JP2002304763A - Optical pickup device, recording and reproducing device and method for correcting fluctuation in spherical aberration of optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device which has a beam-condensing optical system including an objective lens of a high numerical aperture and at least one plastic lens and is capable of maintaining an always good beam-condensing optical state by effectively correcting the fluctuation in the spherical aberrations arising in consequence of temperature and humidity changes, a recording and reproducing device and a method of correcting the fluctuation in the spherical aberrations. SOLUTION: This optical pickup device has the beam-condensing optical system which includes the objective lens 8 for condensing the luminous flux from a light source 1 onto an information recording surface 9' of an optical information recording medium and a beam expander 5 which is arranged in the optical paths of the light source 1 and the objective lens and corrects the fluctuation in the spherical aberrations. The beam-condensing optical system has a multidivision photodetector 15 which includes a plastic lens, detects the reflected light from the information recording surface and detects the fluctuation in the spherical aberration generated by a change in the shape and refractive index of the plastic lens to the changes in temp. and humidity and the fluctuation in the oscillation wavelength of the light source and a uniaxial actuator 11 which drives the beam expander 5 for the purpose of correcting the detected fluctuation in the spherical aberrations.

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 for recording / reproducing information on an optical information recording medium, a recording / reproducing device equipped with the optical pickup device, and correction of spherical aberration fluctuation in the optical pickup device. It is about the method.

[0002]

2. Description of the Related Art In recent years, with the practical use of short-wavelength different red semiconductor lasers, the capacity of conventional optical disks (also referred to as "optical information recording media") has been increased to the size of CDs (compact disks). DV, a high-density optical disc
D (Digital Versatile Disk) has been developed and commercialized, but it is expected that a next-generation optical disk of higher density will appear in the near future. In such an optical system of an optical information recording / reproducing apparatus using a next-generation optical disk as a medium, an objective lens is used in order to increase the density of a recording signal or reproduce a high-density recording signal, by shortening the wavelength of a laser as a light source. The numerical aperture (Nurmerical Aperture: NA) has been increased. However, as the NA of the objective lens is increased, it is expected that problems that can be almost ignored when recording or reproducing a relatively low-density optical disk such as a CD or DVD will become more apparent.

For example, a spherical aberration caused by a thickness error of a protective layer (also referred to as a “transparent substrate”) of an optical disk occurs in proportion to the fourth power of the numerical aperture of an objective lens. The influence of the thickness error of the protective layer increases, and there is a possibility that stable recording or reproduction of information cannot be performed.

A semiconductor laser used as a light source in an optical pickup device has an oscillation wavelength of ± 10n.
There is about m variation between individuals. When a semiconductor laser with an oscillation wavelength shifted from the reference wavelength is used as the light source, the spherical aberration generated by the objective lens increases as the numerical aperture increases, so that a semiconductor laser with an oscillation wavelength shifted from the reference wavelength cannot be used. In addition, it is necessary to select a semiconductor laser used as a light source.

A plastic lens generally used in an optical pickup device is easily deformed by a change in temperature or humidity, and has a large change in refractive index. The change in the refractive index of the plastic lens with respect to the change in temperature is approximately −10 × 10 ⁻⁵ / ° C. Since the spherical aberration caused by the change in the refractive index occurs in proportion to the fourth power of the numerical aperture of the objective lens, the change in the spherical aberration due to the change in the refractive index, which is not so problematic in the optical system used in the conventional optical pickup device, can also be obtained. However, when the numerical aperture of the objective lens is increased, the amount cannot be ignored.

[0006]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned problems, and has a condensing optical system including a high numerical aperture objective lens and at least one plastic lens. An optical pickup device, which is capable of effectively correcting a variation in spherical aberration generated due to a change in temperature and / or humidity and constantly maintaining a good light-collecting state, and including the optical pickup device. It is an object of the present invention to provide a method for correcting spherical aberration fluctuation in a recording / reproducing device and an optical pickup device.

Further, the thickness error of the protective layer of the optical disk,
An optical pickup device capable of effectively correcting fluctuations in spherical aberration caused by minute fluctuations in the oscillation wavelength of the light source and manufacturing errors of the optical elements included in the light-collecting optical system, and always maintaining a good light-collecting state. And a method for correcting spherical aberration fluctuation in the optical pickup device.

[0008]

To achieve the above object, a first optical pickup device according to the present invention converges a light source and a light beam from the light source on an information recording surface of an optical information recording medium. An optical pickup device comprising: a condensing optical system including an objective lens, and a spherical aberration correction unit disposed in an optical path between the light source and the objective lens, and for correcting a variation in spherical aberration. The condensing optical system includes at least one plastic lens, detects reflected light from the information recording surface, and changes at least one of the shape and the refractive index of the plastic lens with respect to at least a change in temperature and / or humidity. And / or a spherical aberration detecting means for detecting a variation in spherical aberration caused by a variation in the oscillation wavelength of the light source; and a variation in spherical aberration detected by the spherical aberration detecting means. Characterized in that it comprises a driving means for driving the spherical aberration correcting means for correcting.

According to this optical pickup device, the spherical aberration detecting means causes at least a change in the shape and the refractive index of the plastic lens and / or a change in the oscillation wavelength of the light source with respect to a change in temperature and / or humidity. Since the fluctuation of the spherical aberration is detected and the spherical aberration correcting means is driven by the driving means to correct the fluctuation of the spherical aberration, even if the optical pickup device has an objective lens with a high numerical aperture, the temperature and the It is possible to use plastic lenses that are susceptible to changes in humidity.

In a second optical pickup device according to the present invention, a light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and an optical system comprising the light source and the objective lens An optical pickup device provided in the optical path and including a converging optical system including a spherical aberration correction unit for correcting a variation in spherical aberration, by detecting reflected light from the information recording surface. A spherical aberration detecting unit configured to detect a variation of the spherical aberration, and a driving unit configured to drive the spherical aberration correcting unit in accordance with a detection result of the spherical aberration detecting unit. Splitting means for performing amplitude splitting or wavefront splitting on a light beam to be split, an optical element for giving a spherical aberration of a different size or a different sign to the split light beam or wavefront, and Characterized in that it comprises a multi-division photodetector for receiving the light flux that has given a spherical aberration, an I.

According to this optical pickup device, the spherical aberration can be detected with high accuracy by giving spherical aberrations having different magnitudes or different signs to the split light beams or wavefronts in the spherical aberration detecting means, and detecting. By driving the spherical aberration correcting means by the means, the fluctuation of the spherical aberration can be accurately corrected.

Further, a third optical pickup device according to the present invention comprises a light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and a light source and the objective lens. An optical pickup device provided in the optical path and including a converging optical system including a spherical aberration correction unit for correcting a variation in spherical aberration, by detecting reflected light from the information recording surface. A spherical aberration detecting unit that detects a change in the spherical aberration; and a driving unit that drives the spherical aberration correcting unit in accordance with a detection result of the spherical aberration detecting unit. A multi-split photodetector having a first light receiving surface and a second light receiving surface whose areas are distributed so as to cause a change in the amount of light received according to a change in the spherical aberration of the light beam; Multi-segment light detection A first light beam, which is disposed in an optical path with the light receiving device and receives reflected light from the information recording surface on the first light receiving surface, has the same paraxial focus position or best focus position as the first light beam. And split into a second light beam received by the second light receiving surface and the first light beam.
An optical element for giving an excessive spherical aberration to the light beam of the above, and giving an under spherical aberration to the second light beam, wherein the difference in the magnitude of the spherical aberration between the first light beam and the second light beam or By detecting a difference between the amount of light on the first light receiving surface and the amount of light on the second light receiving surface caused by the difference in sign, the amount of change in the spherical aberration is detected, and the amount of change in the spherical aberration is detected. The driving means is driven so as to reduce the pressure.

According to this optical pickup device, the amount of light on the first light receiving surface generated by the spherical aberration detecting means due to the difference in the magnitude or sign of the spherical aberration between the first light beam and the second light beam. By detecting the difference between the light amounts on the first and second light receiving surfaces, the spherical aberration can be accurately detected, and the driving unit drives the spherical aberration correction unit to accurately correct the fluctuation of the spherical aberration.

It is preferable that the first light receiving surface and the second light receiving surface are formed on the same substrate.

Further, a fourth optical pickup device according to the present invention comprises a light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and An optical pickup device provided in the optical path and including a converging optical system including a spherical aberration correction unit for correcting a variation in spherical aberration, by detecting reflected light from the information recording surface. A spherical aberration detecting unit configured to detect a change in the spherical aberration, and a driving unit configured to drive the spherical aberration correcting unit in accordance with a detection result of the spherical aberration detecting unit. The first light receiving unit, the second light receiving unit, and the first light receiving unit, whose areas are distributed so as to cause a change in the amount of light received according to the change in the spherical aberration of the incident light beam, in the order of An opposing third light receiving unit, A multi-segment photodetector having a light-receiving surface divided into at least four regions of a fourth light-receiving unit opposed to the second light-receiving unit; the spherical aberration correction unit, the multi-segment photodetector, and the spherical aberration 4 is arranged in the optical path with the correction means, the wavefront of the reflected light from the information recording surface is received by each light receiving surface of the multi-segmented photodetector, and the paraxial focal position or the best focus position is the same. While dividing the wavefront into two regions, giving an excessive spherical aberration to the wavefronts received by the first light receiving unit and the third light receiving unit, and receiving light by the second light receiving unit and the fourth light receiving unit. An optical element that gives an under-spherical aberration to the wavefront to be obtained, and the multi-divided light detection generated due to a difference in the magnitude or sign of the spherical aberration of the wavefront divided into the four regions. Light-receiving surface of each device By detecting the difference between the definitive amount, detecting the variation of the spherical aberration, characterized in that to drive the drive means so as to reduce the variation of the spherical aberration.

According to this optical pickup device, each of the multi-divided photodetectors generated by the spherical aberration detecting means due to the difference in the magnitude or sign of the spherical aberration of the wavefront divided into four regions is generated. By detecting the difference in the amount of light on the light receiving surface, the spherical aberration can be accurately detected, and the driving unit drives the spherical aberration correction unit to accurately correct the fluctuation of the spherical aberration.

It is preferable that an optical path from the light source to the information recording surface of the optical information recording medium and an optical path from the information recording surface to the multi-segmented photodetector are shared. Preferably, the multi-segment photodetector is formed on the same substrate.

The optical pickup device may further include a driving unit for driving the objective lens, and a tracking error of the objective lens and a tracking error of the objective lens by detecting reflected light from the information recording surface with a second photodetector. And / or an error detecting means for detecting a focusing error, wherein an optical path from the information recording surface to the second photodetector and an optical path from the information recording surface to the multi-segment photodetector are provided. Preferably shared. In this case, it is preferable that the second photodetector and the multi-segment photodetector are formed on the same substrate.

Further, the optical pickup device collects reflected light from the information recording surface on a light receiving surface of the multi-segmented photodetector in an optical path between the spherical aberration correcting means and the multi-segmented photodetector. It is preferable that a condensing lens for emitting light is provided, and the condensing lens imparts a spherical aberration having a different size or a different sign to at least an incident light beam and also performs amplitude division or wavefront division.

Further, the optical pickup device has a condensing lens disposed in an optical path of the spherical aberration correcting means and the multi-segmented photodetector, and the condensing lens has at least an annular diffraction structure. It is preferable to have it on one surface.

According to a fifth optical pickup device of the present invention, there is provided a light source, a coupling lens for converting a divergence of a light beam emitted from the light source, and a light beam from the light source for recording information on an optical information recording medium. An objective lens for converging on a surface, disposed in an optical path of the light source and the objective lens,
Spherical aberration correction means for correcting fluctuations in spherical aberration,
An optical pickup device provided with a condensing optical system including: a spherical aberration detecting means for detecting a change in the spherical aberration by detecting light reflected from the information recording surface; and detecting the spherical aberration detecting means. A driving unit for driving the spherical aberration correction unit according to the result, wherein the coupling lens and a condenser lens included in the spherical aberration detection unit, and a light included in the spherical aberration detection unit. A condenser lens disposed in an optical path between the detector and the spherical aberration correcting means substantially matches in characteristics of the light source with respect to wavelength fluctuation and temperature change.

According to this optical pickup device, when the temperature changes or the oscillation wavelength of the light source fluctuates, the cup for the spherical aberration of the reflected light from the information recording surface, which is detected by the photodetector of the spherical aberration detecting means, has The contribution of the ring lens can be canceled by the condenser lens. Thus, the fluctuation of the spherical aberration occurring between the spherical aberration correcting means and the optical information recording medium can be detected with high accuracy by the spherical aberration detecting means.

In this case, it is preferable that the coupling lens and the condenser lens are optically the same optical element.

Further, a sixth optical pickup device according to the present invention includes a condensing optical system including a light source and an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium. An optical pickup device, wherein the condensing optical system includes at least two lens groups each of which is independently movable along an optical axis direction, wherein all of the movable lens groups are made of a plastic material; And a driving means for shifting the lens group along the optical axis direction.

According to this optical pickup device, since the optical elements that can move along the optical axis are all formed of a plastic material, the load on the driving means can be reduced, and the driving power of the driving means can be reduced. Since it is possible to make it smaller and to make it possible to move with a smaller driving means,
The optical pickup device can be downsized.

The optical pickup device may further include a spherical aberration correcting unit disposed in an optical path between the light source and the objective lens for correcting a variation in spherical aberration, and detecting a reflected light from the information recording surface. And a spherical aberration detecting means for detecting a change in the spherical aberration, wherein the spherical aberration correcting means has at least one movable element movable along an optical axis direction, and a movable element along the optical axis direction. At least one lens group of the movable lens groups is the movable element, and at least one of the lens groups other than the movable element is a movable lens group along the optical axis direction.
Preferably, one lens group is the objective lens.

It is preferable that the following equation (1) is satisfied, where ΔSA is a spherical aberration variation that can be detected by the spherical aberration detecting means.

ΔSA ≧ 0.030λrms (1) where λ: oscillation wavelength (nm) of the light source

It is preferable that the following equation (2) is satisfied, where ΔSA is the amount of spherical aberration change that can be detected by the spherical aberration detecting means.

ΔSA ≧ 0.010λrms (2)

Further, the spherical aberration detecting means generates a spherical aberration error signal corresponding to a variation amount of the spherical aberration generated in the condensing optical system, and the driving is performed so that the spherical aberration error signal becomes substantially zero. Preferably, the means is driven.

Preferably, a predetermined numerical aperture on the image side of the objective lens required for recording or reproducing information on or from the information recording surface of the optical information recording medium is 0.65 or more.

Preferably, a predetermined numerical aperture on the image side of the objective lens required for recording or reproducing information on or from the information recording surface of the optical information recording medium is 0.75 or more.

It is preferable that the objective lens includes a first lens having a positive refractive power and a second lens having a positive refractive power arranged in order from the light source side, and satisfies the following expression (3).

0.07 <NA · WD / f <0.35 (3) where, NA: a predetermined image-side numerical aperture necessary for performing recording and / or reproduction on the optical information recording medium WD: the objective lens Working Distance (m
m) f: focal length (mm) of the entire system of the objective lens

It is preferable that the objective lens is a single lens and satisfies the following equation (4).

0.10 <NA · WD / f <0.40 (4) where NA is a predetermined numerical aperture on the image side necessary for recording and / or reproducing on the optical information recording medium. WD is the objective lens. Working Distance (m
m) f: focal length (mm) of the entire system of the objective lens

It is preferable that the objective lens is aberration-corrected so as to minimize aberration with respect to a parallel light beam from an object at infinity.

In addition, it is preferable that the objective lens is aberration-corrected so that aberration is minimized with respect to a divergent light beam from an object at a finite distance.

In addition, it is preferable that the objective lens is aberration-corrected so as to minimize aberration with respect to a convergent light beam directed to an image-side object.

Preferably, the light source emits light having a wavelength of 500 nm or less.

Further, the condensing optical system has a coupling lens in an optical path between the light source and the objective lens for converting a divergence angle of a divergent light beam from the light source, and the coupling lens is made of a glass material. Preferably,

The condensing optical system has a coupling lens in an optical path between the light source and the objective lens for converting a divergence angle of a divergent light beam from the light source, and the coupling lens has a refraction function. It is preferable that the composite lens is a composite lens composed of a glass lens and an optical element made of a plastic material and / or an ultraviolet curable resin having an optical surface formed on one surface and an optical surface formed on the other surface. . Thereby, the change in the divergence and the change in the divergence of the light emitted from the coupling lens due to the change in the focal length of the coupling lens itself can be canceled each other. Can always emit a light beam with a constant divergence from the coupling lens

The coupling lens is a collimating lens for converting a divergent light beam from a light source into a parallel light beam. It is preferable to have a beam shaping element for alleviating the astigmatic difference of the light beam.

It is preferable that all the optical elements other than the coupling lens included in the condensing optical system are formed of a plastic material.

The condensing optical system has a coupling lens in an optical path between the light source and the objective lens for converting a divergence angle of a divergent light beam from the light source, and the coupling lens is made of a plastic material. Preferably,

It is preferable that the light source emits a substantially circular light beam.

Further, the light source comprises a semiconductor laser and a wavelength conversion element for converting the wavelength of light emitted from the semiconductor laser, and the condensing optical system includes a light source for emitting light from the wavelength conversion element. Is condensed on the information recording surface, and the wavelength of light emitted from the semiconductor laser is set to λ0n
m, it is preferable that the following expression (5) is satisfied, where λ nm is the wavelength of light after wavelength conversion by the wavelength conversion element.

Λ = λ0 / m (m = 2, 3,...) (5)

Preferably, the numerical aperture of the coupling lens is 0.13 or less.

Further, it is preferable that the optical pickup device has a beam shaping element in an optical path between the light source and the coupling lens for reducing astigmatic difference of a light beam emitted from the light source.

Further, it is preferable that all the optical elements included in the condensing optical system are formed of a plastic material.

It is preferable that the condensing optical system has at least one diffractive optical element having a ring-shaped diffractive structure on at least one surface.

Further, the diffractive optical element can be included in the spherical aberration correcting means.

Further, the diffractive optical element may be included in a coupling lens which is arranged in an optical path between the light source and the objective lens and converts a divergent angle of a divergent light beam from the light source.

Further, the diffractive optical element can be included in the objective lens.

Further, it is preferable that the spherical aberration correcting means has at least one movable element movable along the optical axis direction.

The spherical aberration correcting means is a coupling lens arranged in an optical path between the light source and the objective lens for changing a divergence angle of a divergent light beam from the light source. Preferably, at least one lens group is the movable element.

The condensing optical system has a collimating lens disposed in an optical path between the light source and the objective lens for converting a divergent light beam from the light source into parallel light. A beam expander disposed in an optical path between the collimator lens and the objective lens, wherein at least one beam constituting the beam expander is provided.
Preferably, one lens group is said movable element.

The driving means for driving the movable element can be constituted by a voice coil actuator or a piezo actuator.

The spherical aberration correcting means can be configured so that the refractive index distribution along a direction perpendicular to the optical axis is variable.

Further, a sound and / or image recording / reproducing apparatus according to the present invention is characterized in that the above-described optical pickup devices are mounted.

The first method of correcting spherical aberration fluctuation according to the present invention includes a light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, the light source and the objective lens. A converging optical system, which is disposed in the optical path with the lens and includes a spherical aberration correcting unit for correcting the fluctuation of the spherical aberration, and the fluctuation of the spherical aberration by detecting the reflected light from the information recording surface. Spherical aberration detecting means for detecting
A driving unit for driving the spherical aberration correction unit in accordance with the detection result of the spherical aberration detection unit. A method of correcting spherical aberration fluctuation in an optical pickup device, wherein the spherical aberration detection unit includes at least an incident light beam. With respect to the amplitude division or wavefront division, an optical element that gives a spherical aberration of a different magnitude or a different sign to the divided light beam or wavefront, and a multi-divided photodetector that receives the light beam passing through the optical element, Detecting the difference in the amount of light on the light-receiving surface of the multi-segment photodetector, which is caused by the difference in the magnitude or sign of the spherical aberration of the split light beam or wavefront, thereby obtaining the spherical aberration. Is detected, and the driving unit is driven so as to reduce the fluctuation amount of the spherical aberration.

According to the method of correcting the fluctuation of spherical aberration in the optical pickup device, the difference in the amount of light on the light receiving surface caused by the difference in the magnitude or sign of the spherical aberration of the split light beam or wavefront is detected. By doing so, spherical aberration can be accurately detected. Thereby, the spherical aberration correcting means is driven by the driving means, and the fluctuation of the spherical aberration can be corrected with high accuracy.

A second method of correcting spherical aberration variation according to the present invention includes a light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, the light source and the objective lens. A converging optical system, which is disposed in the optical path with the lens and includes a spherical aberration correcting unit for correcting the fluctuation of the spherical aberration, and the fluctuation of the spherical aberration by detecting the reflected light from the information recording surface. Spherical aberration detecting means for detecting
A driving unit that drives the spherical aberration correction unit in accordance with the detection result of the spherical aberration detection unit. A method of correcting spherical aberration variation in an optical pickup device, wherein the spherical aberration detection unit is configured to: A multi-divided photodetector having a first light receiving surface and a second light receiving surface whose areas are distributed so as to cause a change in the amount of light received in response to a change in spherical aberration; A first light beam, which is disposed between photodetectors and receives reflected light from the information recording surface on the first light receiving surface, has the same paraxial focus position or best focus position as the first light beam; An optical element that splits the light into a second light beam received on the second light receiving surface, gives an excessive spherical aberration to the first light beam, and gives an under spherical aberration to the second light beam And have The difference between the amount of light on the first light receiving surface and the amount of light on the second light receiving surface caused by the difference in the magnitude or sign of the spherical aberration between the first light beam and the second light beam. By detecting, the variation of the spherical aberration is detected, and the driving unit is driven so as to reduce the variation of the spherical aberration.

According to the method of correcting the spherical aberration fluctuation in the optical pickup device, the first light receiving surface generated due to the difference in the magnitude or sign of the spherical aberration between the first light beam and the second light beam. By detecting the difference between the light amount at the second light receiving surface and the light amount at the second light receiving surface, the spherical aberration can be accurately detected. Thereby, the spherical aberration correcting means is driven by the driving means, and the fluctuation of the spherical aberration can be corrected with high accuracy.

A third method for correcting spherical aberration fluctuation according to the present invention includes a light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, the light source and the objective lens. A converging optical system, which is disposed in the optical path with the lens and includes a spherical aberration correcting unit for correcting the fluctuation of the spherical aberration, and the fluctuation of the spherical aberration by detecting the reflected light from the information recording surface. Spherical aberration detecting means for detecting
A driving unit for driving the spherical aberration correction unit in accordance with the detection result of the spherical aberration detection unit, wherein the spherical aberration detection unit has a clockwise direction. In order, the first light receiving unit, the second light receiving unit, and the first light receiving unit oppose the first light receiving unit, the areas of which are distributed so as to cause a change in the amount of light received according to a change in the spherical aberration of the incident light beam. A third light receiving unit, a multi-segmented photodetector having a light receiving surface divided into at least four regions of a fourth light receiving unit facing the second light receiving unit;
Disposed between the spherical aberration corrector and the multi-divided photodetector and the spherical aberration corrector, the wavefront of the reflected light from the information recording surface is received by each light-receiving surface of the multi-divided photodetector, And while paraxial focus position or best focus position is divided into four regions of the same wavefront, the first light receiving unit and the third light receiving unit give an excessive spherical aberration to the wavefront received by the third light receiving unit, An optical element for providing an under-spherical aberration to a wavefront received by the second light-receiving unit and the fourth light-receiving unit; and a difference in magnitude of spherical aberration between the wavefronts divided into the four regions. Alternatively, by detecting a difference in the amount of light on each light receiving surface of the multi-segment photodetector generated due to a difference in sign, the amount of change in the spherical aberration is detected, and the amount of change in the spherical aberration is reduced. So that the drive And wherein the driving means.

According to the method of correcting spherical aberration fluctuation in the optical pickup device, the multi-split photodetector generated due to the difference in the magnitude or sign of the spherical aberration of the wavefront divided into four regions is used. By detecting the difference between the amounts of light on the respective light receiving surfaces, the spherical aberration can be accurately detected. Thereby, the spherical aberration correcting means is driven by the driving means, and the fluctuation of the spherical aberration can be corrected with high accuracy.

The method of correcting a spherical aberration variation is a method of correcting a spherical aberration variation in an optical pickup device including at least one plastic lens in the condensing optical system, wherein at least a temperature and / or humidity change is corrected. It is preferable to correct a change in spherical aberration caused by a change in at least one of the shape and the refractive index of the plastic lens and / or a change in the oscillation wavelength of the light source.

[0070]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, optical pickup devices according to first to sixth embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>

FIG. 1 is a diagram showing a schematic configuration of an optical pickup device according to the first embodiment, and FIG. 2 is a schematic view of a light receiving surface of the multi-segmented photodetector of FIG. 1 viewed from a direction A of FIG. FIG. 3 is a perspective view showing a hologram element as an example of the spherical aberration adding element shown in FIG.

As shown in FIG. 1, the optical pickup device according to the present embodiment has a negative lens 5 as spherical aberration correcting means.
This uses a beam expander 5 composed of a and a positive lens 5b.

In the optical pickup device shown in FIG. 1, a light beam emitted from a light source 1 comprising a semiconductor laser is coupled to a coupling lens 2, a beam shaping prism pair 3, deflection beam splitters 4, 4 ', beam expanders 5, 1/4. Wave plate 6
After passing through the stop 7, the objective lens 8 condenses the light on the information recording surface 9 ′ via the transparent substrate 9 of the optical information recording medium.

Further, the reflected light from the information recording surface 9 ′ passes again through the objective lens 8 and the beam expander 5 and the like, and a part thereof is reflected by the deflecting beam splitter 4 ′ and the spherical aberration adding element 12 and the condensing light After passing through the lens 13 and going to the multi-segmented photodetector 15, the remainder passes through the deflecting beam splitter 4 ′, and is reflected by the deflecting beam splitter 4 to the tracking / focusing error detecting means 19.

The optical pickup apparatus shown in FIG. 1 has a biaxial actuator 10 for driving the objective lens 8 in two axial directions for tracking / focusing as objective lens driving means, and as a driving means for spherical aberration correcting means. There is provided a one-axis actuator 11 for driving the negative lens 5a of the beam expander 5 in the optical axis direction.

The tracking error / focusing error detecting means 19 detects the focusing error,
After the focus servo pull-in operation is performed by the two-axis actuator 10, the variation of the spherical aberration is detected by the multi-segment photodetector 15. Note that the detection of the tracking error / focusing error can be performed by using a known push-pull method, an astigmatism method, or the like, and a description thereof will be omitted.

Next, the principle of detecting the variation of the spherical aberration and correcting the variation of the spherical aberration in the present embodiment will be described.

As shown in FIGS. 2A and 2B, the multi-split photodetector 15 has a light receiving surface 14a and a light receiving surface 14b having a predetermined area, and the light receiving surface 14a and the light receiving surface 14b are It has a configuration formed on the same substrate. Light receiving surface 14a
Are light receiving sections A1 and A1 having a predetermined area by a dividing line 19.
The light receiving surface 14b is divided by a dividing line 20 into light receiving portions B1 and B2 having a predetermined area.

As shown in FIG. 1, the light beam 1 reflected by the information recording surface 9 ′, passed through the objective lens 8 and the beam expander 5 of the spherical aberration correcting means, and reflected by the deflection beam splitter 4.
6 (hereinafter, referred to as “reflected light 16”) is transmitted to the first light beam 16a received by the light receiving surface 14a when passing through the spherical aberration adding element 12 having one surface formed as a hologram surface, and to the light receiving surface 14b. The light is split into two light beams of the received second light beam 16b, and the first light beam is
The second light beam 16b has an excessive spherical aberration component, and the second light beam 16b has an excessive spherical aberration component. This spherical aberration component is preferably the same as the spherical aberration component generated due to the thickness error of the transparent substrate 9 of the optical information recording medium, and the magnitude is the maximum amount obtained by adding the spherical aberration component due to temperature change and wavelength fluctuation. Is preferred. At this time, the paraxial focal positions of the first light beam 16a and the second light beam 16b are the same, and the light receiving surfaces 14a and 14b of the multi-segment photodetector 15 are arranged at this position.

As the spherical aberration adding element 12, a hologram element 12a as shown in FIG. 3 can be used. From the predetermined amount of spherical aberration at the light source wavelength and the predetermined amount of light flux separation on the multi-segmented photodetector 15, the hologram surface 12b
Is determined, one of the ± 1st-order diffracted lights has an under spherical aberration and the other has an over spherical aberration. The hologram surface 12b has a wavelength of λ / λ of the light source wavelength (λ).
A sine wave or rectangular wave type grating having a phase difference of 2 may be used.

FIGS. 2C and 2D show the information recording surface 9 'on the light receiving surfaces 14a and 14b when the reflected light 16 has no fluctuation in spherical aberration (hereinafter referred to as "reference state").
2 shows a light receiving pattern of reflected light from the light source. Light receiving parts A1, A
2, the size of B1, B2 and the shape of the spherical aberration adding element 12 are such that the light receiving amounts A1,
A2, B1, and B2 (each received light amount is represented by the same reference numeral as each light receiving unit) are determined so as to satisfy A1 = A2 B1 = B2.

In the above-described reference state, the spot received on the light receiving surface 14a has a state of under spherical aberration, and the spot received on the light receiving surface 14b has a state of over spherical aberration. That is, a nucleus having a relatively high light density is formed at the center, and a flare having a low light density is formed at the periphery.

Here, when the spherical aberration of the reflected light 16 fluctuates in an under direction (hereinafter referred to as an "under state"), the light receiving pattern becomes as shown in FIGS. 2 (e) and 2 (f). That is, as shown in the figure, the spot received on the light receiving surface 14a is emphasized with an under spherical aberration, and the intensity of the peripheral flare is higher and the intensity of the central nucleus is lower than in the reference state. On the other hand, in the spot received by the light receiving surface 14b, excessive spherical aberration is reduced, and the intensity of the peripheral flare is small and the intensity of the central nucleus is large as compared with the reference state.

When the spherical aberration of the reflected light 15 fluctuates in an excessive direction (hereinafter, referred to as “over state”).
, The light receiving pattern is as shown in FIGS. 2 (g) and 2 (h). That is, as shown in the figure, the spots received on the light receiving surface 14a are reduced in under spherical aberration, and the intensity of the peripheral flare is small and the intensity of the central nucleus is large compared to the reference state. On the other hand, the spots received on the light receiving surface 14b have excessive spherical aberration emphasized, and the intensity of the peripheral flare is larger and the intensity of the central nucleus is smaller than in the reference state.

Table 1 below shows changes in the amounts of light A1, A2, B1, and B2 received by the light receiving portions of the light receiving surfaces 14a and 14b with respect to the reference state. In Table 1, “+” indicates that the light amount increases as compared to the reference state, and “−” indicates that the light amount decreases as compared to the reference state.

[0087]

[Table 1]

The spherical aberration error signal ΔSA is detected by the following calculation based on the amount of light received at each light receiving section of the multi-segment photodetector 15.

ΔSA = (A2 + B1)-(A1 + B2)

From Table 1, it can be seen that ΔSA <
0, ΔSA> 0 in the over state.

In the multi-segment photodetector 15 shown in FIG.
When it is detected that A <0, the one-axis actuator 11 which is a driving means of the beam expander 5 controls the negative lens 5a so that the distance between the negative lens 5a and the positive lens 5b is increased as compared with the reference state. ΔSA = 0 along the axial direction
It is changed so that it becomes. On the other hand, when ΔSA> 0 is detected, the uniaxial actuator 11 which is the driving means of the beam expander 5 is driven so as to reduce the distance between the negative lens 5a and the positive lens 5b as compared with the reference state. The lens 5a is shifted along the optical axis direction so that ΔSA = 0.

The light receiving surface of the multi-segment photodetector 15 is arranged as described above with respect to the first light beam 16a and the second light beam 1a.
The position is not limited to the paraxial focus position 6b but may be inside or outside thereof, and the fluctuation of spherical aberration can be detected and corrected by the same principle as the method described above. Next, a modified example of the optical pickup device of FIG. 1 will be described with reference to FIG. In the optical pickup device of FIG. 4, the coupling lens can be displaced along the optical axis direction as a spherical aberration correcting means, and the same effect as in FIG. 1 can be obtained.

As shown in FIG. 4, the light beam from the light source 1 passes through the deflecting beam splitters 4 and 4 ′, the quarter-wave plate 6, the coupling lens 2, and the stop 7, and optical information is recorded by the objective lens 8. The light is focused on the information recording surface 9 'via the transparent substrate 9 of the medium. The reflected light from the information recording surface 9 'passes through the objective lens 8, the coupling lens 2, etc.
A part is reflected by the deflecting beam splitter 4 'and passes through the spherical aberration adding element 12 to the multi-segmented photodetector 15, and the rest passes through the deflecting beam splitter 4' and is reflected by the deflecting beam splitter 4 to perform tracking /
The process proceeds to the focusing error detecting means 19.

The coupling lens 2 as a spherical aberration correcting means is configured to be displaceable along the optical axis direction in FIG. 1 by a one-axis actuator 11 as a driving means of the spherical aberration correcting means. In FIGS. 1 and 4, a voice coil actuator, a piezo actuator, or the like can be used as a driving unit (single-axis actuator 11) for driving the beam expander 5 and the coupling lens 2.

The condenser lens 13 in FIG. 1 for condensing the reflected light from the information recording surface 9 ′ on the multi-segmented photodetector 15 is the same optical element as the coupling lens 2 and is omitted. This makes it possible to reduce the size of the optical pickup device, reduce the number of components, and the like.

When the multi-segment photodetector 15 of the optical pickup device shown in FIG. 4 detects that the spherical aberration error signal ΔSA <0, the driving means 11 of the coupling lens 2 compares the spherical aberration error signal with the reference state. The coupling lens 2 is moved so as to reduce the distance between the ring lens 2 and the objective lens 8.
Is shifted along the optical axis direction so that ΔSA = 0. On the other hand, when ΔSA> 0 is detected, the coupling lens 2 is driven by the driving means 11 of the coupling lens 2 so that the distance between the coupling lens 2 and the objective lens 8 is increased as compared with the reference state. The displacement is made along the optical axis direction so that ΔSA = 0.

Next, another modified example of the optical pickup device of FIG. 1 will be described with reference to FIG. The optical pickup device of FIG. 5 uses a variable refractive index distribution element instead of the beam expander 5 of FIG. 1 as a spherical aberration correction unit, and can obtain the same effect as that of FIG.

As shown in FIG. 5, the luminous flux from the light source 1 is transmitted to the deflecting beam splitters 4 and 4 'and the refractive index distribution variable element 17.
And the like, and is focused on the information recording surface 9 'by the objective lens 8 via the transparent substrate 9 of the optical information recording medium. The reflected light from the information recording surface 9 'passes through the objective lens 8, the refractive index distribution variable element 17, and the like, and is partially reflected by the deflecting beam splitter 4' and passes through the spherical aberration adding element 12 and the condenser lens 13. Toward the multi-segment photodetector 15
After the rest passes through the deflection beam splitter 4 ′, it is reflected by the deflection beam splitter 4 and travels to the tracking / focusing error detecting means 19.

The variable refractive index distribution element 17 having a variable refractive index distribution as the spherical aberration correcting means shown in FIG. 5 includes, for example, an optically transparent electrode layer 1 electrically connected to each other.
7a, 17b, 17c and electrode layers 17a, 17b, 17
c are electrically insulated from each other and the refractive index distribution variable layers 17 d and 17 e whose refractive index distribution changes according to the voltage applied from the driving means 18 are alternately laminated, and the electrode layers 17 a and 17 e are alternately laminated.
An element in which 7b and 17c are divided into a plurality of regions can be used.

When the multi-segment photodetector 15 of the optical pickup device of FIG. 5 detects the spherical aberration error signal ΔSA, the driving means 18 of the variable refractive index element 17 applies a voltage to the electrode layers 17a, 17b, 17c. Is applied, the refractive index of the refractive index distribution variable layers 17d and 17e is changed depending on the location, and the phase of light emitted from the refractive index distribution variable element 17 is changed by Δ
Control is performed so that SA becomes zero.

Further, as an element having a variable refractive index distribution, a liquid crystal element a in which liquid crystal molecules are arranged in an arbitrary X direction within a plane perpendicular to the optical axis, and a liquid crystal molecule perpendicular to the optical axis. Liquid crystal elements b aligned in the Y direction perpendicular to the X direction in the plane can also be used. The liquid crystal element a and the liquid crystal element b are alternately laminated with the glass substrate c interposed therebetween, and a voltage is applied to each of the liquid crystal element a and the liquid crystal element b, so that the phase of the light emitted from the spherical aberration correction unit is changed. By independently controlling the X-direction component and the Y-direction component, the fluctuation of the spherical aberration can be corrected.

Further, by forming the condenser lens 13 as a diffractive lens, the condenser lens 13 may have the function of the spherical aberration adding element 12. By using the spherical aberration adding element 12 and the condensing lens 13 in common, the number of components of the optical pickup optical system can be reduced, and a simpler configuration can be achieved.

<Second Embodiment>

FIG. 12 is a diagram showing a schematic configuration of an optical pickup device according to the second embodiment.

The optical pickup device according to the present embodiment shown in FIG. 12 shares an optical path from the light source 1 to the information recording surface 9 'and an optical path from the information recording surface 9' to the multi-segmented photodetector 15, 1 is omitted, the light source 1 and the multi-segment photodetector 15 are formed on the same substrate, and the positive lens 5b of the beam expander 5 is further provided.
1 is basically the same as that of FIG. 1 except that the variation of spherical aberration is corrected by displacing along the optical axis direction by a one-axis actuator 11, so that the same parts are denoted by the same reference numerals, and the description thereof will be omitted. Is omitted.

As shown in FIG. 12, the light source 1 and the multi-segment photodetector 1 are installed in the light source / multi-segment photodetector integrated unit 24 '.
5, the hologram 20 and the spherical aberration adding element 12 are unitized.

The light beam emitted from the light source 1 includes a hologram 20, a coupling lens 2, a beam shaping prism pair 3, a deflecting beam splitter 4, a beam expander 5,
After passing through the 波長 wavelength plate 6 and the aperture 7, the light is focused on the information recording surface 9 ′ by the objective lens 8 via the transparent substrate 9 of the optical information recording medium. The reflected light from the information recording surface 9 ′ passes again through the objective lens 8, the diaphragm 7, the １ ／ wavelength plate 6, and the beam expander 5, and is partially reflected by the deflection beam splitter 4 to detect a tracking error / focusing error. To the means 19 and the rest to the deflection beam splitter 4
Passes through the beam shaping prism pair 3 and the coupling lens 2 and is diffracted by the hologram 20 toward the spherical aberration detecting means. According to such an optical pickup device of FIG. 12, the same effect as that of FIG. 1 can be obtained.

The condenser lens 13 in FIG. 1 for condensing the reflected light from the information recording surface 9 ′ on the multi-segmented photodetector 15 is the same optical element as the coupling lens 2 and is omitted. This makes it possible to reduce the size of the optical pickup device, reduce the number of components, and the like.

When the beam shaping prism pair 3 for reducing the astigmatic difference of the light beam emitted from the light source is used as in each of the optical pickup devices shown in FIGS. 1, 5, 6 and 12, the beam shaping is performed. In order to prevent astigmatism from occurring in the prism pair 3, the divergence of the light beam incident on the beam shaping prism pair 3 needs to be always kept constant. For this reason, the coupling lens 2 is preferably a glass lens. Thereby, even when a temperature change and / or a humidity change occur, the divergence of the light beam incident on the beam shaping prism pair 3 can be kept constant. Further, this glass coupling lens is a diffractive lens, and the movement of the focal point of the coupling lens when the wavelength of the light source is slightly changed is suppressed to be small, so that the light is incident on the beam shaping prism pair 3 even when the wavelength of the light source is slightly changed. This is more preferable because the divergence of the light beam can be kept constant.

When the temperature and / or humidity changes, the distance from the light source to the coupling lens 2 changes due to the change in the shape of the lens frame holding the coupling lens 2, and the light emitted from the coupling lens 2 changes. The divergence of light may change. Coupling lens 2
A composite lens comprising: a glass lens having a refraction function; and an optical element made of a plastic material and / or an ultraviolet curable resin having one surface joined to the glass lens and the other surface formed with an optical surface. Then, the change in the divergence described above and the change in the divergence of the light emitted from the coupling lens 2 due to the change in the focal length of the coupling lens 2 itself can be canceled each other. A light beam having a constant divergence can always be emitted from the coupling lens 2 with respect to a change in humidity. As such a compound lens type coupling lens 2, a coupling lens as disclosed in Japanese Patent Application No. 2000-053858 filed by the same applicant can be used.

<Third Embodiment>

FIG. 13 is a diagram showing a schematic configuration of an optical pickup device according to the third embodiment.

The optical pickup device according to the present embodiment shown in FIG. 13 has the condensing lens 13 of FIG. 1 for condensing the reflected light from the information recording surface 9 ′ on the multi-segmented photodetector 15 similarly to FIG. The coupling lens 2 is the same optical element, and the light source 1 and the coupling lens 2 are different from those in FIG.
4 except that a beam shaping lens 21 for reducing the astigmatic difference of the luminous flux emitted from the light source 1 is arranged in the optical path of the same. And description thereof is omitted.

As the beam shaping lens 21 shown in FIG. 13, an anamorphic lens can be used.
The surface shape of the anamorphic lens is determined by the magnitude of the astigmatic difference of the light beam emitted from the light source.

As shown in FIG. 13, the light beam emitted from the light source 1 is divided into a beam shaping lens 21, a deflecting beam splitter 4 ', a deflecting beam splitter 4, a coupling lens 2, a beam expander 5, and a 波長 wavelength plate. 6. After passing through the stop 7, the light is focused on the information recording surface 9 'by the objective lens 8 via the transparent substrate 9 of the optical information recording medium. The reflected light from the information recording surface 9 ′ passes again through the objective lens 8, the 波長 wavelength plate 6, the beam expander 5, and the coupling lens 2, and is partially reflected by the deflecting beam splitter 4 ′ so that the tracking error / After heading toward the focusing error detecting means 19, the rest passes through the deflecting beam splitter 4 'and is reflected by the deflecting beam splitter 4 toward the spherical aberration detecting means. According to the optical pickup device of FIG. 13, the same effect as that of FIG. 4 can be obtained.

Further, in the optical pickup device shown in FIG.
Since the beam shaping element is arranged in the optical path between the light source 1 and the coupling lens 2, the coupling lens 2 can be a plastic lens. Spherical aberration caused by a change in the divergence of a light beam emitted from the coupling lens 2 when a temperature change or a humidity change or a minute wavelength change of the light source occurs is caused by the coupling lens 2 being moved by a one-axis actuator. It can be corrected by shifting in the optical axis direction.

As shown in FIGS. 1, 5, 6, 12, and 13, the beam shaping prism pair 3 or the beam shaping for reducing the astigmatic difference of the light beam emitted from the light source 1. The use of the lens 21 is preferable because the light beam from the light source can be entirely taken in by the coupling lens 2 without losing the light amount, so that the light source of a low output type can be applied. Further, since the driving voltage of the light source can be reduced, the life of the light source can be extended.

<Fourth Embodiment>

FIG. 14 is a diagram showing a schematic configuration of an optical pickup device according to the fourth embodiment.

The optical pickup device according to the present embodiment shown in FIG. 14 is similar to FIG. 4 in that the condensing lens 13 shown in FIG. Since the coupling lens 2 and the coupling lens 2 are the same optical element and have basically the same configuration as that of FIG. 4, the same portions are denoted by the same reference numerals and description thereof will be omitted.

As shown in FIG. 14, the optical path from the information recording surface 9 'to the second photodetector 19 for tracking error / focusing error detection and the optical path from the information recording surface 9' to the multi-segment photodetector 15 Are shared, and the second photodetector for tracking error / focusing error detection and the multi-segment photodetector 15 are formed on the same substrate. The multi-split photodetector 15, the second photo-detector 19, and the hologram 20 in the multi-split photodetector / second photodetector integrated unit 25 '.
And the spherical aberration adding element 12 is unitized.

Further, the objective lens 8 is of a finite conjugate type that converges the divergent light beam from the light source 1 onto the information recording surface 9 ', so that a large working distance is ensured and the optical information recording medium and the objective lens 8 To prevent collisions. Further, the correction of the spherical aberration fluctuation is performed by a coupling lens 2 which is disposed in the optical path between the light source 1 and the objective lens 8 and can move along the optical axis direction.

As shown in FIG. 14, the light beam emitted from the light source 1 passes through the deflecting beam splitter 4, the coupling lens 2, the quarter-wave plate 6, and the stop 7, and is then subjected to optical information recording by the objective lens 8. The light is focused on the information recording surface 9 'via the transparent substrate 9 of the medium. The reflected light from the information recording surface 9 ′ passes again through the objective lens 8, the 波長 wavelength plate 6, and the coupling lens 2, is reflected by the deflection beam splitter 4, and enters the hologram 20. Of the diffracted light generated by the hologram 20, m-order diffraction goes to the spherical aberration detecting means, and n-order diffracted light (where m ≠ n) goes to the tracking error / focusing error detecting means 19.
According to such an optical pickup device of FIG. 14, FIG.
The same effect as described above can be obtained.

<Fifth Embodiment>

FIG. 15 is a diagram showing a schematic configuration of an optical pickup device according to the fifth embodiment.

In the optical pickup device according to the present embodiment shown in FIG. 15, the objective lens 8 is connected to two positive lenses 22 and 2.
3 are composed of two groups, each lens 2
4 and 23 can be displaced along the optical axis direction and / or the direction perpendicular to the optical axis, and have basically the same configuration as that of FIG. 4 except that the coupling lens 2 of FIG. 4 is omitted. Are denoted by the same reference numerals, and description thereof is omitted.

The first lens 22 on the light source side is displaced by the one-axis actuator 11 in order to correct the spherical aberration fluctuation, and the second lens 23 on the optical information recording medium side is moved in two axes to reduce the tracking error / focusing error. It is displaced by the actuator 10.

As shown in FIG. 15, the light beam emitted from the light source 1 passes through the deflecting beam splitter 4, the deflecting beam splitter 4 ', the quarter-wave plate 6, and the stop 7, and is then subjected to optical information by the objective lens 8. The light is focused on the information recording surface 9 'via the transparent substrate of the recording medium. The reflected light from the information recording surface 9 'passes through the objective lens 8 and the quarter-wave plate 6 again, and is partially reflected by the deflecting beam splitter 4' to the tracking error / focusing error detecting means 19, while the rest is reflected. After passing through the deflecting beam splitter 4 ', the light is reflected by the deflecting beam splitter 4 and travels to the spherical aberration detecting means. According to such an optical pickup device of FIG. 14, the same effect as that of FIG. 4 can be obtained.

The above-mentioned FIG. 1, FIG. 5, FIG. 6, FIG.
In each of the optical pickup devices 3, when a high-power semiconductor laser or a light source capable of emitting a substantially circular light beam having almost no astigmatism is used as the light source 1, the astigmatic difference of the light beam emitted from the light source 1 is used. This is preferable because the beam shaping prism pair 3 or the beam shaping lens 21 for alleviating the distortion can be omitted, and the coupling lens can be a plastic lens.

When a high-power semiconductor laser is used as a light source, an elliptical light beam emitted from the light source is shaped into a circular shape by utilizing the light-shading effect of the coupling lens 2. At this time, the numerical aperture of the coupling lens 2 is preferably set to 0.13 or less in order to sufficiently capture the light amount in the direction in which the spread angle is small.

A light source capable of emitting a substantially circular light beam having almost no astigmatic difference is an SHG in front of a semiconductor laser.
(Second Harmonic Generation: Second Harmonic Generation) A light source having an element can be used.

<Sixth Embodiment>

FIG. 6 is a diagram showing a schematic configuration of an optical pickup device according to the sixth embodiment, and FIG. 7 is a schematic view of the light receiving surface of the multi-segmented photodetector shown in FIG. 6 viewed from the direction AA in FIG. FIG.

As shown in FIG. 6, the optical pickup device of the present embodiment uses a beam expander composed of a positive lens 5a and a negative lens 5b as the spherical aberration correcting means as in FIG. Since the light receiving surface of the multi-segment photodetector has the same configuration except that it is further divided,
The same portions are denoted by the same reference numerals, and description thereof will be omitted.

The principle of detecting the fluctuation of the spherical aberration and correcting the fluctuation of the spherical aberration in the present embodiment will be described with reference to FIG. As shown in FIG. 7A, the multi-segment photodetector 2
5, the light receiving surface 24 is divided by the dividing lines 21 and 22.
a and a light receiving surface 24b. The light receiving surface 24a and the light receiving surface 24b
a2, a1 ', a2' and b1, b2, b1 ', b2'
Is divided into Light receiving units a1, a2 and light receiving units a1 ', a
2 ′, the light receiving portions b1, b2 and the light receiving portions b1 ′, b2 ′ are located at positions facing each other.

In the optical pickup device shown in FIG. 6, when the reflected light from the information recording surface 9 ′ passes through the spherical aberration adding element 12, the reflected light in the XZ plane shown in FIG. An excessive spherical aberration component is added to a light ray received on the surface 24b, and an under spherical aberration component is added to a light ray in the YZ plane, that is, a light ray received on the light receiving surface 24a. At this time, the best focus positions of the light beam in the XZ plane and the light beam in the YZ plane are made the same, and the light receiving surface 24 of the multi-segmented photodetector 25 receives the light beam in the XZ plane and the Y- It is arranged outside the best focus position of the light ray in the Z plane.

FIG. 7B shows the light receiving surface 2 in the reference state.
4 shows a light receiving pattern of reflected light from the information recording surface of No. 4; Light receiving units a1, a2, b1, b2, a1 ', a2', b
The size of 1 ′, b2 ′ and the shape of the spherical aberration adding element 12 are such that the light receiving amounts a1, a
2, b1, b2, a1 ', a2', b1 ', b2' (each light receiving amount is represented by the same reference numeral as each light receiving unit): a1 = a2, a1 '= a2' b1 = b2, b1 '= b2 Or, (a2 + b1)-(a1 + b2) = 0 (a2 '+ b1')-(a1 '+ b2') = 0 The relational expression is determined so as to hold.

The spot received by the light receiving surface 24a has a state in which the spherical aberration is under, that is, a nucleus having a relatively large light density is formed at the center and a flare having a small light density is formed in the periphery. The spot received by the light receiving surface 24b is in a state where the spherical aberration is over, that is, a ring-shaped spot having a relatively large light beam density is formed around the spot.

In the under state, the light receiving pattern is as shown in FIG.
(C). In the spot received by the light receiving surface 24a, under spherical aberration is emphasized, and the intensity of the peripheral flare is higher and the intensity of the central nucleus is lower than in the reference state. On the other hand, the spots received on the light receiving surface 24b are reduced in excessive spherical aberration, and the peripheral ring-shaped spots approach a uniform intensity distribution.

In the over state, the light receiving pattern is as shown in FIG. In the spot received by the light receiving surface 24a, the under spherical aberration is reduced, and the spot approaches a uniform intensity distribution. On the other hand, the spots received on the light receiving surface 24b have excessive spherical aberration emphasized, and the intensity of the peripheral ring-shaped bot is greater than that in the reference state.

Table 2 below shows changes in the amount of light received by each light receiving portion of each of the light receiving surfaces 24a and 24b with respect to the reference state. In Table 2, “+” indicates that the light amount increases as compared with the reference state, and “−” indicates that the light amount decreases as compared with the reference state.

[0142]

[Table 2]

The spherical aberration error signal ΔSA is detected by the following calculation based on the amount of light received by each light receiving section of the multi-segment photodetector 25. ΔSA = (A2 + B1) − (A1 + B2) or ΔSA = (A2 ′ + B1 ′) − (A1 ′ + B2 ′) or ΔSA = (A2 + B1 + A2 ′ + B1 ′) − (A1 + B
2 + A1 '+ B2')

From Table 2, it can be seen that ΔSA <
0, ΔSA> 0 in the over state.

In the multi-segment photodetector 25, ΔSA <0
Is detected, the driving means 11 of the beam expander 5 moves the negative lens 5a along the optical axis direction so that the distance between the negative lens 5a and the positive lens 5b is larger than that in the reference state by ΔSA = 0. It is changed so that it becomes. On the other hand, when ΔSA> 0 is detected, the negative lens 5a is moved by the beam expander driving means 11 in the optical axis direction so as to reduce the distance between the negative lens 5a and the positive lens 5b as compared with the reference state. Along the line so that ΔSA = 0.

In the case where the light receiving surface 14 of the multi-segmented photodetector 15 is located inside the best focus position of the light beam in the XZ plane and the light beam in the YZ plane, the same method as described above is applied. The fluctuation of the spherical aberration can be detected and corrected by the principle described above.

As in FIGS. 4 and 5, as the spherical aberration correcting means in the optical pickup device shown in FIG. 6, a coupling lens or a variable refractive index distribution element which can be displaced along the optical axis direction may be used. good.

[0148]

Next, the present invention will be described more specifically with reference to Examples 1 and 2. The aspherical surface of the lens according to the present embodiment is expressed by the following equation (1), where the optical axis direction is X axis, the height in the direction perpendicular to the optical axis is h, and the radius of curvature of the refraction surface is r. Where κ
Is a cone coefficient, and A2i is an aspheric coefficient.

[0149]

(Equation 1)

The ring-shaped diffraction surface provided in the lens of this embodiment can be expressed by the following equation 2 as an optical path difference function Φb. Here, h is a height perpendicular to the optical axis, and b2
i is a coefficient of the optical path difference function.

[0151]

(Equation 2)

<Example 1>

Table 3 shows data of an optical system preferable for use in the optical pickup device shown in FIG. In this embodiment, the image side numerical aperture of the objective lens is 0.85, the oscillation wavelength of the light source for recording or reproducing information is 405 nm, and all components are made of a plastic material having a high internal transmittance in a short wavelength region. Formed. A beam expander composed of one negative lens and one positive lens is used as the spherical aberration correcting means, and the fluctuation of the spherical aberration generated in the optical system is shifted by moving the negative lens along the optical axis. Corrected. In the present embodiment, of the constituent lenses of the beam expander, the positive lens may be shifted, or both the positive lens and the negative lens may be shifted in order to correct the fluctuation of the spherical aberration.

[0154]

[Table 3]

Table 4 shows the variation in the oscillation wavelength of the light source of ± 10 nm, the temperature change of ± 30 ° C., and ± 0.02 mm in Example 1.
5 shows the result of correcting the fluctuation of the spherical aberration caused by the transparent substrate thickness error. Chromatic aberration, which is a problem when using a short-wavelength laser light source with an oscillation wavelength of about 400 nm, was corrected by using a double-sided diffractive lens as the positive lens of the beam expander. FIG. 8 is an optical path diagram according to the first embodiment,
FIG. 9 shows a spherical aberration diagram according to the first embodiment.

[0156]

[Table 4]

<Example 2>

Table 5 shows data of an optical system preferable for use in the optical pickup device shown in FIG. In this embodiment, the image side numerical aperture of the objective lens is 0.85, the oscillation wavelength of the light source for recording or reproducing information is 405 nm, and all components are made of plastic having a high internal transmittance in a short wavelength region. Formed from material. A coupling lens is used as the spherical aberration correcting means, and the fluctuation of the spherical aberration generated in the optical system is corrected by moving the coupling lens along the optical axis. In the present embodiment, the coupling lens is configured as one group, but may be configured as a plurality of lens groups.

[0159]

[Table 5]

Table 6 shows the variation in the oscillation wavelength of the light source of ± 10 nm, the temperature change of ± 30 ° C., and ± 0.02 mm in Example 2.
5 shows the result of correcting the fluctuation of the spherical aberration caused by the transparent substrate thickness error. Chromatic aberration, which is a problem when using a short-wavelength laser light source having an oscillation wavelength of about 400 nm, was corrected by using the light-source-side surface of the coupling lens as a diffraction surface. FIG. 10 is an optical path diagram according to the second embodiment, and FIG.
FIG. 1 shows a spherical aberration diagram according to the second embodiment.

[0161]

[Table 6]

In the above table, E (or e) is used to express a power of 10, for example, E-02 (= 10
^-2 ).

[0163]

As described above, in the optical pickup device according to the present invention, the spherical aberration detecting means changes at least one of the shape and the refractive index of the plastic lens and / or the refractive index at least with respect to the temperature and / or humidity.
Alternatively, the variation of the spherical aberration caused by the variation of the oscillation wavelength of the light source is detected, and the spherical aberration correcting means is driven by the driving means to correct the variation of the spherical aberration. Even in the case of a device, it is possible to use a plastic lens that is easily affected by changes in temperature and humidity.

Furthermore, the optical pickup device of the present invention
Not only fluctuations in spherical aberration due to changes in temperature and humidity, but also spherical aberrations caused by errors in the thickness of the protective layer of the optical disk, slight fluctuations in the oscillation wavelength of the light source, and manufacturing errors in the optical elements included in the condensing optical system. Can be corrected satisfactorily. 1. It becomes possible to use a plastic lens for the condensing optical system, and it is possible to significantly reduce the cost and weight. 2. Since the selection of the laser light source is not required, the requirement for the manufacturing accuracy of the laser light source is not too severe, so that the mass productivity of the laser light source can be improved. Further, the manufacturing time of the optical pickup device can be reduced. 3. Since the required accuracy for the manufacturing error of the optical information recording medium is not too severe, the mass productivity of the optical information recording medium can be improved. 4. Since the demands on the manufacturing accuracy of the optical elements included in the condensing optical system do not become too severe, the mass productivity of the optical elements included in the condensing optical system can be increased. There are advantages such as
Nevertheless, a light-collecting optical system that can always maintain good light-collecting characteristics can be obtained.

Further, in the optical pickup device according to the present invention, it is preferable that all the optical elements that can move along the optical axis are formed of a plastic material. This allows
Since the load on the actuator can be reduced, the driving power of the actuator can be reduced, and the transition can be performed with a smaller actuator, so that the optical pickup device can be downsized. An optical element that can be shifted along the optical axis direction includes, for example, an objective lens that is shifted by a two-axis actuator to reduce tracking error / focusing error, and an optical element that is shifted along the optical axis direction to correct fluctuations in spherical aberration. This is an optical element included in the spherical aberration correcting means that is shifted.

In the optical pickup device according to the present invention, at least one of the optical elements included in the condensing optical system is preferably formed of a plastic material from the viewpoint of weight reduction and cost reduction. It is more preferable that at least one of the beam expander and the coupling lens as the spherical aberration correcting means is formed of a plastic material. Furthermore, it is particularly preferred that all of the above-mentioned optical elements are formed from a plastic material.

It is preferable that the objective lens used in the optical pickup device according to the present invention satisfies the above expression (3) or (4). By satisfying the expression (3) or the expression (4), even with an objective lens having a high numerical aperture, it is possible to ensure a sufficient working distance, reduce the lens diameter, and reduce the manufacturing error sensitivity.
When the objective lens is corrected for aberration so as to minimize the aberration with respect to a parallel light beam from an object at infinity, even if the objective lens is moved to reduce a tracking error / focusing error, the objective lens is not moved. Since the change in the incident condition is small, the change in aberration is small. Further, when the objective lens is subjected to aberration correction so as to minimize the aberration with respect to a divergent light beam from an object at a finite distance, a larger working distance can be ensured. Collision can be prevented. Further, when the objective lens is corrected for aberration so that the aberration is minimized with respect to the convergent light beam directed to the image-side object, the angle of incidence of the light beam on the objective lens becomes small, so that the eccentricity error at the time of manufacturing causes Aberration deterioration can be suppressed, and an objective lens that is easy to manufacture can be provided.

Further, in the optical pickup device according to the present invention, at least one ring-shaped diffractive structure is provided in the condensing optical system.
It is preferable to have a diffractive optical element on one surface.
This makes it possible to correct axial chromatic aberration, which is a problem when a light source having an oscillation wavelength of 500 nm or less is used.
This diffractive optical element may be an optical element such as an objective lens, a beam expander, or a coupling lens included in the light-collecting optical system, or may be provided separately from the above-described optical element.

In the present specification, the spherical aberration correcting means disposed in the optical path between the light source and the objective lens means a beam expander, a coupling lens, a variable refractive index distribution element, a light source and an objective lens. It also includes a lens.
Therefore, the optical element that can move along the optical axis of the spherical aberration correcting means includes a lens group included in the beam expander or the coupling lens, or a lens group provided separately from the beam expander or the coupling lens. In addition to the above, a light source movable along the optical axis and a lens group included in the objective lens are also included.

In this specification, the beam expander includes at least one lens group having a positive refractive power and at least one lens group having a negative refractive power, and has a light beam diameter a (mm). A generally well-known optical element capable of emitting a substantially parallel light beam having a light beam diameter b (mm) (a ≠ b) when a substantially parallel light beam of Not only that, but also one that reduces the light beam diameter is included.

In this specification, a coupling lens refers to an optical element that converts the degree of divergence of a divergent light beam from a light source. The light beam emitted is a divergent light beam, and the emitted light beam is a parallel light beam. (Collimating lens), and a case where the emitted light beam is a convergent light beam. Further, it is assumed that not only a lens group composed of one lens group but also a lens group composed of a plurality of lens groups is included.

In this specification, the optical information recording medium includes not only a medium having a transparent substrate on the surface but also a medium having no transparent substrate. When the optical information recording medium has a transparent substrate, the objective lens used in the optical pickup device of the present invention is aberration-corrected to minimize aberration under a combination with a transparent substrate having a specific thickness. Is preferred.

Further, in this specification, the slight fluctuation of the oscillation wavelength of the light source means ± 10 n with respect to the oscillation wavelength of the light source.
It indicates a wavelength variation within the range of m. In the present specification, “correcting various aberrations” means “satisfactorily diffraction-limited performance of 0.07λrms or less (where λ is the oscillation wavelength of the light source used) when the wavefront aberration is obtained. It is preferred that

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical pickup device according to a first embodiment.

2 (a) and 2 (b) are schematic plan views of light receiving surfaces 14a and 14b of the multi-segmented photodetector of FIG. 1 viewed from a direction A of FIG. 1, and FIG. 2 (c). 2D are plan views schematically showing light receiving patterns on the light receiving surfaces 14a and 14b in the reference state, and FIGS. 2E and 2F are light receiving patterns on the light receiving surfaces 14a and 14b in the under state. FIG. 2G and FIG. 2H are plan views schematically showing the light receiving patterns on the light receiving surfaces 14a and 14b in the same over state.

FIG. 3 is a perspective view showing a hologram element as an example of the spherical aberration adding element in FIG. 1;

FIG. 4 is a diagram showing a modification of the optical pickup device of FIG. 1;

FIG. 5 is a view showing another modification of the optical pickup device of FIG. 1;

FIG. 6 is a diagram showing a schematic configuration of an optical pickup device according to a sixth embodiment.

7A is a schematic plan view of the divided light receiving surface 24 of the multi-segmented photodetector 25 in FIG. 6 viewed from a direction AA in FIG. 6, and FIG. Light receiving surface 24 in state
FIG. 7 is a plan view schematically showing a light receiving pattern in FIG.
FIG. 7C is a plan view schematically showing a light receiving pattern on the light receiving surface 24 in the under state, and FIG. 7D is a plan view schematically showing a light receiving pattern on the light receiving surface 24 in the over state.

FIG. 8 is an optical path diagram according to the first embodiment.

FIG. 9 is a spherical aberration diagram relating to Example 1.

FIG. 10 is an optical path diagram according to a second embodiment.

FIG. 11 is a spherical aberration diagram relating to Example 2.

FIG. 12 is a diagram illustrating a schematic configuration of an optical pickup device according to a second embodiment.

FIG. 13 is a diagram illustrating a schematic configuration of an optical pickup device according to a third embodiment.

FIG. 14 is a diagram illustrating a schematic configuration of an optical pickup device according to a fourth embodiment.

FIG. 15 is a diagram showing a schematic configuration of an optical pickup device according to a fifth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Laser semiconductor, light source 2 Coupling lens 3 Beam shaping prism 4 Polarization beam splitter 4 'Polarization beam splitter 5 Beam expander 6 1/4 wavelength plate 7 Aperture 8 Objective lens 9 Transparent substrate of optical information recording medium 9' Optical information recording Information recording surface of medium 10 Biaxial actuator (objective lens driving means) 11 Uniaxial actuator (driving means of spherical aberration correcting means) 12 Spherical aberration adding element 12a Hologram element 13 Condensing lens 14a, 14b Light receiving surface 24 Light receiving surface 24a , 24b Light-receiving surface 15, 25 Multi-split photodetector 16 Reflected light 16a Light-receiving surface 14a of multi-split photodetector 15
Light beam 16b received by the light receiving surface 14b of the multi-segment photodetector 15
The second light flux received by the light source 17 The variable refractive index distribution element 18 The driving means of the variable refractive index distribution element 19 The tracking error / focusing error detecting means, the second photodetector 20 The hologram 21 The beam shaping lens 22 The first lens 23 Second lens 24 'light source / multi-segmented photodetector integrated unit 25' multisegmented photodetector / second photodetector integrated unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H044 AC04 2H051 AA14 BA45 BA70 CB02 CB29 CC02 2H087 KA13 LA01 LA26 NA01 PA02 PA03 PA17 PB02 PB03 QA03 QA06 QA14 QA21 QA26 QA33 QA39 QA41 QA45 RA05 RA12 RA13 RA45 FA05 JA02 JA06 JA09 JA43 JA44 JA49 JB01 JB02 KA04 KA19

Claims (50)

[Claims] 1. A light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and an objective lens disposed in an optical path between the light source and the objective lens to reduce a variation in spherical aberration. An optical pickup device including a converging optical system including a spherical aberration correcting unit for correcting the light, wherein the converging optical system includes at least one plastic lens, and detects reflected light from the information recording surface. And a spherical aberration detecting means for detecting a change in at least one of the shape and refractive index of the plastic lens and / or a change in spherical aberration caused by a change in oscillation wavelength of the light source with respect to at least a change in temperature and / or humidity Driving means for driving the spherical aberration correcting means in order to correct the fluctuation of the spherical aberration detected by the spherical aberration detecting means. Optical pickup device. 2. A light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and an objective lens disposed in an optical path between the light source and the objective lens to reduce a variation in spherical aberration. An optical pickup device including a condensing optical system including: a spherical aberration correction unit for correcting the spherical aberration, wherein the spherical aberration detection detects a change in the spherical aberration by detecting light reflected from the information recording surface. Means, and driving means for driving the spherical aberration correction means in accordance with the detection result of the spherical aberration detection means, wherein the spherical aberration detection means performs amplitude division or wavefront division on at least the incident light beam. Splitting means, an optical element for giving spherical aberration of a different size or a different sign to each of the split light beam or wavefront, and possibly receiving a light beam having a spherical aberration given by the optical element. Optical pickup apparatus comprising: the light detector, a. 3. A light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and an objective lens disposed in an optical path between the light source and the objective lens to reduce a variation in spherical aberration. An optical pickup device including a condensing optical system including: a spherical aberration correction unit for correcting the spherical aberration, wherein the spherical aberration detection detects a change in the spherical aberration by detecting light reflected from the information recording surface. Means, and driving means for driving the spherical aberration correcting means in accordance with the detection result of the spherical aberration detecting means, wherein the spherical aberration detecting means receives light in accordance with a change in spherical aberration of an incident light beam. A multi-segment photodetector having a first light-receiving surface and a second light-receiving surface whose areas are distributed so as to cause a change in the amount of light, and arranged in an optical path of the spherical aberration correcting means and the multi-segment photodetector From the information recording surface The first light beam that receives the reflected light on the first light receiving surface is the same as the paraxial focal position or the best focus position of the first light beam, and the second light beam is received on the second light receiving surface. And an optical element that gives an excessive spherical aberration to the first light beam and gives an under spherical aberration to the second light beam, wherein the first light beam and the second light beam Detecting the difference between the amount of light on the first light receiving surface and the amount of light on the second light receiving surface caused by the difference in the magnitude or sign of the spherical aberration of the light beam of Detect the amount,
An optical pickup device, wherein the driving means is driven so as to reduce the variation of the spherical aberration. 4. The apparatus according to claim 3, wherein said first light receiving surface and said second light receiving surface are formed on a same substrate.
An optical pickup device according to item 1. 5. A light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and an optical lens disposed in an optical path between the light source and the objective lens to reduce a variation in spherical aberration. An optical pickup device including a condensing optical system including: a spherical aberration correction unit for correcting the spherical aberration, wherein the spherical aberration detection detects a change in the spherical aberration by detecting light reflected from the information recording surface. Means, and driving means for driving the spherical aberration correction means in accordance with the detection result of the spherical aberration detection means, wherein the spherical aberration correction means is arranged to sequentially rotate the spherical aberration of the light beam in the clockwise direction. The first light receiving unit and the second light receiving unit, the areas of which are distributed so that the amount of light received in response to the change in
A third light receiving unit facing the first light receiving unit;
A multi-segment photodetector having a light-receiving surface divided into at least four regions of a fourth light-receiving unit opposed to the second light-receiving unit, the spherical aberration correction unit, the multi-segment photodetector, and the spherical aberration 4 is arranged in the optical path with the correction means, the wavefront of the reflected light from the information recording surface is received by each light receiving surface of the multi-segmented photodetector, and the paraxial focal position or the best focus position is the same. The first light receiving portion and the third light receiving portion give an excessive spherical aberration to the wavefronts received by the first light receiving portion and the third light receiving portion.
An optical element that gives an under-spherical aberration to the wavefront received by the fourth light-receiving unit and the fourth light-receiving unit; and the difference or the sign of the magnitude of the spherical aberration of the wavefront divided into the four regions By detecting a difference in the amount of light on each light receiving surface of the multi-segment photodetector that occurs due to the difference, the amount of change in the spherical aberration is detected, and the amount of change in the spherical aberration is reduced. An optical pickup device for driving a driving unit. 6. An optical path from the light source to an information recording surface of the optical information recording medium and an optical path from the information recording surface to the multi-segmented photodetector are shared. The optical pickup device according to any one of the above. 7. The optical pickup device according to claim 6, wherein the light source and the multi-segment photodetector are formed on the same substrate. 8. An optical pickup device comprising: a driving unit for driving the objective lens; and a second photodetector detecting reflected light from the information recording surface to thereby reduce a tracking error and a tracking error of the objective lens. And / or an error detecting means for detecting a focusing error; and an optical path from the information recording surface to the second photodetector;
8. An optical path from the information recording surface to the multi-segment photodetector is shared.
An optical pickup device according to the item. 9. The photodetector according to claim 8, wherein the second photodetector and the multi-segment photodetector are formed on the same substrate.
An optical pickup device according to item 1. 10. The optical pickup device collects reflected light from the information recording surface on a light receiving surface of the multi-segmented photodetector in an optical path between the spherical aberration corrector and the multi-segmented photodetector. A condenser lens for causing light to be emitted, wherein the condenser lens imparts a spherical aberration having a different size or a different sign to at least an incident light beam and performs amplitude division or wavefront division. 10. The optical pickup device according to any one of 9. 11. The optical pickup device has a condensing lens disposed in an optical path between the spherical aberration correcting unit and the multi-segmented photodetector, and the condensing lens has at least an annular diffraction structure. The optical pickup device according to any one of claims 2 to 10, wherein the optical pickup device is provided on one surface. 12. A light source, a coupling lens for converting a divergence of a light beam emitted from the light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, An optical pickup device provided with a converging optical system, which is disposed in an optical path between a light source and the objective lens, and includes a spherical aberration correcting unit for correcting a variation in spherical aberration, comprising: A cup comprising: a spherical aberration detecting unit configured to detect a change in the spherical aberration by detecting reflected light; and a driving unit configured to drive the spherical aberration correcting unit in accordance with a detection result of the spherical aberration detecting unit. A ring lens and a condenser lens included in the spherical aberration detection unit, and a condenser lens disposed in an optical path of the photodetector and the spherical aberration correction unit included in the spherical aberration detection unit, Said The optical pickup apparatus characterized by substantially coincides in the characteristic with respect to wavelength variation and temperature change of the source. 13. The optical pickup device according to claim 12, wherein the coupling lens and the condenser lens are optically the same optical element. 14. An optical pickup device provided with a condensing optical system including a light source and an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, wherein The optical system includes at least two lens groups that are independently movable along the optical axis direction, wherein the movable lens groups are all made of a plastic material, and the movable lens groups are moved along the optical axis direction. An optical pickup device comprising a driving unit for causing the optical pickup device to operate. 15. An optical pickup device, comprising: a spherical aberration correcting unit disposed in an optical path between the light source and the objective lens for correcting a variation in spherical aberration; and detecting reflected light from the information recording surface. And a spherical aberration detecting means for detecting a change in the spherical aberration, wherein the spherical aberration correcting means has a movable element movable along at least one optical axis direction, and along the optical axis direction. At least one lens group among the movable lens groups is the movable element; and at least one lens among the lens groups other than the movable element is a movable lens group along the optical axis direction. 2. A group according to claim 1, wherein said group is said objective lens.
5. The optical pickup device according to 4. 16. The optical pickup device according to claim 1, wherein the following equation is satisfied, where ΔSA is a spherical aberration variation that can be detected by the spherical aberration detecting means. ΔSA ≧ 0.030λrms, where λ: oscillation wavelength (nm) of the light source 17. The optical pickup device according to claim 16, wherein the following equation is satisfied when the spherical aberration fluctuation amount detectable by the spherical aberration detecting means is ΔSA. ΔSA ≧ 0.010λrms 18. The spherical aberration detecting means generates a spherical aberration error signal corresponding to a variation amount of a spherical aberration generated in the condensing optical system, and controls the driving so that the spherical aberration error signal becomes substantially zero. 18. The optical pickup device according to claim 1, wherein the means is driven. 19. A predetermined numerical aperture on the image side of the objective lens required for recording or reproducing information on an information recording surface of the optical information recording medium is 0.65 or more. An optical pickup device according to any one of claims 1 to 18. 20. The object-specific predetermined numerical aperture on the image side of the objective lens required for recording or reproducing information on or from the information recording surface of the optical information recording medium is 0.75 or more. The optical pickup device according to claim 19. 21. The objective lens according to claim 19, wherein the objective lens comprises a first lens having a positive refractive power and a second lens having a positive refractive power arranged in order from the light source side, and satisfies the following expression. An optical pickup device as described in the above. 0.07 <NA.WD / f <0.35, where NA: a predetermined image-side numerical aperture necessary for recording and / or reproducing on the optical information recording medium WD: Working distance (m) of the objective lens
m) f: focal length (mm) of the entire system of the objective lens 22. The objective lens is a single lens,
21. The optical pickup device according to claim 19, wherein the following expression is satisfied. 0.10 <NA.WD / f <0.40, where NA: a predetermined image-side numerical aperture required for recording and / or reproducing on the optical information recording medium WD: Working distance (m) of the objective lens
m) f: focal length (mm) of the entire system of the objective lens 23. The apparatus according to claim 19, wherein the objective lens is aberration-corrected so as to minimize aberration with respect to a parallel light beam from an object at infinity. Optical pickup device. 24. The apparatus according to claim 19, wherein the objective lens is aberration-corrected so that aberration of a divergent light beam from an object at a finite distance is minimized. An optical pickup device as described in the above. 25. The apparatus according to claim 19, wherein the objective lens is aberration-corrected so that aberration is minimized with respect to a convergent light beam directed to an image-side object. Optical pickup device. 26. The optical pickup device according to claim 1, wherein the light source generates light having a wavelength of 500 nm or less. 27. The condensing optical system has a coupling lens in an optical path between the light source and the objective lens for changing a divergence angle of a divergent light beam from the light source, and the coupling lens is made of a glass material. 2. The method according to claim 1, wherein
27. The optical pickup device according to any one of items 26 to 26. 28. The condensing optical system has a coupling lens in an optical path between the light source and the objective lens, the coupling lens changing a divergence angle of a divergent light beam from the light source, and the coupling lens has a refraction function. A composite lens composed of a glass lens and an optical element made of a plastic material and / or an ultraviolet curable resin having one surface bonded to the glass lens and the other surface having an optical surface. The optical pickup device according to any one of claims 1 to 27. 29. The coupling lens, wherein the coupling lens is a collimating lens that converts a divergent light beam from a light source into a parallel light beam, and the optical pickup device emits the light from the light source in an optical path between the collimating lens and the objective lens. 29. The optical pickup device according to claim 27, further comprising a beam shaping element for reducing an astigmatic difference of the luminous flux. 30. The optical pickup device according to claim 1, wherein all optical elements other than the coupling lens included in the condensing optical system are formed of a plastic material. . 31. The condensing optical system has a coupling lens in an optical path between the light source and the objective lens, the coupling lens changing a divergence angle of a divergent light beam from the light source, and the coupling lens is made of a plastic material. The optical pickup device according to any one of claims 1 to 26, wherein: 32. The optical pickup device according to claim 31, wherein the light source emits a substantially circular light beam. 33. A light source comprising: a semiconductor laser; and a wavelength conversion element for converting a wavelength of light emitted from the semiconductor laser, wherein the condensing optical system includes a light emitted from the wavelength conversion element. Are condensed on the information recording surface, and the following expression is satisfied when the wavelength of light emitted from the semiconductor laser is λ0 nm and the wavelength of light after wavelength conversion by the wavelength conversion element is λnm. The optical pickup device according to claim 32, wherein: λ = λ0 / m (m = 2, 3,...) 34. The optical pickup device according to claim 31, wherein a numerical aperture of the coupling lens is 0.13 or less. 35. The optical pickup device according to claim 31, further comprising a beam shaping element in an optical path between the light source and the coupling lens for reducing an astigmatic difference of a light beam emitted from the light source. Item 32. The optical pickup device according to item 31, 36. The optical pickup device according to claim 1, wherein all optical elements included in the condensing optical system are formed of a plastic material. 37. The light-collecting optical system according to claim 1, wherein the condensing optical system has at least one diffractive optical element having an annular diffractive structure on at least one surface. Optical pickup device. 38. The optical pickup device according to claim 37, wherein the diffractive optical element is included in the spherical aberration correction unit. 39. The diffractive optical element is included in a coupling lens that is disposed in an optical path between the light source and the objective lens and that converts a divergence angle of a divergent light beam from the light source. 39. The optical pickup device according to 37 or 38. 40. The optical pickup device according to claim 37, wherein the diffractive optical element is included in the objective lens. 41. The optical pickup device according to claim 1, wherein the spherical aberration correction means has at least one movable element movable along an optical axis direction. 42. A coupling lens arranged in an optical path between the light source and the objective lens, the coupling lens changing a divergence angle of a divergent light beam from the light source,
The at least one lens group constituting the coupling lens is the movable element.
2. The optical pickup device according to 1. 43. The condensing optical system has a collimating lens disposed in an optical path between the light source and the objective lens, the collimating lens converting a divergent light beam from the light source into parallel light. 43. A beam expander disposed in an optical path between the collimating lens and the objective lens, wherein at least one lens group constituting the beam expander is the movable element. An optical pickup device according to item 1. 44. A driving unit for driving the movable element,
The optical pickup device according to any one of claims 41 to 43, wherein the optical pickup device is a voice coil actuator or a piezo actuator. 45. The optical pickup device according to claim 1, wherein the spherical aberration correction unit has a variable refractive index distribution along a direction perpendicular to an optical axis. 46. An optical pickup device according to claim 1, wherein the optical pickup device is mounted on the optical pickup device.
A device for recording audio and / or images and / or reproducing audio and / or images. 47. A light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and disposed in an optical path between the light source and the objective lens to reduce a variation in spherical aberration. A focusing optical system including: a spherical aberration correction unit for correcting; a spherical aberration detection unit for detecting a change in the spherical aberration by detecting light reflected from the information recording surface; and the spherical aberration detection unit. A driving means for driving the spherical aberration correcting means in accordance with the detection result of the above, wherein a spherical aberration fluctuation correction method in an optical pickup device comprising: An optical element that splits the wavefront and gives a spherical aberration of a different size or a different sign to the split light beam or wavefront, A split photodetector, and detects a difference in the amount of light on the light receiving surface of the multi-split photodetector caused by a difference in the magnitude or sign of the spherical aberration of the split light beam or wavefront. By that
A method of correcting spherical aberration fluctuation in an optical pickup device, comprising: detecting a fluctuation amount of the spherical aberration and driving the driving unit so as to reduce the fluctuation amount of the spherical aberration. 48. A light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and an objective lens disposed in an optical path between the light source and the objective lens to reduce a variation in spherical aberration. A focusing optical system including: a spherical aberration correction unit for correcting; a spherical aberration detection unit for detecting a change in the spherical aberration by detecting light reflected from the information recording surface; and a spherical aberration detection unit. A driving means for driving the spherical aberration correcting means in accordance with the detection result of the above, wherein a spherical aberration fluctuation correction method in an optical pickup device, wherein the spherical aberration detecting means detects a change in spherical aberration of an incident light beam. A multi-divided photodetector having a first light-receiving surface and a second light-receiving surface whose areas are distributed so as to cause a change in the amount of light received in response to the change between the spherical aberration correcting means and the multi-divided photodetector Placed in A first light beam that receives reflected light from the information recording surface on the first light receiving surface is the same as a paraxial focus position or a best focus position with the first light beam; An optical element that splits the light into a second light beam received on a light receiving surface, gives an excessive spherical aberration to the first light beam, and gives an under spherical aberration to the second light beam; Detecting a difference between the amount of light on the first light receiving surface and the amount of light on the second light receiving surface caused by a difference in magnitude or sign of spherical aberration between the first light beam and the second light beam. By detecting the fluctuation amount of the spherical aberration,
A method for correcting spherical aberration fluctuation in an optical pickup device, wherein the driving unit is driven so as to reduce the fluctuation amount of the spherical aberration. 49. A light source, an objective lens for condensing a light beam from the light source on an information recording surface of an optical information recording medium, and an objective lens disposed in an optical path between the light source and the objective lens to reduce a variation in spherical aberration. A focusing optical system including: a spherical aberration correction unit for correcting; a spherical aberration detection unit for detecting a change in the spherical aberration by detecting light reflected from the information recording surface; and a spherical aberration detection unit. A driving means for driving the spherical aberration correcting means in accordance with the detection result of the above, wherein the spherical aberration detecting means sequentially enters in a clockwise direction. A first light-receiving portion, a second light-receiving portion, the areas of which are distributed so as to cause a change in the amount of light received according to a change in the spherical aberration of the light beam.
A third light receiving unit facing the first light receiving unit;
A multi-segment photodetector having a light-receiving surface divided into at least four regions of a fourth light-receiving unit opposed to the second light-receiving unit, the spherical aberration correction unit, the multi-segment photodetector, and the spherical aberration And four correction means for receiving the wavefront of the reflected light from the information recording surface on each of the light receiving surfaces of the multi-segmented photodetector and having the same paraxial focus position or best focus position. While dividing the wavefront into regions, the wavefronts received by the first and third light receiving portions are given excessive spherical aberration, and are received by the second and fourth light receiving portions. An optical element that gives an under-spherical aberration to the wavefront, and the multi-segmented photodetector generated due to a difference in magnitude or sign of the spherical aberration of the wavefront divided into the four regions. On each light receiving surface Detecting a difference in the amount of spherical aberration in the optical pickup device by detecting the variation in the spherical aberration and driving the driving unit so as to reduce the variation in the spherical aberration. Correction method. 50. The method of correcting spherical aberration variation, wherein the method of correcting spherical aberration variation in an optical pickup device including at least one plastic lens in the condensing optical system, wherein at least temperature and / or humidity changes 47. A method according to claim 46, wherein a change in at least one of the shape and the refractive index of the plastic lens and / or a change in spherical aberration caused by a change in oscillation wavelength of the light source are corrected.
49. The method of correcting spherical aberration variation according to any one of items 48 to 48.