coefficient of the square of the power series on the orbicular diffractive surface of the objective lens is described in the fourth embodiment.
This is different from the objective lens of the first embodiment, whereby it is also possible to correct axial chromatic aberration. Further, according to the objective lens of the present embodiment, the information recording surface 2 is applied to each optical disc 20 similarly to the fourth embodiment.
2 is the diffraction limit (0.07λrm)
s) is almost the same or less.

Next, an optical pickup device according to a sixth embodiment of the present invention will be described.

[0413] In the optical pickup device of the present embodiment,
For a first optical disk (for example, DVD) and a second optical disk (for example, next-generation high-density optical disk using a blue laser), a light beam emitted from a light source is converted into parallel light by a coupling lens, and a third optical disk (for example, CD) , The light beam emitted from the light source is diverged by the coupling lens, and is condensed by the objective lens. The thickness of the transparent substrate 21 of the first and second optical disks is 0.6 mm, and the thickness of the transparent substrate 21 of the third optical disk is
Has a thickness of 1.2 mm.

In the present embodiment, the first optical disc and the second
The spherical aberration of both the optical disc and the optical disc is corrected within the diffraction limit by the effect of the diffractive surface, and the spherical aberration caused by the disc thickness being larger than that of the first and second optical discs is mainly applied to the objective lens for the third optical disc. The spherical aberration caused by the incidence of the divergent light beam is canceled out, and the spherical aberration at a predetermined numerical aperture NA required for recording / reproducing of the third optical disc, for example, NA 0.5 or NA 0.45 or less is corrected within the diffraction limit. ing.

Therefore, λ ₁ , λ ₂ , λ ₃ (λ ₁ <λ ₂ <λ ₃ )
The predetermined numerical apertures required for performing recording / reproducing with respect to the optical information recording medium corresponding to each wavelength of NA1, NA2, N
When the A3, for each wavelength, 0.07λ ₁ an RMS wavefront aberration in the range of NA1 or less, 0.07λ ₂ below, in the range of NA2, be corrected to 0.07Ramuda ₂ below, in the range of NA3 Can be.

For the third optical disc, it is not preferable that the beam spot diameter becomes too small due to a light beam having a numerical aperture NA larger than a predetermined numerical aperture NA.
Therefore, as in the fourth embodiment, it is preferable that the spherical aberration be flare at a numerical aperture larger than the required numerical aperture.

The optical pickup devices according to the fourth to sixth embodiments having the three light sources having different wavelengths as described above include, for example, CD, CD-R, CD-RW, CD-Video,
CD-ROM, DVD, DVD-ROM, DVD-RA
Players or drives compatible with two or more different optical information recording media such as M, DVD-R, DVD-RW, MD, etc., or AV devices, personal computers, etc. incorporating them. Information terminals, etc.
Recording of audio and / or images, and / or audio and / or image reproducing apparatus.

[0418]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the objective lens according to the present invention will be described below. <Examples 1 to 8>

[0419] The objective lenses of Examples 1 to 8 are specific examples of the objective lens according to the first embodiment.
The refractive surface has an aspherical shape represented by

[0420]

(Equation 3) Here, Z is an axis in the optical axis direction, h is an axis perpendicular to the optical axis (height from the optical axis: the traveling direction of light is defined as positive), R0 is a paraxial radius of curvature, κ is a cone coefficient, and A Is an aspheric coefficient, and 2i is a power number of the aspheric surface. Further, in Examples 1 to 3 and 6 to 8, the diffractive surface is represented by [Equation 1] as a phase difference function ΦB in radians, and similarly, in Examples 4 and 5, the optical path in which the diffractive surface is in mm is used. It is represented by [Equation 2] as a difference function Φb.

[0421]

(Equation 1)

(Equation 2) (Example 1)

FIG. 1 shows an optical path diagram of a diffractive optical lens (objective lens having a diffractive surface) which is the objective lens of the first embodiment. FIG. 2 shows a spherical aberration diagram of the diffractive optical lens of Example 1 with respect to λ = 635 nm up to a numerical aperture of 0.60. FIGS. 3 and 4 show spherical aberration diagrams of the diffractive optical lens of Example 1 with respect to a wavelength λ = 780 nm up to numerical apertures 0.45 and 0.60, respectively. Although the diffractive optical lens of FIG. 1 has a blazed concentric ring-shaped diffractive portion on the entire surface of the lens, the relief shape of the diffractive portion is omitted in the drawing. In many of the drawings that follow, the relief shape of the diffractive portion is omitted.

According to the diffractive optical lens of Embodiment 1, FIG.
As shown in FIG.
All apertures up to 60 are almost stigmatic. Further, as shown in FIG. 3, for the wavelength λ = 780 nm, there is almost no aberration up to NA 0.45 which is the actual use range. As for the outer part of NA 0.45 to 0.60, the spherical aberration is largely under, as shown in FIG. 4, resulting in flare. This makes it possible to obtain an appropriate spot diameter for the wavelength λ = 780 nm.

FIGS. 5 and 6 show wavefront aberration diagrams for the diffractive optical lens of Example 1 with respect to λ = 635 nm and wavelength λ = 780 nm, respectively. As can be seen from these figures, according to the diffractive optical lens of Example 1, there is almost no aberration on the optical axis for any wavelength, and even at an image height of 0.03 mm, the level is practically close to no aberration. It has become.

The following shows the lens data of the first embodiment.
In Table 1, R is the radius of curvature, d is the surface spacing, n is the refractive index at the main wavelength, and ν is the Abbe number.

Example 1

When light source wavelength λ1 = 635 nm Focal length f1 = 3.34 Numerical aperture NA1 = 0.60 Infinite specification

When the light source wavelength is λ2 = 780 nm, focal length f2 = 3.36, numerical aperture NA2 = 0.45, infinite specification

In this embodiment, the + 1st order diffracted light is generated more in the λ1 light beam than the other orders, and the + 1st order diffracted light is also generated in the λ2 light beam in the λ1 light beam. Generate a lot. Assuming that the diffraction efficiency of the + 1st-order diffracted light with respect to λ1 is 100%, the diffraction efficiency with respect to λ2 is 84%.
%. Assuming that the diffraction efficiency of the + 1st-order diffracted light with respect to λ2 is 100%, the diffraction efficiency with respect to λ1 is 89%.

[0430]

[Table 1] Aspherical surface coefficient Aspherical surface 1 Aspherical surface 2 κ = -0.17021 κ = -11.653 A4 = -0.00003215 A4 = 0.038456 A6 = -0.0058160 A6 = -0.020800 A8 = -4.6316 × 10 ⁻⁵ A8 = 0.00007864 A10 = −3.798858 × 10 ⁻⁵ A10 = −0.000019431 A12 = −6.0308 × 10 ⁻⁶ A12 = 0.00024343

Diffraction surface coefficient B2 = -96.766 B4 = -2.9950 B6 = 2.1306 B8 = -0.161414 B10 = -0.095285

(Examples 2 and 3)

Next, Embodiments 2 and 3 will be described. 7 and 8 show optical path diagrams of the diffractive optical lens, which is the objective lens of the second embodiment, at λ = 405 nm and 635 nm, respectively. 9 and FIG.
9 shows spherical aberration diagrams of the diffractive optical lens of Example 2 for λ = 405 nm and 635 nm up to a numerical aperture of 0.60, respectively. FIGS. 11 and 12 show wavefront aberration diagrams for the diffractive optical lens of Example 2 at wavelengths λ = 405 nm and 635 nm, respectively.

FIGS. 13 and 14 show optical path diagrams of the diffractive optical lens, which is the objective lens of the third embodiment, at λ = 405 nm and 635 nm, respectively. FIGS. 15 and 16 show spherical aberration diagrams of the diffractive optical lens of Example 3 at λ = 405 nm and 635 nm up to a numerical aperture of 0.60, respectively. FIG.
7 and 18 show wavefront aberration diagrams for the diffractive optical lens of Example 3 for wavelengths λ = 405 nm and 635 nm, respectively.

In Examples 2 and 3, the wavelength λ = 405
For nm and wavelength λ = 635 nm, both the substrate thickness is 0.6 mm and the NA is 0.60, and the wavefront aberration is almost no aberration on the optical axis and practically close to no aberration even at an image height of 0.03 mm. Level.

Hereinafter, lens data of Examples 2 and 3 will be shown.

Example 2

When light source wavelength λ1 = 405 nm, focal length f1 = 3.23, numerical aperture NA1 = 0.60, infinite specification

When the light source wavelength λ2 = 635 nm Focal length f2 = 3.34 Numerical aperture NA2 = 0.60 Infinite specification

In this embodiment, the + 1st order diffracted light is generated more in the λ1 light beam than the other order diffracted light, and the + 1st order diffracted light is also generated in the λ2 light beam in comparison with the other order diffracted light. Generate a lot.

[0441]

[Table 2] Aspherical surface coefficient Aspherical surface 1 Aspherical surface 2 κ = -0.15079 κ = -3.8288 A4 = -0.0021230 A4 = 0.036962 A6 = -0.0076528 A6 = -0.020858 A8 = -8.848557 × 10 ^-5 A8 = 0.0097732 A10 = -3.49803 x 10 ^-5 A10 = -0.00001813 A12 = -2.38916 x 10 ^-6 A12 = 0.0002504

Diffraction surface coefficient B2 = 0.0 B4 = −6.7169 B6 = 2.0791 B8 = −0.3970 B10 = 0.00016708

Embodiment 3

When light source wavelength λ 1 = 405 nm Focal length f 1 = 3.31 Numerical aperture NA 1 = 0.60 Infinite specification

When light source wavelength λ2 = 635 nm Focal length f2 = 3.34 Numerical aperture NA2 = 0.60 Infinite specification

In this embodiment, the + 1st order diffracted light is generated more in the λ1 light beam than the other orders, and the + 1st order diffracted light is also generated in the λ2 light beam in the λ1 light beam. Generate a lot.

[0447]

[Table 3] Aspherical surface coefficient Aspherical surface 1 Aspherical surface 2 κ = -0.10929 κ = 6.4430 A4 = 0.0030538 A4 = 0.037045 A6 = -0.00001019 A6 = -0.021474 A8 = -7.5747 × 10 ^-5 A8 = 0.00007875 A10 = -6.7599 × 10 ^-5 A10 = -0.00001664 A12 = -3.3788 x 10 ^-6 A12 = 0.00014332

Diffraction surface coefficient B2 = −96.766 B4 = −2.9950 B6 = −0.2560 B8 = −0.08789 B10 = 0.014562

(Examples 4 and 5)

Next, Embodiments 4 and 5 in which chromatic aberration correction is performed will be described. FIG. 19 shows an optical path diagram of the diffractive optical lens which is the objective lens of the fourth embodiment. FIG. 20 shows λ of the diffractive optical lens of the fourth embodiment.
= Spherical aberration diagrams up to numerical aperture 0.50 for 635 nm, 650 nm and 780 nm, respectively. Also,
FIG. 21 shows an optical path diagram of the diffractive optical lens which is the objective lens of the fifth embodiment. FIG. 22 shows λ = 635 nm and 650 nm for the diffractive optical lens of Example 5.
And spherical aberration diagrams up to a numerical aperture of 0.50 for 780 nm and 780 nm, respectively.

As can be seen from FIGS. 20 and 22, according to the diffractive optical lenses of Examples 4 and 5, the wavelength λ = 635.
nm and wavelength λ = 780 nm, the color shift is almost completely corrected, and for wavelength λ = 650 nm,
It has been corrected to such an extent that there is no practical problem.

The lens data of Examples 4 and 5 are shown below.

Embodiment 4

When light source wavelength λ1 = 635 nm Focal length f1 = 3.40 Numerical aperture NA1 = 0.50 Infinite specification

When light source wavelength λ2 = 780 nm, focal length f2 = 3.41 numerical aperture NA2 = 0.50 infinite specification

In this embodiment, the + 1st order diffracted light is generated more in the λ1 light beam than the other order diffracted light, and the + 1st order diffracted light is also generated in the λ2 light beam in comparison with the other order diffracted light. Generate a lot.

[0457]

[Table 4] Aspherical surface coefficient Aspherical surface 1 Aspherical surface 2 κ = −0.53245 κ = 7.3988 A4 = 0.24033 × 10 ⁻² A4 = 0.9408 × 10 ⁻² A6 = −0.9147 × 10 ⁻³ A6 = −0.1704 × 10 ⁻² A8 = 0.15590 × 10 ⁻⁴ A8 = −0.47368 × 10 ⁻³ A10 = −0.11311 × 10 ⁻³ A10 = 0.16891 × 10 ⁻³

Diffraction surface coefficient b 2 = −0.36764 × 10 ⁻² b 4 = −0.9127 × 10 ⁻⁴ b 6 = −0.3903 × 10 ⁻⁴ b 8 = 0.7785 × 10 ⁻⁵ b 10 = −0. 15750 × 10 ^-5

Embodiment 5

When light source wavelength λ1 = 635 nm, focal length f1 = 3.40, numerical aperture NA1 = 0.50, infinite specification

When light source wavelength λ2 = 780 nm, focal length f2 = 3.40, numerical aperture NA2 = 0.50, infinite specification

In this embodiment, the + 1st order diffracted light is generated more in the λ1 light beam than the other orders, and the + 1st order diffracted light is also generated in the λ2 light beam in comparison with the other orders. Generate a lot.

[0463]

[Table 5] Aspherical surface coefficient Aspherical surface 1 Aspherical surface 2 κ = -0.17066 κ = -400.782 A4 = -0.3563 × 10 ^-2 A4 = 0.73447 × 10 ^-2 A6 = -0.445199 × 10 ^-3 A6 = 0.85177 × 10 ⁻³ A8 = 0.58811 × 10 ⁻⁵ A8 = −0.82795 × 10 ⁻³ A10 = −0.1302 × 10 ⁻⁴ A10 = 0.23029 × 10 ⁻³

Diffraction surface coefficient b 2 = −0.74461 × 10 ⁻² b 4 = 0.1193 × 10 ⁻² b 6 = −0.8825 × 10 ⁻³ b 8 = 0.550517 × 10 ⁻³ b 10 = −0.1242 × 10 ^-3

(Examples 6 to 8)

Next, Examples 6 to 8 will be described. FIGS. 23, 30 and 37 show optical path diagrams with respect to λ = 650 nm of the diffractive optical lenses which are the objective lenses of Examples 6 to 8, respectively. 24, 31, and 38.
Λ = 780 nm of the diffractive optical lenses of Examples 6 to 8
The optical path diagrams for (NA = 0.5) are shown respectively. 25, 32, and 39 show spherical aberration diagrams of the diffractive optical lenses of Examples 6 to 8 up to a numerical aperture of 0.60 with respect to λ = 650 ± 10 nm, respectively. 26, 33, and 40 show spherical aberration diagrams of the diffractive optical lenses of Examples 6 to 8 with respect to λ = 780 ± 10 nm up to a numerical aperture of 0.50, respectively. 27, 34, and 41 show spherical aberration diagrams of the diffractive optical lenses of Examples 6 to 8 with respect to λ = 780 nm up to a numerical aperture of 0.60, respectively.

FIGS. 28, 35 and 42 show that λ = 650 nm for the diffractive optical lenses of Examples 6 to 8.
Respectively show wavefront aberration rms diagrams. FIG.
9, FIG. 36 and FIG. 43 show the wavefront aberration rms for the diffractive optical lenses of Examples 6 to 8 with respect to λ = 780 nm.
The figures are shown respectively. 44, 45 and 46.
7 shows graphs showing the relationship between the number of diffraction zones and the height from the optical axis for the diffractive optical lenses of Examples 6 to 8, respectively. Here, the number of diffraction zones is defined as a value obtained by dividing the phase difference function by 2π.

In Examples 6 to 8, as shown in the spherical aberration diagram, for a wavelength λ = 650 nm, all apertures up to NA 0.60 are almost free of aberration. Also, the wavelength λ =
For 780 nm, the practical use range of NA 0.50
Are almost aberration-free, but NA0.
The portion between 50 and 0.60 has large spherical aberration and is flare. Thereby, the wavelength λ = 780 nm
With regard to (1), it is possible to obtain an appropriate spot diameter.

Hereinafter, lens data of Examples 6 to 8 will be shown. [Table 6] to [Table 8] and further [Table 15] to [Table 18]
In the figure, STO denotes an aperture and IMA denotes an image plane, which is expressed in a form including the aperture. OBJ represents an object point (light source), and is the same in each of the following tables.

Example 6

When the wavelength of the light source is λ = 650 nm, the focal length f = 3.33, the image-side numerical aperture NA = 0.60, infinite specification

When light source wavelength λ = 780 nm Focal length f = 3.37 Image side numerical aperture NA = 0.50 (NA = 0.60) Infinity specification w (13.5% of light beam of 780 nm on image plane) Intensity beam diameter) = 1.20 μm

In this embodiment, as shown in FIG. 44, the -1st-order diffracted light is not reflected at the center of the luminous flux of λ1 or λ2 at the center where the height from the optical axis is about half or less of the effective diameter. More diffracted light of other orders is generated, and in the peripheral portion where the height from the optical axis is about half or more of the effective diameter, more + 1st-order diffracted light is generated than diffracted light of other orders. However, in the present embodiment, the orbicular zone pitch is multiplied by an integer to obtain ±
Instead of first-order diffracted light, higher-order same-order diffracted light may be generated.

In this embodiment, as shown in FIG. 27, in the second optical information recording medium, NA1 = 0.6
, The spherical aberration is +29 μm, and NA2 = 0.5
In this case, the spherical aberration is +1 μm. Further, in the present embodiment, the pitch of the diffraction portions at a numerical aperture (NA) of 0.4 is 14 μm.

[0475]

[Table 6] Aspherical surface coefficient Aspherical surface 1 Aspherical surface 2 κ = -1.07952 κ = -3.4452929 A4 = 0.519125 × 10 ^-2 A4 = 0.15912992 × 10 ^-1 A6 = 0.1988861 × 10 ^-2 A6 = −0.444528738 × 10 ⁻² A8 = −0.444386519 × 10 ⁻³ A8 = 0.6543404 × 10 ⁻³ A10 = 5.40513737 × 10 ⁻⁵ A10 = −4.776799 × 10 ⁻⁵

Diffraction surface coefficient B2 = 29.443104 B4 = -14.403683 B6 = 3.9425951 B8 = −2.1471955 B10 = 0.31859248

Example 7

When light source wavelength λ = 650 nm Focal length f = 3.33 Image side numerical aperture NA = 0.60 Infinite specification

When Light Source Wavelength λ = 780 nm Focal Length f = 3.37 Image Side Numerical Value NA = 0.50 (NA = 0.60) Finite Specification

In this embodiment, as shown in FIG. 45, the light beam of λ1 and the light beam of λ2
The first-order diffracted light is generated more than the other-order diffracted lights. However, in the present embodiment, the orbicular zone pitch may be multiplied by an integer to generate a higher-order homogenous diffracted light instead of the + 1st-order diffracted light.

[0481]

[Table 7] Aspherical surface coefficient Aspherical surface 1 Aspherical surface 2 κ = -1.801329 κ = −8.871647 A4 = 0.615422 × 10 ⁻¹ A4 = 0.14925111 × 10 ⁻¹ A6 = −0.4937969 × 10 ^-3 A6 = −0.444445 × 10 ⁻² A8 = 0.11038322 × 10 ⁻³ A8 = 0.60067143 × 10 ⁻³ A10 = −2.1823306 × 10 ⁻⁵ A10 = −3.4684206 × 10 ⁻⁵

Diffraction surface coefficient B2 = −17.150237 B4 = −4.127045 B6 = 1.1902249 B8 = −0.262022222 B10 = 0.188845315

Example 8

When the light source wavelength is λ = 650 nm Focal length f = 3.33 Image side numerical aperture NA = 0.60 Infinite specification

When light source wavelength λ = 780 nm Focal length f = 3.35 Image side numerical aperture NA = 0.50 (NA = 0.60) Infinity specification w (13.5% of light beam of 780 nm on image plane) Beam diameter of intensity) = 1.27 μm

In this embodiment, as shown in FIG. 46, in the luminous flux of λ1 and the luminous flux of λ2, the −1st-order diffracted light is generated more in the very peripheral portion than in the diffracted lights of other orders. Others generate + 1st-order diffracted light more than diffracted lights of other orders. However, in the present embodiment, the annular zone pitch may be multiplied by an integer to generate higher-order same-order diffracted light instead of ± 1st-order diffracted light.

In this embodiment, as shown in FIG. 41, in the second optical information recording medium, NA1 = 0.6
, The spherical aberration is +68 μm, and NA2 = 0.5
In this case, the spherical aberration is +9 μm.

In the present embodiment, the numerical aperture (NA)
The pitch at 0.4 is 61 μm.

[0489]

[Table 8] Aspherical surface coefficient Aspherical surface 1 Aspherical surface 2 κ = -1.2532 κ = −9.151362 A4 = 0.107 × 10 ⁻¹ A4 = 0.133327 × 10 ⁻¹ A6 = −0.885849 × 10 ^-3 A6 = −0.378862 × 10 ⁻² A8 = −1.5773 × 10 ⁻⁵ A8 = 0.3001 × 10 ⁻³ A10 = 3.2855 × 10 ⁻⁵ A10 = 4.02211 × 10 ⁶

Diffraction surface coefficient B 2 = 3.4251 × 10 ⁻²¹ B 4 = 0.076977 B 6 = −5.5386 B 8 = 0.05938 B 10 = 0.2224 Here, based on Examples 6 to 8, Consider the cause of the fluctuation of the wavelength of the incident semiconductor laser. The individual variation of the wavelength of the semiconductor laser is about ± 2 to 3 nm,
It is considered that the width of the multimode oscillation is about ± 2 nm and the mode hop at the time of writing is about 2 nm. A case will be described in which a change in the spherical aberration of the lens due to a change in the wavelength of the semiconductor laser due to these factors is considered.

That is, when the thickness of the transparent substrate of the optical disk is different for each of the two different light sources, as can be understood from the data relating to the sixth embodiment, the infinite light (parallel light flux) from the different two wavelength light sources is understood. In a lens corrected to have no aberration, the variation in spherical aberration is relatively large with respect to a change of a wavelength of about 10 nm by one light source. In the sixth embodiment, the wavefront aberration is 0.001 at the wavelength of 650 nm.
Although it is λrms, at the wavelengths of 640 nm and 660 nm, the wavefront aberration deteriorates to about 0.035 λrms. As a matter of course, the sixth embodiment can be sufficiently used for an optical system in which the wavelength of the laser is well controlled. On the other hand, as in the lens of Example 7, there is almost no aberration for infinite light from one of the light sources, and almost no aberration for finite light (non-parallel light flux) from the other wavelength light source. For a lens corrected for aberration, the wavelength of one light source is 10
For a change of about nm, it is possible to suppress the fluctuation of the spherical aberration to a very small value.

Next, the temperature change of the performance of the diffractive optical system (optical system having a diffractive optical lens) of the present embodiment will be considered. First, the wavelength of a semiconductor laser tends to increase by about 6 nm when the temperature rises by 30 ° C. On the other hand, if the diffractive optical system is composed of a plastic lens,
When the temperature rises by 30 ° C., the refractive index tends to decrease by about 0.003 to 0.004. In the lens which is corrected to have no aberration for infinite light of both wavelengths as in the sixth embodiment, the factor due to the temperature change of the wavelength of the semiconductor laser and the factor due to the temperature change of the refractive index of the plastic lens are compensated. An effect can be produced, and an optical system that is extremely resistant to temperature changes can be created. In Example 6,
Even when the material is glass, it is possible to make the optical system tolerable to temperature changes. Also in the seventh embodiment, although it is not as good as the sixth embodiment, the deterioration of the wavefront aberration is about 0.035 λrms at a temperature change of 30 ° C., and sufficient temperature compensation for practical use is achieved.

[0493] The effect of compensating for the above-mentioned temperature change will be further described. When recording and / or reproducing two types of optical information recording media having different thicknesses of the transparent substrate by two light sources having different wavelengths, the information recording surface of each optical disc is used by using an objective lens having a diffraction pattern. The rms value of the wavefront aberration is 0.07 of each wavelength even at the numerical aperture required for
Since the following can be achieved, it is possible to obtain an imaging characteristic equivalent to that of a dedicated objective lens. In order to provide a low-cost and compact optical pickup device, a semiconductor laser is used as a light source and a plastic lens is often used as an objective lens.

There are various types of plastic materials for lenses, and the change in refractive index with temperature and the coefficient of linear expansion are larger than those of glass. In particular, temperature changes in the refractive index affect various characteristics of the lens. The temperature change of the refractive index in the vicinity of 25 ° C. is from −0.0002 / ° C. to −0.02 for a plastic material used as an optical element of an optical pickup.
0005 / ° C. Further, the low birefringence material is -0.0
Most are 001 / ° C. Further, some thermosetting plastics for lenses have a large change in the refractive index with respect to a change in temperature, and some of them are out of the above range.

As for a semiconductor laser manufactured by the current technology, the oscillation wavelength has a temperature dependence, and the temperature change of the oscillation wavelength near 25 ° C. is 0.05 nm.
/ ° C to 0.5 nm / ° C.

When the wavefront aberration of a light beam for reproducing information on an optical information recording medium or recording information on the optical information recording medium changes with temperature and the rms value becomes 0.07 or more of the wavelength, the characteristics as an optical pickup device are reduced. It is difficult to maintain, and in particular, it is necessary to pay attention to the temperature change of the wavefront aberration in a higher density optical information medium. In the change of the wavefront aberration due to the temperature change of the plastic lens, both the defocus and the change of the spherical aberration occur. However, the former is important because the focus is controlled in the optical pickup device. Here, the plastic material has a temperature change ΔT
When the amount of change in the refractive index when (° C.) occurs is Δn, −0.0002 / ° C. <Δn / ΔT <−0.00005 /
And the semiconductor laser satisfies the relationship of 0.05 nm / ° C <Δλ1 / ΔT <0.5 nm / ° C, where Δλ1 is the change amount of the oscillation wavelength when there is a temperature change ΔT. In addition, the fluctuation of the wavefront aberration caused by the temperature change of the refractive index of the plastic lens and the fluctuation of the wavefront aberration caused by the temperature change of the wavelength of the semiconductor laser light source cancel each other, so that a compensation effect can be obtained.

When the environmental temperature change is ΔT (° C.), the change amount of the third-order spherical aberration component of the wavefront aberration is expressed by ΔWS
If A3 (λrms), this is proportional to the fourth power of the numerical aperture (NA) of the light beam passing through the objective lens on the optical information medium side of the objective lens, and the focal length f (m
m), and is inversely proportional to the wavelength λ (mm) of the light source because the wavefront aberration is evaluated in wavelength units. Therefore, the following equation is established. ΔWSA3 = k · (NA) ⁴ · f · ΔT / λ (a1) where k is an amount depending on the type of the objective lens. Incidentally, a plastic double-sided aspherical objective lens which is optimized when the focal length is 3.36 mm, the numerical aperture on the optical information medium side is 0.6, and the incident light beam is parallel light, is MO.
C / GRIN'97 Technical Digest C5 p40-p43, "The Tempera
ture characteristics of a new optical system with
quasi-finite conjugate plastic objective for high
Density optical disk use ", the graph in this document shows that WSA3 changes by 0.045λrms at a temperature change of 30 ° C., and since it is used for DVD, the wavelength is λ = 650 nm. By substituting the above data into equation (a1), k = 2.2 × 1
0 ^-6 is obtained. Although there is no description about the effect of wavelength change due to temperature change, when the temperature change of the oscillation wavelength is small, the effect of refractive index change due to temperature is greater for an objective lens that does not use diffraction.

For an optical pickup device for recording and / or reproducing data on a DVD, k must be equal to or less than the above value. When recording and / or reproducing information on two types of optical information recording media having different thicknesses of the transparent substrate, the influence of a wavelength change due to a temperature change cannot be neglected in an objective lens having a diffraction pattern. Especially k
The value of k differs depending on the focal length, the temperature change of the refractive index of the plastic material, the difference in the thickness of the transparent substrate, the difference in the oscillation wavelengths of the two light sources, and the like. A factor due to the temperature change and a factor due to the temperature change in the refractive index of the plastic lens cause a compensation effect. Even if the objective lens is a plastic lens, the change in the wavefront aberration due to the temperature change is small, and according to the simulation, k = 2.2 × the 10 ^-6 /℃,k=0.4×10 ^-6 / ℃.

As k, the range of 0.3 <k <2.2 can be taken. Therefore, from equation (a1),

Since k = ΔWSA3 · λ / ｛f · (NA1) ⁴ · ΔT (NA)｝ (a2), 0.3 × 10 ⁻⁶ / ° C <ΔWSA3 · λ / ｛f · (NA1) ⁴ ΔT｝ <2.2 × 10 ⁻⁶ / ° C. (a3) In the equation (a3), if the value of k exceeds the upper limit, it becomes difficult to maintain the characteristics of the optical pickup device due to the temperature change, and if the value of k exceeds the lower limit, the change with respect to the temperature change is small. However, it is likely to be difficult to maintain the characteristics of the optical pickup device when the wavelength changes.

In the eighth embodiment, as compared with the sixth embodiment, the performance of one wavelength, that is, the wavelength of 780 nm is slightly degraded within the allowable range, so that the other wavelength, that is, the wavelength of 650 nm is reduced. Variations in spherical aberration in the vicinity of the wavelength ± 10 nm can be reduced. In the sixth embodiment, the wavefront aberration at the wavelength of 640 nm or 660 nm is about 0.035 λrms, but in the eighth embodiment, the wavefront aberration at the wavelength of 640 nm or 660 nm can be improved to about 0.020 λrms. Although these two factors have a trade-off relationship, it is important to maintain a balance. If the ratio exceeds 0.07 λrms, the lens performance deteriorates, and it becomes difficult to use the optical system as an optical system for optical disks.

Next, the relationship between the amount of change in the spherical aberration of the marginal ray and the amount of change in the axial chromatic aberration with respect to the change in wavelength will be described based on Example 6. As in the sixth embodiment, a light beam having a shorter wavelength is used for an information recording medium having a thin transparent substrate, and a light beam having a longer wavelength is used for an information recording medium having a thick transparent substrate. In one optical pickup device using the above, in the objective lens used for the light flux, by the action of the diffraction surface, when the wavelength becomes longer for a certain wavelength, by displacing the spherical aberration to the under side, The spherical aberration caused by the difference in the thickness of the transparent substrate can be corrected.

In this objective lens, if the amount of change in the spherical aberration and the amount of axial chromatic aberration of the marginal ray with respect to a minute change in the wavelength used by at least one of the light sources are △ SA and △ CA, respectively: It is desirable to satisfy 1 <△ SA / △ CA <−0.2. This equation shows the ratio between the amount of change in the spherical aberration of the marginal ray and the amount of change in the axial chromatic aberration when the wavelength used changes.By exceeding the lower limit of this conditional expression, the spacing between the diffraction zones can be increased. It is easy to manufacture a diffractive surface with high diffraction efficiency, and by falling below the upper limit of the conditional expression, it can be suppressed that the diffractive surface has a negative and large refracting power. It is possible to suppress a change in the focal position with respect to a wavelength change such as pop. Note that a minute change in wavelength means a change of about 10 nm or less. In the sixth embodiment, as shown in FIG.
At 0 nm, the value of △ SA / △ CA is -0.7.

Here, the relationship between the diffraction power and the lens shape will be described. FIG. 47 schematically shows the relationship between the diffraction power and the lens shape. FIG. 47 (a) is a diagram showing a positive lens shape in which the diffraction power is all parts, and FIG.
(B) is a figure which shows the lens shape where diffraction power is negative in all parts. As shown in FIG. 47 (c), the lens of Example 6 is designed such that the diffraction power is negative near the optical axis, and switches to a positive power halfway. This makes it possible to prevent the pitch of the diffraction zones from becoming too fine. Also, as in Example 8,
By designing the diffraction power to switch from positive power to negative power near the periphery of the lens, good aberration can be obtained between two wavelengths. FIG. 47 (d)
For example, the diffraction power is positive near the optical axis, and can be switched to negative power halfway.

In FIG. 47 (c), the diffraction surface has a plurality of blazed diffraction zones, and in the diffraction zone near the optical axis, the step is located on the side far from the optical axis. In the diffraction ring zone away from the optical axis, the step is located closer to the optical axis. In FIG. 47 (d), the diffraction surface has a plurality of blazed diffraction zones, and in the diffraction zone near the optical axis, the step is located on the side near the optical axis. In the diffraction ring zone away from the optical axis, the step portion is located on the side away from the optical axis.

<Examples 9 and 10>

The objective lenses of the ninth and tenth embodiments have the aspherical shape represented by the above-mentioned [Equation 3] on the refracting surface.
Example 9 is a finite conjugate type corresponding to two light sources, and Example 10 is a specific example of the objective lens according to the second embodiment, which is a finite conjugate type corresponding to three light sources. In the ninth and tenth embodiments, the diffractive surface is represented by the above-described [Equation 1] as the phase difference function ΦB in radians.

FIGS. 50 and 51 are optical path diagrams at λ = 650 nm and λ = 780 nm of the objective lens of the ninth embodiment. FIG. 52 shows a spherical aberration diagram of the objective lens of Example 9 with respect to λ = 650 nm up to a numerical aperture of 0.60. 53 and 54 show spherical aberration diagrams of the objective lens of Example 9 with respect to a wavelength λ = 780 nm up to numerical apertures 0.45 and 0.60, respectively. 55 and 56 show λ = 650 nm and wavelength λ = 780 for the objective lens of the ninth embodiment.
Wavefront aberration diagrams for nm are shown.

FIGS. 57 to 59 show that the objective lens of Example 10 has λ = 650 nm, λ = 400 nm, and λ = 780.
The optical path diagram in nm is shown. 61 and 61.
FIG. 14 shows a spherical aberration diagram of the objective lens of Example 10 for λ = 650 nm and λ = 400 nm up to a numerical aperture of 0.65. 62 and 63 show Example 10.
FIG. 3 shows spherical aberration diagrams up to numerical apertures 0.45 and 0.65 with respect to a wavelength λ = 780 nm for the objective lens of FIG. FIGS. 64 to 66 show wavefront aberration diagrams for the objective lens of Example 10 with respect to λ = 650 nm, λ = 400 nm, and wavelength λ = 780 nm, respectively.

According to the objective lenses of the ninth and tenth embodiments, in each of the embodiments, a large spherical aberration occurs for a 780 nm wavelength light when the light flux exceeds NA of 0.45 in practical use, and information is recorded as a flare. And / or does not contribute to regeneration.

The lens data of Examples 9 and 10 are shown below. In Table 9 and Table 10, r is the radius of curvature of the lens,
d is the surface spacing, n is the refractive index at each wavelength, and ν is the Abbe number. For reference, the refractive index at d-line (λ = 587.6 nm) and νd (Abbe number) are described. In addition, the number of the surface No. is displayed including the aperture, and in the present embodiment, for convenience, the air gap is expressed in two places before and after the portion corresponding to the transparent substrate of the optical disc. .

Example 9 f = 3.33 Image side NA 0.60 magnification -0.194 (when wavelength λ = 650 nm) f = 3.35 Image side NA 0.45 (NA 0.60) Magnification -0.195 (when wavelength λ = 780 nm)

[0513]

[Table 9] Aspheric surface 1 κ = -0.1295292 Diffraction surface 1 B2 = 0 A4 = -0.0045445253 B4 = -7.6489594 A6 = -0.0011967305 B6 = 0.9933123 A8 = -0.00011777995 B8 = -0.28305522 A10 = -5.3843777 × 10 ^-5 B10 = 0.011289605 A12 =- 9.0807729 × 10 ^-6

Aspherical surface 2 κ = -5.161871 A4 = 0.019003845 A6 = -0.010002187 A8 = 0.004087239 A10 = -0.00085994626 A12 = 7.5491556 x 10 ^-5

Example 10 f = 3.31 Image side NA 0.65 magnification -0.203 (when wavelength λ = 650 nm) f = 3.14 Image side NA 0.65 magnification -0.190 (when wavelength λ = 400 nm) f = 3.34 Image side NA 0.45 ( NA 0.65) Magnification -0.205 (when wavelength λ = 780nm)

[0516]

[Table 10] Aspheric surface 1 κ = -0.08796008 Diffraction surface 1 B2 = 0 A4 = -0.010351744 B4 = -61.351934 A6 = 0.0015514472 B6 = 5.9668445 A8 = -0.00043894535 B8 = -1.2923244 A10 = 5.481801 × 10 ^-5 B10 = 0.041773541 A12 = -4.2588508 × 10 ^-6

Aspheric surface 2 κ = -302.6352 Diffraction surface 2 B2 = 0 A4 = 0.002 B4 = 341.19136 A6 = -0.0014 B6 = -124.16233 A8 = 0.0042 B8 = 49.877242 A10 = -0.0022 B10 = -5.9599182 A12 = 0.0004

[0518] The specific example of the objective lens of Example 10 can be similarly applied to the third embodiment.

<Examples 11 to 14>

The objective lenses of Examples 11 to 14 have the aspherical shape represented by the above-mentioned [Equation 3] on the refraction surface. In Examples 11 to 13, the diffraction surface has a unit of radian. It is expressed by the above [Equation 1] as the obtained phase difference function ΦB. In the fourteenth embodiment, the diffraction surface is represented by the above-mentioned [Equation 2] as the optical path difference function Φb with the unit being mm.

In obtaining the objective lens characteristics of Examples 11 to 14, the light source wavelength for the first optical disk (DVD) was 650 nm, and the light source wavelength for the second optical disk (next generation high-density optical disk using a blue laser) was 400 nm. The thickness t1 of the transparent substrate of each of the first and second optical disks is t1 = 0.6 mm. The light source wavelength for the third optical disk (CD) having a transparent substrate thickness t2 = 1.2 mm different from t1 was 780 nm. Further, 0.65, 0.65, and 0.5 are assumed as the numerical apertures NA corresponding to the light source wavelengths of 400 nm, 650 nm, and 780 nm, respectively.

(Example 11)

Example 11 is a specific example of the objective lens according to the fourth embodiment, and is configured so that parallel light enters the objective lens. In this embodiment, the coefficient of the phase difference function of the diffraction surface does not include the square term (B2 = 0), and
Only the coefficients of terms other than the squared term are used.

FIGS. 68 to 70 show that the objective lens of Example 11 has λ = 650 nm, λ = 400 nm, and λ = 780.
The optical path diagram in nm is shown. FIG. 71 and FIG.
Λ = 650 nm for the objective lens of Example 11
And spherical aberration diagrams up to a numerical aperture of 0.65 for λ = 400 nm. FIGS. 73 and 74 show spherical aberration diagrams of the objective lens of Example 11 up to a numerical aperture of 0.45 and 0.65 with respect to a wavelength λ = 780 nm, respectively. FIGS. 75 to 77 show wavefront aberration diagrams for the objective lens of Example 11 with respect to λ = 650 nm, λ = 400 nm, and λ = 780 nm, respectively.

[0525] The lens data of Example 11 is shown below.
In Table 11, r is the radius of curvature of the lens, d is the surface spacing, and n
Indicates the refractive index at each wavelength. Also, the numbers of the surface numbers are displayed including the aperture.

Example 11 f = 3.33 Image-side NA 0.65 (when wavelength λ = 650 nm) f = 3.15 Image-side NA 0.65 (when wavelength λ = 400 nm) f = 3.37 Image-side NA 0.45 (NA 0.65) (wavelength λ (When = 780nm)

[0527]

[Table 11] Aspheric surface 1 κ = -0.1847301 Diffraction surface 1 B2 = 0 A4 = -0.0090859227 B4 = -69.824562 A6 = 0.0016821871 B6 = 0.35641549 A8 = -0.00071180761 B8 = 0.6877372 A10 = 0.00012406905 B10 = -0.18333885 A12 = -1.4004589 × 10 ^-5

Aspherical surface 2 κ = -186.4056 Diffraction surface 2 B2 = 0 A4 = 0.002 B4 = 745.72117 A6 = -0.0014 B6 = -334.75078 A8 = 0.0042 B8 = 81.232224 A10 = -0.0022 B10 = -5.3410176 A12 = 0.0004

Example 11 (and Example 12 to be described later)
In an optical pickup device having an objective lens and three light sources as described above, by appropriately designing the aspheric coefficient and the coefficient of the phase difference function, the spherical aberration and the wavelength caused by the difference in the thickness of the transparent substrate can be used. The chromatic aberration of the generated spherical aberration can be corrected for each disk.
As is clear from FIG. 74, in the third optical disc, the outside of the numerical aperture NA of 0.45 in practical use is a flare.

(Example 12)

The objective lens of the twelfth embodiment is configured so that divergent light from a finite distance enters. In this embodiment, the coefficient of the phase difference function of the diffractive surface does not include the square term (B2 = 0), and only the coefficient of the term other than the square term is used.

FIGS. 78 to 80 show that the objective lens of Example 12 has λ = 650 nm, λ = 400 nm, and λ = 780.
The optical path diagram in nm is shown. 81 and 82.
Λ = 650 nm for the objective lens of Example 12
And spherical aberration diagrams up to a numerical aperture of 0.65 for λ = 400 nm. FIGS. 83 and 84 show spherical aberration diagrams of the objective lens of Example 12 with respect to the wavelength λ = 780 nm up to numerical apertures 0.45 and 0.65, respectively. FIGS. 85 to 87 show wavefront aberration diagrams for the objective lens of Example 12 with respect to λ = 650 nm, λ = 400 nm, and λ = 780 nm, respectively.

The following shows the lens data of the twelfth embodiment.

Example 12 f = 3.31 Image side NA 0.65 magnification -0.203 (when wavelength λ = 650 nm) f = 3.14 Image side NA 0.65 magnification -0.190 (when wavelength λ = 400 nm) f = 3.34 Image side NA 0.45 ( NA 0.65) Magnification -0.205 (when wavelength λ = 780nm)

[0535]

[Table 12] Aspheric surface 1 κ = -0.08796008 Diffraction surface 1 B2 = 0 A4 = -0.010351744 B4 = -61.351934 A6 = 0.0015514472 B6 = 5.9668445 A8 = -0.00043894535 B8 = -1.2923244 A10 = 5.481801 × 10 ^-5 B10 = 0.041773541 A12 = -4.2588508 × 10 ^-6

Aspheric surface 2 κ = -302.6352 Diffraction surface 2 B2 = 0 A4 = 0.002 B4 = 341.19136 A6 = -0.0014 B6 = -124.16233 A8 = 0.0042 B8 = 49.877242 A10 = -0.0022 B10 = -5.9599182 A12 = 0.0004

In the optical pickup device having the objective lens and the three light sources as in the twelfth embodiment, each disk is corrected for the spherical aberration caused by the difference in the thickness of the transparent substrate and the chromatic aberration of the spherical aberration caused by the difference in the wavelength. It is possible to As is apparent from FIG. 84, the third optical disc has a numerical aperture NA of 0.4 in actual use.
The outside of 5 is a flare.

(Example 13)

The objective lens of Example 13 is another specific example of the objective lens according to the fourth embodiment, and is configured so that parallel light from an infinite distance enters.
In this embodiment, a square term and terms other than the square term are used as coefficients of the phase difference function of the diffraction surface.

FIGS. 88 to 90 show that the objective lens of Example 13 has λ = 650 nm, λ = 400 nm, and λ = 780.
The optical path diagram in nm is shown. 91 and 92.
Λ = 650 nm for the objective lens of Example 13
FIG. 4 shows spherical aberration diagrams up to a numerical aperture of 0.60 for λ = 400 nm. FIGS. 93 and 94 show spherical aberration diagrams of the objective lens of Example 13 up to a numerical aperture of 0.45 and 0.60 with respect to a wavelength λ = 780 nm, respectively. FIGS. 95 to 97 show wavefront aberration diagrams for the objective lens of Example 13 with respect to λ = 650 nm, λ = 400 nm, and λ = 780 nm, respectively.

The following shows the lens data of the thirteenth embodiment.

Example 13 f = 3.31 Image side NA 0.60 (when wavelength λ = 650 nm) f = 3.14 Image side NA 0.60 (when wavelength λ = 400 nm) f = 3.34 Image side NA 0.45 (NA 0.60) (wavelength λ (When = 780nm)

[0543]

[Table 13] Aspheric surface 1 κ = -0.3363369 Diffraction surface 1 B2 = -177.66083 A4 = -0.0025421455 B4 = -46.296284 A6 = -0.0010660122 B6 = -6.8014831 A8 = 4.7189743 x 10 ^-5 B8 = 1.6606499 A10 = 1.5406396 x 10 ^-6 B10 =- 0.39075825 A12 = -7.0004876 × 10 ^-6

Aspheric surface 2 κ = 43.44262 Diffraction surface 2 B2 = 241.52445 A4 = 0.002 B4 = 402.41974 A6 = -0.0014 B6 = -191.87213 A8 = 0.0042 B8 = 64.779696 A10 = -0.0022 B10 = -8.6741764 A12 = 0.0004

In this embodiment, since the square term and terms other than the square term are used as the coefficients of the phase difference function of the diffractive surface, the difference in spherical aberration and wavelength caused by the difference in the thickness of the transparent substrate. It is possible to correct the chromatic aberration of the spherical aberration and the axial chromatic aberration generated by each of the disks. In addition, as is apparent from FIG. 94, in the third optical disk, the outer side of the numerical aperture NA of 0.45 in practical use is a flare.

(Example 14)

The objective lens of Example 14 is a specific example of the objective lens according to the sixth embodiment. Parallel light having wavelengths of 400 nm and 650 nm is incident from an infinite distance, and divergent light having a wavelength of 780 nm is incident from a finite distance. It is configured to be incident. In this embodiment, a square term and terms other than the square term are used as coefficients of the optical path difference function of the diffraction surface.

FIG. 98 shows that the λ =
The optical path diagram at 400 nm is shown. FIGS. 99 and 101 show that the objective lens of Example 14 has λ = 4.
FIG. 4 shows spherical aberration diagrams up to a numerical aperture of 0.65 for 00 nm ± 10 nm, λ = 650 nm ± 10 nm, and λ = 780 nm ± 10 nm.

Hereinafter, the lens data of the fourteenth embodiment will be shown.

Example 14 f = Image side NA 0.65 (when wavelength λ = 650 nm) f = Image side NA 0.65 (when wavelength λ = 400 nm) f = Image side NA 0.45 (NA 0.65) (wavelength λ = 780 nm) When)

[0551]

[Table 14] Aspheric surface 1 κ = -2.080 Diffraction surface b2 = -0.51589 × 10-3 A4 = 0.18168 × 10 ^-1 b4 = -0.24502 × 10 ^-3 A6 = -0.91791 × 10 ^-3 b6 = 0.49557 × 10 ^-4 A8 = 0.16455 × 10 ^-3 b8 = -0.14497 × 10 ^-4 A10 = -0.11115 × 10 ^-4

Aspheric surface 2 κ = 3.1831 A4 = 0.14442 × 10 ^-1 A6 = -0.17506 × 10 ^-2 A8 = 0.21593 × 10 ^-4 A10 = 0.12534 × 10 ^-4

The present invention is not limited to the above embodiment. Although the diffraction is formed on both surfaces of the objective lens, it may be provided on one surface of an optical element in the optical system of the optical pickup device. Further, although the orbicular diffraction surface is formed on the entire lens surface, the diffraction surface may be partially formed. Furthermore, as a next-generation high-density optical disk using a blue laser, a light source wavelength of 4
Although the optical design was advanced on the assumption that the thickness of the transparent substrate was 00 nm and the thickness of the transparent substrate was 0.6 mm, the present invention can be applied to an optical disc having other specifications.

Next, a seventh embodiment of the present invention will be described.

FIG. 117 is a schematic configuration of the objective lens and the optical pickup device including the same according to the present embodiment. As shown in FIG. 117, a first semiconductor laser 111 and a second semiconductor laser 112 are unitized as light sources.
A beam splitter 120 is disposed between the collimator 13 and the objective lens 16, and the light substantially collimated by the collimator 13 passes through the beam splitter 120 and passes through the objective lens 1.
Go to 6. Further, the optical path is changed so that the light flux reflected from the information recording surface 22 is directed to the photodetector 30 by the beam splitter 120 as an optical path changing means. The objective lens 16 has a flange 16a on its outer periphery.
6a allows the objective lens 16 to be easily attached to the optical pickup device. Further, since the flange portion 16a has a surface extending in a direction substantially perpendicular to the optical axis of the objective lens 16, mounting with higher accuracy can be easily performed.

[0556] When reproducing the first optical disk, the light beam emitted from the first semiconductor laser 111 is reflected by the collimator 1
3 and becomes a parallel light flux. Furthermore, beam splitter 1
After passing through 20, the aperture 17 stops down, and the light is focused on the information recording surface 22 by the objective lens 16 via the transparent substrate 21 of the first optical disc 20. Then, the light flux modulated and reflected by the information pits on the information recording surface 22 passes through the objective lens 16 and the aperture 17 again and passes through the beam splitter 120.
Is reflected by the cylindrical lens 180, is given astigmatism by the cylindrical lens 180, passes through the concave lens 50, is incident on the photodetector 30, and is recorded on the first optical disc 20 using a signal output from the photodetector 30. A read signal of the obtained information is obtained.

Also, a change in the light amount due to a change in the shape and position of the spot on the photodetector 30 is detected, and focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 150 moves the objective lens 16 so that the light beam from the first semiconductor laser 111 forms an image on the information recording surface 22 of the first optical disk 20, and the first semiconductor laser Moving the objective lens 16 so that the light beam from the laser 111 is focused on a predetermined track;

Next, when reproducing the second optical disk,
The light beam emitted from the second semiconductor laser 112 passes through the collimator 13 and becomes a parallel light beam. Further, the light is stopped down by the stop 17 through the beam splitter 120, and is condensed by the objective lens 16 on the information recording surface 22 via the transparent substrate 21 of the second optical disc 20. The light flux modulated and reflected by the information pits on the information recording surface 22 is reflected again by the beam splitter 120 via the objective lens 16 and the aperture 17, is given astigmatism by the cylindrical lens 180, and is given a concave lens 50. After that, the signal is incident on the photodetector 30 and a signal for reading information recorded on the second optical disc 20 is obtained using a signal output from the photodetector 30. Further, a change in the light amount due to a change in the shape and position of the spot on the photodetector 30 is detected, and focus detection and track detection are performed. Based on this detection, the objective lens 16 is moved so that the light beam from the two-dimensional actuator 15 or the first semiconductor laser 112 is focused on the information recording surface 22 of the second optical disc 20, and the second semiconductor laser 112 is moved. The objective lens 16 is moved so that the light flux from the lens is focused on a predetermined track.

The objective lens (diffraction lens) 16 has a larger numerical aperture (maximum numerical aperture) among the numerical apertures required for recording and / or reproducing the first optical disc and the second optical disc.
Up to the incident light from each semiconductor laser,
It is designed to be 0.07 λrms or less for each wavelength (λ). For this reason, the wavefront aberration of each light beam on the image plane is 0.07λrms or less. Therefore, there is no flare during recording and / or reproduction of either optical disk on the imaging surface and on the detector 30.
The characteristics of focusing error detection and track error detection are improved.

The first optical disk is a DVD (light source wavelength 650 nm), and the second optical disk is a CD (light source wavelength 7
80 nm), the first optical disk may be a next-generation high-density optical disk (light source wavelength 400 nm), and the second optical disk may be a DVD (light source wavelength 650 nm). If there is a large difference in the number, in the above case, the spot may be too small compared to the required spot diameter. In this case, the aperture limiting means described elsewhere in this specification may be introduced to obtain a desired spot diameter.

Hereinafter, as a specific example of the objective lens according to the seventh embodiment, a practical example of a spherical aberration correcting lens,
16, 17, and 18 will be described. The wavefront aberration in each embodiment is
The maximum numerical aperture is corrected to 0.07λrms or less. In the following, the image side means the optical information recording medium side.

<Example 15>

FIG. 118 shows an optical path diagram of the diffractive optical lens (objective lens having a diffractive surface) which is the objective lens of the fifteenth embodiment. FIG. 119 shows the wavelength (λ) of the diffractive optical lens of Example 15 = 640, 650, 660n.
FIG. 4 shows spherical aberration diagrams up to a numerical aperture of 0.60 with respect to m. FIG. 120 shows an optical path diagram of the diffractive optical lens of Example 15 when the transparent substrate of the optical information recording medium is thicker than that in FIG. FIG. 121 shows spherical aberration diagrams of the diffractive optical lens in the case of FIG. 120 up to a numerical aperture of 0.60 for wavelengths λ = 770, 780, and 790 nm, respectively.

According to the diffractive optical lens of Embodiment 15, as shown in FIG. 119, for a wavelength λ = 650 nm, N
All apertures up to A0.60 are almost stigmatic. Further, as shown in FIGS. 120 and 121, when the transparent substrate is thick, there is almost no aberration up to NA 0.60 for a wavelength λ = 780 nm. Note that the predetermined numerical aperture when λ = 780 nm is 0.45.

As described above, in the fifteenth embodiment, the spherical aberration in the case where the transparent substrate of the optical information recording medium is thick and the wavelength is 780 nm is smaller in the transparent substrate than in the first, sixth and eighth embodiments. Is the same as the numerical aperture (NA
0.60).

[0566] The lens data of Example 15 is shown below.

When light source wavelength λ = 650 nm Focal length f = 3.33 Image side numerical aperture NA = 0.60 Infinite specification (parallel light beam incidence)

When light source wavelength λ = 780 nm, focal length f = 3.38, image side numerical aperture NA = 0.60, infinite specification

[0569]

[Table 15] Aspherical surface coefficient Aspherical surface 1 K = −1.0358 A ₄ = 4.8632 × 10 ⁻³ A ₆ = 5.3833 × 10 ⁻⁴ A ₈ = −1.5773 × 10 ⁻⁴ A ₁₀ = 3.8683 × 10 ^-7

Aspherical surface 2 K = −9.256352 A ₄ = 1.5887 × 10 ⁻² A ₆ = −5.97242 × 10 ⁻³ A ₈ = 1.11313 × 10 ⁻³ A ₁₀ = −9.33962 × 10 ^-5

Diffraction surface coefficient (reference wavelength: 650 nm) b ₂ = 6.00 × 10 ⁻³ b ₄ = −1.317 × 10 ⁻³ b ₆ = 1.5274 × 10 ⁻⁴ b ₈ = −6.5575 × 10 ^-5 b ₁₀ = 6.221 × 10 ^-6

<Example 16>

FIG. 122 shows an optical path diagram of the diffractive optical lens (objective lens having a diffractive surface) which is the objective lens of the sixteenth embodiment. FIG. 123 shows the wavelength (λ) of the diffractive optical lens of Example 16 = 640, 650, 660n.
FIG. 4 shows spherical aberration diagrams up to a numerical aperture of 0.60 with respect to m. FIG. 124 shows an optical path diagram of the diffractive optical lens of Example 16 when the transparent substrate of the optical information recording medium is thicker than FIG. FIG. 125 shows spherical aberration diagrams of the diffractive optical lens in the case of FIG. 124 up to a numerical aperture of 0.60 for wavelengths λ = 770, 780, and 790 nm, respectively.

According to the diffractive optical lens of Embodiment 16, as shown in FIG. 123, for a wavelength λ = 650 nm, N
All apertures up to A0.60 are almost stigmatic. As shown in FIGS. 124 and 125, when the transparent substrate is thick, there is almost no aberration up to NA 0.60 for a wavelength λ = 780 nm. Note that the predetermined numerical aperture when λ = 780 nm is 0.45.

As described above, in the sixteenth embodiment, the spherical aberration in the case where the transparent substrate of the optical information recording medium is thick and the wavelength is 780 nm is smaller in the transparent substrate than in the first, sixth and eighth embodiments. Is the same as the numerical aperture (NA
0.60). In Examples 15 and 16, in order to correct the spherical aberration due to the difference in the thickness of the transparent substrate to NA of 0.6, it is necessary that the spherical aberration due to diffraction has a strong correcting action. Is narrowed, but the paraxial power of diffraction is made negative to alleviate the decrease in pitch.

[0576] The lens data of Example 16 is shown below.

When light source wavelength λ = 650 nm Focal length f = 3.33 Image side numerical aperture NA = 0.60 Infinite specification

When light source wavelength λ = 780 nm, focal length f = 3.36, image side numerical aperture NA = 0.60, infinite specification

[0579]

[Table 16] Aspherical surface coefficient Aspherical surface 1 K = −1.1331 A ₄ = 4.5375 × 10 ⁻³ A ₆ = 1.2964 × 10 ⁻³ A ₈ = −3.6164 × 10 ⁻⁴ A ₁₀ = 2.0765 × 10 ^-5

Aspheric surface 2 K = −4.356298 A ₄ = 1.57427 × 10 ⁻² A ₆ = −4.91198 × 10 ⁻³ A ₈ = 7.72605 × 10 ⁻⁴ A ₁₀ = −5.775456 × 10 ^-5

Diffraction surface coefficient (reference wavelength: 650 nm) b ₂ = 2.1665 × 10 ⁻³ b ₄ = −2.0272 × 10 ⁻³ b ₆ = 5.5178 × 10 ⁻⁴ b ₈ = −1.8391 × 10 ^-4 b ₁₀ = 1.8148 × 10 ^-5

<Example 17>

FIG. 126 shows an optical path diagram of the diffractive optical lens (objective lens having a diffractive surface) which is the objective lens of the seventeenth embodiment. FIG. 127 shows the wavelength (λ) of the diffractive optical lens of Example 17 = 640, 650, 660n.
FIG. 4 shows spherical aberration diagrams up to a numerical aperture of 0.60 with respect to m. FIG. 128 shows an optical path diagram of the diffractive optical lens of Example 17 when the transparent substrate of the optical information recording medium is thicker than that of FIG. FIG. 129 shows spherical aberration diagrams of the diffractive optical lens in the case of FIG. 128 up to a numerical aperture of 0.60 for wavelengths λ = 770, 780, and 790 nm, respectively.

According to the diffractive optical lens of the seventeenth embodiment, as shown in FIG. 127, for a wavelength λ = 650 nm, N
All apertures up to A0.60 are almost stigmatic. Further, as shown in FIGS. 128 and 129, when the transparent substrate is thick, there is almost no aberration up to NA 0.60 for a wavelength λ = 780 nm. Note that the predetermined numerical aperture when λ = 780 nm is 0.45. In Examples 15 to 17, the axial chromatic aberration is different, and the ring pitch is also different.

As described above, in the seventeenth embodiment, the spherical aberration in the case where the transparent substrate of the optical information recording medium is thick and the wavelength is 780 nm is smaller than that in the first, sixth and eighth embodiments. Is the same as the numerical aperture (NA
0.60).

[0586] The lens data of Example 17 is shown below.

When light source wavelength λ = 650 nm Focal length f = 3.33 Image side numerical aperture NA = 0.60 Infinite specification

When light source wavelength λ = 780 nm, focal length f = 3.34, image side numerical aperture NA = 0.60, infinite specification

[0589]

[Table 17] Aspherical surface coefficient Aspherical surface 1 K = −1.0751 A ₄ = 5.0732 × 10 ⁻³ A ₆ = 4.3722 × 10 ⁻⁴ A ₈ = −1.4774 × 10 ⁻⁴ A ₁₀ = 9.6694 × 10 ^-7

Aspheric surface 2 K = -10.41111 A ₄ = 1.59463 × 10 ⁻² A ₆ = −6.0293 × 10 ⁻³ A ₈ = 1.11268 × 10 ⁻³ A ₁₀ = −9.3151 × 10 ^-5

Diffraction surface coefficient (reference wavelength 650 nm) b ₂ = −2.000 × 10 ⁻³ b ₄ = −1.4462 × 10 ⁻³ b ₆ = 1.1331 × 10 ⁻⁴ b ₈ = −6.6621 × 10 ^-5 b ₁₀ = 6.8220 × 10 ^-6

<Embodiment 18>

FIG. 130 shows an optical path diagram of the diffractive optical lens (objective lens having a diffractive surface) which is the objective lens of the eighteenth embodiment. FIG. 131 shows the wavelength (λ) of the diffractive optical lens of Example 18 = 390, 400, 410n.
FIG. 4 shows a spherical aberration diagram for a numerical aperture up to 0.70. FIG. 132 shows an optical path diagram of the diffractive optical lens of Example 18 when the transparent substrate of the optical information recording medium is thicker than FIG. FIG. 133 shows spherical aberration diagrams of the diffractive optical lens in the case of FIG. 132 up to a numerical aperture of 0.70 for wavelengths λ = 640, 650, and 660 nm, respectively.

According to the diffractive optical lens of Example 18, as shown in FIG.
All apertures up to A0.70 are almost stigmatic. Further, as shown in FIGS. 132 and 133, when the transparent substrate is thick, there is almost no aberration up to NA 0.70 for a wavelength λ = 650 nm.

As described above, in the seventeenth embodiment, the spherical aberration in the case where the transparent substrate of the optical information recording medium is thick and the wavelength is 650 nm is smaller in the transparent substrate than in the first, sixth and eighth embodiments. Is the same numerical aperture (NA
0.70).

Hereinafter, the lens data of Example 18 will be shown.

When light source wavelength λ = 400 nm, focal length f = 3.33, image side numerical aperture NA = 0.70, infinite specification

When light source wavelength λ = 650 nm Focal length f = 3.43 Image side numerical aperture NA = 0.70 Infinite specification

[0599]

[Table 18] Aspherical surface coefficient Aspherical surface 1 K = 0.0 A ₄ = −7.9616 × 10 ⁻⁴ A ₆ = −5.7265 × 10 ⁻⁴ A ₈ = 8.3209 × 10 ⁻⁵ A ₁₀ = −4.1599 × 10 ^-5

Aspherical surface 2 K = 0.0 A ₄ = 3.11131 × 10 ^-2 A ₆ = −1.18548 × 10 ⁻² A ₈ = 1.63937 × 10 ⁻³ A ₁₀ = −6.60514 × 10 ^-5

Diffraction surface coefficient (reference wavelength: 400 nm) b ₂ = −1.4046 × 10 ⁻³ b ₄ = −8.6959 × 10 ⁻⁴ b ₆ = 2.3488 × 10 ⁻⁴ b ₈ = −5.2455 × 10 ^-5 b ₁₀ = 3.6385 × 10 ^-6

Next, the pitch of a plurality of annular zones of each of the diffractive optical lenses of Examples 1 to 3 and 14 to 18 will be described. The plurality of orbicular zones are formed substantially concentrically around the optical axis, and have a pitch Pf (mm) of the orbicular zones corresponding to the maximum numerical aperture on the image side of the lens, and a numerical aperture of の of the maximum numerical aperture. The pitches of the annular zones Ph (mm) and ((Ph / P
Table 19 shows each value of f) -2).

[0603]

[Table 19] 0.4 ≦ | (Ph / Pf) −2 | ≦ 25 (b1)

According to a further study by the present inventors, when the above-mentioned expression (b1) is satisfied, that is, when the value is equal to or more than the lower limit of this expression, the effect of diffraction for correcting high-order spherical aberration is weakened. Therefore, the difference in spherical aberration between the two wavelengths caused by the difference in the thickness of the transparent substrate can be corrected by the effect of diffraction. If the difference is less than the upper limit, the pitch of the diffraction ring zone becomes too small. It has been found that it is difficult to produce such a lens, and it becomes possible to manufacture a lens having high diffraction efficiency.

The above relational expression is preferably the following expression (b2), and more preferably expression (b3).

0.8 ≦ | (Ph / Pf) −2 | ≦ 6.0 (b2)

1.2 ≦ | (Ph / Pf) −2 | ≦ 2.0 (b3)

Next, an eighth embodiment of the present invention will be described.

The required numerical aperture NA1 on the optical information recording medium side of the objective lens required for recording and reproducing a DVD using a light source having a wavelength of 650 nm is about 0.6, and reproducing a CD using a light source having a wavelength of 780 nm. The required numerical aperture NA2 of the objective lens on the optical information recording medium side required for the recording is about 0.45 (about 0.5 for recording). Therefore, the above-mentioned diffraction pattern for aberration correction is not essential up to the numerical aperture NA1.

Further, since the depth of focus is large near the optical axis and the amount of spherical aberration is small, the diffraction pattern is not essential.

[0611] By forming a diffraction pattern on the minimum necessary portion and using the remaining portion as a refracting surface, damage to the tool at the time of mold processing, improvement in mold releasability at the time of molding, unnecessarily on the CD side It is possible to prevent performance degradation when there is an error in the thickness of the disc due to the focusing spot being narrowed or when the disc is tilted.

For this purpose, the diffraction pattern of the objective lens is rotationally symmetric with respect to the optical axis, and the luminous flux from the first light source is reflected from the circumference of the diffraction pattern of the objective lens that is most distant from the optical axis. The + 1st-order diffracted light is converted into a luminous flux whose numerical aperture of the optical information recording medium is NAH1, and the + 1st-order diffracted light of the luminous flux from the first light source from the circumference closest to the optical axis of the diffraction pattern of the diffraction pattern of the objective lens is: When the numerical aperture on the optical information recording medium side is converted into a light beam of NAL1, the following condition may be satisfied. NAH1 <NA1 0 ≤ NAL1 ≤ NA2

If the first optical information recording medium is a DVD, the wavelength λ1 of the first light source is 650 nm, and the second optical information recording medium is a CD, the wavelength λ2 of the second light source or 780 nm, NAH1 is 0. 43 to 0.55 NAL1 is preferably 0.10 to 0.40.

The optical design of the objective lens for the portion having the diffraction pattern is performed so that the + 1st-order diffracted light of the light beam incident on the objective lens from the first light source becomes an almost aberration-free condensed spot. On the other hand, the optical design of the objective lens with respect to the portion having no diffraction pattern is performed such that the light beam incident on the objective lens from the first light source becomes a substantially aberration-free focused spot.

[0615] The light condensing positions of both need to be substantially coincident. Furthermore, it is important that the phases of the respective light beams are also aligned. Regarding the phase, when k is a small integer, even if the phase shifts by 2kπ, the light-collecting characteristics at the design wavelength hardly change, but when the absolute value of | k |
It becomes vulnerable to wavelength fluctuation. | K | is preferably 1 to 10.

At this time, of the luminous flux from the second light source,
The + 1st-order diffracted light from the circumference farthest from the optical axis of the diffraction pattern of the objective lens has a numerical aperture of NAH on the optical information recording medium side.
2, and at the same time, the + 1st-order diffracted light from the circumference of the diffraction pattern closest to the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAL2,

[0617] A spot enabling recording and reproduction on the second optical information recording medium is illuminated by using a light flux having a numerical aperture of NAH2 or less when passing through the objective lens among the light flux from the second light source. The objective lens is formed such that the light-condensing position and the phase difference between the light beam from the portion having the diffraction pattern and the light beam from the portion without the diffraction pattern are optimal, so as to be formed on the information recording surface of the information recording medium. The spherical aberration of the transmitted light beam is set.

Actually, among the light beams from the first light source, the light beam having a numerical aperture of not more than NA1 when passing through the objective lens is the wavefront at the best image point through the transparent substrate of the first optical information recording medium. The aberration is 0.07λrms or less, and
Of the luminous flux from the second light source, the luminous flux having a numerical aperture of not more than NAH2 when passing through the objective lens has a wavefront aberration of 0. 0 at the best image point through the transparent substrate of the second optical information recording medium.
It is desirable to be not more than 07λrms.

In particular, among the light beams from the first light source, the light beam having a numerical aperture of not more than NA1 when passing through the objective lens is the wavefront at the best image point through the transparent substrate of the first optical information recording medium. It is desirable that the spherical aberration component of the aberration is 0.05 λrms or less.

At least one collimator is provided between the first light source and the objective lens and between the second light source and the objective lens, and a light beam incident on the objective lens from the first light source and from the second light source to the objective lens By using an optical pickup device in which incident light beams are parallel lights,
Adjustment of the pickup becomes easy.

Also, by using a common collimator for the light beam from the first light source and the light beam from the second light source, the cost of the optical pickup device can be reduced.

When the first light source and the second light source are separate packages, the positions of the respective light sources with respect to the collimator may be set such that the light beams incident on the objective lens become parallel lights. .

When the first light source and the second light source are in the same package, the difference between the positions of the respective light sources in the direction of the optical axis is appropriately set so that the light incident on the objective lens is parallel light. Alternatively, when the adjustment cannot be performed, the collimator whose chromatic aberration is optimized may be used so that the light incident on the objective lens becomes parallel light.

Further, the light beam incident on the objective lens may be a convergent light beam or a divergent light beam. In particular, the light beam incident on the objective lens from the second light source rather than the light beam incident on the objective lens from the first light source. By making the luminous flux having a higher divergence, under spherical aberration occurs due to the difference in the divergence, and the amount of spherical aberration corrected by the diffraction pattern can be reduced.

FIG. 114 shows a case where the numerical apertures NAH2 and NAL2 are the same and paraxial chromatic aberration is not corrected (ΔfB = 0).
FIG. 2 is a schematic diagram illustrating spherical aberration of a light beam that has passed through a transparent substrate of an optical information recording medium (CD).

The convergence position of the luminous flux contributing to the reproduction of the second optical information recording medium of NAH2 or less is at point B when not corrected by the diffraction pattern, but is corrected by the diffraction pattern, and ΔfB is made substantially zero. To converge on point A. However, the aberration is not corrected by the diffraction pattern outside NAH2, and the aberration is represented by the aberration curve S due to only the refraction surface.
Will be shown.

As is clear from the figure, the convergence point of the light beam and N
The jump of the spherical aberration in AH2 increases by the correction amount ΔfB of the paraxial chromatic aberration, and the position where the flare component from NAH2 to NA1 converges is the convergence position of the light beam contributing to the reproduction of the second optical information recording medium of NAH2 or lower. And the influence of the flare component on the photodetector is reduced.

Also, by correcting the paraxial chromatic aberration at λ1 and λ2, the paraxial chromatic aberration is reduced near λ1 and λ2, and when recording information on the optical information recording medium, the oscillation wavelength is changed due to laser power fluctuation. Does not easily occur, and high-speed recording becomes possible.

As described above, in order to keep the convergence position of the flare component from NAH2 to NA1 and the convergence position of the light beam equal to or smaller than NAH2, the second diffraction pattern must be placed outside the diffraction pattern. The + 1st-order diffracted light of the second diffraction pattern is converged on the convergence position for the light beam from the first light source, and the light beam from the second light source is not diffracted by the second diffraction pattern. By designing the second diffraction pattern so as to transmit the light, the aberration correction situation shown in FIG. 115 can be obtained.

[0630] That is, Fig. 60A shows the state of correction of the aberration of the light beam from the first light source, and the aberration due to the relatively large refraction surface is equal to or less than the NAH1. As a result, the light is focused on the convergence position without aberration. However, as shown in FIG.
The light beam from the light source is a zero-order light beam that does not undergo a diffraction effect when the light beam passes through a diffraction pattern portion outside the NAH2. Therefore, the aberration correction state shows an aberration that is not corrected by the diffraction pattern. , The convergence position of the flare component and the convergence position of the luminous flux contributing to the reproduction of information are largely separated, so that the influence of the flare component on the photodetector is reduced.

In this second diffraction pattern, the first diffraction pattern
The second diffraction pattern may be designed so that the light beam from the light source is not diffracted, and the light beam from the second light source mainly becomes -1st-order diffracted light. As a result, as shown in FIG. 113, the spherical aberration due to the diffraction of the light beams from NAH2 to NA1 is made to be more excessive, so that the second light source has a light beam having a numerical aperture of not more than NAH2 when passing through the objective lens. The spherical aberration when passing through the transparent substrate of the second optical information recording medium is well corrected, while the spherical aberration of the light beam outside the NAH2 can be increased. As a result, as shown in FIG.
, The convergence position of the flare component and the convergence position of the luminous flux contributing to the reproduction of information are largely separated, so that the influence of the flare component on the photodetector is reduced.

Similarly, the light beam from the first light source is transmitted in the optical path from the light source to the objective lens, and passes through the region of the light beam of the second light source opposite to the optical axis of the first diffraction pattern. By providing an aperture limiting means that does not allow the transmitted light flux to pass, and reducing the flare component reaching the photodetector, the effect can be reduced.

The aperture restricting means transmits the light beam from the first light source through the optical path after the light beam emitted from the first light source and the light beam emitted from the second light source are combined by the light combining means. An annular filter that reflects or absorbs a light beam that passes through a region of the light beam of the second light source that is opposite to the optical axis of the first diffraction pattern may be provided.

As such a filter, for example, a dichroic filter using a multilayer film can be used. Of course, any of the surfaces of the objective lens can have the above-described filter effect.

[0635] Also, the aperture limiting means is an orbicular zone that transmits a light beam from the first light source and diffracts a light beam of the second light source that passes through a region opposite to the optical axis of the diffraction pattern. It may be a filter.

Hereinafter, first to seventh optical pickup devices according to an eighth embodiment of the present invention will be described in detail with reference to the drawings.

The first optical pickup device shown in FIG. 102 has a semiconductor laser 111 as a first light source for reproducing a first optical disk and a semiconductor laser 112 for reproducing a second optical disk.

First, when reproducing the first optical disk, a beam is emitted from the first semiconductor laser 111, and the emitted light beam passes through the beam splitter 190, which is a means for combining the light emitted from both semiconductor lasers 111 and 112. Then, the light passes through the polarization beam splitter 120, the collimator 130, and the quarter-wave plate 14, and becomes a parallel light beam of circular polarization. This light beam is stopped down by the stop 170, and is focused on the information recording surface 220 via the transparent substrate 210 of the first optical disc 200 by the objective lens 160.

[0639] The light flux modulated and reflected by the information bit on the information recording surface 220 is again reflected by the objective lens 160,
The light passes through the stop 170, the quarter-wave plate 140, and the collimator 130, enters the polarization beam splitter 120, is reflected there, is given astigmatism by the cylindrical lens 18, and is incident on the photodetector 300. Using the output signal, a signal for reading information recorded on the first optical disc 200 is obtained.

Also, by detecting a change in the light amount due to a change in the shape and position of the spot on the photodetector 300, focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 150 moves the objective lens 160 so that the light beam from the first semiconductor laser 111 forms an image on the recording surface 220 of the first optical disc 200, and the light beam from the semiconductor laser 111 The objective lens 160 is moved so that is imaged on a predetermined track.

In reproducing the second optical disk, a beam is emitted from the second semiconductor laser 112, and the emitted light beam is reflected by a beam splitter 190 which is a light combining means, and is emitted in the same manner as the light beam from the first semiconductor 111. The light is condensed on the information recording surface 220 via the transparent substrate 210 of the second optical disc 200 via the polarizing beam splitter 120, the collimator 130, the quarter-wave plate 140, the stop 170, and the objective lens 160.

[0641] The light flux modulated and reflected by the information pits on the information recording surface 220 is again reflected by the objective lens 16.
0, stop 170, quarter-wave plate 140, collimator 13
0, the light enters the photodetector 300 via the polarizing beam splitter 120 and the cylindrical lens 180, and a read signal of information recorded on the second optical disc 200 is obtained using the output signal.

Also, as in the case of the first optical disk, a change in the light amount due to a change in the shape or position of the spot on the photodetector 300 is detected, focus detection and track detection are performed, and the two-dimensional actuator 150 The objective lens 160 is moved for focusing and tracking.

[0644] The second optical pickup device shown in FIG.
Although the configuration is suitable for an optical system for recording and reproduction, the case of reproduction will be described. In the following embodiment, FIG.
The same members as those of the optical pickup device 02 are denoted by the same reference numerals.

When reproducing the first optical disk, a beam is emitted from the first semiconductor laser 111, and the emitted light beam is reflected by the polarization beam splitter 121, and passes through the collimator 131 and the quarter-wave plate 141. It becomes parallel light of circular polarization. Further, the light passes through a beam splitter 190 as a light synthesizing means, is stopped down by a stop 170, and is transmitted through a transparent substrate 21 of the first optical disc 200 by an objective lens 160.
The light is condensed on the information recording surface 220 through 0.

[0646] The light flux modulated and reflected by the information bit on the information recording surface 220 is again reflected by the objective lens 160,
Via an aperture 170, a beam splitter 190,
The light passes through the 波長 wavelength plate 141 and the collimator 131, enters the polarization beam splitter 121, passes through it, is given astigmatism, enters the photodetector 301, and uses the output signal to A read signal of information recorded on the first optical disc 200 is obtained.

[0647] Further, by detecting a change in the light amount due to a change in the shape and position of the spot on the photodetector 301, focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 150 moves the objective lens 160 so that the light beam from the first semiconductor laser 111 forms an image on the recording surface 220 of the second optical disc 200, and the light beam from the semiconductor laser 111 The objective lens 160 is moved so that is imaged on a predetermined track.

When reproducing the second optical disc, a beam is emitted from the second semiconductor laser 112, and the emitted light beam is reflected by the polarization beam splitter 122, passes through the collimator 132, and passes through the quarter-wave plate 142. It becomes parallel light of circular polarization. Further, the light is reflected by a beam splitter 190 which is a light combining means, and is condensed on an information recording surface 220 via a transparent substrate 210 of the second optical disc 200 by a stop 170 and an objective lens 160.

The light flux modulated and reflected by the information bits on the information recording surface 220 is again reflected by the objective lens 160 and
The light is reflected by the beam splitter 190 via the stop 170, passes through the 波長 wavelength plate 142 and the collimator 132, enters the polarization beam splitter 122, passes therethrough, is given astigmatism, and is given a photodetector 302. Incident on it,
Using the output signal, a read signal of information recorded on the second optical disc 200 is obtained.

[0650] Also, by detecting a change in the light amount due to a change in the shape and position of the spot on the photodetector 302, focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 150 moves the objective lens 160 so that the light beam from the second semiconductor laser 112 forms an image on the recording surface 220 of the first optical disc 200, and the light beam from the semiconductor laser 112 Moving the objective lens 160 so as to form an image on a predetermined track is the same.

The third optical pickup device shown in FIG.
Although the configuration is suitable for an optical system for recording and reproduction, the case of reproduction will be described.

In reproducing the first optical disk, a beam is emitted from the first semiconductor laser 111 and transmitted through the coupling lens 60 for reducing the degree of divergence of the divergent light beam, the beam splitter 190 as a light combining means, and the beam splitter 120. Then, the light passes through the collimator 130 and the quarter-wave plate 140 to become circularly polarized parallel light. Further, the aperture is stopped down by the stop 170 and the first
Is focused on the information recording surface 220 via the transparent substrate 210 of the optical disc 200.

The light flux modulated and reflected by the information bit on the information recording surface 220 is again reflected by the objective lens 160,
The light passes through the 波長 wavelength plate 140 and the collimator 130 via the stop 170 and is incident on the beam splitter 120.
Here, the reflected light is given astigmatism by the cylindrical lens 180, enters the photodetector 301 via the concave lens 50, and uses the output signal thereof to generate the first optical disc 2.
A read signal of the information recorded at 00 is obtained.

Also, a change in light amount due to a change in the shape and position of the spot on the photodetector 301 is detected, and focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 150 moves the objective lens 160 so that the light beam from the first semiconductor laser 111 is focused on the recording surface 220 of the first optical disc 200, and the light beam from the semiconductor laser 111 is The objective lens 160 is moved so that an image is formed on a predetermined track.

[0655] The second semiconductor laser 112 for reproducing the second optical disk is a laser / detector integrated unit 40.
At 0, the light detector 302 and the hologram 230 are unitized. “Unit” or “unitization” means that the members and means that are unitized can be integrated into an optical pickup device, and are assembled as one part when assembling the device. Can be put on is tight.

[0656] The light beam emitted from the second semiconductor laser 112 passes through the hologram 230, is reflected by the beam splitter 190 as a light combining means, and is reflected by the beam splitter 1.
20, a collimator 130, and a quarter-wave plate 140 to become a parallel light flux. Further, aperture 170, objective lens 160
Is focused on the information recording surface 220 via the transparent substrate 210 of the second optical disc 200.

[0657] The light beam modulated and reflected by the information pits on the information recording surface 220 is again reflected by the objective lens 16.
0, the light passes through the quarter-wave plate 140, the collimator 130, and the beam splitter 120 via the stop 170, is reflected by the beam splitter 190, is diffracted by the hologram 230, and is incident on the photodetector 302. Thus, a read signal of information recorded on the second optical disc 200 is obtained.

[0658] Also, a change in the light amount due to a change in the shape or position of the spot on the photodetector 302 is detected, focus detection or track detection is performed, and a two-dimensional actuator 150 is used for focusing and tracking. The lens 160 is moved.

In the fourth optical pickup device of FIG. 105, when reproducing the first optical disk, the first semiconductor laser 111 is unitized with the photodetector 301 and the hologram 231 by the integrated laser / detector unit 410. The light beam emitted from the first semiconductor laser 111 passes through the hologram 231 and passes through the beam splitter 190 and the collimator 130, which are light combining means, to become a parallel light beam. It is further stopped down by the stop 170, and the objective lens 16
By 0, the light is focused on the information recording surface 220 via the transparent substrate 210 of the first optical disc 200.

[0660] The light beam modulated and reflected by the information pits on the information recording surface 220 is again reflected by the objective lens 16.
0, the light passes through the collimator 130 and the beam splitter 190 via the stop 170, is diffracted by the hologram 231 and is incident on the photodetector 301.
A read signal of information recorded on the first optical disc 200 is obtained.

Also, a change in the amount of light due to a change in the shape and position of the spot on the photodetector 302 is detected, and focus detection and track detection are performed. The two-dimensional actuator 150 is used for focusing and tracking. The lens 160 is moved.

When reproducing the second optical disk, the second semiconductor laser 112 is controlled by the laser / detector integrated unit 42.
The light beam emitted from the second semiconductor laser 112 is unitized with the photodetector 302 and the hologram 232.
The light passes through the hologram 232, is reflected by the beam splitter 190 that is a light combining unit, passes through the collimator 130, and becomes a parallel light flux. Further, aperture 170, objective lens 16
The light is condensed on the information recording surface 220 via the transparent substrate 210 of the second optical disc 200 via the optical disc 200.

The light beam modulated and reflected by the information pits on the information recording surface 220 is again reflected by the objective lens 16.
0, transmitted through the collimator 130 through the aperture 170,
The hologram 232 is reflected by the beam splitter 190,
The light is diffracted by the light source and is incident on the photodetector 302, and a read signal of information recorded on the second optical disc 200 is obtained using the output signal.

Also, a change in the amount of light due to a change in the shape or position of the spot on the photodetector 302 is detected, and focus detection or track detection is performed. The objective lens 160 is moved for tracking.

In the fifth optical pickup device shown in FIG. 106, the first semiconductor laser 111 and the second semiconductor laser 1
12, the light detecting means 30 and the hologram 230 are unitized as a laser / detector integrated unit 430.

When reproducing the first optical disk, the light beam emitted from the first semiconductor laser 111 is reflected on the hologram 2
30, the light passes through the collimator 130 and becomes a parallel light flux. Further, the aperture is stopped down by the stop 170, and the light is focused on the information recording surface 220 by the objective lens 160 via the transparent substrate 210 of the first optical disc 200.

The light beam modulated and reflected by the information pits on the information recording surface 220 is again
0, transmitted through the collimator 130 through the aperture 170,
The light is diffracted by the hologram 230 and is incident on the photodetector 300, and a read signal of information recorded on the first optical disc 200 is obtained using the output signal.

Also, by detecting a change in the light amount due to a change in the shape and position of the spot on the photodetector 300, focus detection and track detection are performed, and a two-dimensional actuator 150 is used for focusing and tracking. The lens 160 is moved.

When reproducing the second optical disk, the light beam emitted from the second semiconductor laser 112 is reflected by the hologram 2
30, the light passes through the collimator 130 and becomes a substantially parallel light flux. Further, the second light passes through an aperture 170 and an objective lens 160.
Is focused on the information recording surface 220 via the transparent substrate 210 of the optical disc 200.

[0670] The light beam modulated and reflected by the information pits on the information recording surface 220 is again reflected by the objective lens 16.
0, transmitted through the collimator 130 through the aperture 170,
The light is diffracted by the hologram 230 and is incident on the photodetector 300, and a read signal of information recorded on the second optical disc 200 is obtained using the output signal.

Also, a change in the amount of light due to a change in the shape and position of the spot on the photodetector 300 is detected, and focus detection and track detection are performed. The objective lens 160 is moved for tracking.

In the sixth optical pickup device shown in FIG. 107, the first semiconductor laser 111 and the second semiconductor laser 1
12. First light detecting means 301, second light detecting means 30
2. Hologram 230 is laser / detector integrated unit 4
It is unitized as 30.

When reproducing the first optical disk, the luminous flux emitted from the first semiconductor laser 111 is the hologram 2
The light is transmitted through the collimator 130 on the surface of the disk 30 on the disk side and becomes a parallel light flux. Further, the aperture is stopped down by the stop 170, and the transparent substrate 2 of the first optical disc 200 is stopped by the objective lens 160.
The light is condensed on the information recording surface 220 via.

The light beam modulated and reflected by the information pits on the information recording surface 220 is again reflected by the objective lens 16.
0, transmitted through the collimator 130 through the aperture 170,
The light is diffracted by the surface of the hologram 230 on the disk side, enters the photodetector 301 corresponding to the first light source, and a read signal of information recorded on the first optical disk 200 is obtained using the output signal. .

Also, by detecting a change in the light amount due to a change in the shape or position of the spot on the photodetector 301, focus detection or track detection is performed, and a two-dimensional actuator 150 is used for focusing and tracking. The lens 160 is moved.

When reproducing the second optical disk, the light beam emitted from the second semiconductor laser 112 is reflected by the hologram 2
30 is diffracted by the surface on the semiconductor laser side, and the collimator 1
The light passes through 30 and becomes a substantially parallel light beam. The surface of the hologram on the semiconductor laser side functions as a light combining means. Further, the second light passes through an aperture 170 and an objective lens 160.
Is focused on the information recording surface 220 via the transparent substrate 210 of the optical disc 200.

[0677] The light beam modulated and reflected by the information pits on the information recording surface 220 is again reflected by the objective lens 16.
0, transmitted through the collimator 130 through the aperture 170,
The light is diffracted on the disk-side surface of the hologram 230 and is incident on the photodetector 302 corresponding to the second light source, and a read signal of information recorded on the second optical disk 200 is obtained using the output signal.

Also, a change in the light amount due to a change in the shape or position of the spot on the photodetector 302 is detected, and focus detection or track detection is performed. The objective lens 160 is moved for tracking.

The seventh optical pickup device shown in FIG.
Although the configuration is suitable for an optical system for recording and reproduction, the case of reproduction will be described.

When reproducing the first optical disk, a beam is emitted from the first semiconductor laser 111 and transmitted through the coupling lens 60 for reducing the degree of divergence of the divergent light beam, the beam splitter 190 as a light combining means, and the beam splitter 120. Then, the light passes through the collimator 130 and the quarter-wave plate 140 to become circularly polarized parallel light. Further, the aperture is stopped down by the stop 170 and the first
Is focused on the information recording surface 220 via the transparent substrate 210 of the optical disc 200.

The light flux modulated and reflected by the information bits on the information recording surface 220 is again reflected by the objective lens 160,
The light passes through the 波長 wavelength plate 140 and the collimator 130 via the stop 170 and is incident on the beam splitter 120.
Here, the reflected light is given astigmatism by the cylindrical lens 180, enters the photodetector 301 via the concave lens 50, and uses the output signal thereof to generate the first optical disc 2.
A read signal of the information recorded at 00 is obtained.

Also, by detecting a change in light amount due to a change in the shape and position of the spot on the photodetector 301, focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 150 moves the objective lens 160 so that the light beam from the first semiconductor laser 111 is focused on the recording surface 220 of the first optical disc 200, and the light beam from the semiconductor laser 111 is The objective lens 160 is moved so that an image is formed on a predetermined track.

The second semiconductor laser 112 for reproducing the second optical disk is the laser / detector integrated unit 40.
At 0, the light detector 302 and the hologram 230 are unitized.

[0684] The light beam emitted from the second semiconductor laser 112 passes through the hologram 230, is reflected by the beam splitter 190 which is a light combining means, and is reflected by the beam splitter 1.
20, a collimator 130, and a quarter-wave plate 140 to become a parallel light flux. Further, aperture 170, objective lens 160
Is focused on the information recording surface 220 via the transparent substrate 210 of the second optical disc 200.

[0686] The light beam modulated and reflected by the information pits on the information recording surface 220 is again reflected by the objective lens 16
0, the light passes through the quarter-wave plate 140, the collimator 130, and the beam splitter 120 via the stop 170, is reflected by the beam splitter 190, is diffracted by the hologram 230, and is incident on the photodetector 302. Thus, a read signal of information recorded on the second optical disc 200 is obtained.

Also, a change in the light amount due to a change in the shape and position of the spot on the photodetector 302 is detected to detect focus and track, and a two-dimensional actuator 150 is used to detect an object for focusing and tracking. The lens 160 is moved.

The thickness t1 of the transparent substrate is almost the same as that of the first optical disc, and the required numerical aperture NA of the objective lens on the optical information recording medium side required for recording and reproducing with the first light source having the wavelength λ1 is also the same. A third Super equivalent to one optical disc
A case of recording and reproducing a RENS type disc will be described.

[0688] The disc of the Super RENS system is
Currently being studied energetically, an example of the configuration is shown in FIG. The recording / reproduction is based on near-field optics, and there are a method using reflected light and a method using transmitted light as a reproduction signal. The configuration of this embodiment shows a method for obtaining a reproduction signal using transmitted light.

When recording / reproducing a third disc of the Super RENS system, a beam is emitted from the first semiconductor laser 111 to reduce the degree of divergence of a divergent light beam, and the beam splitter 190 is a light combining means. , Through the beam splitter 120, and further through the collimator 130 and the 波長 wavelength plate 140 to become a parallel light flux. Further, the aperture is stopped down by the stop 170 and the transparent substrate 21 of the first optical disc 200 is stopped by the objective lens 160.
0, the light is condensed on the nonlinear optical film 250 via the first protective film 240. A minute opening is formed in the nonlinear optical film 250, and energy is transmitted to the information recording surface 220 on the information recording layer via the second protective film 260. The light modulated by the information pits and transmitted through the information recording surface 220 passes through the third protective film 270, is collected by the condenser lens 90 on the side opposite to the objective lens, and reaches the photodetector 305. The read signal of the information recorded on the third optical disc 200 is obtained from the output signal.

On the other hand, the light beam reflected from the nonlinear optical film 250 passes through the objective lens 160 and the stop 170 again,
The light passes through the quarter-wave plate 140 and the collimator 130, enters the beam splitter 120, is reflected there, is given astigmatism by the cylindrical lens 180, and is incident on the photodetector 301 via the concave lens 50. I do. By detecting a change in the light amount due to a change in the shape and position of the spot on the photodetector 301, focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 150 converts the light beam from the first semiconductor laser 111 into the first optical disc 20.
Objective lens 1 to form an image on the non-linear optical film 250
The objective lens 160 is moved so that the light beam from the semiconductor laser 111 is focused on a predetermined track.
To move.

As an objective lens of the above-described optical pickup device, a stray aberration-free parallel light beam enters from the first light source,
Using a special objective lens designed to form an aberration-free spot through the transparent substrate of D, parallel light having no aberration from the second light source is incident on the objective lens, and the spot is passed through the transparent substrate of the CD. If it is formed, the wavelength dependence of the refractive index of the objective lens causes a difference in the thickness of the transparent substrate of the optical information recording medium.The wavelength dependence of the refractive index of the transparent substrate causes spherical aberration, but it has already been mentioned that this is mostly due to .

The spherical aberration caused by this factor is almost equal to | t2−t at the numerical aperture NA2 required for recording and reproduction of CD.
1 | and (NA2) ⁴ . FIG. 110 shows a special lens designed to be aberration-free through a transparent substrate of a DVD when a parallel light beam having a wavelength λ1 = 650 nm is incident on the objective lens.
FIG. 9 shows the relationship between the imaging magnification M2 and the wavefront aberration when the numerical aperture of the light beam emitted from the objective lens is 0.45 when a light source having a wavelength λ2 = 780 nm is used.
When the imaging magnification M2 is 0, a parallel light beam enters the objective lens as in the case of DVD.

As shown, when M2 = 0, about 0.
Spherical aberration of 13λrms occurs, which is larger than the Marechal limit of diffraction-limited performance of 0.07λrms. Therefore, it is necessary to set the spherical aberration by some means so that the wavefront aberration of both DVD and CD is less than Marechal's limit.

In this objective lens, when the imaging magnification is made negative, a negative spherical aberration occurs in the objective lens and M ≒
When the value is −0.06, the minimum value is obtained, and the value is within the Marechal limit. As described above, the amount of spherical aberration that must be corrected differs depending on the imaging magnification. In the illustrated example,
When M ≒ −0.06, it is not necessary to correct the spherical aberration by another means. When the NA required for recording information on a CD-R is 0.5, the spherical aberration to be further corrected is large.

Next, preferred collimating adjusting means in each of the above optical pickup devices will be described. For the sake of simplicity, consider an optical pickup device using a condensing optical system including a collimator and an objective lens. As for the distance between the collimator and the light source, a desired parallel light is emitted from the collimator by arranging the light source at a focal position on the optical axis of the collimator. Since the back focus of the collimator, the distance between the mounting position of the semiconductor laser and the light emitting point, and the manufacturing variation of the housing of the optical pickup device for mounting the collimator and the semiconductor laser are kept small, the distance between the semiconductor laser and the collimator must be adjusted. However, a parallel light with a practically accurate accuracy can be obtained.

Incidentally, in the case of recording and / or reproducing two types of optical information recording media having different thicknesses of the transparent substrate by two light sources having different wavelengths, an objective lens having a diffraction pattern is used. When diffracted light of the same order other than 0 is used, the fluctuation of the spherical aberration due to the fluctuation of the oscillation wavelength of the laser is larger than that of the existing double-sided aspheric objective lens. In particular, in the objective lens like Example 6, the wavefront aberration is 0.001λms at the wavelength of 650 nm, but the wavelength is ± 1.
If it changes by 0 nm, it deteriorates to about 0.035 λrms.
What occurs at this time is spherical aberration. Semiconductor lasers have individual differences in oscillation wavelength, and when a semiconductor laser having a large individual difference is applied to an optical pickup device, there arises a problem that the standard of spherical aberration of an objective lens having a diffraction pattern becomes strict.

In the objective lens used in the optical pickup device, negative tertiary spherical aberration increases when the incident light beam changes from parallel light to divergent light, and positive third-order aberration increases when the incident light changes from parallel light to convergent light.
Although the secondary spherical aberration increases, the tertiary spherical aberration can be controlled by changing the divergence of the light beam incident on the objective lens. In the objective lens according to the sixth embodiment, the main component of the spherical aberration generated due to the individual difference of the oscillation wavelength of the semiconductor laser is the third-order spherical aberration.
By changing the divergence of the light beam incident on the objective lens,
Third-order spherical aberration of the entire condensing optical system can be set as designed.

If the condensing optical system has a coupling lens such as a collimator, it can be moved in the optical axis direction to control the third-order spherical aberration of the objective lens. In the case where a coupling lens such as a collimator is provided, the object is similarly achieved by moving the semiconductor laser in the optical axis direction. Of course, even when there is a coupling lens such as a collimator, the semiconductor laser may be moved in the optical axis direction.

<Example 19>

FIG. 111 and Tables 20 and 21 show Example 19 of the spherical aberration correcting lens as a specific example of the objective lens according to the eighth embodiment.

In Table 20, ri is the radius of curvature of the refraction surface, d
i and di 'indicate the surface spacing, and ni and ni' indicate the refractive index at the main wavelength. The surface shape equation is shown in the following [Equation 4].

[0702]

(Equation 4) Here, X is the axis in the optical axis direction, h is the axis perpendicular to the optical axis, and the traveling direction of light is positive, r is the paraxial radius of curvature, κ is the number of cones, Aj is the aspheric coefficient, and Pj (Pi ≧ 3) is an aspheric power.

The diffraction surface is as shown in Expression 1 as an optical path difference function. The unit is expressed as mm.

[0704]

[Table 20] di and ni are the first optical information recording medium (t1 = 0.6 m
Value at m)

[0705] di 'and ni' are values in the case of the second optical information recording medium (t2 = 1.2 mm).

[0706]

[Table 21] FIG. 111 shows a lens sectional view of the above embodiment, and FIG. 112 shows its spherical aberration. In FIG. 111, a portion S2d including the optical axis of the second surface S2 has a diffraction pattern, and a portion S2r outside the portion is an aspheric refraction surface. FIG. 112A shows a wavelength of 635 nm and a first optical information recording medium (t1 = 0.6 m).
In the spherical aberration diagram at m), the aberration is sufficiently corrected. FIG. 13B shows a wavelength of 780 nm and a second optical information recording medium (t2 =
1.2 mm) is a spherical aberration diagram showing the first split surface S2d.
Are corrected for spherical aberration by the effect of diffraction, and the light beam passing through the second divided surface S2r becomes flare light, which has the same effect as a stop.

The lens of the above embodiment has NAH2 = 0.5.
Where NAL2 = 0. The diffraction pattern portion of this lens is a pattern on an annular zone centered on the optical axis, and the number of steps is about thirteen. The boundary between the refraction surface and the circumferential portion of the diffraction pattern that is farthest from the optical axis has a step of about 21 μm.

In the case where NAH2 = 0.45, the number of steps of the diffraction pattern is about 9, and the step amount is about 13 μm. The step amount and the number of steps of the diffraction pattern are almost proportional to the fourth power of NAH2.

When NAL2 = 0 as in this example,
The number of steps of the diffraction pattern increases in proportion to the spherical aberration to be corrected.

In the objective lens of the present invention, a good effect can be obtained even when the depth of the diffraction pattern in the optical axis direction is 2 μm or less. Since it becomes difficult, it is desirable that the number of steps is as small as possible.

[0711] In this method, the imaging magnification of CD is made slightly smaller than that of DVD, and the amount of spherical aberration to be corrected is reduced in advance. Preferably, mCD (magnification at the time of recording and reproduction of CD)-mDVD (magnification at the time of recording and reproduction of DVD) is preferably -1/15 to 0, in a small part of the numerical aperture deep and deep This can be achieved by not providing a diffraction pattern.

For example, if the imaging magnification of DVD is 0 and the imaging magnification of CD is -0.03, the spherical aberration to be corrected is halved. Therefore, in order to support CD-R, NAH2 is set to 0.5. In this case, the number of steps is about 7, and the step amount is also about 11 μm.

When the amount of the step is small, the shape of the step S2s may be such that it smoothly transitions from the diffraction pattern portion S2d to the refraction surface portion S2r.

In the case where both the imaging magnification of DVD and the imaging magnification of CD are 0, for example, if NAL2 = 0.36, the residual spherical aberration component WSA of the wavefront aberration of the light beam having a numerical aperture of NAL2 or less is obtained. NAL2) is about 0.053λrm
s. By attaching the optimal diffraction pattern to this,
The RMS value of the wavefront aberration up to NAH2 can be reduced while keeping the wavefront aberration of the DVD at almost zero.

The residual spherical aberration component WSA (NAH2) of the wavefront aberration of a light beam having a numerical aperture of NAH2 or less can be approximated by the following equation.

WSA (NAH2) = (NAL2 / NAH)
2) 2 × WSA (NAL2) Therefore, when NAH2 = 0.45, the above value is 0.03
0.027λrm when 4λrms and NAH2 = 0.5
s, which is sufficiently smaller than Marechal's limit value.

At this time, over spherical aberration occurs below NAL2. Therefore, instead of setting the spherical aberration from NAL2 to NAH2 to 0, it is preferable that the spherical aberration almost matches the best focus of the light beam below NAL2. good.
Since this best focus position is a position beyond the paraxial focus, the amount of spherical aberration corrected by the diffraction pattern can be small. Further, a diffraction pattern is not required for a light beam of NAL2 or less. With these two effects, NAH2
= 0.5, the number of steps in the diffraction pattern is about 6, N
When AH2 = 0.45, the number of steps of the diffraction pattern is four.

Of course, by making the imaging magnification of the CD smaller than the imaging magnification of the DVD, the diffraction pattern can be further reduced, and if there are at least two steps, the compatible reproduction of the DVD and the CD becomes possible.

Incidentally, a high-density optical information recording medium having a transparent substrate thickness of 0.1 mm has been proposed. For recording and reproduction, a blue semiconductor laser is used, a two-lens objective lens is used, and an NA1 of 0.85 is required. On the other hand, CD-RW has a transparent substrate thickness of 1.2 mm and a wavelength of 7 mm.
80 light sources, and NA2 is set to 0.55. In this compatible optical system, DVD, CD-R (NAH2
= 0.5), NA2 is larger and t1-
Since t2 is also large, the correction amount of the spherical aberration is also 2.7 times larger. Therefore, the number of steps of the diffraction pattern is also about 35.

Further, in order to correct paraxial chromatic aberration, the number of steps of the diffraction pattern is increased. Further, if the correction including the paraxial chromatic aberration is performed up to NA1, the number of steps is several hundred. In such a case, it is also possible to apply a diffraction pattern to a plurality of optical surfaces.

[0721] If necessary, NAL2 to NAH
A portion up to 2 may be used as a refraction surface.

Further, if t1> t2, the sign of the generated spherical aberration is reversed, so that the -1 order light is used.

Similarly, also in the case of DVD and CD, the imaging magnification of the CD of the objective lens becomes considerably smaller than the imaging magnification of DVD, and when spherical aberration of under remains, similarly, -1.
The next light will be used.

[0724] DVDs and CDs, which are currently of major interest, are
The above shows an example in which recording or two lasers having different wavelengths are used and a single objective lens is used. As described above, when the wavelength of the first light source is λ1 and the wavelength of the second light source is λ2 (λ2> λ1), t1 <t
In the case of 2, the + 1st-order diffracted light is used, and in the case of t1> t2, the first diffraction pattern using the -1st-order diffracted light is introduced. DVD (using the first light source) and C
The case of D (using the second light source) is the former.

Incidentally, light sources of various wavelengths, such as a blue semiconductor laser and an SHG laser, have recently been put to practical use, and it is expected that many new optical information recording media will appear in the future. In this case, the required spot size is determined from the recording density of the optical information recording medium, but the NA required for recording or recording / reproducing is determined.
Varies with the wavelength of the light source used. For this reason,
The thickness of the transparent substrate of the optical information recording medium and the required NA are classified into the following four for the two optical information recording media. (1) t1 <t2, NA1> NA2 (2) t1 <t2, NA1 <NA2 (3) t1> t2, NA1> NA2 (4) t1> t2, NA1 <NA2

In the above description, the diffraction order for each light source of the first diffraction pattern and the range of the first diffraction pattern (NA
H1, NAL1, NAH2, NAL2), the type and NA range of the light source for which the diffraction pattern part and the transmission part need to collect light at the same position, and the NA for setting the spherical aberration for each light source
, The NA where the wavefront aberration needs to be 0.07 λ rms or less for each light source, the diffraction order for each light source of the second diffraction pattern and the same position as the first diffraction pattern. The necessity and the conditions for restricting the luminous flux from which light source when the aperture restriction is introduced have been described in detail. In the case of (2), (3) and (4), the details of (1) are described. Therefore, detailed description is omitted.

Also, at the time of manufacturing a lens, it is possible to integrally mold a plastic material or a glass material by using a mold having a diffraction pattern cut therein. An optical surface including a diffraction pattern may be formed. Further, it may be manufactured by coating or direct processing.

As described above, the optical surface having the effect of the present invention may be provided on an optical element different from the objective lens, and the optical element may be provided on the light source side or the optical information recording medium side of the objective lens. good. Of course, it may be arranged on an optical surface through which both the light beam from the first light source and the light beam from the second light source of the collimator or the light combining means pass. However, when the objective lens moves due to tracking or the like, the optical axis of the diffraction pattern and the optical axis of the objective lens move relatively, so that the amount of tracking is limited.

Also, for convenience of explanation, the diffraction pattern is concentric with the optical axis, but is not limited to this.

[0730] Although the objective lenses specifically shown in the above Examples 1 to 19 have all been described as being composed of single lenses,
The objective lens may be composed of a plurality of lenses, and the case where at least one surface thereof has the diffraction surface of the present invention is also included in the present invention.

In the present invention, “selectively generating diffracted light of a specific order” means that the diffraction efficiency of a diffracted light of a specific order is different from that of a predetermined wavelength for light of a predetermined wavelength. As described above, it is higher than the diffraction efficiency of light. However, for each light of two wavelengths different from each other, the diffraction efficiency of the diffraction light of the specific order is different from that of each of the other orders. Is preferably higher than the diffraction efficiency by 10% or more, more preferably higher by 30% or more, and the diffraction efficiency of the diffracted light of the specific order is preferably 50% or more. Preferably, it is 70% or more, since the loss of light amount is small and it is practically preferable.

The diffractive surface of the present invention can be used as described in the above embodiment and specific examples of the lens.
Due to the presence of the diffractive surface, when diffracted lights of specific orders selectively generated at least two wavelengths different from each other are focused, when there is no diffractive surface, that is, the surface enclosing the relief of the diffractive surface It is desirable that the spherical aberration be improved as compared with a case assumed by simulation or the like.

Further, in the present invention, diffracted light of a specific order, which is selectively generated with respect to each light (wavelength λ) of at least two different wavelengths, is
It is preferable that the wavefront aberration on the imaging plane be 0.07 λrms or less in order to obtain a practically effective desired spot. It should be noted that the above-described embodiments can be modified by those skilled in the art without departing from the technical idea and scope of the present invention.

[0734]

As described above, according to the present invention, spherical aberration and axial chromatic aberration can be corrected for at least two different wavelengths of light with a simple configuration using at least one optical element having a diffractive surface. , An optical pickup device, a recording / reproducing device, a lens, an optical element, a diffractive optical system for an optical disc, an audio and / or image recording and / or reproducing device, and an objective lens. Further, it is possible to at least reduce the size, weight, and cost of the optical system. When the optical element has a diffraction surface that maximizes the diffraction efficiency of the same order diffracted light with respect to at least two different wavelengths of light, the diffraction surface maximizes the diffraction efficiency of the different order diffracted light. The loss of light amount can be reduced as compared with the case of performing the operation.

[0732] In particular, with regard to the inventions as set forth in claims 208 to 224, by providing a diffractive lens on the refraction surface, the diffractive lens is used in a recording / reproducing optical system having two light sources having different wavelengths. On the other hand, it is possible to obtain a diffractive optical system in which the loss of the light amount is small and the aberration is corrected to almost the diffraction limit.

[0736] In particular, as for the inventions described in claims 225 to 234, as described above, information is recorded on different optical discs by one objective lens for three light sources having different wavelengths from each other and / or information is recorded. In addition to enabling reproduction, since no coupling lens such as a collimator is used, it is possible to reduce the thickness of the optical pickup device and eliminate the problem of high cost.

[0732] In the optical pickup apparatus having three light sources of different wavelengths, the aspherical coefficient and the coefficient of the phase difference function are appropriately designed so that the thickness of the transparent substrate can be reduced. It is possible to provide an optical pickup device and an objective lens in which the chromatic aberration of spherical aberration caused by the difference in wavelength and the chromatic aberration of spherical aberration caused by the difference in wavelength, and the axial chromatic aberration are corrected.

[0738] Also, in particular, in the invention as set forth in claims 249 to 317, transparent substrates having different thicknesses can be obtained by providing a plurality of division surfaces on the objective lens and disposing a diffraction surface on the first division surface. It is possible to provide a recording / reproducing spherical aberration correction objective lens and an optical pickup device for an optical information recording medium capable of recording and reproducing with an optical information recording medium using light beams having different wavelengths by a single light condensing optical system.

Further, the objective lens for the optical pickup device comprises a plurality of concentrically divided annular zones, each of which includes a plurality of light sources having different wavelengths and / or a transparent substrate having a different recording surface thickness. , The aberration is corrected to the diffraction limit, and the flare light incident on the photodetector is reduced.

[Brief description of the drawings]

FIG. 1 is an optical path diagram of a diffractive optical lens according to a first embodiment of the present invention.

FIG. 2 is a spherical aberration diagram for a wavelength λ = 635 nm of the diffractive optical lens according to the first embodiment of the present invention.

FIG. 3 is a diagram of spherical aberration up to NA of 0.45 with respect to a wavelength λ = 780 nm by the diffractive optical lens of Example 1 of the present invention.

FIG. 4 is a diagram of spherical aberration up to NA 0.60 with respect to a wavelength λ = 780 nm by the diffractive optical lens of Example 1 of the present invention.

FIG. 5 is a wavefront aberration diagram for a wavelength λ = 635 nm by the diffractive optical lens of Example 1 of the present invention.

FIG. 6 is a wavefront aberration diagram for a wavelength λ = 780 nm of the diffractive optical lens according to the first embodiment of the present invention.

FIG. 7 is an optical path diagram for a wavelength λ = 405 nm of the diffractive optical lens according to the second embodiment of the present invention.

FIG. 8 is an optical path diagram for a wavelength λ = 635 nm by the diffractive optical lens according to the second embodiment of the present invention.

FIG. 9 is a spherical aberration diagram for a wavelength λ = 405 nm of the diffractive optical lens according to the second embodiment of the present invention.

FIG. 10 is a spherical aberration diagram for a wavelength λ = 635 nm of the diffractive optical lens according to the second embodiment of the present invention.

FIG. 11 is a wavefront aberration diagram for a wavelength λ = 405 nm of the diffractive optical lens according to the second embodiment of the present invention.

FIG. 12 is a wavefront aberration diagram for a wavelength λ = 635 nm of the diffractive optical lens according to the second embodiment of the present invention.

FIG. 13 is an optical path diagram for a wavelength λ = 405 nm of the diffractive optical lens according to the third embodiment of the present invention.

FIG. 14 is an optical path diagram for a wavelength λ = 635 nm of the diffractive optical lens according to the third embodiment of the present invention.

FIG. 15 is a spherical aberration diagram for a wavelength λ = 405 nm of the diffractive optical lens according to the third embodiment of the present invention.

FIG. 16 is a spherical aberration diagram for a wavelength λ = 635 nm of the diffractive optical lens according to the third embodiment of the present invention.

FIG. 17 is a wavefront aberration diagram for a wavelength λ = 405 nm of the diffractive optical lens according to the third embodiment of the present invention.

FIG. 18 is a wavefront aberration diagram for a wavelength λ = 635 nm of the diffractive optical lens according to the third embodiment of the present invention.

FIG. 19 is an optical path diagram of the diffractive optical lens according to the fourth embodiment of the present invention.

FIG. 20 is a diagram of spherical aberration with respect to wavelengths λ = 635 nm, 650 nm, and 780 nm by the diffractive optical lens of Example 4 of the present invention.

FIG. 21 is an optical path diagram of the diffractive optical lens according to the fifth embodiment of the present invention.

FIG. 22 is a diagram of spherical aberration with respect to wavelengths λ = 635 nm, 650 nm, and 780 nm obtained by the diffractive optical lens of Example 5 of the present invention.

FIG. 23 is an optical path diagram for a wavelength λ = 650 nm of the diffractive optical lens according to Example 6 of the present invention.

FIG. 24 is an optical path diagram for a wavelength λ = 780 nm (NA = 0.5) of the diffractive optical lens according to Example 6 of the present invention.

FIG. 25 is a diagram of spherical aberration up to a numerical aperture of 0.60 with respect to a wavelength λ = 650 ± 10 nm by the diffractive optical lens of Example 6 of the present invention.

FIG. 26 is a diagram of spherical aberration up to a numerical aperture of 0.50 with respect to a wavelength λ = 780 ± 10 nm by the diffractive optical lens of Example 6 of the present invention.

FIG. 27 is a diagram of spherical aberration up to a numerical aperture of 0.60 with respect to a wavelength λ = 780 nm, obtained by the diffractive optical lens of Example 6 of the present invention.

FIG. 28 is a wavefront aberration rms diagram for a wavelength λ = 650 nm of the diffractive optical lens according to the sixth embodiment of the present invention.

FIG. 29 is a diagram illustrating a wavefront aberration rms with respect to a wavelength λ = 780 nm by the diffractive optical lens according to the sixth example of the present invention.

FIG. 30 is an optical path diagram for a wavelength λ = 650 nm of the diffractive optical lens according to Example 7 of the present invention.

FIG. 31 is an optical path diagram for a wavelength λ = 780 nm (NA = 0.5) of the diffractive optical lens according to Example 7 of the present invention.

FIG. 32 is a diagram of spherical aberration up to a numerical aperture of 0.60 with respect to a wavelength λ = 650 ± 10 nm by the diffractive optical lens of Example 7 of the present invention.

FIG. 33 is a diagram of spherical aberration up to a numerical aperture of 0.50 with respect to a wavelength λ = 780 ± 10 nm by the diffractive optical lens of Example 7 of the present invention.

FIG. 34 is a diagram of spherical aberration up to a numerical aperture of 0.60 with respect to a wavelength λ = 780 nm by the diffractive optical lens of Example 7 of the present invention.

FIG. 35 is a wavefront aberration rms diagram for a wavelength λ = 650 nm of the diffractive optical lens of Example 7 of the present invention.

FIG. 36 is a wavefront aberration rms diagram with respect to a wavelength λ = 780 nm of the diffractive optical lens according to the seventh embodiment of the present invention.

FIG. 37 is an optical path diagram for a wavelength λ = 650 nm of the diffractive optical lens according to the eighth embodiment of the present invention.

FIG. 38 is an optical path diagram for a wavelength λ = 780 nm (NA = 0.5) of the diffractive optical lens according to Example 8 of the present invention.

FIG. 39 is a diagram of spherical aberration up to a numerical aperture of 0.60 with respect to a wavelength λ = 650 ± 10 nm by the diffractive optical lens of Example 8 of the present invention.

FIG. 40 is a diagram of spherical aberration up to a numerical aperture of 0.50 with respect to a wavelength λ = 780 ± 10 nm by the diffractive optical lens of Example 8 of the present invention.

FIG. 41 is a diagram of spherical aberration up to a numerical aperture of 0.60 with respect to a wavelength λ = 780 nm by the diffractive optical lens of Example 8 of the present invention.

FIG. 42 is a diagram illustrating a wavefront aberration rms with respect to a wavelength λ = 650 nm by the diffractive optical lens according to Example 8 of the present invention.

FIG. 43 is a diagram illustrating a wavefront aberration rms with respect to a wavelength λ = 780 nm of the diffractive optical lens according to Example 8 of the present invention.

FIG. 44 is a graph showing the relationship between the number of diffraction zones and the height from the optical axis for the diffractive optical lens according to Example 6 of the present invention.

FIG. 45 is a graph showing the relationship between the number of diffraction zones and the height from the optical axis for the diffractive optical lens according to Example 7 of the present invention.

FIG. 46 is a graph showing the relationship between the number of diffraction zones and the height from the optical axis for the diffractive optical lens according to Example 8 of the present invention.

FIG. 47 is a diagram schematically showing a relationship between a diffractive lens power and a lens shape in the diffractive optical lens according to the example of the present invention.

FIG. 48 is an optical path diagram showing a configuration of an optical pickup device according to a second embodiment of the present invention.

FIG. 49 is an optical path diagram showing a configuration of an optical pickup device according to a third embodiment of the present invention.

FIG. 50 shows a wavelength λ = 6 of the objective lens according to the ninth embodiment of the present invention.
It is an optical path diagram with respect to 50 nm.

FIG. 51 shows a wavelength λ = 7 of the objective lens according to the ninth embodiment of the present invention.
It is an optical path diagram with respect to 80 nm.

FIG. 52 is a spherical aberration diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 9 of the present invention.

FIG. 53 is a diagram showing spherical aberration up to NA of 0.45 with respect to a wavelength λ = 780 nm of the objective lens according to Example 9 of the present invention;

FIG. 54 is a diagram of spherical aberration up to NA 0.60 with respect to a wavelength λ = 780 nm of the objective lens according to Example 9 of the present invention;

FIG. 55 is a wavefront aberration diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 9 of the present invention.

FIG. 56 is a diagram showing a wavefront aberration with respect to a wavelength λ = 780 nm of the objective lens according to Example 9 of the present invention.

FIG. 57 is an optical path diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 10 of the present invention.

FIG. 58 is an optical path diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 10 of the present invention.

FIG. 59 is an optical path diagram with respect to a wavelength λ = 780 nm of the objective lens according to Example 10 of the present invention.

FIG. 60 is a spherical aberration diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 10 of the present invention.

FIG. 61 is a diagram showing spherical aberration with respect to a wavelength λ = 400 nm of the objective lens according to Example 10 of the present invention;

FIG. 62 is a diagram showing spherical aberration up to NA of 0.45 with respect to a wavelength λ = 780 nm of the objective lens according to Example 10 of the present invention;

FIG. 63 is a diagram showing spherical aberration up to NA 0.65 with respect to a wavelength λ = 780 nm of the objective lens according to Example 10 of the present invention;

FIG. 64 is a wavefront aberration diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 10 of the present invention.

FIG. 65 is a wavefront aberration diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 10 of the present invention.

FIG. 66 is a wavefront aberration diagram with respect to a wavelength λ = 780 nm of the objective lens according to Example 10 of the present invention.

FIG. 67 is a diagram showing a configuration of an optical pickup device according to a fourth embodiment of the present invention.

FIG. 68 is an optical path diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 11 of the present invention.

FIG. 69 is an optical path diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 11 of the present invention.

FIG. 70 is an optical path diagram with respect to a wavelength λ = 780 nm of the objective lens according to Example 11 of the present invention;

FIG. 71 is a spherical aberration diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 11 of the present invention.

FIG. 72 is a spherical aberration diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 11 of the present invention.

FIG. 73 is a diagram of spherical aberration up to a numerical aperture of 0.45 with respect to a wavelength λ = 780 nm of the objective lens according to Example 11 of the present invention;

FIG. 74 is a diagram of spherical aberration up to a numerical aperture of 0.65 with respect to a wavelength λ = 780 nm of the objective lens according to Example 11 of the present invention;

FIG. 75 is a diagram illustrating a wavefront aberration with respect to a wavelength λ = 650 nm of the objective lens according to Example 11 of the present invention;

FIG. 76 is a wavefront aberration diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 11 of the present invention.

FIG. 77 is a wavefront aberration diagram with respect to a wavelength λ = 780 nm of the objective lens according to Example 11 of the present invention.

FIG. 78 is an optical path diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 12 of the present invention.

FIG. 79 is an optical path diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 12 of the present invention;

FIG. 80 is an optical path diagram with respect to a wavelength λ = 780 nm of the objective lens according to Example 12 of the present invention;

FIG. 81 is a spherical aberration diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 12 of the present invention;

FIG. 82 is a spherical aberration diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 12 of the present invention;

FIG. 83 is a diagram of spherical aberration up to a numerical aperture of 0.45 with respect to a wavelength λ = 780 nm of the objective lens according to Example 12 of the present invention;

FIG. 84 is a diagram of spherical aberration up to a numerical aperture of 0.65 with respect to a wavelength λ = 780 nm of the objective lens according to Example 12 of the present invention;

FIG. 85 is a wavefront aberration diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 12 of the present invention.

86 is a wavefront aberration diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 12 of the present invention. FIG.

FIG. 87 is a wavefront aberration diagram with respect to a wavelength λ = 780 nm of the objective lens according to Example 12 of the present invention;

FIG. 88 is an optical path diagram for a wavelength λ = 650 nm of the objective lens according to Example 13 of the present invention.

FIG. 89 is an optical path diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 13 of the present invention.

FIG. 90 is an optical path diagram with respect to a wavelength λ = 780 nm of the objective lens according to Example 13 of the present invention.

FIG. 91 is a spherical aberration diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 13 of the present invention.

FIG. 92 is a spherical aberration diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 13 of the present invention.

FIG. 93 is a diagram of spherical aberration up to a numerical aperture of 0.45 with respect to a wavelength λ = 780 nm of the objective lens according to Example 13 of the present invention;

FIG. 94 is a diagram of spherical aberration up to a numerical aperture of 0.65 with respect to a wavelength λ = 780 nm of the objective lens according to Example 13 of the present invention;

FIG. 95 is a wavefront aberration diagram with respect to a wavelength λ = 650 nm of the objective lens according to Example 13 of the present invention.

FIG. 96 is a wavefront aberration diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 13 of the present invention.

FIG. 97 is a diagram showing a wavefront aberration with respect to a wavelength λ = 780 nm of the objective lens according to Example 13 of the present invention;

FIG. 98 is an optical path diagram with respect to a wavelength λ = 400 nm of the objective lens according to Example 13 of the present invention.

FIG. 99 shows a spherical aberration diagram with respect to a wavelength λ = 400 nm ± 10 nm of the objective lens according to Example 13 of the present invention.

FIG. 100 shows a spherical aberration diagram with respect to a wavelength λ = 650 nm ± 10 nm of the objective lens according to Example 13 of the present invention.

FIG. 101 shows a spherical aberration diagram of the objective lens according to Example 13 of the present invention with respect to a wavelength λ = 780 nm ± 10 nm.

FIG. 102 is an optical path diagram showing a first configuration of an optical pickup device according to an eighth embodiment of the present invention.

FIG. 103 is an optical path diagram showing a second configuration of the optical pickup device according to the eighth embodiment of the present invention.

FIG. 104 is an optical path diagram showing a third configuration of the optical pickup device according to the eighth embodiment of the present invention.

FIG. 105 is an optical path diagram showing a fourth configuration of the optical pickup device according to the eighth embodiment of the present invention.

FIG. 106 is an optical path diagram showing a fifth configuration of the optical pickup device according to the eighth embodiment of the present invention.

FIG. 107 is an optical path diagram showing a sixth configuration of the optical pickup device according to the eighth embodiment of the present invention.

FIG. 108 is an optical path diagram showing a seventh configuration of the optical pickup device according to the eighth embodiment of the present invention.

FIG. 109 is a schematic diagram showing a configuration of an optical disk of a Super RENS system.

FIG. 110 is a graph showing the relationship between the imaging magnification m2 and the wavefront aberration of the objective lens of Example 15 according to the eighth embodiment of the present invention.

FIG. 111 is a sectional view of Example 15 according to the eighth embodiment of the present invention;

112 is a diagram showing the spherical aberration of the fifteenth embodiment. FIG.

FIG. 113 is an explanatory diagram of an action of a diffraction pattern.

FIG. 114 is a schematic view showing the influence of chromatic aberration on the spherical aberration of the objective lens according to the eighth embodiment of the present invention.

FIG. 115 is a schematic diagram showing the influence of + 1st-order diffraction on the spherical aberration of the objective lens according to the eighth embodiment of the present invention.

FIG. 116 is a schematic view showing the influence of -1st-order diffraction on the spherical aberration of the objective lens according to the eighth embodiment of the present invention.

FIG. 117 is an optical path diagram showing a configuration of an optical pickup device according to a seventh embodiment of the present invention.

FIG. 118 is an optical path diagram of a diffractive optical lens (an objective lens having a diffractive surface) which is the objective lens of Example 15 according to the seventh embodiment of the present invention.

119 is a diagram showing spherical aberration up to a numerical aperture of 0.60 with respect to wavelength (λ) = 640, 650, and 660 nm for the diffractive optical lens of FIG. 118;

120 is an optical path diagram of a diffractive optical lens when the transparent substrate of the optical information recording medium is thicker than that in FIG. 118 in Example 15. FIG.

FIG. 121: Numerical aperture 0.6 for wavelength λ = 770, 780, 790 nm for the diffractive optical lens of FIG. 120
It is a spherical aberration figure to 0.

FIG. 122 is an optical path diagram of a diffractive optical lens (an objective lens having a diffractive surface) which is the objective lens of Example 16 according to the seventh embodiment of the present invention.

123 is a diagram showing spherical aberration up to a numerical aperture of 0.60 with respect to wavelength (λ) = 640, 650, and 660 nm for the diffractive optical lens in FIG. 122;

124 is an optical path diagram of a diffractive optical lens when the transparent substrate of the optical information recording medium is thicker than that in FIG. 122 in Example 16. FIG.

FIG. 125: Numerical aperture 0.6 for wavelengths λ = 770, 780, 790 nm for the diffractive optical lens of FIG. 124
It is a spherical aberration figure to 0.

FIG. 126 is an optical path diagram of a diffractive optical lens (an objective lens having a diffractive surface) which is the objective lens of Example 17 according to the seventh embodiment of the present invention.

127 is a diagram of spherical aberration up to a numerical aperture of 0.60 with respect to wavelength (λ) = 640, 650, and 660 nm for the diffractive optical lens of FIG. 126;

128 is an optical path diagram of a diffractive optical lens in Example 17 when the transparent substrate of the optical information recording medium is thicker than FIG. 126.

FIG. 129. Numerical aperture 0.6 for wavelengths λ = 770, 780, 790 nm for the diffractive optical lens of FIG. 128.
It is a spherical aberration figure to 0.

FIG. 130 is an optical path diagram of a diffractive optical lens (an objective lens having a diffractive surface) which is the objective lens of Example 18 according to the seventh embodiment of the present invention.

131 is a diagram showing spherical aberration of the diffractive optical lens of FIG. 130 up to a numerical aperture of 0.70 at wavelengths (λ) of 390, 400, and 410 nm.

132 is an optical path diagram of a diffractive optical lens when the transparent substrate of the optical information recording medium is thicker than that in FIG. 130 in Example 18. FIG.

FIG. 133: Numerical aperture 0.7 for wavelength λ = 640, 650, 660 nm for the diffractive optical lens of FIG. 132
It is a spherical aberration figure to 0.

FIG. 134 is a diagram for explaining a pitch of a diffraction ring zone and a depth of a step in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Objective lens 2 Collimator lens 3 Aperture 4 Optical axis 5 Condensing optical system 6, 7 Beam splitter 10 Optical pickup device 11 First semiconductor laser 12 Blue laser 13 Second semiconductor laser 16 Objective lens 16a Flange part 20 Optical disk 21 Transparent substrate 22 Information recording surface 111, 112 Semiconductor laser 120, 121, 122 Polarizing beam splitter 130, 131, 132 Collimator 140, 141, 142 Quarter-wave plate 150 Two-dimensional actuator 160 Objective lens 170 Aperture 180 Cylindrical lens 190 Beam splitter 200 Optical disk 210 Transparent substrate 220 Information recording surface 230, 231, 232 Hologram 240 First protective film 250 Nonlinear optical film 260 Second protective film 270 Third protective film 300, 301, 3 02,305 Photodetector 400,410,420,430 Laser / detector integrated unit 50 Concave lens 60 Coupling ring lens 90 Condensing lens

 ──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 11-15010 (32) Priority date January 22, 1999 (22 January 1999) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 11-257466 (32) Priority date September 10, 1999 (September 10, 1999) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 11-312701 (32) Priority Date November 2, 1999 (November 11, 1999) (33) Priority Country Japan (JP) (72) Inventor Toshiyuki Kojima 2970 Ishikawacho, Hachioji-shi, Tokyo Address Konica Corporation (72) Inventor Toshihiko Kiriki 2970 Ishikawacho, Hachioji-shi, Tokyo F-term (reference) 2K049 AA03 AA04 AA17 AA51 AA57 2H087 KA13 RA03 RA12 RA46 5D119 AA11 AA23 DA01 DA05 EC01 FA08 JA13 JA43 JB02 (54) [Title of the Invention] Optical pickup device, this Recording reproducing apparatus having a pickup device, an optical element, the recording playback method information, an optical system, a lens, an optical disk diffraction optical system, objective lenses for reproducing device and an optical pickup device

Claims (339)

[Claims] 1. An optical pickup device for reproducing information from an optical information recording medium or recording information on the optical information recording medium, wherein a first light source for emitting a first light beam having a first wavelength is provided. And a second light source that emits a second light beam having a second wavelength different from the first wavelength; and a condensing optical system having an optical axis, a diffraction unit, and a photodetector, As the first light beam passes through the diffracting portion, at least one order of diffracted light in which the n-th order diffracted light amount of the first light beam is larger than any other order diffracted light amount of the first light beam Is generated, and the second light flux passes through the diffraction section, so that the n-th order diffracted light quantity of the second light flux is larger than the diffracted light quantity of any other order of the second light flux. A light pipe characterized in that diffraction light of the order is generated. Up apparatus. Here, n is an integer other than 0. 2. A method for reproducing or recording information on at least two types of optical information recording media, wherein the first light flux of the first light source reproduces information from a first optical information recording medium. Or for recording information on a first optical information recording medium, wherein the second light flux of the second light source is used for reproducing information from a second optical information recording medium. The optical pickup device according to claim 1, wherein the optical pickup device is used for recording information on a second optical information recording medium. 3. The condensing optical system reaches the diffraction section to reproduce information recorded on the first optical information recording medium or to record information on the first information recording medium. Collecting the n-th order diffracted light of the first light beam generated by the diffracted portion by the first light beam on the first information recording surface of the first optical information recording medium via a first transparent substrate. The condensing optical system may be provided on the diffraction unit for reproducing information recorded on the second optical information recording medium or for recording information on the second information recording medium. The second reached
Converging the n-th order diffracted light of the second light flux generated in the diffractive portion by the light flux on a second information recording surface of the second optical information recording medium via a second transparent substrate. The photodetector may include the first information recording surface or the second information recording surface.
3. The optical pickup device according to claim 2, wherein a light beam reflected from said information recording surface can be received. 4. The condensing optical system has an objective lens, and the condensing optical system converts the nth-order diffracted light of the first light flux that has passed through the diffractive portion into the first optical information recording medium. 0.07λrm on the first information recording surface within a predetermined numerical aperture of the first light flux on the image side of the objective lens.
s or less, and the condensing optical system converts the nth-order diffracted light of the second light flux passing through the diffractive portion onto a second information recording surface of the second optical information recording medium. 0.07λrm within the predetermined numerical aperture of the second light flux on the image side of the objective lens
4. The optical pickup device according to claim 2, wherein light can be collected in a state of s or less. 5. The first optical information recording medium has a first transparent substrate having a thickness of t1, and the second optical information recording medium has a second transparent substrate having a thickness of t2 different from the thickness t1. The optical pickup device according to claim 2, further comprising a substrate. 6. The condensing optical system has an objective lens, and the condensing optical system converts the n-th order diffracted light of the first light flux passing through the diffractive portion into a first optical information recording medium. 0.07λrm on the first information recording surface within a predetermined numerical aperture of the first light flux on the image side of the objective lens.
s or less, and the condensing optical system converts the nth-order diffracted light of the second light flux passing through the diffractive portion onto a second information recording surface of the second optical information recording medium. 0.07λrm within the predetermined numerical aperture of the second light flux on the image side of the objective lens
The optical pickup device according to claim 5, wherein light can be collected in a state of s or less. 7. The optical pickup device according to claim 5, wherein the following conditional expression is satisfied. λ1 <λ2 t1 <t2 where λ1: wavelength of the first light source λ2: wavelength of the second light source t1: thickness of the first transparent substrate t2: thickness of the second transparent substrate 8. The optical pickup device according to claim 7, wherein the focusing optical system has an objective lens and satisfies the following conditional expression. NA1> NA2 Here, NA1: a predetermined numerical aperture on the image side of the objective lens required for recording or reproduction of the first optical information recording medium with light having a wavelength of λ1 NA2: the second numerical aperture with light having a wavelength of λ2 A predetermined numerical aperture on the image side of the objective lens required for recording or reproduction of the optical information recording medium 9. The optical pickup device according to claim 1, wherein the nth-order diffracted light is a + 1st-order diffracted light. 10. The optical pickup device according to claim 8, wherein the following conditional expression is satisfied. 0.55 mm <t1 <0.65 mm 1.1 mm <t2 <1.3 mm 630 nm <λ1 <670 nm 760 nm <λ2 <820 nm 0.55 <NA1 <0.68 0.40 <NA2 <0.55 11. The condensing optical system includes an objective lens,
The objective lens has the diffractive portion, and λ1 = 650 nm t1 = 0.6 mm NA1 = 0.6, and the first light flux, which is parallel light having a uniform intensity distribution, is incident on the objective lens. The spot diameter at the best focus when the light is converged on the first information recording surface via the first transparent substrate is 0.88 to 0.91 μm. An optical pickup device as described in the above. 12. The focusing optical system includes an objective lens,
The objective lens has the diffractive portion, and λ1 = 650 nm t1 = 0.6 mm NA1 = 0.65, and the first light flux, which is parallel light having a uniform intensity distribution, is incident on the objective lens. The spot diameter at the best focus is 0.81 to 0.84 μm when condensed on the first information recording surface via the first transparent substrate. An optical pickup device as described in the above. 13. The optical pickup device according to claim 10, wherein the following conditional expression is satisfied. t1 = 0.6 mm t2 = 1.2 mm λ1 = 650 nm λ2 = 780 nm NA1 = 0.6 NA2 = 0.45 14. The light-collecting optical system includes an objective lens,
Wherein the objective lens has the diffractive portion, and the condensing optical system condenses the n-order diffracted light of the second light beam on the second information recording surface of the second optical information recording medium. The optical pickup device according to claim 8, wherein the spherical aberration has at least one discontinuous portion. 15. The optical pickup device according to claim 14, wherein the spherical aberration has a discontinuity near the NA2. 16. The optical pickup device according to claim 14, wherein the spherical aberration has a discontinuity at a numerical aperture (NA) of 0.45. 17. The optical pickup device according to claim 14, wherein the spherical aberration has a discontinuity at a numerical aperture (NA) of 0.5. 18. The condensing optical system, wherein the numerical aperture has the NA
The n-th order diffracted light of the first light flux of 1 or less is condensed on the first information recording surface of the first optical information recording medium such that the wavefront aberration at the best image point is 0.07λrms. The condensing optical system is configured to convert the n-th order diffracted light of the second light beam having a numerical aperture equal to or less than the numerical aperture serving as the discontinuous portion onto the second information recording surface of the second optical information recording medium, with the best image The optical pickup device according to claim 14, wherein the light is condensed so that the wavefront aberration at the point is 0.07? Rms. 19. The condensing optical system has an objective lens,
The objective lens has the diffractive portion, and in order to perform recording or reproduction on the second optical information recording medium, the condensing optical system is configured such that the n-th light beam in the second light beam passing through the diffractive portion The spherical aberration is continuous and does not have a discontinuous portion when condensing light is condensed on the second information recording surface of the second optical information recording medium. Optical pickup device. 20. The optical pickup device according to claim 19, wherein the spherical aberration is 20 μm or more at NA1, and the spherical aberration is 10 μm or less at NA2. 21. The optical pickup device according to claim 5, wherein the following conditional expression is satisfied. λ1 <λ2 t1> t2 where λ1: wavelength of the first light source λ2: wavelength of the second light source t1: thickness of the first transparent substrate t2: thickness of the second transparent substrate 22. The optical pickup device according to claim 21, wherein the nth-order diffracted light is a −1st-order diffracted light. 23. When the diffraction efficiency of the n-th order diffracted light of the first light beam in the diffractive portion is A% and the diffraction efficiency of another order diffracted light is B%, AB ≧ 10. A′−B ′ ≧ 10, where A ′% is the diffraction efficiency of the n-th order diffracted light of the second light flux in the diffracting unit, and B ′% is the diffraction efficiency of the diffracted light of another certain order. The optical pickup device according to claim 1, wherein: 24. When the diffraction efficiency of the n-th order diffracted light of the first light flux in the diffractive portion is A% and the diffraction efficiency of another order diffracted light is B%, AB ≧ 50. A′−B ′ ≧ 50, where the diffraction efficiency of the n-th order diffracted light of the second light flux in the diffracting unit is A ′% and the diffraction efficiency of the diffracted light of another certain order is B ′%. The optical pickup device according to claim 1, wherein: 25. The light according to claim 1, wherein a difference between a wavelength of the first light beam and a wavelength of the second light beam is 80 nm or more and 400 nm or less. Pickup device. 26. The diffractive portion has a plurality of annular zones as viewed from the direction of the optical axis, and the annular zones are substantially concentric with respect to the optical axis or a point near the optical axis. 26. The method according to claim 1, wherein
An optical pickup device according to the item. 27. A phase difference function represented by a power series indicating each position of the plurality of orbicular zones of the diffraction section, wherein at least one term other than a square term has a coefficient other than 0. The optical pickup device according to claim 26, wherein 28. The method according to claim 26, wherein a phase difference function represented by a power series indicating each position of the plurality of orbicular zones of the diffraction unit has a coefficient other than 0 in a square term. An optical pickup device as described in the above. 29. The optical pickup device according to claim 26, wherein a phase difference function represented by a power series indicating each position of the plurality of orbicular zones of the diffraction unit does not include a square term. . 30. The optical pickup according to claim 26, wherein the sign of the diffractive action added by the diffractive portion is switched at least once in a direction perpendicular to the optical axis and away from the optical axis. apparatus. 31. The plurality of orbicular zones of the diffractive portion are blazed, and in an orbicular zone closer to the optical axis, a step portion is located on a side away from the optical axis, and 31. The optical pickup device according to claim 30, wherein a step portion is located on a side closer to the optical axis in an annular zone away from the axis. 32. The plurality of orbicular zones of the diffractive portion are blazed, and in an orbicular zone closer to the optical axis, a step portion is located on a side closer to the optical axis. 31. The optical pickup device according to claim 30, wherein the stepped portion is located on a side away from the optical axis in an annular zone away from the optical axis. 33. The condensing optical system has an objective lens,
A pitch Pf of the annular zone of the diffractive portion corresponding to a maximum numerical aperture on the image side of the objective lens, and の of the maximum numerical aperture
28. The optical pickup device according to claim 26, wherein a pitch Ph of the orbicular zone of the diffractive portion corresponding to the following condition satisfies the following conditional expression. 0.4 ≦ | (Ph / Pf) −2 | ≦ 25 34. The diffraction section has a first diffraction pattern and a second diffraction pattern, wherein the second diffraction pattern is farther from the optical axis than the first diffraction pattern. 3. The method according to claim 2, wherein
7. The optical pickup device according to 6. 35. In the first light beam that has passed through the first diffraction pattern of the diffraction section, the n-order diffracted light is generated more than diffracted lights of other orders, and Also in the second light flux that has passed through the first diffraction pattern, the n-th order diffracted light is generated more than the other order diffracted light, and the second order that has passed through the second diffraction pattern of the diffractive portion. In the first light beam, the n-th order diffracted light is generated more than the other order diffracted light, and in the second light beam passing through the second diffraction pattern of the diffractive portion, the 0th order light is 35. The optical pickup device according to claim 34, wherein the optical pickup device generates more light than diffracted light of other orders. 36. In the first light beam that has passed through the first diffraction pattern of the diffraction section, the n-order diffracted light is generated more than diffracted lights of other orders, and Also in the second light flux that has passed through the first diffraction pattern, the n-order diffracted light is generated more than diffracted light of other orders, and the n-th order diffracted light has passed through the second diffraction pattern of the diffractive portion. In the first light beam, the 0-order diffracted light is generated more than the other order diffracted light, and in the second light beam that has passed through the second diffraction pattern of the diffractive portion, the n 35. The optical pickup device according to claim 34, wherein diffracted light of a negative order other than the order is generated more than diffracted lights of other orders. 37. The optical pickup according to claim 26, wherein the condensing optical system has an objective lens, and all light beams having a maximum numerical aperture or less on the image side of the objective lens pass through the diffraction portion. apparatus. 38. The condensing optical system has an objective lens, and among the light beams having a maximum numerical aperture on the image side of the objective lens,
27. The optical pickup device according to claim 26, wherein a part of the light beam passes through the diffraction portion, and another part of the light beam does not pass through the diffraction portion. 39. The number of steps of the plurality of orbicular zones of the diffractive portion is 2 or more and 45 or less.
7. The optical pickup device according to 6. 40. The number of steps of the plurality of orbicular zones of the diffractive portion is 2 or more and 15 or less.
10. The optical pickup device according to item 9. 41. The optical pickup device according to claim 26, wherein a depth of the step portion of the plurality of orbicular zones of the diffraction portion in the optical axis direction is 2 μm or less. 42. The condensing optical system has an objective lens,
27. The optical pickup device according to claim 26, wherein the diffraction section is provided in the objective lens, and the pitch of the diffraction section at a numerical aperture (NA) of 0.4 is 10 to 70 [mu] m. 43. The optical pickup device according to claim 1, wherein the condensing optical system has a lens having a refractive surface, and the diffractive portion is provided on the lens. 44. The optical pickup device according to claim 43, wherein the lens provided with the diffraction section is an objective lens. 45. The optical pickup device according to claim 44, wherein the objective lens provided with the diffraction surface has a flange portion on an outer periphery. 46. The optical pickup device according to claim 44, wherein the refraction surface of the objective lens provided with the diffraction section is an aspheric surface. 47. The optical pickup device according to claim 43, wherein the lens provided with the diffraction portion is made of a material having an Abbe number νd larger than 50. . 48. The optical pickup device according to claim 43, wherein the lens provided with the diffraction section is a plastic lens. 49. The lens provided with the diffraction section is a glass lens.
48. The optical pickup device according to any one of items 47 to 47. 50. The method according to claim 1, wherein the n-th order diffracted light is a + 1st order diffracted light or a −1st order diffracted light.
50. The optical pickup device according to any one of items 49 to 49. 51. The diffraction efficiency of the n-th order diffracted light in the diffractive portion is maximum at a wavelength between the wavelength of the first light flux and the wavelength of the second light flux. The optical pickup device according to any one of Items 50 to 50. 52. The diffraction efficiency of the n-th order diffracted light in the diffractive portion is maximum at the wavelength of the first light beam or the wavelength of the second light beam.
The optical pickup device according to any one of Items 50 to 50. 53. The condensing optical system has an objective lens, wherein the wavelength of the second light beam is longer than the wavelength of the first light beam, and the second light beam and the second light beam The optical pickup device according to claim 1, wherein the axial chromatic aberration with the first light beam satisfies the following conditional expression. −λ2 / ｛2 × (NA2) ² ｝ ≦ Z ≦ λ2 / ｛2 × (N
A2) ^{2 、} where λ2: wavelength of the second light beam NA2: predetermined numerical aperture on the image side of the objective lens with respect to the second light beam 54. The apparatus according to claim 54, further comprising a third light source for emitting a third light beam, wherein the wavelength of the third light beam is different from the wavelengths of the first light beam and the second light beam. 1 to
53. The optical pickup device according to any one of the items 53. 55. The optical pickup according to claim 54, wherein even in the third light flux that has passed through the diffraction section, the n-order diffracted light is generated more than diffracted lights of other orders. apparatus. 56. The condensing optical system, comprising: an objective lens; and shielding or diffracting the first light beam outside a predetermined numerical aperture on the image side of the objective lens when using the first light beam; The second light flux transmits or passes through the aperture limiting means, or shields or diffracts the second light flux outside a predetermined numerical aperture on the image side of the objective lens when the second light flux is used, and Aperture limiting means through which the light beam of 1 is transmitted;
The optical pickup device according to claim 1, comprising: 57. The condensing optical system has an objective lens, and shields or diffracts the first light beam outside a predetermined numerical aperture on the image side of the objective lens when using the first light beam. The aperture limiting means for transmitting the second light beam also shields or diffracts the second light beam outside a predetermined numerical aperture on the image side of the objective lens when the second light beam is used, 2. The optical pickup device according to claim 1, wherein the first light flux does not have an aperture limiting means that transmits the first light flux. 58. The light according to claim 1, wherein the condensing optical system has a lens having a refractive surface, the diffractive portion is provided on the lens, and the following conditional expression is satisfied. Pickup device. −0.0002 / ° C <Δn / ΔT <−0.00005 ° C 0.05 nm / ° C <Δλ1 / ΔT <0.5 nm / ° C, where ΔT (° C): temperature change Δn: change in refractive index of the lens Amount Δλ1 (nm): Amount of change in wavelength of the first light source when there is a temperature change ΔT 59. The condensing optical system has an objective lens,
The optical pickup device according to claim 1, wherein the following conditional expression is satisfied. 0.2 × 10 ^-6 / ° C <ΔWSA3 · λ1 / {f · (NA1) ⁴ · ΔT} <
2.2 × 10 ⁻⁶ / ° C. Here, NA1: a numerical aperture of the objective lens on the image side required when reproducing or recording on the optical information recording medium using the first light beam λ1: Wavelength of the first light beam f: focal length of the objective lens in the first light beam ΔT: change in environmental temperature. ΔWSA3 (λ1 rms): the amount of change in the third-order spherical aberration component of the wavefront aberration of the light beam focused on the information recording surface when reproducing or recording on the optical information recording medium using the first light beam 60. The condensing optical system has an objective lens, and when the first light beam is used, the first light beam within a predetermined numerical aperture on the image side of the objective lens is the first light beam. The light is condensed on the first information recording surface of the optical information recording medium in a state of not more than 0.07 λ rms, and when the first light flux is used, the light passes through a predetermined numerical aperture on the image side of the objective lens. The first light beam is in a state larger than 0.07 λrms on the first optical information recording medium, and the second light beam passing through a predetermined numerical aperture on the image side of the objective lens when using the second light beam is used. Both the second light beam and the second light beam that has passed outside the predetermined numerical aperture are placed on the second information recording surface of the second optical information recording medium at 0.07λrms.
The second light flux which is condensed in the following state, or which is within a predetermined numerical aperture on the image side of the objective lens when using the second light flux, is used for the second optical information recording medium. The second light flux condensed on the second information recording surface in a state of not more than 0.07 λ rms and passing outside a predetermined numerical aperture on the image side of the objective lens when the second light flux is used. Is larger than 0.07 λrms on the second optical information recording medium. When the first light flux is used, the first light flux passing through a predetermined numerical aperture on the image side of the objective lens is used. In addition, the first light flux that has passed outside the predetermined numerical aperture also has 0.07λrms on the first information recording surface of the first optical information recording medium.
The optical pickup device according to claim 1, wherein the light is collected in the following state. 61. The condensing optical system has an objective lens, and when using the first light beam, the first light beam within a predetermined numerical aperture on the image side of the objective lens is the first light beam. The light is condensed on the first information recording surface of the optical information recording medium in a state of not more than 0.07 λ rms, and when the first light flux is used, the light passes through a predetermined numerical aperture on the image side of the objective lens. The first light flux is condensed on the first optical information recording medium in a state of 0.07 λrms or less, or is shielded and does not reach the first information recording surface; When using the luminous flux, the second luminous flux that has passed through a predetermined numerical aperture on the image side of the objective lens, and the second luminous flux that has passed outside the predetermined numerical aperture, are also used for second optical information recording. 0.07λrms on the second information recording surface of the medium
The second light flux that is condensed in the following state or is within a predetermined numerical aperture on the image side of the objective lens when the second light flux is used is a second optical information recording medium. 0.07λr on the second information recording surface
ms, and the second light flux that has passed outside the predetermined numerical aperture on the image side of the objective lens when the second light flux is used is on the second optical information recording medium. In this case, the light is condensed or shielded in a state of 0.07 λrms or less and does not reach the second information recording surface, and the image side of the objective lens when using the first light flux is used. Both the first light flux that has passed through the predetermined numerical aperture and the first light flux that has passed outside the predetermined numerical aperture have 0.07λ rms on the first information recording surface of the first optical information recording medium.
The optical pickup device according to claim 1, wherein the light is collected in the following state. 62. The condensing optical system has an objective lens. When the first light beam is used, the first light beam, which is a non-parallel light beam, is incident on the objective lens, and the second light beam 2. The optical pickup device according to claim 1, wherein, in the case of using, the second light flux that is a non-parallel light flux is incident on the objective lens. 3. 63. The optical pickup device according to claim 62, wherein the non-parallel light beam is divergent light. 64. The optical pickup device according to claim 62, wherein the non-parallel light beam is a convergent light. 65. The condensing optical system has an objective lens. When the first light beam is used, the first light beam, which is a parallel light beam, is incident on the objective lens, and the second light beam is In the case of using, the second light beam which is a non-parallel light beam is made to enter the objective lens, or in the case of using the first light beam, the first light beam which is a non-parallel light beam is applied to the objective lens. The optical pickup device according to claim 1, wherein, when the second light beam is used, the second light beam, which is a parallel light beam, is incident on the objective lens. 66. The optical pickup device according to claim 65, wherein the non-parallel light beam is divergent light. 67. The optical pickup device according to claim 65, wherein the non-parallel light beam is a convergent light. 68. The condensing optical system has an objective lens. When the first light beam is used, the first light beam, which is a parallel light beam, is incident on the objective lens, and the second light beam is 2. The optical pickup device according to claim 1, wherein, when used, the second light flux, which is a parallel light flux, is incident on the objective lens. 69. The optical pickup according to claim 1, wherein the condensing optical system has an objective lens and a divergence changing unit that changes a divergence of a light beam incident on the objective lens. apparatus. 70. The optical pickup device according to claim 1, wherein the photodetector is common to the first light beam and the second light beam. . 71. A light source, further comprising a second light detector, wherein the light detector is for the first light beam and the second light detector is for the second light beam. The optical pickup device according to any one of claims 1 to 69. 72. The optical pickup according to claim 1, wherein the photodetector and the first light source or the second light source are unitized. apparatus. 73. The optical pickup according to claim 1, wherein the photodetector, the first light source and the second light source are unitized. apparatus. 74. The apparatus according to claim 74, further comprising a second photodetector, wherein the photodetector is for the first light beam, the second photodetector is for the second light beam, The optical pickup device according to claim 1, wherein a detector, the second light detector, and the first light source and the second light source are unitized. 75. The first light source and the second light source,
2. The optical pickup device according to claim 1, wherein the optical pickup is unitized. 76. The optical pickup device according to claim 1, wherein the overshoot is 0 to 20%. 77. An optical element used in an optical pickup device for reproducing information from an optical information recording medium or recording information on the optical information recording medium, comprising: an optical axis and a diffraction section. The first light beam passes through the diffraction section, so that the n-th order diffracted light amount of the first light beam is larger than the diffracted light amount of any other order of the first light beam. Diffracted light is generated, and the wavelength difference from the first light flux is 80n.
When the second light beam having a wavelength of m to 400 nm passes through the diffraction section, at least one of the n-th order diffracted light amount of the second light beam is larger than the diffracted light amount of any other order of the second light beam. An optical element wherein diffracted light of the order is generated. Here, n is an integer other than 0. 78. The optical pickup device, comprising:
The optical element according to claim 77, further comprising: a first light source that emits a light beam, a second light source that emits the second light beam, and a photodetector. 79. The optical pickup device is capable of reproducing or recording information on at least two types of optical information recording media, and the first light flux of the first light source is a first optical information recording medium. The second light source of the second light source is used for reproducing information from a medium or for recording information on a first optical information recording medium; 78. The optical element according to claim 77, wherein the optical element is used for reproducing information or for recording information on a second optical information recording medium. 80. The optical pickup device includes a converging optical system, wherein the converging optical system is used for reproducing information recorded on a first optical information recording medium or for reproducing information recorded on the first information recording medium. In order to record information, the n-th order diffracted light of the first light flux generated in the diffraction portion by the first light flux that has reached the diffraction portion of the optical element is transmitted through a first transparent substrate. The first optical information recording medium can be focused on a first information recording surface of the first optical information recording medium, and the focusing optical system is used for reproducing information recorded on a second optical information recording medium or the second optical information recording medium. In order to record information on the information recording medium, the n-th order diffracted light of the second light flux generated in the diffraction portion by the second light flux that has reached the diffraction portion of the optical element is converted into a second transparent light. On a second information recording surface of the second optical information recording medium via a substrate The optical element according to claim 79, characterized in that it is possible to light. 81. The optical pickup device has an objective lens, and the condensing optical system converts the nth-order diffracted light of the first light beam on a first information recording surface of the first optical information recording medium. In the image side of the objective lens, within the predetermined numerical aperture of the first light flux, the light can be focused in a state of not more than 0.07 λrms, and the focusing optical system converts the n-th order diffracted light of the second light flux. The second optical information recording medium is capable of condensing light on the second information recording surface of the objective lens in a state of 0.07 λrms or less within a predetermined numerical aperture of the second light flux on the image side of the objective lens. The optical element according to claim 80, wherein 82. The first optical information recording medium has a thickness t1.
80. The optical element according to claim 79, further comprising: a first transparent substrate having a thickness of t2, wherein the second optical information recording medium has a thickness t2 different from the thickness t1. 83. The optical pickup device has a condensing optical system including an objective lens, and the condensing optical system converts the n-th order diffracted light in the first light flux passing through the diffractive portion to the first light beam. On the first information recording surface of the optical information recording medium, 0.07λrm on the image side of the objective lens within a predetermined numerical aperture of the first light flux.
s or less, and the condensing optical system converts the n-th order diffracted light of the second light beam onto the second information recording surface of the second optical information recording medium by the image of the objective lens. 83. The optical element according to claim 82, wherein light can be collected in a state of 0.07? Rms or less within a predetermined numerical aperture of the second light flux on the side. 84. The optical element according to claim 82, wherein the following conditional expression is satisfied. λ1 <λ2 t1 <t2 where λ1: wavelength of the first light source λ2: wavelength of the second light source t1: thickness of the first transparent substrate t2: thickness of the second transparent substrate 85. The optical element according to claim 84, wherein the optical pickup device has an objective lens and satisfies the following conditional expression. NA1> NA2 Here, NA1: a predetermined numerical aperture on the image side of the objective lens required for recording or reproduction of the first optical information recording medium with light having a wavelength of λ1 NA2: the second numerical aperture with light having a wavelength of λ2 A predetermined numerical aperture on the image side of the objective lens required for recording or reproduction of the optical information recording medium 86. The optical element according to claim 77, wherein the nth-order diffracted light is a + 1st-order diffracted light. 87. The optical element according to claim 85, wherein the following conditional expression is satisfied. 0.55 mm <t1 <0.65 mm 1.1 mm <t2 <1.3 mm 630 nm <λ1 <670 nm 760 nm <λ2 <820 nm 0.55 <NA1 <0.68 0.40 <NA2 <0.55 88. The optical element is the objective lens, λ1 = 650 nm t1 = 0.6 mm, NA1 = 0.6, and the first lens is a parallel light having a uniform intensity distribution. Wherein the spot diameter at the best focus is 0.88 to 0.91 μm when the light beam is incident on the first information recording surface via the first transparent substrate. An optical element according to claim 87. 89. The optical element is the objective lens, λ1 = 650 nm t1 = 0.6 mm, NA1 = 0.65, and the first lens is a parallel light having a uniform intensity distribution. Wherein the spot diameter at the best focus is 0.81 to 0.84 μm when the luminous flux is incident and condensed on the first information recording surface via the first transparent substrate. An optical element according to claim 87. 90. The optical element according to claim 87, wherein the following conditional expression is satisfied. t1 = 0.6 mm t2 = 1.2 mm λ1 = 650 nm λ2 = 780 nm NA1 = 0.6 NA2 = 0.45 91. The optical element, wherein the optical element is the objective lens, wherein the n-th order diffracted light of the second light flux is converged on the second information recording surface of the second optical information recording medium. 86. The optical element according to claim 85, wherein the spherical aberration has at least one discontinuous portion. 92. The optical element according to claim 91, wherein said spherical aberration has a discontinuity near said NA2. 93. The optical element according to claim 91, wherein the spherical aberration has a discontinuity at a numerical aperture (NA) of 0.45. 94. The optical element according to claim 91, wherein the spherical aberration has a discontinuity at a numerical aperture (NA) of 0.5. 95. The objective lens, wherein the numerical aperture is the NA.
Condensing the n-order diffracted light of the first light flux of 1 or less on the first information recording surface of the first optical information recording medium such that the wavefront aberration at the best image point is 0.07λrms; The objective lens is configured to convert the n-th order diffracted light of the second light flux having a numerical aperture equal to or smaller than the numerical aperture serving as the discontinuous portion onto the second information recording surface of the second optical information recording medium at a wavefront aberration at a best image point. 90. The optical element according to claim 91, wherein light is condensed so as to be 0.07λrms. 96. The optical element is the objective lens, and in order to perform recording or reproduction on the second optical information recording medium, a condensing optical system including the objective lens of the pickup device controls the diffraction section. When the nth-order diffracted light of the passed second light flux is collected on the second information recording surface of the second optical information recording medium, the spherical aberration is continuous and has a discontinuous portion. 9. The method according to claim 8, wherein
6. The optical element according to 5. 97. The optical element according to claim 96, wherein the spherical aberration is 20 μm or more at NA1, and the spherical aberration is 10 μm or less at NA2. 98. The optical element according to claim 82, wherein the following conditional expression is satisfied. λ1 <λ2 t1> t2 where λ1: wavelength of the first light source λ2: wavelength of the second light source t1: thickness of the first transparent substrate t2: thickness of the second transparent substrate 99. The optical element according to claim 98, wherein said nth-order diffracted light is a -1st-order diffracted light. 100. When the diffraction efficiency of the n-th order diffracted light of the first light flux in the diffractive portion is A%, and the diffraction efficiency of another order diffracted light is B%, AB ≧ 10. A′−B ′ ≧ 10, where A ′% is the diffraction efficiency of the n-th order diffracted light of the second light flux in the diffracting unit, and B ′% is the diffraction efficiency of the diffracted light of another certain order. The optical element according to any one of claims 77 to 99, wherein: 101. When the diffraction efficiency of the n-th order diffracted light of the first light flux in the diffractive portion is A% and the diffraction efficiency of another order diffracted light is B%, AB ≧ 50. A′−B ′ ≧ 50, where the diffraction efficiency of the n-th order diffracted light of the second light flux in the diffracting unit is A ′% and the diffraction efficiency of the diffracted light of another certain order is B ′%. The optical element according to any one of claims 77 to 99, wherein: 102. The diffractive portion has a plurality of zones when viewed from the direction of the optical axis, and the zones are substantially concentric with respect to the optical axis or a point near the optical axis. The optical element according to any one of claims 77 to 101, wherein the optical element is formed as follows. 103. A phase difference function represented by a power series indicating each position of the plurality of orbicular zones of the diffraction section, wherein at least one term other than a square term has a coefficient other than 0. The optical element according to claim 102, wherein 104. A phase difference function represented by a power series indicating each position of the plurality of orbicular zones of the diffraction unit is represented by a square term,
103. The optical element according to claim 102, having a coefficient other than?. 105. The optical element according to claim 102, wherein a phase difference function represented by a power series indicating each position of the plurality of orbicular zones of the diffraction unit does not include a square term. 106. The optical element according to claim 102, wherein the sign of the diffractive action added by the diffractive portion is switched at least once in a direction perpendicular to the optical axis and away from the optical axis. . 107. The plurality of orbicular zones of the diffractive portion are blazed, and in an orbicular zone nearer to the optical axis, a step portion is located on a side away from the optical axis, and 107. The optical element according to claim 106, wherein a step portion is located on a side closer to the optical axis in an annular zone away from the axis. 108. The plurality of orbicular zones of the diffractive portion are blazed, and in an orbicular zone nearer to the optical axis, a step portion is located on a side closer to the optical axis. 107. The optical element according to claim 106, wherein the step portion is located on a side away from the optical axis in an annular zone away from the optical axis. 109. The optical pickup device has an objective lens, and has a pitch Pf of the orbicular zone of the diffractive portion corresponding to a maximum numerical aperture on the image side of the objective lens and a half of the maximum numerical aperture. Pitch P of the corresponding annular zone of the diffraction section
The optical element according to claim 102, wherein h satisfies the following conditional expression. 0.4 ≦ | (Ph / Pf) −2 | ≦ 25 110. The diffraction section has a first diffraction pattern and a second diffraction pattern, wherein the second diffraction pattern is farther from the optical axis than the first diffraction pattern. 2. The method according to claim 1, wherein
02. The optical element according to item 02. 111. In the first light beam that has passed through the first diffraction pattern of the diffraction section, the n-order diffracted light is generated more than diffracted lights of other orders, and Also in the second light flux that has passed through the first diffraction pattern, the n-th order diffracted light is generated more than the other order diffracted light, and the second order that has passed through the second diffraction pattern of the diffractive portion. In the first light beam, the n-th order diffracted light is generated more than the other order diffracted light, and in the second light beam passing through the second diffraction pattern of the diffractive portion, the 0th order light is The optical element according to claim 110, wherein the optical element is generated more than diffracted light of other orders. 112. In the first light beam that has passed through the first diffraction pattern of the diffraction section, the n-order diffracted light is generated more than diffracted lights of other orders, and Also in the second light flux that has passed through the first diffraction pattern, the n-order diffracted light is generated more than diffracted light of other orders, and the n-th order diffracted light has passed through the second diffraction pattern of the diffractive portion. In the first light beam, the 0th-order diffracted light is generated more than the other order diffracted light, and in the second light beam that has passed through the second diffraction pattern of the diffractive portion, n
The optical element according to claim 110, wherein diffracted light of a negative order other than the order is generated more than diffracted lights of other orders. 113. The optical element according to claim 102, wherein the diffractive portion is provided on substantially the entire surface of the optical element on which a light beam enters or a surface from which the light beam exits. 114. The optical element according to claim 102, wherein 10% or more and less than 90% of the area of the surface of the optical element on which the light beam enters or the surface from which the light beam exits is the diffraction portion. 115. The optical element according to claim 102, wherein the number of steps of the plurality of annular zones of the diffractive portion is 2 or more and 45 or less. 116. The optical element according to claim 115, wherein the number of steps of the plurality of annular zones of the diffractive portion is 2 or more and 15 or less. 117. The optical element according to claim 102, wherein a depth in the optical axis direction of a step portion of the plurality of orbicular zones of the diffractive portion is 2 μm or less. 118. The optical element according to claim 102, wherein the optical element is an objective lens of the optical pickup device, and a pitch of the diffractive portion at a numerical aperture (NA) of 0.4 is 10 to 70 μm. Optical element. 119. The optical element according to claim 77, wherein said optical element is a lens having a refractive surface. 120. The optical pickup according to claim 119, wherein the optical element is an objective lens of the optical pickup device.
An optical element according to item 1. 121. The optical element according to claim 119, wherein said optical element is a collimator lens of said optical pickup device. 122. The optical element according to claim 77, wherein said optical element is neither an objective lens nor a collimator lens of said optical pickup device. 123. The optical element according to claim 120, wherein said objective lens has a flange portion on an outer periphery. 124. The optical element according to claim 120, wherein the refraction surface of the objective lens is an aspheric surface. 125. The lens according to claim 1, wherein the lens is made of a material having an Abbe number νd larger than 50.
20. The optical element according to 19. The optical element according to any one of claims 119 to 125, wherein the lens is a plastic lens. The optical element according to any one of claims 119 to 125, wherein the lens is a glass lens. 128. The n-th order diffracted light is a +1 order diffracted light or a −1 order diffracted light.
127. The optical element according to any one of items 102 to 127. 129. The diffraction efficiency of the n-th order diffracted light in the diffractive portion is maximum at a wavelength between the wavelength of the first light flux and the wavelength of the second light flux. 129. The optical element according to any one of -128. 130. The diffraction device according to claim 77, wherein the diffraction efficiency of the n-th order diffracted light in the diffraction section is the maximum at the wavelength of the first light beam or the wavelength of the second light beam. Item 2. The optical element according to item 1. 131. The optical device according to claim 77, wherein the optical element satisfies the following conditional expression.
An optical element according to the item. −0.0002 / ° C. <Δn / ΔT <−0.00005 ° C. where ΔT (° C.): temperature change Δn: change in refractive index of the optical element 132. The optical pickup device has an objective lens, and when the first light beam is used, the first light beam within a predetermined numerical aperture on the image side of the objective lens is a first light beam. The light is condensed on the first information recording surface of the information recording medium in a state of 0.07 λ rms or less, and when the first light flux is used, the second light that has passed outside a predetermined numerical aperture on the image side of the objective lens. The first light beam is in a state larger than 0.07 λrms on the first optical information recording medium, and the second light beam passing through a predetermined numerical aperture on the image side of the objective lens when the second light beam is used. And the second light flux that has passed outside the predetermined numerical aperture is placed on the second information recording surface of the second optical information recording medium at 0.07λrms.
The second light flux which is condensed in the following state, or which is within a predetermined numerical aperture on the image side of the objective lens when using the second light flux, is used for the second optical information recording medium. The second light flux condensed on the second information recording surface in a state of not more than 0.07 λ rms and passing outside a predetermined numerical aperture on the image side of the objective lens when the second light flux is used. Is larger than 0.07 λrms on the second optical information recording medium. When the first light flux is used, the first light flux passing through a predetermined numerical aperture on the image side of the objective lens is used. In addition, the first light flux that has passed outside the predetermined numerical aperture also has 0.07λrms on the first information recording surface of the first optical information recording medium.
The optical element according to claim 77, wherein light is collected in the following state. 133. The optical pickup device has an objective lens, and when the first light beam is used, the first light beam within a predetermined numerical aperture on the image side of the objective lens is a first light beam. The light is condensed on the first information recording surface of the information recording medium in a state of 0.07 λ rms or less, and when the first light flux is used, the second light that has passed outside a predetermined numerical aperture on the image side of the objective lens. The first light flux is condensed on the first optical information recording medium in a state of not more than 0.07 λrms, or is blocked and does not reach the first information recording surface, and the second light flux does not reach the first information recording surface. When using a light beam, both the second light beam that has passed within the predetermined numerical aperture on the image side of the objective lens and the second light beam that has passed outside the predetermined numerical aperture are the second optical information recording medium. 0.07λrms on the second information recording surface of
The second light flux which is condensed in the following state, or which is within a predetermined numerical aperture on the image side of the objective lens when using the second light flux, is used for the second optical information recording medium. The second light flux condensed on the second information recording surface in a state of not more than 0.07 λ rms and passing outside a predetermined numerical aperture on the image side of the objective lens when the second light flux is used. Is focused on the second optical information recording medium in a state of not more than 0.07 λrms or is shielded and does not reach the second information recording surface. In use, neither the first light flux passing through the predetermined numerical aperture on the image side of the objective lens nor the first light flux passing outside the predetermined numerical aperture is the first light flux of the first optical information recording medium. 0.07λrms on the information recording surface
The optical element according to claim 77, wherein light is collected in the following state. 134. The optical element according to any one of claims 77 to 133, wherein the overshoot is 0 to 20%. 135. Reproducing information from an optical information recording medium,
A device for recording information on an optical information recording medium, comprising: an optical pickup device, wherein the optical pickup device emits a first light beam having a first wavelength; A second light source that emits a second light beam having a second wavelength different from the first wavelength, and a light-collecting optical system having an optical axis, a diffraction unit, and a photodetector; When the light beam passes through the diffraction portion, at least one order diffracted light in which the n-th order diffracted light amount of the first light beam is larger than any other order diffracted light amount of the first light beam is generated, As the second light beam passes through the diffractive portion, at least one order diffracted light in which the n-th order diffracted light amount of the second light beam is larger than any other order diffracted light amount of the second light beam Recording / reproducing apparatus characterized in that Here, n is an integer other than 0. 136. A recording and reproducing method for reproducing or recording information on at least two types of optical information recording media by an optical pickup device, wherein the optical pickup device comprises a first light source, a second light source, and a second light source. A light source, a condensing optical system having an optical axis and a diffractive portion, and a second light source having a first light flux from the first light source or a second light flux different from the wavelength of the first light flux from the second light source. Emitting a light beam; and passing the first light beam or the second light beam through the diffractive portion to diffract light of at least one order of the first light beam or at least one order of the second light beam. (Where the n-th order diffracted light amount of the at least one order diffracted light beam of the first light beam is larger than the diffracted light beam of any other order of the first light beam) When the second (The n-order diffracted light amount of the diffracted light of at least one order of the light beam is larger than the diffracted light amount of any other order of the second light beam); The n-order diffracted light of the second optical information recording medium on the first information recording surface of the first optical information recording medium or the n-order diffracted light of the second light flux on the second information recording surface of the second optical information recording medium. An optical pickup device for converging light to record information on or reproduce information from the first optical information recording medium or the second optical information recording medium; Detecting a first reflected light of the emitted n-order diffracted light from the first information recording surface or a second reflected light of the collected n-order diffracted light from the second information recording surface; And a method for recording and reproducing information. Here, n is an integer other than 0. 137. An optical system that includes one or more optical elements and is used for at least one of recording and reproduction of information on an information recording medium, wherein at least one of the optical elements is different from each other. An optical system having a diffraction surface that selectively generates diffracted light of the same order with respect to light of two wavelengths. 138. An optical system that includes one or more optical elements and is used for at least one of recording and reproducing information on an information recording medium, wherein each of the optical systems has at least two different wavelengths. An optical system, characterized in that a diffractive surface for selectively generating diffracted light of a specific order is formed on almost the entire optical surface of at least one of the at least one optical element. 139. The optical system according to claim 138, wherein the specific orders of the diffracted lights selectively generated with respect to each of the at least two different wavelengths are the same. 140. The optical system according to claim 137, wherein the diffracted light of the same order is a first-order diffracted light. 141. One of claims 137 to 140
13. An optical system, wherein at least one optical element of the optical element having a diffractive surface according to the item is a lens having a refractive power. 142. The optical system according to claim 141, wherein said lens has an aspherical refractive surface shape. 143. The lens, wherein the lens changes the diffraction efficiency of diffracted light with respect to light of a certain wavelength that is a wavelength between the maximum wavelength and the minimum wavelength of the at least two different wavelengths from each other. 142. The optical system according to claim 141 or 142, wherein the diffraction efficiency is larger than the diffraction efficiency of the diffracted light with respect to the light having the wavelength. 144. The lens according to claim 1, wherein the lens sets a diffraction efficiency of the diffracted light with respect to the light of the maximum wavelength or the minimum wavelength of the at least two different wavelengths to a wavelength between the maximum wavelength and the minimum wavelength of the at least two different wavelengths. 142. The optical system according to claim 141 or 142, wherein the diffraction efficiency is greater than the diffraction efficiency of the diffracted light with respect to the light. 145. The apparatus according to claim 141, wherein the sign of the diffraction power applied on the diffraction surface of the lens is switched at least once in a direction perpendicular to an optical axis and away from the optical axis. An optical system according to claim 1. 146. The optical system according to claim 145, wherein the diffraction power applied on the diffraction surface of the lens switches once from negative to positive in a direction perpendicular to the optical axis and away from the optical axis. . 147. The diffractive surface is formed of a plurality of orbicular zones as viewed from the optical axis direction, and the plurality of orbicular zones are formed substantially concentrically around an optical axis or a point near the optical axis. The optical system according to any one of claims 137 to 146, wherein: 148. A phase difference function represented by a power series indicating each position of the plurality of orbicular zones is at least one other than a square term.
147. The optical system of claim 147, wherein one term has a non-zero coefficient. 149. The optical device according to claim 147, wherein the phase difference function represented by a power series indicating each position of the plurality of orbicular zones has a coefficient other than zero in a square term. system. The optical system according to claim 147 or 148, wherein the phase difference function represented by a power series indicating each position of the plurality of orbicular zones does not include a square term. 151. The one or more optical elements include an objective lens, and for each of the at least two different wavelengths of light (wavelength λ), a wavefront aberration on an imaging plane is: 2. The image forming apparatus according to claim 1, wherein the numerical aperture is equal to or less than 0.07 .lamda.
The optical system according to any one of Items 37 to 150. 152. Even if one of the at least two different wavelengths λ ₁ fluctuates within a range of ± 10 nm, the wavefront aberration on the image forming surface is reduced by a predetermined value on the image side of the objective lens. the optical system of claim 151, wherein not more than 0.07λ ₁ rms within the numerical aperture. 153. said at least two different ones
Wavelength λ _TwoLight on the image side of the objective lens
The predetermined numerical aperture is the wavelength λ._TwoFrom the numerical aperture of the light
The light of the different wavelength is larger than the light of the different wavelength.
Within a predetermined numerical aperture_TwoWaves on the image plane of light
Surface aberration is 0.07λ_Tworms
The optical system according to claim 151, wherein 154. Within a predetermined numerical aperture for the light of the different wavelength, the wavefront aberration of the light of the wavelength λ ₂ on the imaging plane is equal to 0.
16. The wavelength is not less than 10λ ₂ rms.
4. The optical system according to 3. [Claim 155] and NA1 the predetermined numerical aperture for the light of the further wavelength, when the NA2 a prescribed numerical aperture for said wavelength lambda ₂ of the light, and satisfies the NA1>NA2> 0.5 × NA1 157. The optical system according to claim 153 or 154. 156. The objective lens receives a parallel light beam with respect to at least one of the at least two different wavelengths from the at least two different wavelengths.
The optical system according to any one of claims 151 to 155, wherein a non-parallel light beam is incident on light of two wavelengths. 157. The object lens according to any one of claims 151 to 155, wherein a parallel light beam is incident on at least two wavelengths of the at least two different wavelengths from each other. The optical system according to the item. 158. The object lens according to claim 151, wherein a non-parallel light beam is incident on at least two wavelengths of the at least two different wavelengths from each other. Item 2. The optical system according to item 1. 159. A wavelength longer than any two of the at least two different wavelengths by λ
_3, and when the predetermined numerical aperture on the image side of the objective lens with respect to the light of the wavelength λ ₃ is NA, the axial chromatic aberration between the wavelength λ ₃ and the shorter wavelength is −λ ₃ / (2NA ² ) or more. And +
^{2. The method according} to claim 1, wherein the distance is not more than λ ₃ / (2NA ² ).
The optical system according to any one of Items 51 to 158. 160. The method according to claim 151, wherein the light having at least two different wavelengths is used for information recording media having different thicknesses of transparent substrates.
160. The optical system according to any one of items 159 to 159. 161. The optical system according to claim 151, wherein said at least two different wavelengths are three different wavelengths. 162. The lights of three different wavelengths are respectively λ1, λ2, λ3 (λ1 <λ2 <λ3),
Further, the predetermined numerical aperture on the image side of the objective lens for each of these three different wavelengths of light is NA1,
When NA2 and NA3 are set, 0.60 ≦ NA1, 0.60 ≦ NA2, 0.40 ≦
165. The optical system according to claim 161, wherein NA3 ≦ 0.50 is satisfied. 163. A filter, wherein a filter capable of blocking at least a part of light incident on the objective lens outside the smallest predetermined numerical aperture among the predetermined numerical apertures is provided. 151 to 16
3. The optical system according to any one of 2. The optical element having the diffraction surface is an objective lens.
The optical system according to any one of the above. 165. An optical element having the diffraction surface is the objective lens.
63. The optical system according to any one of items 63. 166. The optical system according to claim 164, wherein said objective lens comprises a single lens. 167. The optical system according to claim 166, wherein said diffraction surfaces are provided on both surfaces of said objective lens. 168. The Abbe number ν of the material of the objective lens
168. The optical system according to any one of claims 164 to 167, wherein d is greater than 50. 169. The optical system according to claim 164, wherein the objective lens is made of plastic. 170. The optical system according to claim 164, wherein said objective lens is made of glass. 171. The optical system according to any one of claims 164 to 168, wherein said objective lens has a resin layer having said diffraction surface formed on a surface of a glass lens. 172. The optical system according to claim 137, wherein a wavelength difference between at least two different wavelengths is 80 nm or more. 173. The optical system according to claim 172, wherein a wavelength difference between at least two different wavelengths is 400 nm or less. 174. The optical system according to claim 173, wherein a wavelength difference between at least two different wavelengths is not less than 100 nm and not more than 200 nm. 175. The diffractive efficiency of the selectively generated diffracted light of a specific order with respect to each of the at least two different wavelengths is different from that of the diffracted light of each of the orders other than the specific order. The efficiency is 10% or more higher than the efficiency.
5. The optical system according to any one of 4. 176. The diffractive efficiency of the selectively generated diffracted light of the specific order is different from the diffracted light of the diffracted light of the orders other than the specific order with respect to the respective lights of at least two different wavelengths. 178. The optical system according to claim 175, wherein the efficiency is 30% or more higher than the efficiency. 177. The diffractive efficiency of the selectively generated diffracted light of the specific order is at least 50% for each of the at least two different wavelengths. 176. The optical system according to any one of 176. 178. The diffractive efficiency of the selectively generated diffracted light of a specific order is 70% or more for each of the lights of at least two different wavelengths. Optical system. 179. The presence of the diffractive surface allows the selectively generated diffracted light of at least two different wavelengths of a specific order to be focused when compared with a case where the diffractive surface is not present. 178. The optical system according to any one of claims 137 to 178, wherein aberration is improved. 180. A wavefront aberration on the image plane of diffracted light of a specific order that is selectively generated with respect to each light (wavelength λ) of at least two different wavelengths is 0.07λrms or less. The optical system according to any one of claims 137 to 179, wherein the optical system is provided. 181. Any one of claims 137 to 180
An optical pickup device comprising the optical system described in the paragraph. 182. An optical system including at least two light sources that output light of mutually different wavelengths, one or more optical elements for condensing light from the light sources on an information recording medium, and An optical pickup device comprising: a light detector that detects transmitted light or reflected light of at least one of the optical elements, wherein at least one of the optical elements is different from light of two different wavelengths output from the at least two light sources. An optical pickup device having a diffraction surface that selectively generates diffracted light of the same order. 183. An optical system including at least two light sources for outputting light having different wavelengths from each other, one or more optical elements for condensing light from the light sources on an information recording medium, and A light detector for detecting the transmitted light or the reflected light, selectively diffracting the diffracted light of a specific order with respect to each of two different wavelengths outputted from the at least two light sources. An optical pickup device, wherein a diffracting surface generated in the optical element is formed on almost the entire optical surface of at least one of the at least one optical element. 184. An optical pickup device, wherein at least one optical element of the optical element having a diffractive surface according to claim 182 or 183 is a lens having a refractive power. 185. The lens, wherein the lens has a diffraction efficiency of diffracted light with respect to light having one wavelength that is a wavelength between a maximum wavelength and a minimum wavelength of two different wavelengths output from the at least two light sources. 183. The optical pickup device according to claim 184, wherein the diffraction efficiency is higher than the diffraction efficiency of the diffracted light with respect to the light having the maximum wavelength and the light having the minimum wavelength. 186. The lens sets the diffraction efficiency of the diffracted light with respect to the light having the maximum wavelength or the minimum wavelength of the two different wavelengths output from the at least two light sources, to the maximum wavelength of the at least two different wavelengths and the minimum. 189. The optical pickup device according to claim 184, wherein the diffraction efficiency is higher than the diffraction efficiency of the diffracted light with respect to light having a wavelength between the wavelengths. 187. The optical pickup device according to claim 184, wherein the lens has a flange portion on an outer periphery. 188. The optical pickup device according to claim 187, wherein the flange portion has a surface extending substantially perpendicular to an optical axis of the lens. 189. The one or more optical elements include an objective lens, and each of two different wavelengths of light (wavelength λ) output from the at least two light sources has an image forming surface. 188. The optical pickup device according to any one of claims 182 to 188, wherein the wavefront aberration of the objective lens is 0.07λrms or less within a predetermined numerical aperture on the image side of the objective lens. 190. An objective lens is included in the one or more optical elements, and light of two different wavelengths (wavelength λ) output from the at least two light sources is formed on an imaging plane. 188. The optical pickup device according to any one of claims 182 to 188, wherein the wavefront aberration of the objective lens is 0.07λrms or less within the maximum numerical aperture on the image side of the objective lens. 191. One of two different wavelengths λ ₁ output from the at least two light sources is ± 1.
Even if it fluctuates within the range of 0 nm, the wavefront aberration on the image plane becomes 0.07 within the predetermined numerical aperture on the image side of the objective lens.
190. The optical pickup device according to claim 189 or 190, wherein λ ₁ rms or less. 192. Among two different wavelengths output from the at least two light sources, a light having a wavelength λ ₂ and a predetermined numerical aperture on the image side of the objective lens are larger than a predetermined numerical aperture regarding the light having the wavelength λ _2. The wavelength of the light of the wavelength λ ₂ is greater than 0.07 λ ₂ rms on the imaging surface within a predetermined numerical aperture of the light of the other wavelength. 189. The optical pickup device according to claim 189. 193. Within a predetermined numerical aperture for the light of the different wavelength, the wavefront aberration of the light of the wavelength λ ₂ on the imaging surface is equal to 0.
20. It is at least 10λ ₂ rms.
3. The optical pickup device according to 2. [Claim 194] and NA1 the predetermined numerical aperture for the light of the further wavelength, when the NA2 a prescribed numerical aperture for said wavelength lambda ₂ of the light, and satisfies the NA1>NA2> 0.5 × NA1 The optical pickup device according to claim 192 or 193. 195. The objective lens, comprising two different wavelengths output from the at least two light sources,
189. A light beam having at least one wavelength receives a parallel light beam, and a light beam having another at least one wavelength receives a non-parallel light beam.
The optical pickup device according to claim 1. 196. The object lens according to claim 18, wherein a parallel light beam is incident on light of two different wavelengths output from the at least two light sources.
The optical pickup device according to any one of items 9 to 194. 197. The object lens according to claim 1, wherein a non-parallel light beam is incident on light of two different wavelengths output from the at least two light sources.
The optical pickup device according to any one of Items 89 to 194. 198. A wavelength longer than two different wavelengths output from the at least two light sources is λ _3, and a predetermined numerical aperture on the image side of the objective lens with respect to the light having the wavelength λ ₃ is NA. When the axial chromatic aberration between the wavelength λ ₃ and the shorter wavelength is −λ ₃ / (2NA ² ) or more and + λ
20. The ratio is not more than ₃ / (2NA ² ).
The optical pickup device according to any one of items 9 to 197. 199. The apparatus according to any one of claims 189 to 194, wherein light of two different wavelengths output from the at least two light sources is used for information recording media having different thicknesses of transparent substrates. 2. The optical pickup device according to claim 1. 200. The diffractive surface includes a plurality of orbicular zones as viewed from the optical axis direction, and the plurality of orbicular zones are formed substantially concentrically around an optical axis or a point near the optical axis. The following relationship exists between a pitch Pf of the orbicular zone corresponding to the maximum numerical aperture on the image side of the objective lens and a pitch Ph of the orbicular zone corresponding to a numerical aperture of 1/2 of the maximum numerical aperture. 200. The optical pickup device according to claim 199, wherein the condition is satisfied. 0.4 ≦ | (Ph / Pf) −2 | ≦ 25 201. The apparatus according to claim 189, wherein the at least two light sources are three light sources.
The optical pickup device according to claim 1. 202. Lights of three different wavelengths output from the three light sources are respectively λ1, λ2, λ3 (λ1 <
.lamda.2 <.lambda.3), and when the predetermined numerical aperture on the image side of the objective lens for each of the three different wavelengths is NA1, NA2, and NA3, respectively, 0.60.ltoreq.NA1, 0.60.ltoreq.NA2. , 0.40 ≦
The optical pickup device according to claim 201, wherein NA3 ≤ 0.50 is satisfied. 203. A filter, wherein a filter capable of blocking at least a part of light incident on the objective lens outside the smallest predetermined numerical aperture among the predetermined numerical apertures is provided. 189 to 20
3. The optical pickup device according to any one of 2. 204. An optical pickup according to any one of claims 189 to 202, further comprising an aperture limiting means for providing said predetermined numerical aperture for each of said two different wavelengths of light. apparatus. 205. The optical pickup device according to claim 189, wherein there is no aperture restriction so that one of the two different wavelengths has the predetermined numerical aperture. . 206. The one or more optical elements include an objective lens, and the objective lens is commonly used when condensing the lights of the different wavelengths on the information recording medium, respectively. The optical pickup device according to claim 182 or 183. 207. The unit according to claim 206, wherein the unit in which the at least two light sources and the objective lens are integrated is driven at least in parallel with the main surface of the information recording medium. Optical pickup device. 208. The optical pickup device according to claim 207, wherein said unit is driven perpendicular to a main surface of said information recording medium. 209. Any one of claims 181 to 208
A recording / reproducing apparatus equipped with the optical pickup device described in the item 1 and capable of recording or reproducing at least one of a sound and an image. 210. A lens used for at least one of recording and reproduction of information on an information recording medium, having a refractive power and having a diffractive surface on at least one optical surface, wherein a diffractive power added by the diffractive surface is provided. Wherein the sign of the sign is switched at least once in a direction perpendicular to the optical axis and away from the optical axis. 211. The diffractive surface has a plurality of blazed diffraction zones, and in the diffraction zone near the optical axis, the step is located on the side away from the optical axis, and the step is located away from the optical axis. 210. The lens according to claim 210, wherein the step portion is located on a side closer to the optical axis in the diffraction ring zone on the other side. 212. The diffractive surface has a plurality of blazed diffraction zones, and in the diffraction zone near the optical axis, the step portion is located on the side near the optical axis and separated from the optical axis. 210. The lens according to claim 210, wherein the step portion is located on a side away from the optical axis in the diffraction zone on the side. 213. An optical element applicable in an optical system for recording and / or reproducing information on an information recording medium, wherein the information on the information recording medium uses light of at least two different wavelengths. When used in an optical system for recording and / or reproduction of a light having at least two different wavelengths, it has a diffractive surface that selectively generates diffracted light of the same order. Characteristic optical element. 214. A lens applicable as an objective lens in an optical system for recording and / or reproducing information on an information recording medium, wherein the information recording medium uses at least two different wavelengths of light. When used as an objective lens in an optical system for recording and / or reproducing information with respect to light, a diffraction surface that selectively generates diffracted light of the same order with respect to the light of at least two different wavelengths is provided. Lens. 215. An optical element applicable to an optical system for recording and / or reproducing information on an information recording medium, wherein the information on the information recording medium uses light of at least two different wavelengths. When used in an optical system for recording and / or reproducing, at least one of the optical surfaces has a diffractive surface for selectively generating diffracted light of a specific order with respect to the at least two different wavelengths of light. An optical element formed substantially over the entire surface of the optical element. 216. A lens applicable as an objective lens in an optical system for recording and / or reproducing information on an information recording medium, wherein the information on the information recording medium uses light of at least two different wavelengths. When used as an objective lens in an optical system for recording and / or reproducing, at least one of the diffractive surfaces that selectively generates diffracted light of a specific order with respect to the light of at least two different wavelengths is provided. A lens formed substantially over the entire optical surface. 217. A recording / reproducing optical system having two light sources having different wavelengths and performing recording / reproducing by the same optical system, wherein the optical system includes an optical surface provided with a diffractive orbicular zone lens on a refractive surface. The aberration caused by the difference in wavelength cancels out the aberration caused in the refraction surface and the aberration caused by the diffractive orbicular zone lens, and the diffracted light used for the cancellation is the same order diffracted light with respect to the two light source wavelengths. Optical system for optical disks. 218. The diffraction optical system for an optical disk according to claim 217, wherein the canceling aberration is a spherical aberration and / or a chromatic aberration. 219. The diffraction optical system for an optical disk according to claim 217, wherein the diffracted light of the same order is a first-order diffracted light. 220. An optical disc diffraction optical system according to claim 217, 218 or 219, wherein the light sources of two different wavelengths correspond to optical discs having different transparent substrate thicknesses. 221. The diffractive optical system for an optical disk according to claim 217, 218, 219 or 220, wherein, of the two light sources having different wavelengths, the shorter light source wavelength is 700 nm or less. 222. The light source according to claim 217, 218, 219, 220 or 221 wherein, of the two light sources having different wavelengths, the longer light source wavelength is 600 nm or more.
2. A diffractive optical system for an optical disk according to claim 1. 223. The diffraction annular lens according to any one of claims 217 to 222, wherein the phase function representing the position of the annular zone includes a coefficient of a term other than the square of the power series. Diffraction optical system for optical disks. 224. The optical disc diffraction optical system according to any one of claims 217 to 223, wherein the optical refraction surface is an aspherical surface. 225. The optical disk according to any one of claims 217 to 224, wherein, for a light source having two wavelengths having different wavelengths, the diffraction efficiency of diffracted light is maximized at a substantially intermediate wavelength. Diffraction optical system. 226. The optical disc according to any one of claims 217 to 225, wherein, for two light sources having different wavelengths, the diffraction efficiency of diffracted light is maximum at one of the light source wavelengths. Diffraction optical system. 227. The diffractive orbicular zone lens on the optical surface corrects the spherical aberration under, and the aspherical surface of the optical surface corrects the spherical aberration over.
27. The diffractive optical system for an optical disk according to any one of 26. 228. The two-wavelength light source having different wavelengths, wherein the wavelength difference is 80 nm or more.
28. The optical disc diffractive optical system according to any one of items 27 to 27. 229. In an objective lens optical system of an optical disk, by providing a diffraction ring lens on an optical surface,
A diffractive optical system for an optical disk, wherein the axial chromatic aberration of one diffracted light of the same order is corrected for each of two different wavelength light sources. 230. The diffractive optical system for an optical disk according to claim 93, wherein a wavelength difference between the two different wavelength light sources is 80 nm or more, and a single lens objective lens satisfying the following conditions is provided. νd> 50 where νd: Abbe number of the glass material of the objective lens 231. One of the lens performances for two different wavelengths has no aberration up to the aperture in actual use,
A diffractive optical system for optical discs, characterized in that the outer portion is flared. 232. Among the lens performances for the two different wavelengths, when the numerical aperture for the wavelength that has no aberration at all apertures is NA1, and the actual numerical aperture for the other wavelength is NA2, The diffraction optical system for an optical disk according to claim 230, wherein the following condition is satisfied. NA1>NA2> 0.5 × NA1 233. The optical disc according to claim 231 or 231 wherein the optical disc thickness for the two different wavelengths is different.
3. A diffractive optical system for an optical disk according to item 2. 234. At least two or more light sources having different wavelengths, and divergent light beams from the respective light sources are recorded on the information recording surface of the optical information recording medium via the transparent substrate by the same objective lens through the transparent substrate. In the recording / reproducing optical system for reproducing information on the information recording surface, the objective lens includes an optical character surface provided with a ring-shaped diffraction surface on a refraction surface. An optical pickup device, wherein a light beam transmitted through an objective lens and a transparent substrate has diffraction-limited performance at the best image point. 235. It has at least two or more light sources having different wavelengths, and records divergent luminous flux from each light source on the information recording surface of the optical information recording medium via the transparent substrate by the same objective lens. In the recording / reproducing optical system for reproducing information on the information recording surface, the objective lens includes an optical surface provided with a ring-shaped diffraction surface on a refraction surface. The luminous flux transmitted through the objective lens and the transparent substrate has diffraction-limited performance at the best image point. For at least one light source, of the luminous flux transmitted through the objective lens and the transparent substrate, to the aperture for practical use The light pickup device has a diffraction-limited performance at its best image point, and the ring-shaped diffractive surface is provided so that a portion outside the light beam is flare. 236. The optical pickup device according to claim 235, comprising at least three light sources having different wavelengths. 237. The optical pickup device according to claim 236, further comprising an optical surface provided with at least two or more annular diffraction surfaces. 238. 235, 236 or 237
3. The optical pickup device according to claim 1, further comprising a ring-shaped filter that shields a part of the light beam outside the aperture in practical use among the light beams incident on the objective lens. 239. The optical pickup device according to claim 235, 236, 237 or 238, wherein the unit including the light source and the objective lens is driven at least in parallel with the optical information recording medium. 240. The optical pickup device according to claim 239, wherein the unit including the light source and the objective lens is further driven vertically to the optical information recording medium. 241. Any one of claims 224 to 240
And / or recording of audio and / or images, wherein the optical pickup device according to (1) is mounted.
An audio and / or video playback device. 242. It has at least two or more light sources having different wavelengths, and records divergent light beams from each light source on the information recording surface of the optical information recording medium via the transparent substrate by the same objective lens. And / or an objective lens used for a recording / reproducing optical system for reproducing information on an information recording surface, wherein the objective lens includes an optical character surface provided with a ring-shaped diffraction surface on a refraction surface, and at least one objective surface. For one light source, the light beam transmitted through the objective lens and the transparent substrate has diffraction-limited performance at the best image point. 243. At least two or more light sources having different wavelengths, and divergent light beams from the respective light sources are recorded on the information recording surface of the optical information recording medium by the same objective lens via the transparent substrate. An objective lens used for a recording / reproducing optical system for reproducing information on an information recording surface, wherein the objective lens includes an optical surface provided with a ring-shaped diffraction surface on a refraction surface, and at least one objective lens. For one light source, the light beam transmitted through the objective lens and the transparent substrate has diffraction-limited performance at the best image point. For at least one light source, the light beam transmitted through the objective lens and the transparent substrate is Among them, the luminous flux up to the aperture in actual use has diffraction-limited performance at its best image point, and the outer portion thereof is provided with the above-mentioned annular diffraction surface so as to be flare. Object lens. 244. A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system including an objective lens, and the first optical information recording medium having different wavelengths from each other. A first light source having a wavelength of λ1 for recording / reproducing data, a second light source having a wavelength of λ2 for recording / reproducing a second optical information recording medium, and a third light source having a wavelength of λ3 for recording / reproducing a third optical information recording medium. In an optical pickup device for recording / reproducing information on / from an optical information recording medium, at least one surface of the objective lens is substantially equal to or less than a diffraction limit by diffracted light of the same order for each optical information recording medium. An optical pickup device having a diffraction surface with spherical aberration corrected. 245. A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system including an objective lens, and the first optical information recording medium having different wavelengths from each other. A first light source having a wavelength of λ1 for recording / reproducing data, a second light source having a wavelength of λ2 for recording / reproducing a second optical information recording medium, and a third light source having a wavelength of λ3 for recording / reproducing a third optical information recording medium. An optical pickup device for recording / reproducing an optical information recording medium, wherein at least one side of the objective lens uses diffracted light of the same order for each optical information recording medium, and at least one optical information recording medium. On the other hand, an optical pickup apparatus characterized in that the aperture up to the aperture in practical use is substantially equal to or less than the diffraction limit, and the aberration outside the aperture is flare. 246. The apparatus according to claim 244, wherein the diffraction surface is formed on both surfaces of the objective lens.
6. The optical pickup device according to 5. 247. The optical pickup apparatus according to claim 244, 245 or 246, wherein the diffracted lights of the same order are first-order diffracted lights. 248. The diffractive surface is formed in an annular shape around the optical axis of the objective lens, and a phase function representing the position of the annular zone includes a coefficient of a term other than the square of a power series. The optical pickup device according to claim 244, 245, 246, or 247. 249. The diffraction surface is formed in an annular shape around the optical axis of the objective lens, and a phase function representing the position of the annular zone includes a coefficient of a power series square term. The optical pickup device according to claim 244, 245, 246, or 247. 250. The diffractive surface is formed in an annular shape around the optical axis of the objective lens, and a phase function representing the position of the annular zone does not include a coefficient of a power series square term. The optical pickup device according to claim 244, 245, 246, or 247. 251. For each of the first light source, the second light source, and the third light source, at a wavelength at both ends or an intermediate band,
The optical pickup device according to any one of claims 244 to 250, wherein the diffraction efficiency of the diffracted light is the maximum. 252. At least one of the objective lenses has an aspherical surface, and spherical aberration is undercorrected on a diffraction surface;
The optical pickup device according to any one of claims 244 to 251, wherein spherical aberration is overcorrected for an aspheric surface. 253. Recording of sound and / or image, wherein the optical pickup device according to any one of claims 244 to 252 having the first light source, the second light source, and the third light source is mounted. And / or audio and / or video playback devices. 254. A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system, and recording / reproducing are performed on first optical information recording media having different wavelengths. An optical information recording apparatus comprising: a first light source having a wavelength λ1, a second light source having a wavelength λ2 for recording / reproducing a second optical information recording medium, and a third light source having a wavelength λ3 for recording / reproducing a third optical information recording medium. An objective lens used in an optical pickup device for recording / reproducing a medium, wherein at least one surface of the objective lens is substantially equal to or less than a diffraction limit by diffracted light of the same order for each optical information recording medium. An objective lens characterized in that a diffraction surface having spherical aberration corrected is formed below. 255. A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system, and recording / reproducing are performed on first optical information recording media having different wavelengths. An optical information recording apparatus comprising: a first light source having a wavelength λ1, a second light source having a wavelength λ2 for recording / reproducing a second optical information recording medium, and a third light source having a wavelength λ3 for recording / reproducing a third optical information recording medium. In an objective lens used for an optical pickup device for recording / reproducing a medium, at least one optical information recording medium is used on at least one surface of the objective lens by using diffracted light of the same order for each optical information recording medium. For the medium, the spherical aberration is corrected to about the same as or less than the diffraction limit up to the aperture in actual use,
An objective lens characterized in that the aberration is flare on the outer part. 256. A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system, and recording / reproducing are performed on first optical information recording media having different wavelengths. An optical information recording apparatus comprising: a first light source having a wavelength λ1, a second light source having a wavelength λ2 for recording / reproducing a second optical information recording medium, and a third light source having a wavelength λ3 for recording / reproducing a third optical information recording medium. In an optical pickup device for recording / reproducing a medium, at least one surface of the condensing optical system corrects spherical aberration to about the same as or less than the diffraction limit by diffracted light of the same order for each optical information recording medium. An optical pickup device characterized in that a diffracted surface is formed. 257. A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system, and recording / reproducing are performed on first optical information recording media having different wavelengths. An optical information recording apparatus comprising: a first light source having a wavelength λ1, a second light source having a wavelength λ2 for recording / reproducing a second optical information recording medium, and a third light source having a wavelength λ3 for recording / reproducing a third optical information recording medium. In an optical pickup device used for an optical pickup device for recording / reproducing a medium, at least one surface of a condensing optical system uses diffracted light of the same order for each optical information recording medium and at least one light beam. An optical pickup device comprising: an information recording medium having an aperture for practical use substantially equal to or less than a diffraction limit, and a diffraction surface having flare in an outer portion thereof is provided. 258. A first light source having a wavelength of λ1, a second light source having a wavelength of λ2 (λ2 ≠ λ1), and a diffraction pattern on at least one surface. An objective lens for condensing the information recording surface of the optical recording medium through a transparent substrate, and a photodetector for receiving reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium, By using at least the m-th order diffracted light (where m is an integer other than 0) of the light beam from the first light source from the diffraction pattern of the objective lens, the first light having a thickness of the transparent substrate of t1 is used. By recording and / or reproducing the information recording medium and utilizing at least n-order diffracted light (where n = m) of the light beam from the second light source from the diffraction pattern of the objective lens, the thickness of the transparent substrate Is t2 (where t
An optical pickup device for recording and / or reproducing the second optical information recording medium of 2 ≠ t1). 259. The wavelength λ of the first and second light sources.
1, λ2 is λ1 <λ2, and the thickness t of the transparent substrate is
1. An optical pickup device wherein t1 and t2 are used in a relationship of t1 <t2, wherein the m-order and n-order diffracted lights are both +1.
258. The optical pickup device of claim 258, wherein the light is a second-order diffracted light. 260. The wavelength λ of the first and second light sources
1, λ2 is λ1 <λ2, and the thickness t of the transparent substrate is
1. An optical pickup device wherein t2 and t2 are used in a relationship of t1> t2, wherein the m-order and n-order diffracted lights are both -1.
258. The optical pickup device of claim 258, wherein the light is a second-order diffracted light. 261. A required aperture on the optical information recording medium side of the objective lens necessary for recording and / or reproducing the first optical information recording medium having a transparent substrate with a thickness of t1 with a first light source having a wavelength of λ1. The number is NA1, the thickness of the transparent substrate is t2 (where t2> t1) and the second optical information recording medium is a second optical information recording medium having a wavelength λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the light source
(Where NA2 <NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the diffraction of the light flux from the first light source by the objective lens is performed. The + 1st-order diffracted light from the circumference farthest from the optical axis of the pattern is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the light flux from the first light source has the highest diffraction pattern of the objective lens. 258. The + 1st-order diffracted light from the circumference on the optical axis side is converted into a light flux with a numerical aperture on the optical information recording medium side of NAL1, and satisfies the condition of NAH1 <NA10 <NAL1 <NA2. An optical pickup device according to item 1. 262. A required aperture on the optical information recording medium side of the objective lens required for recording and / or reproducing the first optical information recording medium having a transparent substrate having a thickness of t1 with a first light source having a wavelength of λ1. The number is NA1, the thickness of the transparent substrate is t2 (where t2> t1) and the second optical information recording medium is a second optical information recording medium having a wavelength λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the light source
When (NA2> NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the diffraction of the light flux from the first light source by the objective lens is performed. The + 1st-order diffracted light from the circumference farthest from the optical axis of the pattern is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the light flux from the first light source has the highest diffraction pattern of the objective lens. 258. The + 1st-order diffracted light from the circumference on the optical axis side is converted into a luminous flux having a numerical aperture on the optical information recording medium side of NAL1, and satisfies the condition of NAH1 <NA2O≤NAL1≤NA1. An optical pickup device according to item 1. 263. A required aperture on the optical information recording medium side of the objective lens required for recording and / or reproducing the first optical information recording medium having a transparent substrate having a thickness of t1 with a first light source having a wavelength of λ1. The number is NA1, the thickness of the transparent substrate is t2 (where t2 <t1) and the second optical information recording medium is the second optical information recording medium having a wavelength λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the light source
(Where NA2 <NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the diffraction of the light flux from the first light source by the objective lens is performed. The -1st-order diffracted light from the circumference of the pattern that is farthest from the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the diffraction pattern of the objective lens of the light flux from the first light source is obtained. The -1st-order diffracted light from the circumference closest to the optical axis is converted into a light flux having a numerical aperture of NAL1 on the optical information recording medium side, and satisfies the condition of NAH1 <NA10 ≦ NAL1 ≦ NA2. Item 258. The optical pickup device according to item 258. 264. A required aperture on the optical information recording medium side of the objective lens necessary for recording and / or reproducing the first optical information recording medium having a transparent substrate having a thickness of t1 with a first light source having a wavelength of λ1. The number is NA1, the thickness of the transparent substrate is t2 (where t2 <t1) and the second optical information recording medium is the second optical information recording medium having a wavelength λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the light source
When (NA2> NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the diffraction of the light flux from the first light source by the objective lens is performed. The -1st-order diffracted light from the circumference of the pattern that is farthest from the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the diffraction pattern of the objective lens of the light flux from the first light source is obtained. The -1st-order diffracted light from the circumference closest to the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAL1, and satisfies the condition of NAH1 <NA2O ≦ NAL1 ≦ NA1. Item 258. The optical pickup device according to item 258. 265. A light beam from the first light source,
269. The light-collecting position of a light beam that does not pass through a diffraction pattern when the numerical aperture when passing through the objective lens is equal to or less than NA1 is substantially equal to the light-collecting position of a light beam that passes through the diffraction pattern. Optical pickup device. 266. The luminous flux from the second light source,
269. The light-condensing position of a light beam that does not pass through a diffraction pattern when the numerical aperture when passing through the objective lens is equal to or less than NA2 is substantially equal to the light-condensing position of a light beam that passes through the diffraction pattern. Optical pickup device. 267. A light beam from the first light source,
263. The light beam according to claim 263, wherein the light-condensing position of the light beam that does not pass through the diffraction pattern when the numerical aperture when passing through the objective lens is equal to or less than NA1 is substantially equal to the light-condensing position of the light beam that passes through the diffraction pattern. Optical pickup device. 268. The light beam from the second light source,
265. The light beam according to claim 264, wherein the condensing position of the light beam that does not pass through the diffraction pattern when the numerical aperture when passing through the objective lens is equal to or less than NA2 is substantially equal to the light condensing position of the light beam that passes through the diffraction pattern. Optical pickup device. 269. The + 1st-order diffracted light of the light beam from the second light source from the circumference farthest from the optical axis of the diffraction pattern of the objective lens has a numerical aperture on the optical information recording medium side of NAH.
The + 1st-order diffracted light of the light beam from the second light source from the circumference closest to the optical axis of the diffraction pattern of the objective lens of the light beam from the second light source is converted into a light beam with a numerical aperture on the optical information recording medium side of NAL2. A spot which is converted so that recording and / or reproduction of the first optical information recording medium can be performed using a light flux having a numerical aperture of not more than NA1 when passing through an objective lens among the light fluxes from the first light source. Is condensed on the information recording surface of the optical information recording medium, and of the light flux from the second light source, the light flux whose numerical aperture when passing through the objective lens is equal to or smaller than NAH2 is used for the second optical information recording medium. 265. The spherical aberration of the light beam passing through the objective lens is set such that a spot enabling recording and / or reproduction is focused on the information recording surface of the optical information recording medium. Optical pickup described Location. 270. The + 1st-order diffracted light of the luminous flux from the second light source from the circumference farthest from the optical axis of the diffraction pattern of the objective lens has a numerical aperture of NAH on the optical information recording medium side.
The + 1st-order diffracted light of the light beam from the second light source from the circumference closest to the optical axis of the diffraction pattern of the objective lens of the light beam from the second light source is converted into a light beam with a numerical aperture on the optical information recording medium side of NAL2. A spot which is converted so that recording and / or reproduction on the first optical information recording medium can be performed using a light flux having a numerical aperture of not more than NAH1 when passing through an objective lens among the light flux from the first light source. Is condensed on the information recording surface of the optical information recording medium, and of the light flux from the second light source, the light flux whose numerical aperture when passing through the objective lens is equal to or less than NA2 is used for the second optical information recording medium. 266. The spherical aberration of a light beam passing through an objective lens is set such that a spot enabling recording and / or reproduction is focused on an information recording surface of an optical information recording medium. Optical pickup described Location. 271. The −1st-order diffracted light of the light beam from the second light source from the circumference of the diffraction pattern of the objective lens that is farthest from the optical axis has a numerical aperture of NAH on the optical information recording medium side.
-1st-order diffracted light of the light beam from the second light source from the circumference closest to the optical axis of the diffraction pattern of the objective lens of the light beam from the second light source is a light beam with a numerical aperture NAL2 on the optical information recording medium side. In the light flux from the first light source, the light flux having a numerical aperture of not more than NA1 when passing through the objective lens can be used for recording and / or reproducing on the first optical information recording medium. The spot is condensed on the information recording surface of the optical information recording medium, and the second optical information recording medium is formed by using a light beam having a numerical aperture of NAH2 or less when passing through an objective lens among the light beams from the second light source. 267. The spherical aberration of a light beam passing through an objective lens is set such that a spot enabling recording and / or reproduction of a light beam is focused on an information recording surface of an optical information recording medium. Optical pickup described in Location. 272. The -1st-order diffracted light of the luminous flux from the second light source from the circumference farthest from the optical axis of the diffraction pattern of the objective lens has a numerical aperture of NAH on the optical information recording medium side.
-1st-order diffracted light of the light beam from the second light source from the circumference closest to the optical axis of the diffraction pattern of the objective lens of the light beam from the second light source is a light beam with a numerical aperture NAL2 on the optical information recording medium side. In the light beam from the first light source, the light beam having a numerical aperture of not more than NAH1 when passing through the objective lens can be used for recording and / or reproducing on the first optical information recording medium. A spot is condensed on an information recording surface of an optical information recording medium, and a second optical information recording medium using a light flux having a numerical aperture of not more than NA2 when passing through an objective lens among light fluxes from the second light source. 268. The spherical aberration of a light beam passing through an objective lens is set such that a spot enabling recording and / or reproduction of a light beam is focused on an information recording surface of an optical information recording medium. Optical pickup described in Location. 273. The light beam from the first light source,
A light beam having a numerical aperture of NA1 or less when passed through the objective lens has a wavefront aberration of 0.07λrms or less at the best image point via the transparent substrate of the first optical information recording medium, and a light beam from the second light source. Of the light fluxes having a numerical aperture of NAH2 or less when passing through the objective lens, the wavefront aberration at the best image point through the transparent substrate of the second optical information recording medium is 0.1.
27 λrms or less.
10. The optical pickup device according to item 9. 274. The light flux from the first light source,
A light beam having a numerical aperture of NAH1 or less when passed through the objective lens has a wavefront aberration of 0.07λrms or less at the best image point through the transparent substrate of the first optical information recording medium, and a light beam from the second light source. Among them, a light beam having a numerical aperture of NA2 or less when passing through the objective lens has a wavefront aberration of 0.02 at the best image point via the transparent substrate of the second optical information recording medium.
290. The optical pickup device according to claim 270, wherein the optical pickup device has a wavelength of 7? Rms or less. 275. Of the light flux from the first light source,
A light beam having a numerical aperture of NA1 or less when passed through the objective lens has a wavefront aberration of 0.07λrms or less at the best image point via the transparent substrate of the first optical information recording medium, and a light beam from the second light source. Of the light fluxes having a numerical aperture of NAH2 or less when passing through the objective lens, the wavefront aberration at the best image point through the transparent substrate of the second optical information recording medium is 0.1.
271. The pulse width is not more than 07λrms.
An optical pickup device according to item 1. 276. In the light flux from the first light source,
A light beam having a numerical aperture of NAH1 or less when passed through the objective lens has a wavefront aberration of 0.07λrms or less at the best image point through the transparent substrate of the first optical information recording medium, and a light beam from the second light source. Among them, a light beam having a numerical aperture of NA2 or less when passing through the objective lens has a wavefront aberration of 0.02 at the best image point via the transparent substrate of the second optical information recording medium.
278. The optical pickup device according to claim 272, wherein the optical pickup device has a wavelength of 7? Rms or less. 277. At least one collimator between the first light source and the objective lens and between the second light source and the objective lens, wherein the light flux incident on the objective lens from the first light source and the objective light from the second light source 258. The light beam incident on the lens is a parallel light, respectively.
76. The optical pickup device according to any one of items 76. 277. The paraxial focal position of the objective lens with respect to the light beam from the first light source substantially coincides with the paraxial focal position of the objective lens with respect to the light beam from the second light source. An optical pickup device according to item 1. 279. A second diffraction pattern is provided outside the diffraction pattern, and + 1st-order diffracted light of the second diffraction pattern with respect to a light beam from the first light source is condensed at the condensing position 280. The optical pickup device according to claim 265, 269 or 273, wherein the second diffraction pattern is set so that the light beam from the second light source is not diffracted by the second diffraction pattern. 280. A second diffraction pattern is provided outside the diffraction pattern, and a light beam from the first light source is
In the second diffraction pattern, it becomes mainly + 1st-order diffraction light, and the light flux from the second light source transmits through the second diffraction pattern,
266, 270, wherein the second diffraction pattern is set so as to be focused at the focusing position.
Or the optical pickup device of 274. 281. A second diffraction pattern is provided outside the diffraction pattern, and -1st-order diffracted light of the second diffraction pattern with respect to a light beam from the first light source is collected at the light condensing position. 280. The optical pickup device according to claim 267, 271 or 275, wherein the second diffraction pattern is set so that light is emitted and the light flux from the second light source is not diffracted by the second diffraction pattern. 282. A second diffraction pattern is provided outside the diffraction pattern, and a light beam from the first light source mainly becomes -1st-order diffracted light in the second diffraction pattern. The light beam passes through the second diffraction pattern,
268, 272, wherein the second diffraction pattern is set so that light is condensed at the light condensing position.
Or the optical pickup device according to 276. 283. A second diffraction pattern is provided outside the diffraction pattern, and transmitted light of the second diffraction pattern with respect to a light beam from the first light source is condensed at the light condensing position, 265, 269, or 273, wherein the second diffraction pattern is set so that the light beam from the second light source mainly becomes -1st-order diffracted light in the second diffraction pattern.
An optical pickup device described in 1. 284. A second diffraction pattern is provided outside the diffraction pattern, a light beam from the first light source passes through a second diffraction pattern, and a light beam from the second light source is second diffracted. 27. The second diffraction pattern is set such that the pattern becomes -1st order light and is collected at the light collection position.
The optical pickup device described in 6,270 or 274. 285. A second diffraction pattern is provided outside the diffraction pattern, and transmitted light of the second diffraction pattern with respect to a light beam from the first light source is condensed at the light condensing position. 258, 275, or 275, wherein the second diffraction pattern is set so that the light beam from the second light source mainly becomes + 1st-order diffraction light in the second diffraction pattern.
An optical pickup device described in 1. 286. A second diffraction pattern is provided outside the diffraction pattern, a light beam from the first light source passes through a second diffraction pattern, and a light beam from the second light source is second diffracted. 27. The second diffraction pattern is set so that the pattern becomes + 1st-order light and is condensed at the condensing position.
The optical pickup device according to 8, 272 or 276. 287. a light beam emitted from the first light source;
An optical multiplexing unit capable of multiplexing an emitted light beam from the second light source; a light beam from the first light source is transmitted between the multiplexing unit and the optical information recording medium; 265, 275, 275, 275, 275, 275, 275, 275 or 275, characterized in that there is an aperture limiting means that does not transmit a light beam passing through a region on the opposite side of the diffraction pattern optical axis from the light source.
An optical pickup device described in 1. 288. a light beam emitted from the first light source;
An optical multiplexing unit capable of multiplexing a light beam emitted from the second light source; a light beam from the second light source is transmitted between the multiplexing unit and the optical information recording medium; 280. The light emitting device according to claim 266, further comprising an aperture limiting unit that does not transmit a light flux of a light flux from a light source that passes through a region opposite to an optical axis of the diffraction pattern. Optical pickup device. 289. The aperture limiting means, wherein the light beam from the first light source is transmitted, and
287. The optical pickup device according to claim 287, wherein the optical pickup device is an annular filter that reflects or absorbs a light beam that passes through a region of the diffraction pattern opposite to the optical axis. 290. A light beam from the second light source is transmitted, and
289. The optical pickup device according to claim 288, wherein the optical pickup device is an annular filter that reflects or absorbs a light beam that passes through a region of the light source that is opposite to the optical axis of the diffraction pattern. 291. The aperture limiting means, wherein the light beam from the first light source is transmitted, and
290. The optical pickup device according to claim 287, wherein the optical pickup device is an annular filter that diffracts a light beam passing through a region on the opposite side of the optical axis of the diffraction pattern. 292. The aperture restricting means, wherein the light beam from the second light source is transmitted, and
289. The optical pickup device according to claim 288, wherein the optical pickup device is an annular filter that diffracts a light beam passing through a region on the opposite side of the optical axis of the diffraction pattern. 293. The light detector according to claim 258, wherein the photodetector is common to the first light source and the second light source.
292. The optical pickup device according to any one of 292. 294. The photodetector is provided with a first photodetector for the first light source and a second photodetector for the second light source, and is located at a spatially separated position. The optical pickup device according to any one of claims 258 to 292, wherein: 295. The light according to claim 294, wherein at least a pair of a first light source and a first light detector or a pair of a second light source and a second light detector is unitized. Pickup device. 296. The optical pickup according to claim 293, wherein said first light source, second light source, and common photodetector (single photodetector) are unitized. apparatus. 297. The photodetector is different from the first photodetector for the first light source and the second photodetector for the second light source, and includes a first light source and a second light source. 299. The optical pickup device according to claim 294, wherein the first photodetector and the second photodetector are unitized. 298. The optical disk drive according to claim 258, further comprising: a photodetector for detecting transmitted light from the optical disk.
297. The optical pickup device according to any one of items 297 to 297. 299. a first light source having a wavelength λ1, a second light source having a wavelength λ2 (where λ1 ≠ λ2), a light beam emitted from the first light source, and a light beam emitted from the second light source. A multiplexing means capable of multiplexing the light, a diffractive optical element having a diffraction pattern on at least one surface, and condensing a light beam from each light source on the information recording surface of the optical information recording medium via a transparent substrate. An objective lens for receiving light reflected from an optical information recording medium of a light beam emitted from the first light source and the second light source; and the objective lens for a light beam from the first light source. By using at least the m-th order diffracted light from the diffraction pattern (where m is an integer other than 0), the first optical information recording medium with a transparent substrate having a thickness of t1 is recorded and / or reproduced. The light flux from the second light source n order diffraction light from the diffraction pattern of the object lens (where, n = m) by at least utilizing the thickness of the transparent substrate is t2 (where,
An optical pickup device for recording and / or reproducing information on a second optical information recording medium (t2 ≠ t1). 300. The wavelength λ of the first and second light sources
1, λ2 is λ1 <λ2, and the thickness t of the transparent substrate is
1. An optical pickup device wherein t1 and t2 are used in a relationship of t1 <t2, wherein the m-order and n-order diffracted lights are both +1.
299. The optical pickup device according to claim 299, wherein the light is second-order diffracted light. 301. The wavelength λ of the first and second light sources
1, λ2 is λ1 <λ2, and the thickness t of the transparent substrate is
1. An optical pickup device wherein t2 and t2 are used in a relationship of t1> t2, wherein the m-order and n-order diffracted lights are both -1.
299. The optical pickup device according to claim 299, wherein the light is second-order diffracted light. 302. The apparatus according to claim 299, wherein the diffractive optical element and the objective lens are driven integrally.
Or the optical pickup device described in 301. 303. The apparatus according to claim 258, wherein the depth of the first diffraction pattern in the optical axis direction is 2 μm or less.
330. The optical pickup device according to any one of Items 302 to 302. 304. At least one surface has a diffraction pattern, and when a light beam of wavelength λ1 is incident, at least the m-th order diffracted light from the diffraction pattern (where m is one integer other than 0) When a light beam having a wavelength of λ2 (where λ2 ≠ λ1) is incident on the first light-collecting position, at least the nth-order diffracted light (where n = m) from the diffraction pattern is collected by the first light-collecting position. An objective lens for an optical pickup device, which is focused at a second focusing position different from the light position. 305. The wavelengths λ1 and λ2 satisfy λ1 <λ2, and the first light-condensing position is set to a first thickness t1 of the transparent substrate.
The light condensing position on the optical information recording medium, the second light condensing position is the light condensing position on the second optical information recording medium having the thickness t2 of the transparent substrate, and the thicknesses t1, t2 of the transparent substrate are t1. 4. When the relation of <t2 is satisfied, the m-order and n-order diffracted lights are both + 1st-order diffracted lights.
04. The objective lens for an optical pickup device according to 04. 306. The wavelengths λ1 and λ2 satisfy λ1 <λ2, and the first light-condensing position is the first light-condensing position having a thickness t1 of the transparent substrate.
The light condensing position on the optical information recording medium, the second light condensing position is the light condensing position on the second optical information recording medium having the thickness t2 of the transparent substrate, and the thicknesses t1, t2 of the transparent substrate are t1. 4. When the relation of> t2 is satisfied, the m-order and n-order diffracted lights are both -1st-order diffracted lights.
04. The objective lens for an optical pickup device according to 04. 307. A diffraction pattern on at least one surface, and when a light beam of wavelength λ1 is incident, at least the m-th order diffracted light from the diffraction pattern (where m is one integer except 0) is transparent. It has a light-condensing position used for recording and / or reproducing on the first optical information recording medium having the thickness t1 of the substrate, and at least when a light beam of wavelength λ2 (where λ2 ≠ λ1) enters, The n-th order diffracted light (where n = m) from the diffraction pattern has a thickness t2 (where t2 ≠) of the transparent substrate.
An objective lens for an optical pickup device, having a focusing position used for recording and / or reproducing the second optical information recording medium of t1). 308. When the wavelengths λ1 and λ2 satisfy λ1 <λ2 and the thicknesses t1 and t2 of the transparent substrate satisfy the relationship of t1 <t2, the m-order and n-order diffracted lights are both + 1st-order diffracted lights. 307. The objective lens for an optical pickup device according to claim 307. 309. When the wavelengths λ1 and λ2 satisfy λ1 <λ2 and the thicknesses t1 and t2 of the transparent substrate satisfy the relationship of t1> t2, the m-order and n-order diffracted lights are both −1st-order diffracted lights. 307. The objective lens for an optical pickup device according to claim 307. 310. A required aperture on the optical information recording medium side of the objective lens necessary for recording and / or reproducing the first optical information recording medium having a transparent substrate having a thickness of t1 with a first light source having a wavelength of λ1. The number is NA1, the thickness of the transparent substrate is t2 (where t2> t1) and the second optical information recording medium is a second optical information recording medium having a wavelength λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the light source
(Where NA2 <NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the diffraction of the light flux from the first light source by the objective lens is performed. The + 1st-order diffracted light from the circumference farthest from the optical axis of the pattern is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the light flux from the first light source has the highest diffraction pattern of the objective lens. 308. The + 1st-order diffracted light from the circumference on the optical axis side is converted into a luminous flux with a numerical aperture on the optical information recording medium side of NAL1, and satisfies the condition of NAH1 <NA10 <NAL1 <NA2. 4. The objective lens for an optical pickup device according to item 1. 311. A required aperture on the optical information recording medium side of the objective lens necessary for recording and / or reproducing the first optical information recording medium having a transparent substrate having a thickness of t1 with a first light source having a wavelength of λ1. The number is NA1, the thickness of the transparent substrate is t2 (where t2> t1) and the second optical information recording medium is a second optical information recording medium having a wavelength λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the light source
When (NA2> NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the diffraction of the light flux from the first light source by the objective lens is performed. The + 1st-order diffracted light from the circumference farthest from the optical axis of the pattern is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the light flux from the first light source has the highest diffraction pattern of the objective lens. 299. The + 1st-order diffracted light from the circumference on the optical axis side is converted into a luminous flux with a numerical aperture on the optical information recording medium side of NAL1, and satisfies the condition of NAH1 <NA2O ≦ NAL1 ≦ NA1. 4. The objective lens for an optical pickup device according to item 1. 312. A required aperture on the optical information recording medium side of the objective lens required for recording and / or reproducing the first optical information recording medium having a transparent substrate with a thickness of t1 with a first light source having a wavelength of λ1. The number is NA1, the thickness of the transparent substrate is t2 (where t2 <t1) and the second optical information recording medium is the second optical information recording medium having a wavelength λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the light source
(Where NA2 <NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the diffraction of the light flux from the first light source by the objective lens is performed. The -1st-order diffracted light from the circumference of the pattern that is farthest from the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the diffraction pattern of the objective lens of the light flux from the first light source is obtained. The -1st-order diffracted light from the circumference closest to the optical axis is converted into a light flux having a numerical aperture of NAL1 on the optical information recording medium side, and satisfies the condition of NAH1 <NA10 ≦ NAL1 ≦ NA2. 309. The objective lens for an optical pickup device according to item 309. 313. A required aperture on the optical information recording medium side of the objective lens necessary for recording and / or reproducing the first optical information recording medium having a transparent substrate with a thickness of t1 with a first light source having a wavelength of λ1. The number is NA1, the thickness of the transparent substrate is t2 (where t2 <t1) and the second optical information recording medium is the second optical information recording medium having a wavelength λ2 (where λ2> λ1).
The required numerical aperture on the optical information recording medium side of the objective lens required for recording and / or reproduction with the light source
When (NA2> NA1), the diffraction pattern provided on at least one surface of the objective lens is rotationally symmetric with respect to the optical axis, and the diffraction of the light flux from the first light source by the objective lens is performed. The -1st-order diffracted light from the circumference of the pattern that is farthest from the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAH1, and the diffraction pattern of the objective lens of the light flux from the first light source is obtained. The -1st-order diffracted light from the circumference closest to the optical axis is converted into a light flux whose numerical aperture on the optical information recording medium side is NAL1, and satisfies the condition of NAH1 <NA2O ≦ NAL1 ≦ NA1. 309. The objective lens for an optical pickup device according to item 309. 314. An optical surface according to any one of claims 304 to 313, wherein the optical surface includes a diffraction pattern portion and a refraction portion, and a boundary between the diffraction portion and the refraction portion includes a step of 5 μm or more. Objective lens for optical pickup devices. 315. The objective lens for an optical pickup device according to any one of claims 304 to 313, wherein the average depth of the diffraction pattern of the diffraction portion closest to the optical axis is 2 μm or less. 316. The average depth of the diffraction pattern of the diffraction portion closest to the optical axis is 2 μm or less, and the average depth of the diffraction pattern of the diffraction portion closest to the optical axis is 2 μm or more. 315. The objective lens for an optical pickup device according to claim 315. 317. The objective lens for an optical pickup device according to claim 304, wherein the diffraction pattern on the optical surface includes an optical axis portion. 318. The optical axis portion of the optical surface is a refraction surface without providing a diffraction pattern.
316. The objective lens for an optical pickup device according to any one of 316. 319. When an image is formed at a predetermined image magnification on an information recording surface through a transparent substrate having a thickness of 0.6 mm at a light source wavelength of 650 nm, the lens has a diffraction-limited performance at least up to a numerical aperture of 0.6. 304. When formed at a predetermined imaging magnification through a transparent substrate of 1.2 mm at a light source wavelength of 780 nm, it has a diffraction-limited performance at least up to a numerical aperture of 0.45. 307, 308 or 310, the objective lens for an optical pickup device. 320. The number of steps of the diffraction pattern is 15
319. The objective lens for an optical pickup device according to claim 319, wherein: 321. The objective lens for an optical pickup device according to claim 304, wherein the optical surface on which the diffraction pattern is provided is a convex surface. 322. The objective lens for an optical pickup device according to claim 321, wherein the refractive portion of the optical surface provided with the diffraction pattern is an aspheric surface. 323. The diffraction pattern has at least one
322. The system of claim 322, comprising two aspheric refractions.
4. The objective lens for an optical pickup device according to item 1. 324. The objective lens for an optical pickup device according to any one of claims 304 to 323, wherein said objective lens comprises a single lens. 325. The objective lens of claim 324, wherein the diffraction pattern is provided only on one optical surface of the single lens. 326. The objective lens of claim 324, wherein the diffraction pattern is provided on one optical surface of the single lens, and the other optical surface is aspheric. 327. A first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 ≠ λ2), and a diffraction pattern on at least one surface. An objective lens that condenses the information recording surface of the optical recording medium through a transparent substrate, and a photodetector that receives reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium, By utilizing at least the m-th order diffracted light (where m is an integer other than 0) of the light beam from the first light source from the diffraction pattern of the objective lens, the first transparent substrate has a thickness of t1. At least one of recording and reproducing of information on an optical information recording medium is performed, and at least n-th order light (where n = m) of a light beam from the second light source from a diffraction pattern of the objective lens is used. By transparent substrate An optical pickup device for performing at least one of recording and reproduction of information on a second optical information recording medium having a thickness of t2 (t2ｔt1), wherein the objective lens is made of a plastic material, and the plastic material is When the amount of change in the refractive index when there is a temperature change ΔT (° C.) is Δn, −0.0002 / ° C. <Δn / ΔT <−0.00005 /
The first light source satisfies the relationship: 0.05 nm / ° C <Δλ1 / ΔT <0, where Δλ1 (nm) is the change in oscillation wavelength when there is a temperature change ΔT (° C). An optical pickup device which satisfies a relationship of 0.5 nm / ° C. 328. a first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 ≠ λ2), and a diffraction pattern on at least one surface. An objective lens that condenses the information recording surface of the optical recording medium through a transparent substrate, and a photodetector that receives reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium, By utilizing at least the m-th order diffracted light (where m is an integer other than 0) of the light beam from the first light source from the diffraction pattern of the objective lens, the first transparent substrate has a thickness of t1. At least one of recording and reproducing of information on an optical information recording medium is performed, and at least n-th order light (where n = m) of a light beam from the second light source from a diffraction pattern of the objective lens is used. By transparent substrate An optical pickup device for performing at least one of recording and reproduction of information on and from a second optical information recording medium having a thickness of t2 (t2 ≠ t1), wherein the wavelengths λ1 and λ2 and the thickness t1 of the transparent substrate are provided. , T2
Has a relationship of λ2> λ1 t2> t1, and a required aperture on the optical information recording medium side of the objective lens necessary for recording and / or reproducing the first optical information recording medium with the first light source. The number is NA1, and the wavelength λ1
(Mm), the focal length of the objective lens is f1 (m
m), and when the environmental temperature change is ΔT (° C.), the change amount of the third-order spherical aberration component of the wavefront aberration of the light beam focused on the information recording surface of the first information recording medium is represented by ΔWSA3 (λ1r
ms), 0.2 × 10 ⁻⁶ / ° C <ΔWSA3 · λ1 / ｛f · (NA
1) An optical pickup device characterized by satisfying a relationship of ⁴ · ΔT｝ <2.2 × 10 ⁻⁶ / ° C. 329. At least one collimator between the first light source and the objective lens and between the second light source and the objective lens, and a light beam incident on the objective lens from the first light source. 327. The optical pickup device according to claim 327, wherein light beams incident on the objective lens from the second light source are substantially parallel lights. The t1 may be from 0.55 mm to 0.6.
5 mm, the t2 is from 1.1 mm to 1.3 mm,
327. The optical pickup device according to claim 327, 328, or 329, wherein the λ1 is 630 nm to 670 nm, and the λ2 is 760 nm to 820 nm. 331. a first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ2 ≠ λ1), and a diffraction pattern on at least one surface. An objective lens focused on the information recording surface via a transparent substrate, and a photodetector that receives reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium. By using at least the m-th order diffracted light (where m is an integer other than 0) of the light beam from the first light source from the diffraction pattern of the objective lens, the first transparent substrate having a thickness of t1 is used. At least one of recording and reproduction of information with respect to the optical information recording medium, and using at least n-order diffracted light (where n = m) of the light flux from the second light source from the diffraction pattern of the objective lens. By doing so, The thickness of the substrate is t2 (where, t2
(T1) an optical pickup device that performs at least one of recording and reproduction of information on and from a second optical information recording medium, wherein the light is incident on the objective lens from at least one of the first and second light sources. An optical pickup device comprising a correction means for correcting the degree of divergence of a light beam to be emitted. 332. The optical pickup device according to claim 331, further comprising at least one collimator between the first light source and the objective lens and between the second light source and the objective lens. 333. The apparatus of claim 332, wherein the correction of the divergence by the correction unit is performed by changing a distance between the first and / or second light source and the at least one collimator. Optical pickup device. 334. A first light source having a wavelength of λ1, a second light source having a wavelength of λ2 (λ1 ≠ λ2), and a diffraction pattern on at least one surface. An objective lens that condenses the information recording surface of the optical recording medium through a transparent substrate, and a photodetector that receives reflected light of the light flux emitted from the first light source and the second light source from the optical information recording medium, By utilizing at least the m-th order diffracted light (where m is an integer other than 0) of the light beam from the first light source from the diffraction pattern of the objective lens, the first transparent substrate has a thickness of t1. At least one of recording and reproducing of information on an optical information recording medium is performed, and at least n-th order light (where n = m) of a light beam from the second light source from a diffraction pattern of the objective lens is used. By transparent substrate An optical pickup device for performing at least one of recording and reproduction of information on and from a second optical information recording medium having a thickness of t2 (t2 ≠ t1), wherein the optical pickup device outputs signals from the first light source and the second light source. Different 2
An optical pickup device characterized in that the wavefront aberration on the image plane for each of the lights of the two wavelengths (λ) is 0.07λrms or less within the maximum numerical aperture on the image side of the objective lens. 335. The light source, wherein the first light source and the second light source are unitized, and the photodetector is common to the first light source and the second light source. The optical pickup device according to any one of items 258 to 292, 334. 336. The focusing optical system has an objective lens, and the objective lens has a marginal margin for a minute change in at least one of the wavelength of the first light source and the wavelength of the second light source. The amount of change in the spherical aberration of the ray is ΔSA,
The optical pickup device according to claim 5, wherein the following conditional expression is satisfied when the amount of change in axial chromatic aberration is △ CA. -1 <ΔSA / ΔCA <−0.2 337. The condensing optical system has an objective lens, and the objective lens has a marginal margin for a minute change in at least one of the wavelength of the first light source and the wavelength of the second light source. The amount of change in the spherical aberration of the ray is ΔSA,
85. The optical element according to claim 82, wherein the following conditional expression is satisfied when the amount of change in axial chromatic aberration is △ CA. -1 <ΔSA / ΔCA <−0.2 338. The objective lens has a change amount of a spherical aberration of a marginal ray with respect to a minute change of at least one of a wavelength of the first light source and a wavelength of the second light source, ΔSA, 11. The optical pickup device according to claim 6, wherein the following conditional expression is satisfied when the change amount of the upper chromatic aberration is △ CA. -1 <△ SA / △ CA <−0.2 339. The objective lens has a change amount of spherical aberration of a marginal ray with respect to a minute change of at least one of a wavelength of the first light source and a wavelength of the second light source, ΔSA; 9. When the change amount of the upper chromatic aberration is △ CA, the following conditional expression is satisfied.
89. The optical element according to 3, 85 or 87. -1 <ΔSA / ΔCA <−0.2