JP2000215500A - Optical pick-up device and object lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove an influence of unwanted light by providing a focusing optical system with a splitting means for splitting a luminous flux of a laser beam into plural pieces of luminous flux in the form of ring belt taking the vicinity of an optical axis as a center, letting a photoreceptor receive the laser beam of shorter wavelengths compared with a part of the outermost luminous flux to be split by a splitting means, and providing the system with a wavelength selecting function to prevent the photoreceptor from receiving the laser beam of longer wavelengths. SOLUTION: A semiconductor laser 12 emits 610-670 nm short wavelength semiconductor laser used when an optical disk 10 is a DVD system. A semiconductor laser 11 emits laser light of 760-830 nm long wavelengths in the case of CD system. A luminous flux from the semiconductor laser 11 is made incident on an objective 32 with the same width of the incident light from the semiconductor laser 12, but is reduced into a predetermined numerical aperture shown by the dotted line by a wavelength selecting function part 33 arranged on a 3rd ring belt of a light source side face of the objective 32, and is made incident on the optical disk 10. As shown by the dotted line, the reflected light is made incident on a light receiving means 50 by reversing the same light path as the incident luminous flux.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium for recording and / or reproducing information on an optical information recording medium by condensing a light beam emitted from a light source on an information recording surface by a condensing optical system. The present invention relates to an objective lens for reproduction and / or an optical pickup device thereof.

[0002]

2. Description of the Related Art In recent years, with the practical use of short-wavelength red semiconductor lasers, conventional optical information recording media (also referred to as optical disks) have been developed.
A DVD, which is a high-density optical information recording medium having a size similar to that of a CD (compact disk) and having a large capacity, has been developed. In this DVD, a track pitch of 0.
The pitch is 74 μm and the shortest pit length is 0.4 μm, and the density is reduced to half or less of the track pitch of CD 1.6 μm and the shortest pit length 0.83 μm. Therefore, 635
A short-wavelength semiconductor laser of nm is used, the numerical aperture NA of the objective lens on the optical disk side is 0.6, and the thickness of the transparent substrate is 0.6 mm. In addition to the above-mentioned CDs and DVDs, optical discs of various standards, for example, CD-R (write-once compact disc), LD (laser disc), M
D (mini disk), MO (magneto-optical disk), and the like have also been commercialized and spread.

As described above, the size, substrate thickness, recording density,
In order to cope with various optical disks having different wavelengths to be used, various optical pickup devices including two light sources having different wavelengths and recording and / or reproducing a plurality of optical disks by one condensing optical system have been proposed. As proposed methods, Japanese Patent Application Laid-Open No. 8-55363,
JP-A-9-17023, JP-A-9-194975, JP-A-10-69675, and Japanese Patent Application No. 9-2869.
An example is shown in No. 54 and the like.

The inventors of the present invention consist of a plurality of concentrically divided annular zones, each of which has a spherical surface with respect to a plurality of light sources having different wavelengths and / or a transparent substrate having a different recording surface thickness. By actively using aberration and phase difference,
For each optical information recording medium, a special objective lens whose aberration has been corrected within the diffraction limit has been developed (Japanese Patent Application No. 8-300).
No. 093, No. 10-183261), and an optical pickup with a simplified configuration using the same has been proposed.

[0005]

The objective lens has a function of automatically obtaining a required numerical aperture according to the wavelength used and / or the thickness of the transparent substrate. However, a light beam transmitted through the outermost annular zone, which is unnecessary for an optical information recording medium having a thick transparent substrate, is reflected by the optical information recording medium and then enters a signal detecting light receiving element to perform signal processing. Could be affected. An object of the present invention is to provide an optical pickup device which is not affected by such unnecessary light and an objective lens therefor.

[0006]

SUMMARY OF THE INVENTION An optical pickup device according to the present invention is a light-collecting device including two laser light sources having different wavelengths and an objective lens for converging laser light from the laser light sources on an information recording surface of an optical information recording medium. An optical system, and a light-receiving element for detecting light reflected from the information recording surface, wherein at least two types of optical information recording media having different thicknesses of transparent substrates have an optical pickup device for recording and / or reproducing. The optical system includes splitting means for splitting the light flux of the laser light into a plurality of light fluxes in an annular shape around the optical axis, and among the outermost light fluxes split by the splitting means in the focusing optical system. At least for a part, a laser beam having a short wavelength is received by the light receiving element, and a wavelength selecting function is provided to prevent the laser light having a long wavelength from being received by the light receiving element. Further, the objective lens of the present invention includes a splitting unit that splits the light beam of the laser beam into a plurality of light beams in an annular shape around the optical axis, and at least a part of the outermost light beam split by the splitting device. On the other hand, of the two laser beams having different wavelengths, the laser beam having the shorter wavelength is received by the light receiving element for detecting the reflected light from the information recording surface of the optical information recording medium, and the laser beam having the longer wavelength is received by the light receiving element. It is characterized by having a wavelength selection function to prevent the wavelength from being changed.

More specifically, the optical system includes a means for dividing the light beam of the condensing optical system into three annular light beams from the vicinity of the optical axis to the outer side, and from the vicinity of the optical axis to the outer side. When the first, second, and third light beams are sequentially formed, the first light beam is used for all optical information recording media having different transparent substrate thicknesses, and the second light beam is mainly used for an optical information recording medium having a thick transparent substrate. The third light flux is for an optical information recording medium having a thin transparent substrate, and the wavelength selecting function is provided in the objective lens itself or another optical element in the light-collecting optical system. And
It is desirable to shift the phase of at least one of the plurality of divided light beams with respect to other light beams so as to increase the intensity of the convergent spot for both optical information recording media having different wavelengths and thicknesses.

[0008]

More specifically, the phase shift is generated by providing a plurality of concentrically divided orbicular zones in an objective lens or other optical element and arranging each of the orbicular zones on an optical axis. By adjusting the position, a predetermined phase shift is caused in each light beam. The luminous flux transmitted through each orbicular zone is corrected for aberrations within a diffraction limit with respect to a plurality of light sources having different wavelengths and transparent substrates having different thicknesses. And the second
The zonal zone must be aberration-corrected within the diffraction limit for thick transparent substrates or the thickness between thick and thin transparent substrates at long wavelengths.

The wavelength selection function can be a multilayer coating in which, of the two light sources, light having a short wavelength is substantially transmitted and light having a long wavelength is substantially reflected. The light beam transmitted through the multilayer coating portion and the light beam transmitted through other regions may be out of phase due to the thickness of the multilayer film, and as a result, the spot intensity on the optical information recording medium may be reduced. Occurs. Therefore, a phase adjuster adjusted so that the phase difference between the two light beams is 2π is provided in the multilayer coating portion or other portions, and thereby the phase shift can be suppressed. Similarly, the wavelength selecting function can be achieved by coating or vapor-depositing a dye that transmits light having a short wavelength substantially and absorbs light having a long wavelength substantially. Adjustment of the phase shift by the thickness of this dye layer
This is the same as the case of the multilayer film. Further, the wavelength selection function can also be achieved by diffracting light of a short wavelength substantially without diffracting light of a short wavelength.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical pickup device according to the present invention will now be described with reference to the drawings. In the optical pickup device shown in FIG. 1, the first semiconductor laser 12
It is a light source for recording information on the first optical disc 10 and / or emitting light for recording and / or reproducing the recorded information. When the first optical disc 10 is a DVD system, the wavelength λ is 610 to 670 nm. Is a short wavelength semiconductor laser. The divergence angle of the light emitted from the first semiconductor laser 12 is converted by the lens 60, which is a divergence angle conversion unit of the light beam, and the light enters the dichroic prism 20. The dichroic prism 20 is a synthesizing unit that makes the optical axis of the light emitted from the first semiconductor laser 12 substantially coincide with the optical axis of the light emitted from the second semiconductor laser 11, which will be described later. Indicates that the light of wavelength λ2 emitted from the second semiconductor laser 11 is reflected,
The light λ1 from the semiconductor laser 12 is transmitted to combine the optical axes. The light from the first semiconductor laser 12 passes through the dichroic prism 20 and a polarization beam splitter 40 described later, and is incident on the condensing unit 30.

The light condensing means 30 for condensing the light from the dichroic prism 20 on the recording surface of the optical disk 10 includes a coupling lens 31 and an objective lens 32. In the illustrated optical system, the coupling lens 31 is a collimator lens that converts light from the dichroic prism 20 and the polarizing beam splitter 40 into parallel light, and the objective lens 32 is an infinite system that collects parallel light on the optical disc 10. It is an objective lens.

A】 wavelength plate 35 and a stop 36 are provided in the focusing means 30. 1/4 wavelength plate 3
Reference numeral 5 changes the light transmitted through the coupling lens 31 from linearly polarized light to circularly polarized light, and the stop 36 restricts the parallel light flux to a numerical aperture on the optical disk 10 side of the objective lens 32 necessary for recording and / or reproducing DVD.

The reflected light flux modulated by the information pits on the optical disk 10 passes through the objective lens 32, the quarter-wave plate 35, and the coupling lens 31 again, and enters the polarization beam splitter 40. The polarization beam splitter 40 receives reflected light from the optical disc 10
, Which is provided between the condensing means 30 and the dichroic prism 20.

A light receiving means 50 for receiving the light reflected by the polarization beam splitter 40 detects a change in the light amount distribution of the reflected light from the optical disk 10 by a photodetector 51, and detects a focus and a track by an arithmetic processing circuit (not shown).・ Information is read. When performing focus detection by the astigmatism method, the light receiving unit 50 includes a cylindrical lens 52 that generates astigmatism. The focus detection and the track detection can be performed by various known methods such as a knife edge method, an SSD method, a push bull method, and a three-beam method.

On the basis of the focus detection obtained by the arithmetic processing circuit, a two-dimensional actuator (not shown) moves the objective lens 32 so that the light from the first semiconductor laser 12 is focused on the first optical disk 10. At this time, the objective lens 32 is driven by the two-dimensional actuator so that the beam spot on the information recording surface of the first optical disc 10 is minimized. In addition, based on the track detection, 2 (not shown)
The dimensional actuator moves the objective lens 32 so that the light from the first semiconductor laser 12 is focused on a predetermined rack.

In FIG. 1, a second semiconductor laser 11 for reproducing a second optical disk is a light source for reproducing information recorded on a second optical disk (at substantially the same position as the first optical disk 10). 2 When the optical disk is of the CD type, the semiconductor laser has a wavelength λ2 (> λ1) of 760 to 830 nm.

The light beam from the second semiconductor laser 11 is
The light enters the objective lens with the same width as the incident light from the semiconductor laser, but is cut into a predetermined numerical aperture as shown by a dotted line by a wavelength selector 33 provided in the third annular zone on the side of the light source of the objective lens 32, The light enters the second disk. The reflected light is incident on the light receiving means 50 through the same optical path as the incident light flux in reverse as shown by the dotted line.

FIG. 2 shows another example of the configuration of the optical pickup device. Members having the same functions as those of the optical pickup device of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The difference is that the light beams from the first semiconductor laser and the second semiconductor laser are polarized between the dichroic prism 20, which is a combining means for matching the optical axes of the two light beams, and the respective semiconductor lasers 11, 12. Beam splitter 4
3 and 44, and light receiving means 53 and 54 suitable for each wavelength are provided in the reflected light path. The polarization beam splitters 43 and 44 and the photodetector 5
5 and 58, cylindrical lenses 56 and 57 for generating astigmatism are arranged. The luminous flux from the second semiconductor laser 11 passes through the objective lens 3
The wavelength is narrowed down to a predetermined width by the wavelength selector 33 having the same diameter as that of the second third annular zone, and the reflected light is separated from the incident light by the polarization beam splitter 43 and enters the light receiving means 53 as shown by a dotted line. . In the case of such an arrangement, the stop 36 is driven for focusing and tracking integrally with the objective lens 32.

The optical pickup device shown in FIG. 3 is an example in which a coupling lens is provided with a wavelength selection function unit. 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 disc, a beam is emitted from the first semiconductor laser 12 and transmitted through the coupling lens 60 for reducing the degree of divergence of the divergent light beam, the beam splitter 20 and the beam splitter 40 as the light combining means, and Ring lens 31, quarter wave plate 35
, And becomes parallel light of circular polarization. Further, it is stopped down by the stop 36 and is focused on the information recording surface by the objective lens 32 via the transparent substrate of the optical disc 10. The luminous flux modulated and reflected by the information recording surface is again reflected by the objective lens 3.
2. The light passes through the quarter-wave plate 35 and the coupling lens 31 through the stop 36, enters the beam splitter 40, is reflected there, is given astigmatism by the cylindrical lens 52, and is given a photodetector. The signal is incident on the optical disk 51, and a read signal of information recorded on the first optical disk 10 is obtained by using the output signal. A change in the light amount due to a change in the shape and position of the spot on the photodetector 51 is detected, and focus detection and track detection are performed. Based on the detection, the light flux from the first semiconductor laser 12 is transmitted by the two-dimensional actuator. The objective lens 36 is moved so that an image is formed on the recording surface of the optical disk 10 and the objective lens is driven so that the light beam from the semiconductor laser 12 is formed on a predetermined track.

The second semiconductor laser 11 for reproducing the second optical disk is integrated with a photodetector 75 and a hologram 23 in a laser / detector integrated unit 70. “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. It can be attached. The light beam emitted from the second semiconductor laser 11 passes through the hologram 23, is reflected by the dichroic prism 20, which is a photosynthesis unit, passes through the beam splitter 40, and has a predetermined wavelength by the wavelength selection function unit 33 on the coupling lens 31. The beam is converged to a parallel light beam by the diameter, and is condensed on the information recording surface via the quarter wave plate 35, the objective lens 32, and the transparent substrate of the second optical disk 10. The luminous flux modulated and reflected on the information recording surface passes through the objective lens 32 and the aperture 36 again, and is returned to the １ ／.
The light passes through the wave plate 35, the coupling lens 31, and the beam splitter 40, is reflected by the dichroic prism 20, is diffracted by the hologram 23, is incident on the photodetector 75, and is output to the second optical disc 20 by using the output signal. A read signal of the recorded information is obtained. In addition, a change in the light amount due to a change in the shape and position of the spot on the photodetector 75 is detected, focus detection and track detection are performed, and the objective lens 32 is moved by a two-dimensional actuator for focusing and tracking. Let it.

As described above, the wavelength selection function section can be disposed at an appropriate position in the optical system. Therefore, only the configuration of the optical pickup device to which the present invention can be applied will be described below. In the optical pickup device shown in FIG. 4, when reproducing the first optical disk, the first semiconductor laser 12 is unitized with the photodetector 76 and the hologram 24 by the laser / detector integrated unit 71, and the first semiconductor laser 12 Are transmitted through the hologram 24, are transmitted through the dichroic prism 20 and the coupling lens 31, which are light combining means, and become parallel light. Further, the aperture is stopped down by the stop 36, and the light is focused on the information recording surface by the objective lens 32 via the transparent substrate of the first optical disc 10. The luminous flux modulated and reflected by the information recording surface passes through the objective lens 32 and the aperture 36 again to the coupling lens 3.
1. The light passes through the dichroic prism 20, is diffracted by the hologram 24, is incident on the photodetector 76, and the read signal of the information recorded on the first optical disk 10 is obtained using the output signal. Further, by detecting a change in the shape of the spot on the photodetector 76 and a change in the amount of light due to a change in position,
Focus detection and track detection are performed, and the objective lens 32 is moved by a two-dimensional actuator for focusing and tracking.

When reproducing the second optical disk, the second semiconductor laser 11 is unitized with the photodetector 75 and the hologram 23 in the integrated laser / detector unit 70,
The light beam emitted from the second semiconductor laser 11 passes through the hologram 23, is reflected by the dichroic prism 20, which is a light combining means, passes through the coupling lens 31, and becomes a parallel light beam. The light is narrowed down to a predetermined diameter by a wavelength selection function unit disposed at an appropriate position, and is condensed on the information recording surface via the transparent substrate of the second optical disc 10 via the objective lens 32. The light beam modulated and reflected by the information pits on the information recording surface again passes through the coupling lens 31 via the objective lens 32, is reflected by the dichroic prism 20, is diffracted by the hologram 23, and is diffracted by the hologram 23 to form a photodetector 75. Incident on it and using its output signal
A read signal of information recorded on the optical disc is obtained. Further, a change in the light amount due to a change in the shape and position of the spot on the photodetector 75 is detected, and focus detection and track detection are performed. Based on this detection, a two-dimensional actuator is used for focusing and tracking. The objective lens 32 is moved.

In the optical pickup device shown in FIG. 5, the first semiconductor laser 12, the second semiconductor laser 11, the light detecting means 59, and the hologram 25 are unitized as a laser / detector integrated unit 72. When reproducing the first optical disk, the light beam emitted from the first semiconductor laser 12 passes through the hologram 25 and the coupling lens 31, and becomes a parallel light beam. Further, the aperture is stopped down by the stop 36, and the light is focused on the information recording surface by the objective lens 32 via the transparent substrate of the first optical disc 10. The light beam modulated and reflected by the information recording surface again passes through the coupling lens 31 via the objective lens 32 and the aperture 36, is diffracted by the hologram 25, enters the photodetector 77, and outputs the light. Using the signal, a signal for reading information recorded on the first optical disk 10 is obtained. Further, a change in the light amount due to a change in the shape and position of the spot on the photodetector 77 is detected to detect focus and track, and the objective lens 32 is moved by a two-dimensional actuator for focusing and tracking. Let it.

When reproducing the second optical disk, the light beam emitted from the second semiconductor laser 11 is
5. The light passes through the coupling lens 31 and becomes a substantially parallel light beam. Further, the light is condensed on the information recording surface via the aperture 36 and the objective lens 32 via the transparent substrate of the second optical disc. Then, the light flux modulated and reflected on the information recording surface is:
Again, the light passes through the coupling lens 31 via the objective lens 32 and the aperture 36, is diffracted by the hologram 25, is incident on the photodetector 77, and uses the output signal to obtain information recorded on the second optical disc. A read signal is obtained. Further, a change in the light amount due to a change in the shape and position of the spot on the photodetector 77 is detected, and focus detection and track detection are performed. Based on this detection, a two-dimensional actuator is used for focusing and tracking. The objective lens 32 is driven.

In the optical pickup device shown in FIG. 6, the first semiconductor laser 12, the second semiconductor laser 11, the first photodetector 78, the second photodetector 79, and the hologram 26 are integrated with a laser / detector integrated unit 73. As a unit. When reproducing the first optical disk, the light beam emitted from the first semiconductor laser 12 passes through the disk-side surface of the hologram 26 and the coupling lens 31 and becomes a parallel light beam. The objective lens 3 is further stopped down by the stop 36.
The light is condensed on the information recording surface via the transparent substrate of the first optical disk 10 by 2. The light beam modulated and reflected on the information recording surface again passes through the coupling lens 31 via the objective lens 32 and the aperture 36 to form the hologram 26.
The light is then diffracted and incident on the photodetector 78 corresponding to the first light source, and a read signal of information recorded on the first optical disc 10 is obtained using the output signal. Also, a change in the light amount due to a change in the shape and position of the spot on the photodetector 78 is detected to detect focus and track, and the two-dimensional actuator moves the objective lens 32 for focusing and tracking. Let it.

When reproducing the second optical disk, the light beam emitted from the second semiconductor laser 11 is
Is diffracted by the surface on the side of the semiconductor laser, passes through the coupling lens 31, 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 light is condensed on the information recording surface via the aperture 36 and the objective lens 32 via the transparent substrate of the second optical disc. Then, the light flux modulated and reflected on the information recording surface is:
The light passes through the coupling lens 31 again through the objective lens 32 and the aperture 36, is diffracted by the disk-side surface of the hologram 26, and is incident on the photodetector 79 corresponding to the second light source. As a result, a signal for reading information recorded on the second optical disk is obtained. Also, the photodetector 79
A change in light amount due to a change in the shape and position of the spot is detected to perform focus detection and track detection, and the objective lens 32 is moved for focusing and tracking by a two-dimensional actuator based on the detection. .

In the optical pickup device shown in FIG. 7, when reproducing the first optical disk, the first semiconductor laser 12
A coupling lens 60 for reducing the degree of divergence of the divergent light beam, the light passes through the dichroic prism 20, which is a light combining means, and the beam splitter 40, and further has a coupling lens 31, a quarter-wave plate 35.
, And becomes parallel light of circular polarization. Further, the light is stopped down by the stop 36 and is focused on the information recording surface by the objective lens 32 via the transparent substrate of the first optical disc 10. The luminous flux modulated and reflected by the information recording surface again passes through the quarter-wave plate 35 and the coupling lens 31 via the objective lens 32 and the diaphragm 36, and is then transmitted to the beam splitter 40.
And is reflected there, whereupon the cylindrical lens 52
As a result, astigmatism is given, the light is incident on the photodetector 51 via the concave lens 50, and a read signal of information recorded on the first optical disk 10 is obtained using the output signal. Further, a change in the light amount due to a change in the shape and position of the spot on the photodetector 51 is detected, and focus detection and track detection are performed. Based on this detection, the two-dimensional actuator moves the objective lens 32 so that the light beam from the first semiconductor laser 12 forms an image on the recording surface of the first optical disc, and the light beam from the semiconductor laser 12 is The objective lens 32 is moved so that an image is formed.

The second semiconductor laser 11 for reproducing the second optical disk is integrated with the photodetector 75 and the hologram 23 in the integrated laser / detector unit 70. The light beam emitted from the second semiconductor laser 11 passes through the hologram 23, is reflected by the dichroic prism 20, which is a photosynthesis unit, passes through the beam splitter 40, the coupling lens 31, and the quarter-wave plate 35, and becomes a parallel light beam. Become. Further, the light is condensed on the information recording surface via the aperture 36 and the objective lens 32 via the transparent substrate of the second optical disc. The light beam modulated and reflected by the information recording surface again passes through the objective lens 32 and the stop 36, and passes through the quarter-wave plate 35, the coupling lens 31, and the beam splitter 4 again.
0, is reflected by the dichroic prism 20,
Diffracted by the hologram 23 and incident on the photodetector 75,
Using the output signal, a signal for reading information recorded on the second optical disc is obtained. In addition, a change in the light amount due to a change in the shape and position of the spot on the photodetector 75 is detected, focus detection and track detection are performed, and the objective lens 32 is moved by a two-dimensional actuator for focusing and tracking. Let it.

The thickness t1 of the transparent substrate is substantially the same as that of the first optical disk, and the required numerical aperture NA of the objective lens on the side of the optical information recording medium required for recording / 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. Super RENS currently under development
FIG. 8 shows an example of the disc of the system. 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. Supe
When recording / reproducing a third disk of the r RENS system, a coupling lens 60 which emits a beam from the first semiconductor laser 12 to reduce the divergence of a divergent light beam, a dichroic prism 20 which is a light combining means, a beam splitter 40 and the coupling lens 3
The light passes through the 1/4 wavelength plate 35 and becomes a parallel light beam. The light is further stopped down by the stop 36, and is condensed by the objective lens 32 onto the nonlinear optical film 83 via the transparent substrate 81 and the first protective film 82 of the first optical disc 10. Nonlinear optical film 83
A small opening is formed, and energy is transmitted to the information recording surface 85 on the information recording layer via the second protective film 84. The light modulated by the information pits and transmitted through the information recording surface 85 passes through the third protective film 86, is collected by the condenser lens 90 on the side opposite to the objective lens, and reaches the photodetector 80. The read signal of the information recorded on the third optical disc is obtained from the output signal. On the other hand, the light beam reflected from the nonlinear optical film 83 passes through the quarter-wave plate 35 and the coupling lens 31 again through the objective lens 32 and the stop 36, and
0, where it is reflected and reflected by the cylindrical lens 5
2, the astigmatism is given, and the light detector 5
1 By detecting a change in the light amount due to a change in the shape and position of the spot on the photodetector 51, focus detection and track detection are performed. Based on this detection, the two-dimensional actuator moves the objective lens 32 so that the light beam from the first semiconductor laser 12 forms an image on the nonlinear optical film 83 of the first optical disc 10, and the light beam from the semiconductor laser 12 is Objective lens 3 so that an image is formed on a predetermined track
Move 2

When the objective lens is provided with these wavelength selecting functions as in the embodiment of FIG. 1, the plurality of orbicular zones are concentrically divided into a plurality of orbicular zones on the light source side of the objective lens or optical information. It can be provided on the refraction surface on the recording medium side. FIG. 9 shows the third orbicular zone surface S3 on the light source side of the objective lens,
This is an example in which a wavelength selection function layer A and a phase adjustment function layer B are provided so as to overlap each other as shown in a partially enlarged view in FIG. The step Ss from the second orbicular zone S2 is for causing a phase shift between the transmitted lights of the respective orbicular zones, and the phase adjustment function layer is included in the step Ss when forming the objective lens. May be. FIG. 10 shows an example in which the wavelength selection function layer A and the phase adjustment function layer B are separately provided on each surface of the objective lens. In this embodiment and the embodiment of FIG. 3, it goes without saying that the wavelength selection function layer A and the phase adjustment function layer B may be such that A is the phase adjustment function layer and B is the wavelength selection function layer. Further, the objective lens may be not only a plastic lens or a glass lens, but also a hybrid lens having a resin layer provided on an optical surface of the glass lens or the plastic lens.

The wavelength selection function may not be provided on the entire surface of the third annular zone S3, but may be provided only on the portion near the optical axis, as shown in FIG. That is,
As shown in a schematic diagram of the aberration correction situation in FIG.
The flare during reproduction of the optical information recording medium is caused by the third orbicular zone S
3, but if the incident light from the inner part S3a can be blocked, the convergence point of the transmitted light of the outer part S3b is sufficiently separated from the convergence point for recording and reproduction. Can be suppressed.

In some cases, the wavelength selecting function need not be provided on the entire surface of the third orbicular zone. As shown in FIG. 12, the outer peripheral circle of the orbicular third light beam is located within a plane substantially perpendicular to the optical axis. The above-mentioned wavelength selection function may be provided in two regions S3c and S3d respectively surrounded by two straight lines substantially symmetric with the center point of the inner circumference circle. At this time, the regions S3c, S3
Assuming that d is a direction substantially orthogonal to the tracking direction, the influence on the tracking accuracy is minimal when the tracking detection method is the three-beam method. FIG. 9B shows an example in which the above-mentioned straight line is substantially tangent to the inner peripheral surface of the third light beam, and it is not preferable that the wavelength selection function area is further reduced. (C) and (d) of FIG.
This is an example in which the wavelength selection function area of (b) is provided only in a portion close to the optical axis in the same way as in the embodiment of FIG.

[0033]

According to the present invention, there is provided an optical pickup device for recording and / or reproducing optical information recording media having different transparent substrate thicknesses by using light sources having different wavelengths. Has the function of automatically obtaining the required numerical aperture according to the thickness of the optical information recording medium, and the luminous flux transmitted through the outermost annular zone, which is unnecessary for an optical information recording medium having a thick transparent substrate, becomes a flare. Thus, the possibility of affecting the signal processing can be eliminated. Also, the embodiment has mainly been described as an example in which the light beam is divided into three zones.
The present invention is not limited to this, and it goes without saying that the present invention can be widely applied to those divided into two or more zones.

[Brief description of the drawings]

FIG. 1 is an optical path diagram showing a configuration of an optical pickup device of the present invention.

FIG. 2 is an optical path diagram showing a second configuration of the optical pickup device of the present invention.

FIG. 3 is an optical path diagram showing a third configuration of the optical pickup device of the present invention.

FIG. 4 is an optical path diagram showing a fourth configuration of the optical pickup device of the present invention.

FIG. 5 is an optical path diagram showing a fifth configuration of the optical pickup device of the present invention.

FIG. 6 is an optical path diagram showing a sixth configuration of the optical pickup device of the present invention.

FIG. 7 is an optical path diagram showing a sixth configuration of the optical pickup device of the present invention.

FIG. 8 is a schematic diagram showing a configuration of an optical disc of the Super RENS system.

FIG. 9 shows an objective lens 1 for an optical pickup device of the present invention.
It is a schematic diagram of an Example.

FIG. 10 is a schematic view of another embodiment of the objective lens for the optical pickup device of the present invention.

FIG. 11 is a schematic view of a third embodiment of the objective lens for an optical pickup device according to the present invention, and the state of aberration correction thereof.

FIG. 12 is a schematic view showing various modifications of the third embodiment of the objective lens for an optical pickup device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Optical disk 11, 40 Semiconductor laser 20 Dichroic prism 23, 24, 25, 26: Hologram 30 Light collecting means 31 Coupling lens 32 Objective lens 33 Wavelength selection function part 35 1/4 wavelength plate 36 Aperture 40, 43, 44 Polarized beam Splitters 50, 53, 54 Light receiving means 51, 55, 5
8 Photodetector 52, 56, 57 Cylindrical lens 60 Divergence angle conversion lens 70, 71, 72, 73 Laser / detector integrated unit 75, 76, 77, 78, 79, 80 Photodetector 81 Transparent substrate 82, 84, 8
6 Protective film 83 Nonlinear optical film 85 Information recording surface 90 Condensing lens

Claims (68)

[Claims] 1. A laser system comprising: two laser light sources having different wavelengths; a condensing optical system including an objective lens for converging laser light from the laser light source on an information recording surface of an optical information recording medium; and reflected light from the information recording surface. An optical pickup device for recording and / or reproducing at least two types of optical information recording media having different thicknesses of transparent substrates, wherein the light-collecting optical system is configured to transmit a light beam of a laser beam near an optical axis. Laser light having a short wavelength for at least a part of the outermost light flux split by the splitting means in the focusing optical system. An optical pickup device having a wavelength selection function for receiving a long-wavelength laser beam received by the light-receiving element and preventing the long-wavelength laser light from being received by the light-receiving element. 2. An innermost light beam including the vicinity of an optical axis is used for recording and / or reproduction of at least two types of optical information recording media having different thicknesses of a transparent substrate by the splitter, and the outermost light beam is used. 2. The optical pickup device according to claim 1, wherein the optical pickup device is used for recording and / or reproduction of an optical information recording medium having a thin transparent substrate among the two types of optical information recording media. 3. The splitting means is a means for splitting the light into three light fluxes. When the light is divided into first, second, and third light fluxes sequentially from near the optical axis to the outside, the first light flux is divided into a transparent substrate. Used for recording and / or reproduction of at least the two types of optical information recording media having different thicknesses, and wherein the second light flux is mainly used for the optical information recording media having a thick transparent substrate among the two types of optical information recording media. Wherein the third light flux is used for recording and / or reproduction of an optical information recording medium having a thin transparent substrate among the two types of optical information recording media. An optical pickup device according to claim 1 or 2. 4. In the condensing optical system, the intensity of a convergent spot is increased with respect to the two types of optical information recording media having different wavelengths of a laser beam and different thicknesses of a transparent substrate.
4. An optical pickup device according to claim 3, wherein a phase shift function is provided for shifting a phase of at least one of the three divided light beams with respect to another light beam. 5. The phase shift function according to claim 1, wherein one optical element in the condensing optical system is provided with a refraction surface having a plurality of concentrically divided orbicular zones, and the light between the respective orbicular refraction surfaces is provided. 5. The optical pickup device according to claim 4, wherein a phase shift of the light beam is performed by adjusting a position on the axis. 6. The optical pickup device according to claim 4, wherein said dividing means has said phase shift function. 7. When the plurality of orbicular zones are three orbicular zones, and the first, second and third orbicular zones are located outward from near the optical axis, the first, second and third orbicular zones are defined as: The first and third zones correspond to the first, second and third luminous fluxes, and the first and third zones have a short wavelength laser beam, and aberrations within a diffraction limit with respect to a thin transparent substrate of the two types of optical information recording media. The second annular zone is a laser beam having a long wavelength, a thick transparent substrate of the two types of optical information recording media or a thick transparent substrate and a thin transparent substrate of the two types of optical information recording media. 7. The optical system according to claim 5, wherein the aberration is corrected within the diffraction limit with respect to the thickness of the lens.
Optical pickup device as described 8. The optical pickup device according to claim 1, wherein said dividing means is an optical element other than an objective lens. 9. The optical pickup device according to claim 1, wherein said dividing means is an objective lens. 10. The optical pickup device according to claim 5, wherein the refractive surface having the plurality of annular zones is provided on an optical element other than the objective lens. 11. The optical pickup device according to claim 5, wherein a refracting surface having the plurality of annular zones is provided on an objective lens. 12. The optical pickup device according to claim 11, wherein a refracting surface having the plurality of annular zones is provided on a surface of the objective lens on a light source side. 13. The optical pickup device according to claim 11, wherein the refracting surface having the plurality of annular zones is provided on a surface of the objective lens on the optical information recording medium side. 14. The optical pickup device according to claim 11, wherein the objective lens is a plastic lens. 15. The optical pickup device according to claim 11, wherein the objective lens is a glass lens. 16. The optical pickup device according to claim 11, wherein the objective lens is a hybrid lens provided with a resin layer on an optical surface of a glass lens. 17. The method according to claim 11, wherein the objective lens is a hybrid lens having a resin layer provided on an optical surface of a plastic lens.
Optical pickup device described in Item 18. The wavelength selection function is a function of substantially transmitting a short-wavelength laser beam and substantially not transmitting a long-wavelength laser beam to at least a part of the outermost light beam. The optical pickup device according to any one of claims 1 to 17, wherein: 19. The wavelength selection function according to claim 1, wherein at least a part of the outermost light beam causes a short wavelength laser beam to reach the information recording surface, and a long wavelength laser beam transmits the information recording surface to the information recording surface. 18. The function according to claim 1, wherein the function is substantially not reached.
Optical pickup device described in Item 20. The wavelength selecting function is a function of substantially transmitting a short-wavelength laser beam and substantially removing a long-wavelength laser beam with respect to at least a part of the outermost light beam. The optical pickup device according to any one of claims 1 to 17, wherein: 21. The wavelength selecting function according to claim 1, wherein, of the two laser light sources, a short-wavelength laser light is almost transmitted, and a long-wavelength light is almost reflected. The optical pickup device according to claim 20. 22. The optical pickup device according to claim 21, further comprising a phase adjusting function for compensating for a phase shift due to a thickness of the multilayer coating. 23. The wavelength selecting function according to claim 1, wherein, of the two laser light sources, a dye layer that transmits laser light having a short wavelength substantially and absorbs light having a long wavelength substantially. The optical pickup device according to claim 20. 24. The optical pickup device according to claim 23, further comprising a phase adjustment function for compensating for a phase shift due to the thickness of the dye layer. 25. The optical pickup device according to claim 22, wherein the phase adjustment function is provided in an optical element other than the objective lens. 26. The optical pickup device according to claim 22, wherein the phase adjustment function is provided on a side surface of the light source of the objective lens. 27. The optical pickup device according to claim 22, wherein the phase adjustment function is provided on a side surface of the optical information recording medium of the objective lens. 28. The optical pickup device according to claim 21, wherein the wavelength selecting function is provided in an optical element other than the objective lens. 29. The optical pickup device according to claim 21, wherein the wavelength selection function is provided on a side surface of a light source of an objective lens. 30. The optical pickup device according to claim 21, wherein the wavelength selecting function is provided on a side surface of the optical information recording medium of the objective lens. 31. The wavelength selection function according to claim 1, wherein, of the two laser light sources, a short wavelength light is hardly diffracted and a long wavelength light is almost diffracted. The optical pickup device according to claim 17. 32. The pickup device according to claim 1, wherein the wavelength selection function functions in an annular shape with respect to a part of the outermost light beam. 33. The wavelength selecting function according to claim 26, wherein the outer peripheral light flux having a ring shape is substantially in contact with an inner circumferential circle in a plane substantially perpendicular to an optical axis and is substantially symmetric with a center point of the inner circumferential circle. The optical pickup according to any one of claims 1 to 31, wherein the optical pickup functions in two regions not including the center point, which are respectively surrounded by a straight line and an outer circumferential circle of the outermost light beam. apparatus 34. The apparatus according to claim 3, wherein the two areas are located in a direction substantially orthogonal to a tracking direction.
3. Optical pickup device according to 3. 35. The optical pickup device according to claim 33, wherein the two straight lines are straight lines substantially parallel to a tracking direction. 36. The wavelength selecting function according to claim 1, wherein the outer peripheral surface of the outermost light flux having a ring shape and a straight line substantially parallel to a tracking direction in a plane substantially perpendicular to an optical axis. 32. The device according to any one of claims 1 to 31, wherein the function is performed in two regions not including the center point, which are respectively surrounded by two straight lines not passing through the center point and an inner circumferential circle of the outermost light beam. 2. The optical pickup device according to claim 1. 37. The light-receiving element according to claim 1, wherein the light-receiving element is a single light-receiving element.
Optical pickup device described in Item 38. A splitting means for splitting a light beam of a laser beam into a plurality of light beams in an annular shape around the vicinity of the optical axis, wherein at least a part of an outermost light beam split by the splitting device is provided. Of the two laser beams having different wavelengths, the shorter wavelength laser light is received by the light receiving element that detects the reflected light from the information recording surface of the optical information recording medium, and the longer wavelength laser light is not received by the light receiving element. Objective lens for optical pickup device characterized by having wavelength selection function 39. The innermost light flux including the vicinity of the optical axis by at least two light sources having different thicknesses of the transparent substrate by the splitting means.
The outermost light flux is used for recording and / or reproduction of an optical information recording medium having a thin transparent substrate among the two types of optical information recording media. The objective lens for an optical pickup device according to claim 38, wherein: 40. The splitting means is a means for splitting the light into three light fluxes. When the light is divided into first, second, and third light fluxes in order from the vicinity of the optical axis to the outside, the first light flux has a thickness of the transparent substrate. Recording of at least two types of optical information recording media different in
Alternatively, the second light flux is used for recording and / or reproduction of an optical information recording medium having a thick transparent substrate among the two types of optical information recording media, and the third light flux is used for the reproduction. The objective lens for an optical pickup device according to claim 38 or 39, wherein the objective lens is used for recording and / or reproduction of an optical information recording medium having a thin transparent substrate among the two types of optical information recording media. 41. The optical pickup device according to claim 38, wherein said dividing means is a refracting surface having a plurality of concentrically divided annular zones. Objective lens 42. The apparatus according to claim 41, further comprising a phase shift function for performing a phase shift of the light beam by adjusting a position on the optical axis between the refraction surfaces of the annular zone. Objective lens for optical pickup device 43. The dividing means is a refracting surface having three concentrically divided annular zones, and is used for two types of optical information recording media having different wavelengths of laser light and different thicknesses of a transparent substrate. 41. The apparatus according to claim 40, further comprising a phase shift function of shifting a phase of at least one of the three light beams with respect to another light beam so as to increase the intensity of the convergent spot. Objective lens for optical pickup device 44. The phase shift function is such that when the three orbicular zones are first, second and third orbicular zones from the vicinity of the optical axis to the outside, the first and third orbicular zones have shorter wavelengths. The aberration is corrected within a diffraction limit with respect to a thin transparent substrate of the light and the two kinds of optical information recording media. 5. The method according to claim 4, wherein aberrations are corrected within a diffraction limit for a thick transparent substrate or a transparent substrate having a thickness between a thick transparent substrate and a thin transparent substrate of the two types of optical information recording media.
3. The objective lens for an optical pickup device according to item 3. 45. The objective lens for an optical pickup device according to claim 41, wherein the refracting surface having the plurality of annular zones is provided on a surface on a light source side. 46. The optical information recording medium according to claim 4, wherein the refraction surface having the plurality of annular zones is provided on the surface on the optical information recording medium side.
The objective lens for an optical pickup device according to any one of claims 1 to 44. 47. The objective lens for an optical pickup device according to claim 38, wherein the objective lens is a plastic lens. 48. The objective lens for an optical pickup device according to claim 38, wherein the objective lens is a glass lens. 49. A hybrid lens in which a resin layer is provided on the optical surface of a glass lens.
The objective lens for an optical pickup device according to any one of claims 8 to 46. 50. The objective lens for an optical pickup device according to claim 38, wherein the hybrid lens is a hybrid lens in which a resin layer is provided on an optical surface of a plastic lens. 51. The wavelength selecting function is a function of substantially transmitting a short-wavelength laser beam and substantially not transmitting a long-wavelength laser beam to at least a part of the outermost light beam. The objective lens for an optical pickup device according to any one of claims 38 to 50, characterized in that: 52. The wavelength selecting function is such that, with respect to at least a part of the outermost light beam, a laser beam having a short wavelength reaches the information recording surface, and a laser beam having a long wavelength transmits the information recording surface. The objective lens for an optical pickup device according to any one of claims 38 to 50, wherein the objective lens has a function that does not substantially reach the objective lens. 53. The wavelength selecting function is a function of substantially transmitting a short-wavelength laser beam and substantially removing a long-wavelength laser beam with respect to at least a part of the outermost light beam. The objective lens for an optical pickup device according to any one of claims 38 to 50, characterized in that: 54. The wavelength selecting function according to claim 38, wherein the laser beam having a short wavelength is substantially transmitted, and the laser beam having a long wavelength is substantially reflected. Objective lens for optical pickup device described in Item 55. The objective lens for an optical pickup device according to claim 54, further comprising a phase adjustment function for compensating for a phase shift due to the thickness of the multilayer coating. 56. The apparatus according to claim 38, wherein the wavelength selecting function is a dye layer that transmits laser light of a short wavelength substantially and absorbs light of a long wavelength substantially. Objective lens for optical pickup device described in 57. The objective lens for an optical pickup device according to claim 56, further comprising a phase adjustment function for compensating for a phase shift due to the thickness of the dye layer. 58. The objective lens for an optical pickup device according to claim 55, wherein the phase adjusting function is provided on a surface on a light source side. 59. The objective lens for an optical pickup device according to claim 55, wherein the phase adjustment function is provided on a surface on an optical information recording medium side. 60. The objective lens for an optical pickup device according to claim 54, wherein the wavelength selection function is provided on a surface on a light source side. 61. The objective lens for an optical pickup device according to claim 54, wherein the wavelength selection function is provided on a surface on an optical information recording medium side. 62. The apparatus according to claim 38, wherein the wavelength selecting function is a diffraction grating that hardly diffracts short-wavelength laser light and substantially diffracts long-wavelength laser light. Item 2. Objective lens for an optical pickup device according to item 1. 63. The objective lens for a pickup device according to claim 38, wherein the wavelength selection function functions in a ring shape with respect to a part of the outermost light flux. 64. The wavelength selecting function is provided in two planes substantially in contact with the inner circumferential circle of the outermost light flux having a ring shape in a plane substantially perpendicular to the optical axis and substantially symmetric with the center point of the inner circumferential circle. 63. The optical pickup according to claim 38, wherein the optical pickup functions in two regions not including the center point, which are respectively surrounded by a straight line and an outer circumferential circle of the outermost light beam. Objective lens for equipment 65. The objective lens for an optical pickup device according to claim 64, wherein said two regions are located in a direction substantially orthogonal to a tracking direction. 66. The objective lens for an optical pickup device according to claim 64, wherein said two straight lines are straight lines substantially parallel to a tracking direction. 67. The wavelength selecting function according to claim 1, wherein the outer peripheral surface of the outermost light flux having a ring shape and a straight line substantially parallel to a tracking direction in a plane substantially perpendicular to an optical axis. 63. The device according to any one of claims 38 to 62, which functions in two regions not including the center point, which are respectively surrounded by two straight lines that do not pass through the center point and an inner circumferential circle of the outermost light beam. 2. The objective lens for an optical pickup device according to claim 1. 68. The optical pickup device according to claim 3, wherein the objective lens for the optical pickup device comprises one single lens.
The objective lens for an optical pickup device according to any one of claims 8 to 67.