JP2009015951A - Correction element for optical pickup device, objective optical element unit, and optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a correction element and the optical element unit for an optical pickup device which can record and/or reproduce information compatibly and the optical pickup device using them with a single optical element unit for BD and HD using the same light beam despite its simplicity and low cost. <P>SOLUTION: When a light beam L parallel with an optical axis is inputted to a first area A1 in an optical plane S1 at a light source side as shown in Fig.2, a part of the light beam is reflected at the first area A1. However, the first area A1 is a circular conical surface, and the reflected light returns in the direction slant to the optical axis. Therefore, the reflected light of the first area A1 is prevented from entering a photo detector of the optical pickup device, thereby regulating generation of an error signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a correction element and an objective optical element unit for an optical pickup apparatus capable of recording and / or reproducing information interchangeably with respect to different types of optical disks using light beams having the same wavelength, and an optical pickup using them. Relates to the device.

  In recent years, research and development of high-density optical disc systems that can record and / or reproduce information (hereinafter, “recording and / or reproduction” is referred to as “recording / reproduction”) using a blue-violet semiconductor laser having a wavelength of about 400 nm. Development is progressing rapidly. As an example, in an optical disc for recording / reproducing information with specifications of NA 0.85 and light source wavelength 405 nm, so-called Blu-ray Disc (hereinafter referred to as BD), DVD (NA 0.6, light source wavelength 650 nm, storage capacity 4, 7 GB) Can record information of 23 to 27 GB per layer on an optical disk with a diameter of 12 cm, which is the same size as the above, and an optical disk that records and reproduces information with specifications of NA 0.65 and light source wavelength 405 nm, so-called With HD DVD (hereinafter referred to as HD), information of 15 to 20 GB per layer can be recorded on an optical disk having a diameter of 12 cm.

  By the way, it can not be said that the value of an optical disc player / recorder (optical information recording / reproducing device) as a product is sufficient only by properly recording / reproducing information on only one high-density optical disc. Considering the convenience of users, it is possible to record / reproduce information on all commercially available high-density optical discs in the same manner, thereby increasing the commercial value as an optical disc player / recorder for high-density optical discs. It leads to an increase. From such a background, an optical pickup device mounted on an optical disc player / recorder for a high density optical disc has a performance capable of appropriately recording / reproducing information while maintaining compatibility with any high density optical disc. It is desirable.

  However, BD and HD are generated based on the difference in the thickness of the protective substrate using the wavelength difference because the thickness of each protective substrate is different although the wavelength of the light beam used is the same. It is difficult to correct spherical aberration. Therefore, it is more difficult to make BD and HD compatible by using one objective optical element, compared to compatibility with other optical disks such as CD and DVD. On the other hand, although it is conceivable to provide an objective optical element for BD and an objective optical element for HD and switch according to the optical disk, there is a problem that the optical pickup device is increased in size.

Under such circumstances, Patent Document 1 describes a pickup device that enables compatibility between BD and HD with one objective optical element by sorting light beams of the same wavelength using a diffraction effect.
JP 2006-147069 A

  However, as in the optical pickup device described in the above-mentioned Patent Document 1, when realizing the compatibility between BD and HD by using the diffraction effect, for example, use of light from the light source passing through the diffraction structure to one optical disk Efficiency (utilization efficiency here is the ratio of the amount of light that contributes to the spot on the optical disk to the amount of light incident on the optical surface on the light source side of the objective optical element) is 40% (theoretically does not exceed 50%). If there is, the utilization efficiency of light traveling from the optical disk through the same diffractive structure toward the photodetector (the utilization efficiency here refers to the amount of light incident on the optical surface of the objective optical element on the optical disk side) Since the ratio of the amount of light that contributes to the upper spot is 40%, the total utilization efficiency (the utilization efficiency here refers to the amount of light incident on the optical surface on the light source side of the objective optical element on the photodetector). of 16% of the light only available in contributing ratio of the amount of light) in the pot, increase the luminous intensity of the light source greatly need practical it can be said to be extremely difficult.

  The present invention takes the above-mentioned problems into consideration and can record and / or reproduce information in a single optical element unit compatible with BD and HD that use the same light beam while being simple and low-cost. Moreover, it is possible to provide a correction element for an optical pickup device and an optical element unit that prevent the reflected light of the optical element from adversely affecting the detection light, and an optical pickup device using the same. Objective.

A light source that emits a first light beam having a wavelength of λ1 (380 nm <λ1 <450 nm); an objective optical element unit that includes a correction element for condensing the first light beam on an information recording surface of an optical disk and an aspherical lens; Then, the first light beam is condensed on the information recording surface of the first optical disc having the protective layer having the thickness t1 through the optical element unit, and the first light beam has the thickness t2 (t1 <t2). In a correction element for an optical pickup device that records and / or reproduces information by focusing on an information recording surface of a second optical disc having a protective layer,
The correction element has a plurality of concentric annular zones centered on the optical axis on the optical surface, and a light beam condensed on the information recording surface of the first optical disc passes through the plurality of annular zones. A first region, and a second region through which a light beam condensed on the information recording surface of the second optical disc passes,
Forming the second region from a spherical surface or an aspherical surface;
At least a part of the first region provided on the light source side optical surface is inclined by 1 ° or more with respect to the direction orthogonal to the optical axis.

  According to the present invention, the correction element has a plurality of concentric ring zones centered on the optical axis on the optical surface, and the plurality of ring zones are collected on the information recording surface of the first optical disc. Since the optical surface has a first area through which the luminous flux passes and a second area through which the luminous flux condensed on the information recording surface of the second optical disc passes, the first area passes through the first area. The divergence angle or convergence angle of the light beam (including zero angle, the same applies hereinafter) is different from the divergence angle or the convergence angle of the light beam that has passed through the second region, and / or has passed through the first region. By using different aberrations for the light beam (including the case where the applied aberration is zero, the same applies hereinafter) and the aberration for the light beam that has passed through the second region, the protective substrate can be used while using the same objective optical element. Good for the information recording surface of any disc with different thickness It can be focused.

  Here, when the aspherical lens has an optical performance for condensing the first light flux so that information can be recorded and / or reproduced on the first optical disk without the correction element, the second region is When the surface is spherical or aspherical, the first region may be a plane extending in the direction perpendicular to the optical axis. However, when the first area on the optical surface on the light source side extends in the direction perpendicular to the optical axis, the light beam applied to the first area from the light source is reflected back in parallel with the optical axis to detect light. There is a possibility of generating an error signal by entering the instrument. Such inconvenience tends to occur particularly when the light is reflected in a region away from the optical axis, for example, because the area ratio to the effective diameter tends to increase. Therefore, in the present invention, at least a part of the first region provided on the light source side optical surface is tilted by 1 ° or more with respect to the optical axis orthogonal direction, so that the light beam reflected by the first region becomes the optical axis. It prevents the return to parallel and increases the light receiving accuracy of the photodetector.

  A correction element for an optical pickup device according to a second aspect is the invention according to the first aspect, wherein the first region and the second region are all refractive surfaces.

  By forming the correction element only from the refracting surface, it is possible to increase the light utilization efficiency compared to the case where the light beam is distributed using the diffraction effect.

  According to a third aspect of the present invention, there is provided a correction element for an optical pickup device according to the first or second aspect of the present invention, wherein a region of 80% or more of the area of all the first regions provided on the light source side optical surface is light. It is characterized by being inclined by 1 ° or more with respect to the direction perpendicular to the axis.

  By tilting an area of 80% or more of the area of the first area with respect to the direction perpendicular to the optical axis, it is possible to further improve the light receiving accuracy of the photodetector.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, a plurality of the first regions are arranged with the second region interposed therebetween. The at least part of the first region is the first region farthest from the optical axis.

  A correction element for an optical pickup device according to a fifth aspect is the invention according to any one of the first to fourth aspects, wherein at least one of the first regions inclined with respect to the direction perpendicular to the optical axis is a light beam. The cross-sectional shape including the axis is an inclined straight line.

  A correction element for an optical pickup device according to a sixth aspect is the invention according to the fifth aspect, wherein at least one of the first regions inclined with respect to the direction perpendicular to the optical axis rotates with respect to the optical axis. It is characterized by a symmetrical shape.

  A correction element for an optical pickup device according to a seventh aspect is the invention according to any one of the first to fourth aspects, wherein at least one of the first regions inclined with respect to the direction perpendicular to the optical axis is a light beam. The cross-sectional shape including the axis is a curve having a paraxial curvature.

  The correction element for an optical pickup device according to an eighth aspect is the invention according to the seventh aspect, wherein at least one of the first regions inclined with respect to the direction perpendicular to the optical axis is a spherical surface. And

  A correction element for an optical pickup device according to a ninth aspect is inclined in the light source side optical surface of the correction element with respect to the optical axis orthogonal direction in the invention according to any one of the first to eighth aspects. When parallel light enters the first region, the parallel light is emitted from the first region of the optical surface of the correction element on the optical disc side.

  By adopting such a configuration, since the incident surface is not perpendicular to the incident light, the reflected light travels in a different optical path from the incident light, and it is possible to prevent the reflected light from being detected by the sensor and to correct it. Since parallel light is emitted from the element, the distance between the correction element and the aspherical lens can be freely changed, so that the degree of freedom in design can be increased.

The correction element for an optical pickup device according to claim 10 is a light source that emits a first light flux having a wavelength λ1 (380 nm <λ1 <450 nm), and for condensing the first light flux on an information recording surface of an optical disc. An objective optical element unit composed of a correction element and an aspheric lens, and the first light beam is condensed on the information recording surface of the first optical disc having a protective layer having a thickness t1 through the optical element unit, In a correction element for an optical pickup device that records and / or reproduces information by condensing the first light flux on an information recording surface of a second optical disc having a protective layer having a thickness t2 (t1 <t2). ,
The correction element has a plurality of concentric annular zones centered on the optical axis on the optical surface, and a light beam condensed on the information recording surface of the first optical disc passes through the plurality of annular zones. A first region, and a second region through which a light beam condensed on the information recording surface of the second optical disc passes,
Forming the first region from a spherical surface or an aspherical surface;
At least a part of the second region provided on the light source side optical surface is inclined with respect to the direction perpendicular to the optical axis.

  Here, when the aspherical lens has an optical performance for condensing the first light flux so that information can be recorded and / or reproduced on the second optical disk without the correction element, the first region is When the spherical surface or the aspherical surface is used, the second region may be a flat surface extending in the direction perpendicular to the optical axis. However, when the second region on the optical surface on the light source side extends in the direction perpendicular to the optical axis, the light beam applied to the second region from the light source is reflected back in parallel with the optical axis to detect light. There is a possibility of generating an error signal by entering the instrument. Therefore, in the present invention, at least a part of the second region provided on the light source side optical surface is tilted by 1 ° or more with respect to the optical axis orthogonal direction so that the light beam reflected by the second region becomes the optical axis. It prevents the return to parallel and increases the light receiving accuracy of the photodetector.

  According to an eleventh aspect of the present invention, in the correction element for an optical pickup device according to the tenth aspect of the present invention, the first region and the second region are all refracting surfaces.

  By forming the correction element only from the refracting surface, it is possible to increase the light utilization efficiency compared to the case where the light beam is distributed using the diffraction effect.

  A correction element for an optical pickup device according to a twelfth aspect of the present invention is the correction element according to the tenth or eleventh aspect, wherein an area of 80% or more of the area of the second area provided on the light source side optical surface is orthogonal to the optical axis. It is characterized by being inclined at least 1 ° with respect to the direction.

  By tilting an area of 80% or more of the area of the first area with respect to the direction perpendicular to the optical axis, it is possible to further improve the light receiving accuracy of the photodetector.

  A correction element for an optical pickup device according to a thirteenth aspect is the invention according to any one of the tenth to twelfth aspects, wherein the second region inclined with respect to the optical axis orthogonal direction includes an optical axis. The cross-sectional shape is an inclined plane.

  A correction element for an optical pickup device according to a fourteenth aspect is the invention according to the thirteenth aspect, wherein the second region inclined with respect to the direction perpendicular to the optical axis is a conical surface. .

  The correction element for an optical pickup device according to claim 15 is the invention according to any one of claims 10 to 12, wherein the second region inclined with respect to the direction perpendicular to the optical axis includes an optical axis. The cross-sectional shape is a surface having a curvature.

  According to a sixteenth aspect of the present invention, in the correction element for an optical pickup device according to the fifteenth aspect, the second region inclined with respect to the optical axis orthogonal direction is a spherical surface.

  The correction element for an optical pickup device according to claim 17 is tilted with respect to a direction orthogonal to the optical axis of the light source side optical surface of the correction element in the invention according to any one of claims 10 to 16. When parallel light enters the second region, the parallel light is emitted from the second region on the optical surface of the correction element on the optical disc side.

  By adopting such a configuration, in order to suppress the adverse effect of the reflected light on the light source side optical surface, even when the second region is tilted from the direction orthogonal to the optical axis, it is used in a design in which the second region is not tilted. Using the same aspherical lens, the first light beam that has passed through the second region can be favorably condensed on the information recording surface of the second optical disk.

  An objective optical element unit according to an eighteenth aspect is characterized in that the correction element according to any one of the first to fifteenth aspects and the aspheric lens are integrally connected.

  An optical pickup device according to a nineteenth aspect includes the objective optical element unit according to the sixteenth aspect.

  The optical pickup apparatus of the present invention records / reproduces information with respect to at least the first optical disc and the second optical disc. The optical pickup device has at least one first light source. Furthermore, the optical pickup device has a condensing optical system for condensing the first light flux on the information recording surface of the first optical disc and condensing the first light flux on the information recording surface of the second optical disc. The optical pickup device also includes a light receiving element that receives a reflected light beam from the information recording surface of the first optical disc or the second optical disc.

  When the optical pickup device is a device for recording / reproducing the third optical disc and / or the fourth optical disc in addition to the first optical disc and the second optical disc, in addition to the first light source, the second light source and / or You may have a 3rd light source. When the optical pickup device is a device that records / reproduces the third optical disc and / or the fourth optical disc in addition to the first optical disc and the second optical disc, the condensing optical system receives the second light from the second light source. The light beam is condensed on the information recording surface of the third optical disk, and the third light beam from the third light source is condensed on the information recording surface of the fourth optical disk. Further, when the optical pickup device is a device for recording / reproducing the third optical disc and / or the fourth optical disc in addition to the first optical disc and the second optical disc, the information recording surface of the third optical disc or the fourth optical disc A light receiving element that receives the reflected light beam from the light source may be included.

  The first optical disc has a protective substrate having a thickness t1 and an information recording surface. The second optical disc has a protective substrate having a thickness t2 (t1 <t2) and an information recording surface. The first optical disc and the second optical disc have the same wavelength of light flux used for recording / reproduction. The first optical disk is preferably a BD and the second optical disk is preferably an HD, but the present invention is not limited to this. When the third optical disk or the fourth optical disk is used, the third optical disk has a protective substrate having a thickness t3 (t2 ≦ t3) and an information recording surface. The fourth optical disc has a protective substrate having a thickness t4 (t3 <t4) and an information recording surface. The third optical disk is preferably a DVD and the fourth optical disk is preferably a CD, but is not limited thereto. The first optical disc, the second optical disc, the third optical disc, or the fourth optical disc may be a multi-layer optical disc having a plurality of information recording surfaces.

  In the BD, information is recorded / reproduced by an objective optical element having an NA of 0.85, and the thickness of the protective substrate is about 0.1 mm. In the HD, information is recorded / reproduced by an objective optical element having an NA of 0.65 to 0.67, and the thickness of the protective substrate is about 0.6 mm. Furthermore, DVD is a general term for DVD series optical discs in which information is recorded / reproduced by an objective optical element having an NA of about 0.60 to 0.67 and the thickness of the protective substrate is about 0.6 mm. ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, and the like are included. Further, in this specification, a CD is a CD series optical disc in which information is recorded / reproduced by an objective optical element having an NA of about 0.45 to 0.51 and the protective substrate has a thickness of about 1.2 mm. It is a generic name and includes CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW, and the like. As for the recording density, the recording density of BD is the highest, followed by HD, DVD, and CD in that order.

  In addition, regarding the thicknesses t1, t2, t3, and t4 of the protective substrate, it is preferable to satisfy the following conditional expressions (1), (2), (3), and (4), but is not limited thereto.

0.0750 mm ≦ t1 ≦ 0.1125 mm (1)
0.5mm ≦ t2 ≦ 0.7mm (2)
0.5mm ≦ t3 ≦ 0.7mm (3)
1.0mm ≦ t4 ≦ 1.3mm (4)

  In the present specification, the light source such as the first light source, the second light source or the third light source is preferably a laser light source. As the laser light source, a semiconductor laser, a silicon laser, or the like can be preferably used.

  When BD is used as the first optical disc and HD is used as the second optical disc, the wavelength λ1 of the first light beam emitted from the first light source is preferably 380 nm or more and 450 nm or less. When a DVD is used as the third optical disk and a CD is used as the fourth optical disk, the wavelength λ2 of the second light beam emitted from the second light source is preferably 630 nm or more and 670 nm or less, and is emitted from the third light source. The wavelength λ3 of the third light flux is preferably 760 nm or more and 820 nm or less.

  As the light receiving element, a photodetector such as a photodiode is preferably used. Light reflected on the information recording surface of the optical disc enters the light receiving element, and a read signal of information recorded on each optical disc is obtained using the output signal. Furthermore, it detects the change in the amount of light due to the change in the shape and position of the spot on the light receiving element, performs focus detection and track detection, and moves the objective optical element for focusing and tracking based on this detection I can do it. The light receiving element may comprise a plurality of photodetectors. The light receiving element may have a main photodetector and a sub photodetector. For example, two sub photodetectors are provided on both sides of a photodetector that receives main light used for recording and reproducing information, and the sub light for tracking adjustment is received by the two sub photodetectors. It is good also as a simple light receiving element. The light receiving element may have a plurality of light receiving portions corresponding to the respective light sources.

  The condensing optical system has an objective optical element unit. The objective optical element focuses the first light flux on the information recording surface of the first optical disc so that information can be recorded / reproduced, and the first light flux is recorded / reproduced on the information recording surface of the second optical disc. Concentrate as much as possible. The condensing optical system may include only the objective optical element unit, but may include a coupling lens such as a collimator lens or a beam expander in addition to the objective optical element unit. The coupling lens is a single lens or a lens group that is disposed between the objective optical element and the light source and changes the divergence angle of the light beam. The beam expander is a lens group that is disposed between the objective optical element and the light source and changes the diameter of the light beam without changing the divergence angle of the light beam. The collimator lens is a kind of coupling lens, and is a lens that changes a light beam incident on the collimator lens into parallel light. Further, the condensing optical system has an optical element such as a diffractive optical element that divides the light beam emitted from the light source into a main light beam used for recording and reproducing information and two sub light beams used for tracking and the like. May be. The condensing optical system may include an objective optical element for the third optical disk and an objective optical element for the fourth optical disk in addition to the objective optical element unit for the first optical disk and the second optical disk. . The objective optical element unit for the first optical disk and the second optical disk may also serve as the objective optical element for the third optical disk and / or the fourth optical disk.

  In this specification, the objective optical element unit or the objective optical element is disposed at a position facing the optical disk in a state where the optical disk is loaded in the optical pickup device, and the light beam emitted from the light source is placed on the information recording surface of the optical disk. An optical system having a function of condensing light. Preferably, the objective optical element is an optical system that is disposed at a position facing the optical disc in the optical pickup device and has a function of condensing a light beam emitted from the light source on the information recording surface of the optical disc, An optical system that can be integrally displaced at least in the optical axis direction by an actuator. The objective optical element unit includes at least a correction element and an aspheric lens. In addition, the objective optical element unit or the objective optical element may have a glass lens, a plastic lens, or an optical path difference providing structure with a photocurable resin on the glass lens. You may have a hybrid lens. The objective optical element unit may have both a glass lens and a plastic lens, or may consist of only one of them. The objective optical element unit may be a combination of a flat optical element having an optical path difference providing structure and an aspherical lens. The objective optical element unit preferably has an aspheric refractive surface. The objective optical element unit may be integrated by directly engaging the aspheric lens and the correction element, or may be integrated by holding the aspheric lens and the correction element by a lens frame. . In this case, the material of the lens frame is not particularly limited, but is preferably made of plastic.

When the objective optical element unit has a plastic lens or a plastic optical element, it is preferable to use a cyclic olefin-based resin material as the plastic material. Among the cyclic olefin-based materials, the temperature is 25 ° C. with respect to a wavelength of 405 nm. The refractive index change rate dN / dT (° C. ⁻¹ ) with respect to a wavelength of 405 nm with a temperature change in the temperature range of −5 ° C. to 70 ° C. It is more preferable to use a resin material within a range of −20 × 10 ^{−5 to} −5 × 10 ⁻⁵ (more preferably −10 × 10 ^{−5 to} −8 × 10 ⁻⁵ ). When the objective optical element unit has a plastic lens, the coupling lens is preferably a plastic lens.

  The objective optical element unit necessary for reproducing and / or recording information on the first optical disk is NA1, and the objective necessary for reproducing and / or recording information on the second optical disk. The image side numerical aperture of the optical element unit is NA2 (NA1> NA2), and the image side numerical aperture of the objective optical element unit or objective optical element necessary for reproducing and / or recording information on the third optical disk is NA3. (NA2 ≧ NA3), and the objective optical element unit or the image side numerical aperture of the objective optical element necessary for reproducing and / or recording information on the fourth optical disk is NA4 (NA3> NA4). NA1 is preferably 0.8 or more and 0.9 or less. NA2 and NA3 are preferably 0.55 or more and 0.7 or less. NA4 is preferably 0.4 or more and 0.55 or less.

  The objective optical element unit has a correction element and an aspheric lens as described above. The correction element is preferably a flat optical element or an optical element having a shape close to a flat plate. The correction element has a plurality of concentric annular zones around the optical axis on its optical surface. The plurality of annular zones has a first region and a second region. The first light flux that has passed through the first region of the correction element and the aspheric lens is condensed on the information recording surface of the first optical disc so that information can be recorded and / or reproduced. The first light flux that has passed through the second region of the correction element and the aspheric lens is condensed on the information recording surface of the second optical disc so that information can be recorded and / or reproduced. On the other hand, the first light flux that has passed through the first region of the correction element and the aspherical lens generates a large aberration on the information recording surface of the second optical disk and cannot be used for recording and / or reproducing information. However, it is not limited to this. Further, the first light flux that has passed through the second region of the correction element and the aspherical lens generates a large aberration on the information recording surface of the first optical disc, and cannot be used for recording and / or reproducing information. However, it is not limited to this.

  Both the first region and the second region of the correction element are preferably refractive surfaces. Particularly preferably, all of the first region and the second region are refractive surfaces. In this case, the light beam that has passed through the first area is condensed on the information recording surface of the first optical disk, and the light beam that has passed through the second area is condensed on the information recording surface of the second optical disk by using the refraction action. Has been achieved. Such a configuration is preferable because the loss of the amount of light can be reduced when the reflected light passes through the correction element. In this case, a light receiving element having a relatively low sensitivity can be used as the light receiving element, so that the cost of the optical pickup device can be reduced. Note that slight diffracted light may be generated at the boundary step. However, when most of the amount of light that has passed through the correction element is due to refracted light, it is considered as a refracting surface here.

  The first region and the second region are preferably provided alternately from the optical axis toward the outside. When the aspherical lens has an optical performance for condensing the first light flux on the information recording surface of the first optical disc so that information can be recorded and / or reproduced without the correction element, The region including the axis is preferably the second region. On the other hand, when the aspherical lens has an optical performance for condensing the first light flux on the information recording surface of the second optical disc so that information can be recorded and / or reproduced without the correction element. The region including the optical axis is preferably the first region.

  In addition, it is preferable that there are a plurality of first regions and second regions, respectively, and the first regions and the second regions are alternately arranged in a total of four or more regions in the direction perpendicular to the optical axis. preferable. That is, it is preferable that the correction element has four or more ring zones.

  In the correction element, it is preferable that the region farthest from the optical axis is the first region. It is preferable that the first region farthest from the optical axis is a region corresponding to NA2 or more.

    In addition, when the aspherical lens has no correction element and the aberration of the first light flux is corrected with respect to the first optical disk at a magnification of 0 (that is, the aspherical lens has no correction element and is parallel light). The first luminous flux is optical performance capable of focusing on the information recording surface of the first optical disc so that information can be recorded and / or reproduced), and the luminous flux that has passed through the first area The aberration to be given (including the case where the given aberration is zero, the same applies hereinafter) and the aberration given to the light beam that has passed through the second region must be different.

  For example, there is an example in which the first region does not give aberration to the first light beam passing through, and the second region has optical performance to give aberration to the first light beam passing through. In this example, the first light beam incident on the first region of the correction element in the form of a parallel light beam is emitted from the correction element in the state of a parallel light beam and is incident on the second region of the correction element in the state of a parallel light beam. The correction element may have an optical performance such that the light beam is emitted from the correction element in a convergent light beam state. As the shapes of the first region and the second region at this time, the first region can be a plane orthogonal to the optical axis, and the second region can be a spherical or aspherical shape.

  However, if the first region on the optical surface on the light source side has a plane perpendicular to the optical axis, the light beam emitted from the light source to the first region is reflected back in parallel to the optical axis and enters the photodetector. May cause an error signal. Therefore, by tilting at least a part of the first region provided on the light source side optical surface by 1 ° or more with respect to the direction perpendicular to the optical axis, it is possible to prevent the light beam reflected by the first region from returning parallel to the optical axis. In addition, it is possible to increase the light receiving accuracy of the photodetector. When a plurality of first regions are arranged with the second region in between, at least a part of the first region is preferably the first region farthest from the optical axis. Moreover, it is preferable that the first region has a point-symmetric shape about the optical axis.

  More preferably, a region of 80% or more of the area of the first region provided on the light source side optical surface is inclined by 1 ° or more with respect to the direction perpendicular to the optical axis. Most preferably, all the first regions provided on the light source side optical surface are inclined by 1 ° or more with respect to the direction perpendicular to the optical axis.

  The shape in which the first region is inclined by 1 ° or more is roughly divided into two. One is to make the first region a shape that is a straight line with an inclined cross-sectional shape including the optical axis. The case where the cross-sectional shape including the optical axis becomes a straight line shape is a case where at least one entire first region is inclined in the same direction as shown in FIG. 6, for example. Further, as shown in FIG. 7, the first region may have a dogleg shape (this may be regarded as a part of a conical surface). In the example shown in FIGS. 6 and 7, the central portion is provided with the second region, the first region on the outside thereof, and the second region on the outside thereof. The other is to make the first region a shape in which the cross-sectional shape including the optical axis is a curve having a paraxial curvature. Examples of the cross-sectional shape including the optical axis being a curved shape having a paraxial curvature include an aspherical shape and a spherical shape, and a spherical shape is preferable.

  Further, even when the first region is tilted by 1 ° or more from the optical axis orthogonal direction, when parallel light is incident on the first region of the light source side optical surface of the correction element, the first region of the optical disk side optical surface of the correction element Therefore, it is preferable to adopt an optical design that emits parallel light, that is, an afocal design.

  The first region is not limited to parallel light, but the first region gives aberration to the passing first light beam, and the second region has aberration to the passing first light beam. The correction element may have an optical performance that does not give the light.

  In addition, when the correction element has an optical performance that does not give aberration to the first light beam passing through the first region and the second region has aberration to give aberration to the first light beam passing through, the correction element is It is preferable that the second region is arranged at least inside and outside the first region in the direction perpendicular to the optical axis. In addition, the thickness Δ1 in the optical axis direction at the boundary between the inner second region and the first region adjacent to the outer side in the optical axis orthogonal direction is equal to the inner second region in the optical axis orthogonal direction. It is preferable that the thickness Δ2 is different from the thickness Δ2 in the optical axis direction at the boundary between the first region and the first region. Further, in this case, it is preferable that Δ1 <Δ2 because it is preferable that the second region has optical performance that diverges the first light flux.

  On the other hand, in the case where the aspherical lens has no correction element and the first light flux is corrected for aberration at a magnification of 0 with respect to the second optical disk (that is, the aspherical lens has no correction element and is parallel light). The first light beam having the optical performance capable of condensing the information on the information recording surface of the second optical disc so that information can be recorded and / or reproduced). Must be different from the aberration given to the light beam that has passed through the second region (including the case where the given aberration is zero, the same applies hereinafter).

  For example, there is an example in which the second region does not give aberration to the first light beam passing through, and the first region has optical performance to give aberration to the first light beam passing through. In this example, the first light beam incident on the second region of the correction element in the state of the parallel light beam is emitted from the correction element in the state of the parallel light beam, and is incident on the first region of the correction element in the state of the parallel light beam. The correction element may have an optical performance such that the light beam is emitted from the correction element in a convergent light beam state. As the shapes of the first region and the second region at this time, the second region can be a plane orthogonal to the optical axis, and the first region can be a spherical or aspherical shape.

  However, if the second region on the optical surface on the light source side has a plane perpendicular to the optical axis, the light beam irradiated from the light source to the second region is reflected back in parallel to the optical axis and enters the photodetector. May cause an error signal. Therefore, by tilting at least a part of the second region provided on the light source side optical surface by 1 ° or more with respect to the direction perpendicular to the optical axis, it is possible to prevent the light beam reflected by the second region from returning parallel to the optical axis. In addition, it is possible to increase the light receiving accuracy of the photodetector. The at least part of the second region is preferably the second region farthest from the optical axis. Note that the second region is preferably point-symmetric with respect to the optical axis.

  More preferably, an area of 80% or more of the area of the second area provided on the light source side optical surface is inclined by 1 ° or more with respect to the direction perpendicular to the optical axis. Most preferably, all the second regions provided on the light source side optical surface are inclined by 1 ° or more with respect to the direction perpendicular to the optical axis.

  The shape in which the second region is inclined by 1 ° or more is roughly divided into two. One is to make the second region a straight line with a cross-sectional shape including the optical axis inclined. As for what becomes the shape of a straight line in which the cross-sectional shape including the optical axis is inclined, there is a case where at least one entire second region is inclined in the same direction. In addition, the second region may have a dogleg shape (this may be regarded as a part of a conical surface). The other is to make the second region a shape in which the cross-sectional shape including the optical axis is a curve having a paraxial curvature. Examples of the cross-sectional shape including the optical axis being a curved shape having a paraxial curvature include an aspherical shape and a spherical shape, and a spherical shape is preferable.

  Even if the second region is tilted by 1 ° or more from the optical axis orthogonal direction, the second region of the optical disk side optical surface of the correction element when parallel light enters the second region of the light source side optical surface of the correction element. Therefore, it is preferable to adopt an optical design that emits parallel light, that is, an afocal design.

  Note that the present invention is not limited to the above-described example, and the second region gives aberration to the first light beam passing through without making the first light beam parallel light, and the first region has aberration with respect to the first light beam passing through. The correction element may have an optical performance that does not give the light.

  When the correction element has an optical performance that does not give aberration to the first light beam passing through the second region and the first region gives aberration to the first light beam passing through, the correction element It is preferable that the first region is arranged at least inside and outside the second region in the direction perpendicular to the axis. In addition, the thickness Δ1 ′ in the optical axis direction at the boundary between the inner first region and the second region adjacent to the outer side in the optical axis orthogonal direction is the optical axis orthogonal direction of the outer first region. It is preferable that the thickness is different from the thickness Δ2 ′ in the optical axis direction at the boundary with the second region adjacent to the inner side. Further, in this case, it is preferable that Δ1 ′> Δ2 ′ because it is preferable to have optical performance that converges the first light flux by the first region.

  When the aspherical lens is not provided with a correction element, information can be recorded and / or reproduced on the information recording surface of the first optical disk and the information recording surface of the second optical disk. If the light cannot be condensed, the first region has an optical performance that gives aberration to the first light beam passing through and the second region also gives aberration to the first light beam passing through the second region. preferable. As the shapes of the first region and the second region at this time, both the first region and the second region are preferably spherical or aspherical. In this case, both the first region and the second region of the light source side optical surface have surfaces that are inclined by 1 ° or more from the direction orthogonal to the optical axis.

  When the correction element has the optical performance and shape as described above, the correction element is divided into a plurality of concentric annular zones centering on the optical axis by changing the step or the surface shape of the optical surface. It will be. That is, a step is provided at the boundary between the first region and the second region, or the optical surface shape of the correction element changes at the boundary. From the viewpoint of improving the image height characteristic, the optical element on the light source side of the correction element is more suitable than a step on only one optical surface of the correction element, or the surface shape is changed for each region only on one optical surface. Both the surface and the optical surface on the optical disk side are preferably divided into a plurality of concentric annular zones by changing the step or the surface shape of the optical surface.

  Here, when there is a large step between the first region and the second region, the depth in the optical axis direction of the step at the boundary between the first region and the adjacent second region is 50 μm or more. In some cases, it is difficult to remove the correction element from the mold when molding the correction element, which causes a problem that molding becomes difficult. Therefore, at least one boundary between the first region and the adjacent second region is provided with an inclined surface of 10 degrees to 70 degrees with respect to the optical axis. It is preferable that the two regions are connected. More preferably, it is 20 degrees or more and 50 degrees or less. Preferably, an inclined surface is provided only at a boundary where the step amount in the optical axis direction at the boundary between the first region and the second region is 50 μm or more. By limiting the step provided with the inclined surface, it is possible to reduce the light loss due to the inclined surface. In addition, when an inclined surface is provided only at the boundary where the level difference is large, the inclined surface provided on the optical surface on the light source side and the inclined surface provided on the optical surface on the optical disk side are orthogonal to the optical axis from the optical axis to each inclined surface. There are cases where the distance in the direction is different and cases where the distance is the same.

  In addition, the first light flux that has passed between the first area of the correction element and the second area adjacent thereto is not condensed on the information recording surface of the first optical disk, and the information on the second optical disk There may be a region on the recording surface where light is not condensed or a region where light flux does not pass. This area is called an unused area. That is, the unused area is an area on the optical surface through which the light beam condensed on the information recording surface of the first optical disk and the light beam condensed on the information recording surface of the second optical disk do not pass. The inclined surface is preferably provided in this unused area. By providing the inclined surface in the unused area, it is possible to prevent the loss of light amount due to the provision of the inclined surface. More preferably, the inclined surface is provided only in the unused area.

  In addition, the unused area on the optical surface on the light source side of the correction element and the unused area on the optical surface on the optical disk side may exist at different positions from the optical axis. In such a case, with respect to the inclined surface provided in the unused area, the light source side inclined surface and the optical disk side inclined surface have different distances in the optical axis orthogonal direction from the optical axis to the respective inclined surfaces.

  Further, the objective optical element unit has a compatible optical path difference providing structure that enables the use of the third optical disk and / or the fourth optical disk on the optical surface of the aspheric lens and / or the optical surface of the correction element. You may do it. Further, the objective optical element unit may have an optical path difference providing structure for correcting an aberration change at the time of temperature change or wavelength change on the optical surface of the aspheric lens and / or the optical surface of the correction element. Good. In addition, the optical path difference providing structure in this specification is a general term for structures that add an optical path difference to an incident light beam. The optical path difference providing structure also includes a phase difference providing structure for providing a phase difference. The phase difference providing structure includes a diffractive structure. The optical path difference providing structure has a step, preferably a plurality of steps. This step adds an optical path difference and / or phase difference to the incident light flux. The optical path difference added by the optical path difference providing structure may be an integral multiple of the wavelength of the incident light flux or a non-integer multiple of the wavelength of the incident light flux, but only the first light flux of wavelength λ1 passes through. In this case, considering the efficiency, it is desirable that the optical path difference is an integral multiple of the wavelength λ1. The steps may be arranged with a periodic interval in the direction perpendicular to the optical axis, or may be arranged with a non-periodic interval in the direction perpendicular to the optical axis.

  The first light beam may be incident on the objective optical element unit as parallel light, or may be incident on the objective optical element unit as divergent light or convergent light. Preferably, the magnification m1 of the first light beam incident on the objective optical element unit satisfies the following formula (8).

−0.02 <m1 <0.02 (8)

  On the other hand, when the first light beam is incident on the objective optical element unit as diverging light, the magnification m1 of the first light beam incident on the objective optical element preferably satisfies the following formula (9).

  -0.10 <m1 <0.00 (9)

  The optical information recording / reproducing apparatus has an optical disc drive apparatus having the optical pickup device described above.

  Here, the optical disk drive apparatus provided in the optical information recording / reproducing apparatus will be described. The optical disk drive apparatus can hold an optical disk mounted from the optical information recording / reproducing apparatus main body containing the optical pickup apparatus or the like. There are a system in which only the tray is taken out and a system in which the optical disk drive apparatus main body in which the optical pickup device or the like is stored is taken out.

  An optical information recording / reproducing apparatus using each of the above-described methods is generally equipped with the following components, but is not limited thereto. An optical pickup device housed in a housing or the like, a drive source of an optical pickup device such as a seek motor that moves the optical pickup device together with the housing toward the inner periphery or outer periphery of the optical disc, and the optical pickup device housing the inner periphery or outer periphery of the optical disc These include a transfer means of an optical pickup device having a guide rail or the like that guides toward the head, a spindle motor that rotates the optical disk, and the like.

  In addition to these components, the former method is provided with a tray that can be held in a state in which an optical disk is mounted and a loading mechanism for sliding the tray, and the latter method has no tray and loading mechanism. It is preferable that each component is provided in a drawer corresponding to a chassis that can be pulled out to the outside.

  According to the present invention, information can be recorded and / or reproduced with a single objective optical element unit compatible with BD and HD that use the same light beam while being simple and low in cost, and the light use efficiency is high. In addition, it is possible to provide a correction element for an optical pickup device and an optical element unit that prevent the reflected light of the optical element from adversely affecting the detection light, and an optical pickup device using them.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an objective optical element unit including a correction element according to this embodiment. FIG. 2 is an enlarged view of an arrow II part of the correction element shown in FIG. In FIG. 1, the objective optical element unit OU is formed by coaxially connecting a correction element OE and an aspheric lens OBJ with a lens frame FR. The light source side optical surface S1 and the optical disc side optical surface S2 of the correction element OE are each composed of only a refractive surface. The aspheric lens OBJ has a shape in which spherical aberration is optimally corrected with respect to the first optical disc BD.

  The light source side optical surface S1 and the optical disc side optical surface S2 alternately form first and second zones A1 and A2, respectively. Here, the optical axis AX passes through the center second region A2. The light beam that has passed through the first area A1 is condensed on the information recording surface of the first optical disk via the aspheric lens OBJ, and the light beam that has passed through the second area A2 is transmitted through the second optical disk via the aspheric lens OBJ. The light is focused on the information recording surface.

  Here, since the thicknesses of the protective layers of the first optical disc and the second optical disc are different, it is necessary to correct the spherical aberration caused by this. Therefore, in the present embodiment, the divergence angle or convergence angle of the light beam that has passed through the first region A1 is set to be different from the divergence angle or convergence angle of the light beam that has passed through the second region A2. Accordingly, the spherical or aspherical shape of the first region A1 is different from the spherical or aspherical shape of the second region A2. Here, the first area A1 is a point-target spherical surface and the second area A2 is an aspherical refracting surface, but is not limited thereto. (In FIGS. 1 and 2, the first region A1 is drawn like a straight line, but is actually a spherical surface.)

  When a light beam L parallel to the optical axis AX is incident on the first region A1 of the light source side optical surface S1 as shown in FIG. 2, a part of the light is reflected by the first region A1, but the first region Since A1 is a spherical surface, the reflected light returns in a direction inclined with respect to the optical axis AX. Thereby, the reflected light of the first region A1 is suppressed from entering the photodetector of the optical pickup device, and the generation of an error signal can be suppressed. The first region A1 is not limited to a spherical surface.

  When the shapes of the first region A1 and the second region A2 are different, as shown in FIG. 2, a step is generated between them. In the present embodiment, the step of the light source side optical surface S1 is connected by the inclined surface CP1 having an inclination angle θ1 with respect to the optical axis, and the step of the optical disc side optical surface S2 is inclined with an inclination angle of θ2 with respect to the optical axis. Since they are connected by the surface CP2, it is possible to give a draft when releasing the correction element OE during molding.

  Of the second region A2 sandwiching the first region A1 in the optical axis orthogonal direction, the inner second region A2 in the optical axis direction at the boundary with the adjacent first region A1 outside the optical axis orthogonal direction. It is desirable that the thickness Δ1 is smaller than the thickness Δ2 in the optical axis direction at the boundary between the outer second region A2 and the adjacent first region A1 in the optical axis orthogonal direction. Further, in the present embodiment, inclined surfaces CP1 and CP2 are formed at the boundary where the step amount δ in the optical axis direction between the first region A1 and the adjacent second region A2 is 50 μm or more.

  Further, when the first region A1 is a spherical afocal surface and the second region A2 is an aspherical refracting surface, the parallel light beam incident on the first region A1 is converted into a parallel light beam as shown in FIG. The light is emitted as it is. On the other hand, the parallel light beam incident on the second region A2 is emitted from the correction element OE as a convergent light beam. Therefore, between the first area A1 and the second area A2, there is an area where the light beam condensed on the information recording surface of the first optical disk and the light beam condensed on the information recording surface of the second optical disk do not pass. This area is called an unused area. Since the unused area is irrelevant to the recording and / or reproduction of information, it may have any shape. Therefore, in the present embodiment, the inclined surfaces CP1 and CP2 are formed in the unused region.

  FIG. 3 schematically shows the configuration of the optical pickup apparatus PU1 of the present embodiment that can appropriately record and / or reproduce information on the BD that is the first optical disc and the HD that is the second optical disc. FIG. Such an optical pickup device PU1 can be mounted on an optical information recording / reproducing device.

  The optical pickup device PU1 includes an objective optical element unit OU, a λ / 4 wavelength plate QWP, a collimating lens CL, a polarizing prism PPS, a semiconductor laser LD (first light source) that emits a 405 nm laser beam (first beam), and a sensor. And a light receiving element PD that receives a reflected light beam from the information recording surface RL1 of the lenses SL and BD and the information recording surface RL2 of the HD.

  The objective optical element unit OU is configured by integrally connecting the correction element OE and the aspherical lens OBJ as shown in FIGS.

  A case of recording / reproducing BD will be described. First, the divergent light beam of the first light beam (λ1 = 405 nm) emitted from the blue-violet semiconductor laser LD is transmitted through the polarization prism PBS, converted into a parallel light beam by the collimator lens CL, and then linearly generated by the λ / 4 wavelength plate QWP. A spot formed on the information recording surface RL1 of the BD through the protective substrate PL1 having a thickness of 0.1 mm by the objective optical element unit OU, which is converted from polarized light to circularly polarized light, and whose beam diameter is regulated by a diaphragm (not shown). It becomes.

  At this time, the light beam that has passed through the first region A1 of the correction element OE is incident on the aspheric lens OBJ in the form of a parallel light beam, and is condensed on the information recording surface of the BD by the aspheric lens OBJ to form a spot. . On the other hand, the light beam that has passed through the second region A2 of the correction element OE is incident on the aspheric lens OBJ in the form of a convergent light beam, and when passing through the aspheric lens OBJ, a condensed spot is formed on the information recording surface of the BD. Do not form.

  The reflected light flux modulated by the information pits on the information recording surface RL1 is again transmitted through the objective optical element unit OU and the diaphragm, and then converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP, and converged by the collimating lens CL. After being reflected by the polarizing prism PBS, it is converged on the light receiving surface of the light receiving element PD by the sensor lens SL. The information recorded on the BD can be read by using the output signal of the light receiving element PD to focus or track the optical element unit OU by the biaxial actuator AC.

  Next, a case where HD recording / reproduction is performed will be described. The divergent light beam of the first light beam (λ1 = 405 nm) emitted from the blue-violet semiconductor laser LD is transmitted through the polarization prism PBS, converted into a parallel light beam by the collimator lens CL, and then converted from linearly polarized light by the λ / 4 wavelength plate QWP. It is converted into circularly polarized light, its light beam diameter is regulated by a diaphragm (not shown), and becomes a spot formed on the information recording surface RL2 of HD via the protective substrate PL2 having a thickness of 0.6 mm by the objective optical element unit OU. .

  At this time, the light beam that has passed through the second region A2 of the correction element OE enters the aspheric lens OBJ in the form of a convergent light beam, and is condensed on the information recording surface of the HD by the aspheric lens OBJ to form a spot. . On the other hand, the light beam that has passed through the first region A1 of the correction element OE enters the aspherical lens OBJ in the state of a parallel light beam, and when it passes through the aspherical lens OBJ, a condensed spot is formed on the information recording surface of the HD. Do not form.

  The reflected light flux modulated by the information pits on the information recording surface RL2 is again transmitted through the objective optical element unit OU and the diaphragm, and then converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP, and converged by the collimating lens CL. After being reflected by the polarizing prism PBS, it is converged on the light receiving surface of the light receiving element PD by the sensor lens SL. Then, using the output signal of the light receiving element PD, the optical element unit OU is focused or tracked by the biaxial actuator AC, so that the information recorded on the HD can be read.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, in view of the fact that return light from a region far from the optical axis in the correction element OE easily generates ghosts, the first region A1 close to the optical axis is a plane, and the first region A1 far from the optical axis is a spherical surface. It is also good. It is optional to provide four or more areas A1 and A2.

Example 1
Next, examples that can be used in the above-described embodiment will be described. The first embodiment includes a correction element and an aspheric lens. In the correction element, the most central region including the optical axis is the second region (inner second region), and from there toward the outer side in the direction orthogonal to the optical axis, the first region (inner first region) and second It has a region (outer second region) and a first region (outer second region). The first region has an aspherical design in which both the inner first region and the outer first region are all aspherical, and the second region has an aspheric shape in both the inner second region and the outer second region. Have. Further, the optical surface on the light source side is provided with an inclined surface between the inner first region and the outer second region. On the other hand, the optical surface on the optical disc side is provided with an inclined surface between the inner second region and the inner first region. Schematic diagrams of the optical element with this objective are shown in FIGS. FIG. 4 is a diagram showing a condensing state when BD is used as the first optical disc, and FIG. 5 is a diagram showing a condensing state when HD is used as the second optical disc.

Table 1 shows lens data of Example 1. In Table 1, ri represents the radius of curvature, di represents the position in the optical axis direction from the i-th surface to the (i + 1) -th surface, and ni represents the refractive index of each surface. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻³ ) is represented using E (for example, 2.5 × E−3). Further, in the optical surface on the light source side of the correction element, the 2-1 surface is an inner second region, the 2-2 surface is an inner first region, the 2-3 surface is an inclined surface, the 2-4 surface is an outer second region, The 2-5 surface is the outer first region. On the other hand, on the optical surface on the optical disc side of the correction element, the 3-1 surface is the inner second region, the 3-2 surface is the inclined surface, the 3-3 surface is the inner first region, the 3-4 surface is the outer second region, The 3-5 plane is the outer first region.

  The optical surface of the objective optical element is formed as an aspherical surface that is symmetric about the optical axis and is defined by a mathematical formula obtained by substituting the coefficient shown in Table 1 into Formula 1.

Here, X (h) is an axis in the optical axis direction (the light traveling direction is positive), κ is a conic coefficient, B _2i is an aspherical coefficient, h is a height from the optical axis, and r is a paraxial curvature. Radius.

  Table 2 summarizes data such as the focal length of Example 1.

It is sectional drawing of the optical element unit containing the correction element concerning this Embodiment. FIG. 2 is an enlarged view of an arrow II part of the correction element shown in FIG. 1. It is a figure which shows schematically the structure of the optical pick-up apparatus which concerns on this Embodiment. It is a figure which shows the condensing state at the time of using BD as a 1st optical disk. It is a figure which shows the condensing state in case HD is used as a 2nd optical disk. It is sectional drawing which shows an example of the correction | amendment element which inclined the 1st area | region. It is sectional drawing which shows another example of the correction | amendment element which inclined the 1st area | region.

Explanation of symbols

A1 First area A2 Second area AX Optical axis FR Lens frame OE Correction element OU Optical element unit S1 Light source side optical surface S2 Optical disk side optical surface PU1 Optical pickup device LD Blue-violet semiconductor laser AC Biaxial actuator PBS Polarizing prism CL Collimating lens PL1 Protective substrate PL2 Protective substrate RL1 Information recording surface RL2 Information recording surface QWP λ / 4 wavelength plate

Claims (19)

A light source that emits a first light beam having a wavelength of λ1 (380 nm <λ1 <450 nm); an objective optical element unit that includes a correction element for condensing the first light beam on an information recording surface of an optical disk and an aspherical lens; Then, the first light beam is condensed on the information recording surface of the first optical disc having the protective layer having the thickness t1 through the optical element unit, and the first light beam has the thickness t2 (t1 <t2). In a correction element for an optical pickup device that records and / or reproduces information by focusing on an information recording surface of a second optical disc having a protective layer,
The correction element has a plurality of concentric annular zones centered on the optical axis on the optical surface, and a light beam condensed on the information recording surface of the first optical disc passes through the plurality of annular zones. A first region, and a second region through which a light beam condensed on the information recording surface of the second optical disc passes,
Forming the second region from a spherical surface or an aspherical surface;
A correction element for an optical pickup device, wherein at least a part of the first region provided on the light source side optical surface is inclined by 1 ° or more with respect to a direction orthogonal to the optical axis.   The correction element for an optical pickup device according to claim 1, wherein the first region and the second region are all refractive surfaces.   3. The optical pickup device according to claim 1, wherein an area of 80% or more of the area of the first area provided on the light source side optical surface is inclined by 1 ° or more with respect to the direction perpendicular to the optical axis. Correction element.   A plurality of the first regions are arranged with the second region in between, and at least a part of the first region is the first region farthest from the optical axis. Item 5. A correction element for an optical pickup device according to Item 1.   5. The light according to claim 1, wherein at least one of the first regions inclined with respect to the direction perpendicular to the optical axis has a cross-sectional shape including an optical axis as an inclined straight line. Correction element for the pickup device.   6. The correction element for an optical pickup device according to claim 5, wherein at least one of the first regions inclined with respect to the optical axis orthogonal direction has a rotationally symmetric shape with respect to the optical axis.   The at least one first region inclined with respect to the optical axis orthogonal direction has a cross-sectional shape including an optical axis as a curve having a paraxial curvature. A correction element for the optical pickup device described.   The correction element for an optical pickup device according to claim 7, wherein at least one of the first regions inclined with respect to the direction perpendicular to the optical axis is a spherical surface.   When parallel light is incident on the first region of the light source side optical surface of the correction element that is inclined with respect to the direction orthogonal to the optical axis, the light is parallel from the first region of the optical surface on the optical disk side of the correction element. The correction element for an optical pickup device according to claim 1, wherein light is emitted. A light source that emits a first light beam having a wavelength of λ1 (380 nm <λ1 <450 nm); an objective optical element unit that includes a correction element for condensing the first light beam on an information recording surface of an optical disk and an aspherical lens; Then, the first light beam is condensed on the information recording surface of the first optical disc having the protective layer having the thickness t1 through the optical element unit, and the first light beam has the thickness t2 (t1 <t2). In a correction element for an optical pickup device that records and / or reproduces information by focusing on an information recording surface of a second optical disc having a protective layer,
The correction element has a plurality of concentric annular zones centered on the optical axis on the optical surface, and a light beam condensed on the information recording surface of the first optical disc passes through the plurality of annular zones. A first region, and a second region through which a light beam condensed on the information recording surface of the second optical disc passes,
Forming the first region from a spherical surface or an aspherical surface;
A correction element for an optical pickup device, wherein at least a part of the second region provided on the light source side optical surface is inclined with respect to a direction orthogonal to the optical axis.   The correction element for an optical pickup device according to claim 10, wherein the first region and the second region are all refractive surfaces.   12. The optical pickup device according to claim 10, wherein an area of 80% or more of the area of the second area provided on the light source side optical surface is inclined by 1 ° or more with respect to the direction perpendicular to the optical axis. Correction element.   The optical pickup device according to any one of claims 10 to 12, wherein the second region inclined with respect to the optical axis orthogonal direction is a flat surface having a cross-sectional shape including the optical axis. Correction element.   14. The correction element for an optical pickup device according to claim 13, wherein the first region inclined with respect to the optical axis orthogonal direction is a conical surface.   The optical pickup device according to claim 10, wherein the second region inclined with respect to the optical axis orthogonal direction is a surface having a curvature in a cross-sectional shape including the optical axis. Correction element.   The correction element for an optical pickup device according to claim 15, wherein the second region inclined with respect to the optical axis orthogonal direction is a spherical surface.   When parallel light is incident on the second region of the light source side optical surface of the correction element that is inclined with respect to the direction orthogonal to the optical axis, the parallel light is incident from the second region of the optical surface on the optical disk side of the correction element. The correction element for an optical pickup device according to any one of claims 10 to 16, wherein light is emitted.   18. An objective optical element unit, wherein the correction element according to claim 1 and an aspherical lens are integrally connected.   An optical pickup device comprising the objective optical element unit according to claim 18.

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