JPWO2008114593A1 - Optical pickup device and objective optical element - Google Patents

Abstract

In order to provide an optical pickup device and an objective optical element that can be compatible with one objective optical element of BD and HD that use the same light beam at low cost without using a complicated mechanism, a wavelength λ1 (380 nm <380 nm < In an optical pickup apparatus having a condensing optical system having a first light source that emits a first light flux of λ1 <450 nm and an objective optical element for condensing the first light flux on an information recording surface of an optical disc. The element is divided into at least a first region including the optical axis and a second region around the first region, and the first light flux that has passed through the first region is recorded on the first optical disc and the second optical disc. Alternatively, the first light beam that has been used for reproduction and passed through the second area is used for recording and / or reproduction of the first optical disk, and the condensing optical system has a correction surface in an area corresponding to the first area of the objective optical element. The correction surface is divided into a plurality of concentric regions centered on the optical axis by steps.

Description

  The present invention relates to an optical pickup device and an objective optical element capable of recording and / or reproducing information interchangeably for different types of optical disks using light beams having the same wavelength.

  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 about 25 GB per layer on an optical disk having a diameter of 12 cm, which is the same size as the above, and an optical disk for recording / reproducing information with specifications of NA 0.65 and light source wavelength 405 nm, so-called HD With a DVD (hereinafter referred to as HD), information of about 15 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 appropriately recording / reproducing information on such a high-density optical disc. In light of the reality that DVDs and CDs (compact discs) on which a wide variety of information is recorded are currently being sold, it is not possible to record / reproduce information on high-density optical discs. Similarly, making it possible to appropriately record / reproduce information on DVDs and CDs leads to an increase in commercial value as an optical disc player / recorder for high-density optical discs. From such a background, an optical pickup device mounted on an optical disc player / recorder for high-density optical discs has a capability of appropriately recording / reproducing information while maintaining compatibility with a plurality of types of optical discs. It is hoped that.

  In particular, 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 even though the wavelength of the light beam used is the same. It is difficult to correct spherical aberration. Therefore, it is more difficult to provide compatibility between BD and HD using a single objective optical element, as compared with compatibility with other optical disks.

  Under such circumstances, Patent Document 1 describes an objective optical element and an optical pickup device that use liquid crystal to give different aberrations during recording / reproduction of BD and HD, and enable compatibility with one objective optical element. Has been.

Patent Document 2 describes a pickup device that enables compatibility between BD and HD with a single objective optical element by sorting light beams having the same wavelength using a diffraction effect.
JP 2007-26540 A JP 2006-147069 A

  However, since the optical pickup device described in Patent Document 1 requires a liquid crystal, power supply and electrical control are necessary, which complicates the mechanism and increases the cost. It was.

  In addition, as in the optical pickup device described in Patent Document 2 above, when realizing the compatibility between BD and HD using a diffraction effect, for example, use of light passing from a light source to one optical disk through a diffraction structure 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) The ratio of the amount of light that contributes to the upper spot) is 40%, so the total use efficiency (here, the use efficiency is the photodetector with respect to the amount of light incident on the optical surface on the light source side of the objective optical element). Upper Tsu ratio bets contributing amount) 16% of the light only can be utilized to increase the emission intensity of the light source greatly need practical can be said to be difficult.

  The present invention takes the above-mentioned problems into consideration, enables BD and HD using the same light beam to be compatible with one objective optical element at low cost without using a complicated mechanism, and An object of the present invention is to provide an optical pickup device and an objective optical element with high light utilization efficiency.

  An optical pickup device according to claim 1 condenses a first light source that emits a first light beam having a wavelength λ1 (380 nm <λ1 <450 nm) and an information recording surface of an optical disc. For recording and / or reproducing information by condensing the first light flux on an information recording surface of a first optical disc having a protective layer having a thickness t1. In the optical pickup apparatus for performing information recording and / or reproduction 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 optical element is divided into at least a first region including the optical axis and a second region around the first region, and the first light flux that has passed through the first region is the first optical disc and the Second light The first light beam used for recording and / or reproducing a disc and passing through the second area is used for recording and / or reproducing the first optical disc, and the condensing optical system is connected to the objective optical element. A correction surface is provided in a region corresponding to the first region, and the correction surface is divided into a plurality of concentric regions centered on the optical axis by a step.

  The optical pickup device according to claim 2 is the invention according to claim 1, wherein the first light beam that has passed through the plurality of regions of the correction surface is information on the first optical disc. The first optical disc is focused so that information can be recorded and / or reproduced on the recording surface, and the first luminous flux that has passed therethrough is not condensed on the information recording surface of the second optical disc, and the first optical disc that has passed therethrough. A first light beam is not condensed on the information recording surface of the first optical disk, and the first light beam that has passed through is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disk. 2 optical disc dedicated area.

  The optical pickup device described in claim 3 is characterized in that, in the invention described in claim 2, the first optical disc is a BD and the second optical disc is an HD.

  The optical pickup device according to claim 4 is the invention according to any one of claims 1 to 3, wherein the first light flux that has passed through the plurality of regions of the correction surface is provided. Includes a region in which the first light beam is condensed on the information recording surface of the first optical disc, and the first light flux that has passed therethrough is also condensed on the information recording surface of the second optical disc.

  The optical pickup device according to claim 5 is the invention according to any one of claims 1 to 4, wherein the objective optical element is a single lens, and the objective optical element Has the correction surface.

The optical pickup device according to claim 6 is the optical axis of all steps provided on the optical surface of the objective optical element according to any one of claims 1 to 5. The sum Δ of the lengths of the direction codes (the sign is positive when the optical path is shorter in the area closer to the optical axis of each step than the area farther away) is:
0.1mm ≦ Δ ≦ 1.0mm
It is characterized by satisfying.

  The optical pickup device according to claim 7 is the optical pickup device according to any one of claims 1 to 4, wherein the objective optical element includes a first optical element and a second optical element. The first optical element has the correction surface.

  The optical pickup device according to claim 8 is the optical pickup apparatus according to claim 7, wherein the first optical element is a flat element and the second optical element is an aspheric lens. It is characterized by that.

  The optical pickup device according to claim 9 is the invention according to any one of claims 1 to 8, wherein the step amount of the step of the correction surface is set to the first light flux. Thus, the step amount gives an optical path difference a times the wavelength λ1. However, a is a positive integer other than 0.

  The optical pickup device according to claim 10 is the invention according to any one of claims 1 to 8, wherein the step amount of the step on the correction surface is relative to the first light flux. Thus, the step difference amount gives an optical path difference of b times the wavelength λ1. However, b is 0 or a positive integer + x, and x is 0.4 or more and 0.6 or less.

  The optical pickup device according to claim 11 is the invention according to any one of claims 1 to 8, wherein the step amount of the step on the correction surface is relative to the first light flux. And a step difference amount that gives an optical path difference of c times the wavelength λ1. However, c is 0 or a positive integer + y, and y is greater than 0, less than 0.4, greater than 0.6, and less than 1.

  The optical pickup device according to claim 12 is the invention according to any one of claims 1 to 11, wherein the objective optical element is configured to match the first region and the second region. And having an annular zone of 3 or more and 10 or less.

  The optical pickup device according to claim 13 is the optical pickup device according to claim 12, wherein the objective optical element includes the first region and the second region in a range of 5 or more and 10 or less. It is characterized by having an annular zone.

  An optical pickup device according to a fourteenth aspect of the present invention is the optical pickup device according to any one of the first to thirteenth aspects of the invention, wherein the objective optical element is recorded and / or reproduced at the time of the first optical disc. The working distance is different from the working distance of the objective optical element during recording and / or reproduction of the second optical disc.

The optical pickup device according to claim 15 is the optical pickup apparatus according to claim 14, in which the working distance WD1 of the objective optical element during recording and / or reproduction of the first optical disc, 2 Working distance WD2 of the objective optical element at the time of recording and / or reproduction of the optical disc is the following conditional expression:
-0.36mm ≤ WD1-WD2 ≤ 0.17mm
It is characterized by satisfying.

  The objective optical element according to claim 16 condenses a first light source that emits a first light beam having a wavelength of λ1 (380 nm <λ1 <450 nm) and an information recording surface of an optical disc. For recording and / or reproducing information by condensing the first light flux on an information recording surface of a first optical disc having a protective layer having a thickness t1. And an objective used in an optical pickup device for recording and / or reproducing information by focusing the first light beam on an information recording surface of a second optical disc having a protective layer having a thickness t2 (t1 <t2). In the optical element, the objective optical element is divided into at least a first region including the optical axis and a second region around the first region, and the first light flux that has passed through the first region is: The first optical device Used for recording and / or reproduction of a disk and the second optical disk, and the first light flux that has passed through the second region is used for recording and / or reproduction of the first optical disk, A correction surface is provided in a region corresponding to the first region of the objective optical element, and the correction surface is divided into a plurality of concentric regions centered on the optical axis by steps.

  The objective optical element according to claim 17 is the information according to claim 16, wherein the first light flux that has passed through the plurality of regions of the correction surface is information on the first optical disc. The first optical disc is focused so that information can be recorded and / or reproduced on the recording surface, and the first luminous flux that has passed therethrough is not condensed on the information recording surface of the second optical disc, and the first optical disc that has passed therethrough. A first light beam is not condensed on the information recording surface of the first optical disk, and the first light beam that has passed through is condensed so that information can be recorded and / or reproduced on the information recording surface of the second optical disk. 2 optical disc dedicated area.

  The objective optical element described in claim 18 is characterized in that, in the invention described in claim 17, the first optical disc is a BD and the second optical disc is an HD.

  The objective optical element according to claim 19 is the invention according to any one of claims 16 to 18, wherein the first light flux that has passed through the plurality of regions of the correction surface is provided. Includes a region in which the first light beam is condensed on the information recording surface of the first optical disc, and the first light flux that has passed therethrough is also condensed on the information recording surface of the second optical disc.

  The objective optical element according to claim 20 is the invention according to any one of claims 16 to 19, wherein the objective optical element comprises a single lens, and the objective optical element Has the correction surface.

The objective optical element according to claim 21 is the optical axis of all steps provided on the optical surface of the objective optical element according to any one of claims 16 to 20. The sum Δ of the lengths of the direction codes (the sign is positive when the optical path is shorter in the area closer to the optical axis of each step than the area farther away) is:
0.1mm ≦ Δ ≦ 1.0mm
It is characterized by satisfying.

  The objective optical element according to claim 22 is the invention according to any one of claims 16 to 19, wherein the objective optical element has a first optical element and a second optical element. The first optical element has the correction surface.

  The objective optical element according to claim 23 is the objective optical element according to claim 22, wherein the first optical element is a flat optical element, and the second optical element is an aspheric lens. It is characterized by being.

  The objective optical element according to Claim 24 is the invention according to any one of Claims 16 to 23, in which the step amount of the step on the correction surface is set with respect to the first light flux. Thus, the step amount gives an optical path difference a times the wavelength λ1. However, a is a positive integer other than 0.

  The objective optical element according to claim 25 is the invention according to any one of claims 16 to 23, in which the step amount of the step of the correction surface is set to the first light flux. Thus, the step difference amount gives an optical path difference of b times the wavelength λ1. However, b is 0 or a positive integer + x, and x is 0.4 or more and 0.6 or less.

  The objective optical element according to Claim 26 is the invention according to any one of Claims 16 to 23, wherein the step amount of the step on the correction surface is relative to the first light flux. And a step difference amount that gives an optical path difference of c times the wavelength λ1. However, c is 0 or a positive integer + y, and y is greater than 0, less than 0.4, greater than 0.6, and less than 1.

  The objective optical element according to claim 27 is the invention according to any one of claims 16 to 26, wherein the objective optical element combines the first region and the second region. And having an annular zone of 3 or more and 10 or less.

  The objective optical element according to claim 28 is the objective optical element according to claim 27, wherein the objective optical element is 5 or more and 10 or less in total of the first region and the second region. It is characterized by having an annular zone.

  The objective optical element according to claim 29 is the invention according to any one of claims 16 to 28, wherein the objective optical element is recorded and / or reproduced on the first optical disc. The working distance is different from the working distance of the objective optical element during recording and / or reproduction of the second optical disc.

The objective optical element according to claim 30 is the objective optical element according to claim 29, wherein a working distance WD1 of the objective optical element at the time of recording and / or reproduction of the first optical disc, 2 Working distance WD2 of the objective optical element at the time of recording and / or reproduction of the optical disc is the following conditional expression:
-0.36mm ≤ WD1-WD2 ≤ 0.17mm
It is characterized by satisfying.

  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.

  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)
0.9mm ≦ 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 Can do. 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. 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, but may include a coupling lens such as a collimator lens and a beam expander in addition to the objective optical element. 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 elements for the first optical disk and the second optical disk. The objective optical element 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 is disposed at a position facing the optical disk in a state where the optical disk is loaded in the optical pickup device, and has a function of condensing the light beam emitted from the light source on the information recording surface of the optical disk. An optical system having 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 may be composed of two or more lenses and optical elements, or may be only a single lens. The objective optical element may be a glass lens, a plastic lens, or a hybrid lens in which an optical path difference providing structure or the like is provided on a glass lens with a photocurable resin or the like. When the objective optical element has a plurality of lenses, a glass lens and a plastic lens may be mixed and used. When the objective optical element has a plurality of lenses, a combination of a flat optical element and an aspherical lens may be used. The objective optical element may have an optical path difference providing structure. The objective optical element preferably has an aspheric refractive surface.

When the objective optical element is a plastic lens, it is preferable to use a cyclic olefin-based resin material. Among the cyclic olefin-based materials, the refractive index at a temperature of 25 ° C. with respect to a wavelength of 405 nm is 1.54 to 1.60. The refractive index change rate dN / dT (° C. ⁻¹ ) for a wavelength of 405 nm accompanying a temperature change within a temperature range of −5 ° C. to 70 ° C. is −20 × 10 ^{−5 to} −5 × 10 ^It is more preferable to use a resin material within a range of ⁻⁵ (more preferably −10 × 10 ^{−5 to} −8 × 10 ⁻⁵ ). When the objective optical element is a plastic lens, the coupling lens is preferably a plastic lens.

  The numerical aperture defined in the standard required for reproducing and / or recording information on the first optical disk is NA1, and the standard defined by the standard necessary for reproducing and / or recording information on the second optical disk. NA4 (NA1> NA2) is set as the numerical aperture, and NA3 (NA2 ≧ NA3) is set as the numerical aperture determined by the standard necessary for reproducing and / or recording information on the third optical disc. The numerical aperture determined by the standard as necessary for reproducing and / or recording information 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 is divided into a first region including at least the optical axis and a second region around the first region. The first region and the second region may have a clear structural difference between the first region and the second region on the optical surface of the objective optical element. On the other hand, the objective optical element may be a convenient area without providing a clear area in terms of configuration.

  The first light beam that has passed through the first area of the objective optical element is used for recording / reproduction of the first optical disk and the second optical disk, and the first light beam that has passed through the second area is used for recording / reproduction of the first optical disk. However, it is not used for recording / reproduction of the second optical disc. That is, it can be said that the first area is a so-called shared area used for both the first optical disk and the second optical disk, and the second area is a so-called dedicated area used only for the first optical disk. The first area is preferably an area of NA2 or less, and the second area is preferably an area larger than NA2 and NA1 or less. For example, when the first optical disk is a BD and the second optical disk is an HD, the first area is preferably an area having an image-side numerical aperture (NA) of 0.65 or less, and the second area is an image. It is preferable that the side numerical aperture is greater than 0.65 and 0.85 or less.

  The objective optical element may have a compatible optical path difference providing structure that enables use of the third optical disk and / or the fourth optical disk. Further, the objective optical element may have an optical path difference providing structure for correcting the aberration change at the time of temperature change or wavelength change. 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 integer multiple of the wavelength of the incident light beam or a non-integer multiple of the wavelength of the incident light beam. 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 optical path difference providing structure is preferably a diffractive structure.

  The condensing optical system of the optical pickup device has a correction surface in a region corresponding to the first region of the objective optical element. The correction surface is divided into a plurality of concentric regions centered on the optical axis by steps. Note that a region corresponding to the outside of the correction surface, that is, a region corresponding to the second region of the objective optical element may be a simple refracting surface.

  Examples of the correction surface are roughly divided into two examples.

  The first example of the correction surface is a case where a plurality of areas on the correction surface include a first optical disk dedicated area and a second optical disk dedicated area. The first optical disk dedicated area condenses the passed first light beam so that information can be recorded / reproduced on the information recording surface of the first optical disk, while the passed first light beam passes the information recording surface of the second optical disk. The region above does not collect light. In the second optical disc dedicated area, conversely, the passed first light beam is not condensed on the information recording surface of the first optical disc, and the passed first light beam is recorded / recorded on the information recording surface of the second optical disc. It is an area where light is collected so that it can be reproduced. Although it is preferable that the first optical disk dedicated area and the second optical disk dedicated area are provided alternately, the present invention is not limited to this. The most central area including the optical axis may be the first optical disk dedicated area or the second optical disk dedicated area.

  The first light flux that has passed through the first optical disc dedicated area has a very small aberration on the information recording surface of the first optical disc, and the aberration is such that information cannot be recorded / reproduced on the information recording surface of the second optical disc. Is big. On the other hand, the first light flux that has passed through the second optical disc dedicated area has a large aberration on the information recording surface of the first optical disc so that information cannot be recorded / reproduced. On the information recording surface of the second optical disc, Aberration is very small. It can be said that the second area is a dedicated area for the first optical disc.

  In the first example, it is preferable that the first optical disk dedicated area and the second optical disk dedicated area on the correction surface are both refractive surfaces, and in this case, the refraction action is used to pass through the first optical disk dedicated area. The light flux that has been collected is condensed on the information recording surface of the first optical disc, and the light flux that has passed through the second optical disc dedicated area is condensed on the information recording surface of the second optical disc. Such a configuration is preferable because a loss of light amount can be reduced when reflected light on the information recording surface of the optical disc passes through the correction surface. 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.

  One of the first optical disk dedicated area and the second optical disk dedicated area transmits the first light beam (has no power with respect to the first light beam), and the other is the optical disk with respect to the passed first light beam. Aberrations may be corrected (having power with respect to the first light flux) so that information can be recorded / reproduced on the information recording surface. In particular, the objective optical element includes a first optical element having a correction surface and a second optical element that is an aspheric lens, and only the aspheric lens protects the first optical disk or the second optical disk. In the case where the aspherical lens has an optical performance capable of condensing the first light beam on the information recording surface via the substrate, it is preferable to adopt the above-described configuration. For example, when the aspherical lens is designed so that only the aspherical lens can focus the first light beam on the information recording surface with respect to the BD, the first optical disk (BD) dedicated area on the correction surface is It is preferable that the second optical disc (HD) dedicated area has a structure that corrects aberration so that the first light flux is condensed on the information recording surface of the HD. .

  On the other hand, the first optical disc dedicated area corrects the aberration so that the first light flux that has passed through is focused on the information recording surface of the first optical disc so that information can be recorded / reproduced. The dedicated area may be configured to correct the aberration so that the information can be recorded / reproduced on the information recording surface of the second optical disc that has passed. In particular, the objective optical element has a first optical element having a correction surface and a second optical element that is an aspheric lens, and the aspheric lens alone protects both the first optical disk and the second optical disk. In the case where the first light beam cannot be condensed on the information recording surface via the substrate, the above-described configuration is preferable. For example, when the aspherical lens is designed so that only the aspherical lens is used and the first light beam cannot be focused on both BD and HD, the first optical disk (BD) dedicated area on the correction surface is the first area. The aberration is corrected so that one light beam is condensed on the BD information recording surface, and the second optical disc (HD) dedicated region is condensed on the HD information recording surface with respect to the first light beam. It is preferable to have a structure that corrects aberrations.

  Next, a second example of the correction surface will be described. In this example, the plurality of regions of the correction surface condense the first light beam that has passed through the information recording surface of the first optical disc, and the first light beam that has passed through also be collected on the information recording surface of the second optical disc. This is a case including a light emitting region. The partial region of the correction surface may be an example of the first correction surface described above, and the remaining region may be the region shown in the second example, or all of the plurality of regions of the correction surface may be included. The region may be the region shown in the first example.

  In this second example, the first light flux that has passed through the area remains focused on the information recording surface of the first optical disc to some extent, but is condensed to such an extent that it can be recorded / reproduced. Even on the information recording surface of the second optical disc, although aberration remains to some extent, the light is condensed to such an extent that recording / reproduction is possible.

  In the above case, the first optical disk priority area and the second optical disk priority area may be included in the plurality of areas on the correction surface. The first optical disc priority area concentrates the passed first light flux so that information can be recorded / reproduced on the information recording surface of the first optical disc, and the passed first light flux is the information recording surface of the second optical disc. This is a region where aberration is corrected so that information can be recorded / reproduced on the top, but aberration is reduced on the information recording surface of the first optical disc. On the other hand, in the second optical disc priority area, the passed first light flux is condensed so that information can be recorded / reproduced on the information recording surface of the first optical disc, and the passed first light flux is information on the second optical disc. This is a region where aberration is corrected so that information can be recorded / reproduced on the recording surface, but aberration is reduced on the information recording surface of the second optical disc. The first optical disc priority area and the second optical disc priority area are preferably provided alternately, but the present invention is not limited to this. The most central area including the optical axis may be the first optical disk priority area or the second optical disk priority area. It is preferable that both the first optical disk priority area and the second optical disk priority area are refractive surfaces.

  Next, the configuration of the correction surface will be described below.

  When the objective optical element is composed of a single lens, the objective optical element may have a correction surface. In this case, a step may be provided in the first area of the aspheric surface of the single lens objective lens, thereby dividing it into a plurality of areas, and the second area may be left as a refractive surface. The first optical disk dedicated area and the second area in the first area are preferably the same aspherical shape, and the second optical disk dedicated area is preferably an aspherical shape different from that.

  Further, from the viewpoint of facilitating the production of the objective optical element, it is preferable that the number of annular zones including the first region and the second region is 3 or more and 10 or less. Here, the number of annular zones means that the first optical disk dedicated area, the second optical disk dedicated area, the first optical disk priority area, the second optical disk priority area, and the first optical disk second optical disk combined area are counted as one annular band. In this case, one ring zone of the diffractive structure is not counted as one of the ring zones here. When the number of ring zones is 3, as shown in FIG. 9, for example, the center area including the optical axis is the first optical disk dedicated area BA1, the surrounding area is the second optical disk dedicated area HA, and the surrounding area is An example in which the outer peripheral area (second area) is the first optical disk dedicated area BA2 can be considered. As a result of earnest research, the present inventor has made the number of annular zones combining the first region and the second region from the viewpoint of reducing the side rope of the spot and facilitating the manufacture of the objective optical element. Has been found to be preferably 5 or more and 10 or less. More preferably, the number of ring zones is 6 or more and 10 or less. In addition, also when the objective optical element as mentioned later has the 1st optical element by the side of a light source, and the 2nd optical element by the side of an optical disk, the said range of preferable ring zones is applicable.

  Next, when performing recording and / or reproduction of the second optical disk, in order to prevent the light beam that has passed through the first optical disk dedicated area from being covered with the defocus area, the light beam that has passed through the first optical disk dedicated area is It is preferable that the objective optical element has a flare on the information recording surface of the second optical disc. Specifically, “to make flare” means that the light flux that has passed through the second optical disk area is condensed on the information recording surface of the first optical disk when recording and / or reproducing the first optical disk. The light beam that has passed through the area for the first optical disk is not condensed on the information recording surface of the second optical disk when the second optical disk is recorded and / or reproduced. Indicates that it is spreading. In order to generate a good flare when the first optical disc is a BD and the second optical disc is an HD, the working distance (WD1) of the objective optical element in the first optical disc (BD) 2 It is preferable that the difference value (WD1−WD2) from the working distance (WD2) of the objective optical element in the optical disc (HD) is −0.36 (mm) or more and 0.17 (mm) or less. More preferably, it is -0.10 (mm) or more and 0.15 (mm) or less.

  Further, in order to obtain the same spot diameter as that of the BD exclusive lens or the HD exclusive lens, it is preferable that the following conditions are satisfied. The following conditions are not limited to the case where the objective optical element is a single lens, but also when the objective optical element includes the first optical element on the light source side and the second optical element on the optical disk side, Conditions are applicable.

  First, when the area closest to the center including the optical axis is the second optical disk dedicated area, the maximum image-side numerical aperture of the first optical disk dedicated area is preferably smaller than NA1. In addition, it is preferable that the maximum effective diameter of the first optical disk dedicated area is smaller than 2 · f1 · NA1. Note that f1 is a focal length of the first optical disc dedicated area of the objective optical element in the first light flux, and NA1 is an image-side numerical aperture determined by the standard as necessary for recording and / or reproduction of the first optical disc. Indicates. For example, when the first optical disk is a BD and the second optical disk is an HD, the maximum image-side numerical aperture of the first optical disk dedicated area is preferably smaller than 0.85. In addition, it is preferable that the maximum effective diameter of the first optical disk dedicated area is smaller than 2 · f1 · 0.85.

  Next, when the area closest to the center including the optical axis is the first optical disk dedicated area, the maximum image-side numerical aperture of the second optical disk dedicated area is preferably smaller than NA2. Further, it is preferable that the maximum effective diameter of the second optical disc dedicated area is smaller than 2 · f2 · NA2. Note that f2 is the focal length of the objective optical element dedicated to the second optical disk in the first light flux, and NA2 is the image-side numerical aperture defined by the standard required for recording and / or reproduction of the second optical disk. Indicates. For example, when the first optical disk is a BD and the second optical disk is an HD, the maximum image-side numerical aperture of the second optical disk dedicated area is preferably smaller than 0.65. In addition, it is preferable that the maximum effective diameter of the second optical disk dedicated area is smaller than 2 · f2 · 0.65.

  Next, as a configuration for improving the off-axis characteristics of the objective optical element that is a single lens, 1) change the aspherical shape between the first optical disk dedicated area and the second optical disk dedicated area, or 2) For example, as shown in FIG. 10, a configuration in which an optical path difference providing structure is provided in the second optical disc dedicated area is conceivable. Here, to improve the off-axis characteristics means that the wavefront aberration becomes 0.1 RMS or less when the light beam enters the objective optical element at an oblique incidence of 0.5 °.

  In the case of the configuration in which the aspherical shapes of the first optical disk dedicated area and the second optical disk dedicated area are different in 1), the working distance (WD1) of the objective optical element during recording and / or reproduction of the first optical disk, It is preferable to design the absolute value (| WD1-WD2 |) of the difference from the working distance (WD2) of the objective optical element during recording and / or reproduction of the optical disc to be 0.1 (mm) or more. Furthermore, it is preferable to satisfy WD1> WD2.

  On the other hand, in order not to cause a large step on the optical surface, it is preferable to provide an off-axis characteristic by providing an optical path difference providing structure in the second optical disc dedicated area as in 2). Depending on other design conditions, the above method 1) or 2) may be used properly.

  Incidentally, on the optical surface of the single objective optical element on the optical disc side, a region through which a light beam used for recording and / or reproduction of the first optical disc passes and a light beam used for recording and / or reproduction of the second optical disc pass. It is preferable to use an objective optical element that does not overlap with the area to be processed because loss of light quantity can be reduced. When this viewpoint is emphasized, it is preferable that the number of annular zones of the objective optical element is small. For example, a three-band objective optical element is preferable.

  Further, from the viewpoint of reducing the thickness of a single objective optical element, a step is provided on the surface of the optical surface of the objective optical element, and the step is a region on the far side of the region closer to the optical axis with the step as a boundary. It is desirable that the level difference be shorter than the optical path. For example, the example shown in FIG. 13 is an example in which a step for thinning the objective optical element is further provided in the area dedicated to the first optical disc, which is the central area, with respect to the objective optical element shown in FIG. Even when such a step is provided, it is desirable that the spherical aberration and the sine condition are corrected to a necessary level.

  The step between the first optical disc dedicated area and the second optical disc dedicated area is not limited to the example shown in FIG. When the objective optical element is made of plastic, it may be a step that produces a diffractive action that compensates for the spherical aberration change caused by the temperature change of the plastic by the change of the laser oscillation wavelength accompanying the temperature change. When the objective optical element is made of glass, the influence of temperature change is small, so that it is easy to obtain a deep step without degrading temperature characteristics.

The sum Δ of the lengths of coding in the optical axis direction of all the steps provided on the optical surface of the objective optical element (sign is a region where the optical path of each step is closer to the optical axis than the region on the far side The case of shortening is positive) is the following conditional expression (6),
0.1 mm ≦ Δ ≦ 1.0 mm (6)
It is desirable to satisfy.
If it is above the lower limit, the effect of thinning is great, and if it is below the upper limit, the sine condition can be corrected to the required level while reducing the thickness. Note that “the sum of the coding lengths” means that when both a positive length value and a negative length value exist, they are added as they are. For example, if the positive length value is +1 and the negative length value is −0.5, (+1) + (− 0.5) = + 0.5, ie, +0. 5 is “the sum of the lengths of encoding”.

  As shown in FIG. 9, when a single objective optical element is provided with a first optical disc dedicated region and a second optical disc dedicated region, a large step (for example, a step of 50 μm or more in the optical axis direction) at the boundary of each region. ) May occur. Such a large step, when the objective optical element is molded using a mold, may become a hindrance when the optical element is removed from the mold, making the objective optical element more difficult to manufacture. Therefore, when a large step (for example, a step of 50 μm or more in the optical axis direction) occurs at the boundary of each region, the inclined surface is inclined with respect to the optical axis at the step portion so that it can be easily removed from the mold. (Taper) is preferably provided. For example, as shown in FIG. 9, in the case where the middle region is recessed in the optical axis direction, as shown in FIG. 14, only the surface SS1 with the step surface facing the optical axis is inclined. The surface SS2 in which the step surface faces in the direction opposite to the optical axis is not inclined, so that the influence on the optical performance can be minimized, and the loss of light amount due to the taper can be reduced. It is preferable because it can be easily removed from.

  Further, the correction surface and the structure of the second region include an optical path difference providing structure (preferably a diffractive structure) for the purpose of compatibility with the third optical disk and the fourth optical disk, and a change in aberration that occurs when the temperature changes or the wavelength changes. An optical path difference providing structure (preferably a diffractive structure) intended to correct the above may be superimposed. One preferable example is that an optical path difference providing structure is provided in which a correction surface is provided in the first region of the objective optical element, and only the second region is corrected for a change in aberration caused by a temperature change or a wavelength change. Is provided. In the above description, the example in which the optical path difference providing structure is provided on the optical surface on the light source side is described. However, the optical path difference providing structure for the above-described purpose may be provided on the optical surface on the optical disc side. .

  When the objective optical element includes the first optical element on the light source side and the second optical element on the optical disk side, the first optical element may have a correction surface. In this case, the first optical element is preferably a flat plate, and the second optical element is preferably a lens having an aspheric surface. However, the present invention is not limited to this, and the first optical element has an aspheric surface. Also good. As a preferable example, for example, a step is provided in a region corresponding to the first region of the flat plate-like first optical element, thereby dividing the region into a plurality of regions, and a region corresponding to the second region of the first optical element is The configuration is a plane. Furthermore, an optical path difference providing structure for the purpose of compatibility with the third optical disk and the fourth optical disk is used for the structure of the correction surface, and an optical path difference for correcting aberration changes that occur when temperature changes or wavelength changes. The providing structure may be overlapped. One preferred example is that a correction surface is provided in the first region of the first optical element, and aberrations that occur when the temperature changes or the wavelength changes only in the second region of the first optical element and / or the second optical element. In this configuration, an optical path difference providing structure for the purpose of correcting the change is provided.

  When the flat plate-like first optical element has a correction surface, the surface on the light source side of the first optical element may have a correction surface. Preferably, the optical disk side of the first optical element (second optical element) The surface (which can also be said to be a side) has a correction surface. This configuration is preferable because the light beam incident on the optical disk and the light beam reflected from the optical disk can be easily prevented from being off-axis even if they are not exactly the same. Further, correction surfaces may be provided on both surfaces of the first optical element.

  When the correction surface is provided on the flat plate-like first optical element, it is preferable that the plurality of regions of the correction surface have a flat plate portion region and an aspherical region. I can't. Any of the plurality of regions of the correction surface provided in the flat plate-like first optical element may have an aspherical surface.

  When the correction surface of the flat plate-shaped first optical element has a flat plate portion region and an aspheric surface region, the flat plate portion region is one of the first optical disk dedicated region and the second optical disk dedicated region. It is preferable that the aspherical region is the other.

  A preferred example in the case where the correction surface is provided on the flat plate-like first optical element will be described with reference to FIG. As shown in FIG. 1, in this example, the objective optical element OE includes a flat plate-like first optical element L1, a second optical element L2 that is an aspheric lens, a first optical element L1, and a second optical element L2. And a frame HE that holds and fixes the frame. The second optical element L2 is designed so as to be able to focus the first light beam on the information recording surface of the BD by itself. A correction surface CS is provided in a region of NA 0.65 or less that is the first region A1 of the first surface S1 of the first optical element L1. A region larger than NA 0.65 that is the second region A2 of the first surface S1 of the first optical element L1 and NA 0.85 or less is a flat surface.

  The correction surface CS is divided into a plurality of regions having a region BA on a plane and a region HA having an aspherical surface by steps. The area BA on the plane and the area HA having the aspherical surface are alternately provided. The area BA on the plane is an area dedicated to the first optical disk (BD), and the area HA having an aspheric surface is an area dedicated to the second optical disk (HD). Since the second optical element is designed to be optimized for BD, the first light beam that has passed through the first optical element, that is, the first light beam that has passed through the BD dedicated area BA, which is an area on the plane, It is condensed on the information recording surface of the BD by the element. On the other hand, since the first light beam is not condensed on the HD information recording surface only by the second optical element, the first light beam passes through the HD dedicated area HA of the first optical element, thereby giving an aberration due to the aspherical shape. Is done. Thus, the first optical element and the second optical element jointly give aberration, whereby the first light flux that has passed through the HD dedicated area is condensed on the information recording surface of the HD. The HD dedicated area having an aspherical shape has a structure in which the step is directed to the opposite side of the optical axis near the optical axis, and the step is directed toward the optical axis in the area away from the optical axis. . In addition, an aspherical surface having no step is provided in the transition region therebetween.

  That is, when BD recording / reproduction is performed, the light beam that has passed through the BD dedicated area BA and the second area A2 of the first area A1 of the first optical element L1 is reflected on the BD information recording surface by the second optical element. The light flux that has been condensed and passed through the HD dedicated area HA of the first area A1 of the first optical element L1 is not condensed on the information recording surface of the BD. On the other hand, when recording / reproducing HD, the first light beam that has passed through the HD dedicated area HA of the first area A1 of the first optical element L1 is condensed on the information recording surface of the HD by the second optical element. Thus, the first light flux that has passed through the BD dedicated area BA and the second area of the first area A1 of the first optical element is not condensed on the HD information recording surface.

  Next, the step amount of the step will be described. Examples of the level difference are roughly divided into three types.

The first example is a case where the step amount of the step on the correction surface is a step amount that gives an optical path difference of a times the wavelength λ1 to the first light flux. Note that a is an arbitrary positive integer other than 0. In this case, the step amount d1 can be expressed by the following equation (7).
d1 = a · λ1 / (n−1) (7)
Here, n is the refractive index of the optical element having a correction surface for the light flux with wavelength λ1.

  For example, when the objective optical element is a single lens optimized for BD, when the first light beam is condensed on the information recording surface of the BD, almost no aberration occurs as shown in FIG. Next, when the first light beam is condensed on the HD information recording surface using only the second optical element, a large aberration occurs as shown in FIG. The aberration diagram shown in FIG. 3 is an aberration diagram of only the first region.

  Therefore, as the objective optical element, an objective optical element having a flat plate-like first optical element having a correction surface as shown in FIG. 1 and a second optical element which is a lens optimized for BD is used, and the amount of the step is set. 4 satisfies the expression (7), the aberration in the first region is as shown in FIG. FIG. 4A shows the aberration in BD, and FIG. 4B shows the aberration in HD. In this case, a = 1.

  Note that the step amount need not be equal for all steps on the correction surface. For example, the step in the region near the optical axis of the correction surface may be increased, and the step in the region far from the optical axis of the correction surface may be decreased. Or the reverse may be sufficient. For example, while the amount of the step satisfies the expression (7), a = 2 is set for the step in the region near the optical axis of the correction surface, and a = 1 is set for the step in the region far from the optical axis of the correction surface. In this case, the aberration in the first region is as shown in FIG. FIG. 7A shows the aberration in BD, and FIG. 7B shows the aberration in HD.

The second example is a case where the step amount of the step on the correction surface is a step amount that gives an optical path difference b times the wavelength λ1 to the first light flux. Note that b is 0 or the sum of any positive integer and x. x is an arbitrary value between 0.4 and 0.6. In this case, the step amount d2 can be expressed by the following equation (8).
d2 = b · λ1 / (n−1) (8)
As the objective optical element, an objective optical element having a flat plate-like first optical element having a correction surface as shown in FIG. 1 and a second optical element which is a lens optimized for BD is used. When the expression (8) is satisfied, the aberration in the first region is as shown in FIG. FIG. 5A shows the aberration in BD, and FIG. 5B shows the aberration in HD. In this case, b = 1 + 0.5.

A third example is a case where the step amount of the step on the correction surface is a step amount that gives an optical path difference c times the wavelength λ1 to the first light flux. Note that c is 0 or the sum of any positive integer and y. y is an arbitrary value greater than 0 and less than 0.4 or greater than 0.6 and less than 1. In this case, the step amount d3 can be expressed by the following equation (9).
d3 = c · λ1 / (n−1) (9)
As the objective optical element, an objective optical element having a flat plate-like first optical element having a correction surface as shown in FIG. 1 and a second optical element which is a lens optimized for BD is used. When the expression (9) is satisfied, the aberration in the first region is as shown in FIG. FIG. 6A shows the aberration in BD, and FIG. 6B shows the aberration in HD. In this case, c = 1 + 0.8.

  In addition, the correction surface is not of a type having a first optical disk (BD) dedicated area and a second optical disk (HD) dedicated area. 1. Condensed light on the information recording surface of one optical disc (although some aberrations remain) so that it can be recorded / reproduced, and the first light flux that has passed through also on the information recording surface of the second optical disc (some aberrations remain) However, when the light is collected so as to be recorded / reproduced, the aberration in the first region is as shown in FIG. FIG. 8A shows the aberration in BD, and FIG. 8B shows the aberration in HD. In this case, since the same amount of aberration occurs in both BD and HD, the first optical disk priority area and the second optical disk priority area do not exist in this example. It can be said that the first optical disc is the second optical disc combined area.

  Note that the following modes can be considered when compatibility with other optical discs as well as the first optical disc and the second optical disc is performed with one objective optical element.

As a first example, for example, a third light beam having a wavelength λ3 emitted from a third light source is condensed on the information recording surface of the fourth optical disk by the objective optical element, and the wavelength λ3 is a wavelength λ1. If it is an approximate integer multiple of 1 and an attempt is made to enable compatibility with the fourth optical disk by the diffraction structure, 1) it becomes difficult to make the diffraction angles different between the first light flux of λ1 and the third light flux of λ3, 2) When a special diffraction structure that can make the diffraction angles of the first light flux and the third light flux different is used, there is a problem that the light use efficiency is lowered. Therefore, a fourth optical disk dedicated area may be provided in the second area in addition to the first optical disk dedicated area and the second optical disk dedicated area. For example, as shown in FIG. 11, in order from the inner area including the optical axis, the fourth optical disk dedicated area CD, the first optical disk dedicated area BD, the second optical disk dedicated area HD, and the second area outside thereof. An example in which the first optical disk dedicated area BD is provided can be considered. Note that the fact that the wavelength λ3 is a substantially integer multiple of the wavelength λ1 means that the following conditional expression (10) is satisfied.
(M−0.2) · λ1 ≦ λ3 ≦ (m + 0.2) · λ1 (10)
Note that m represents an arbitrary positive integer of 2 or more.

  In order to obtain the same spot diameter as that of the CD-dedicated lens when providing the fourth optical disc-dedicated area as described above, the maximum image-side numerical aperture of the fourth optical disc-dedicated area is set to the recording and / or reproduction of the fourth optical disc. It is preferable to make it smaller than the numerical aperture that is the standard used for. Accordingly, it is preferable that the maximum effective diameter of the fourth optical disk dedicated area is smaller than 2 · f4 · NA4. Note that f4 represents the focal length of the fourth optical disk dedicated area of the objective optical element in the third light flux, and NA4 represents the image-side numerical aperture defined by the standard required for recording and / or reproduction of the fourth optical disk. For example, when the fourth optical disk is a CD, it is preferable that the maximum image-side numerical aperture of the fourth optical disk dedicated area is smaller than 0.45. More preferably, it is 0.43 or less. When the fourth optical disk is a CD, the maximum effective diameter of the fourth optical disk dedicated area is preferably smaller than 2 · fCD · 0.45, and more preferably 2 · fCD · 0.43 or less. Note that fCD represents the focal length of the CD-dedicated region of the objective optical element in the CD light flux.

  Furthermore, by providing an optical path difference providing structure in at least one of the fourth optical disk dedicated area, the first optical disk dedicated area, and the second optical disk dedicated area in the second area, the recording of the third optical disk (for example, DVD) is performed. And / or playback may be enabled. For example, as shown in FIG. 12, the fourth optical disk dedicated area CD, the first optical disk dedicated area BD, the second optical disk dedicated area HD, and the second area on the outer side in order from the inner area including the optical axis. Optical path difference providing structure DVD that enables recording and / or reproduction of the third optical disk in the fourth optical disk dedicated area CD, the inner first optical disk dedicated area BD, and the second optical disk dedicated area HD as the first optical disk dedicated area BD An example of providing the can be considered.

When the objective optical element of the present invention is applied to a hybrid optical disk in which recording layers of a plurality of types of optical disks including the first optical disk and the second optical disk are laminated on one optical disk, the objective optical element of the first optical disk a working distance (WD _1), the working distance (WD ₂₎ of the objective optical element in the second optical disk are different, it is preferable. When the first optical disc is BD and the second optical disc is HD, that is, when a hybrid optical disc in which BD and HD are laminated is used, it is more preferable to set the value of the difference between these working distances to (WD1− WD2), preferably 50 μm or more and 250 μm or less. More preferably, it is 100 μm or more and 250 μm or less. An example in which recording layers of a plurality of types of optical disks are stacked on a single optical disk is a hybrid disk in which recording layers of BD / HD / DVDs are stacked on one side as disclosed in JP-A-2007-42254. Can be mentioned. Also, WD1 and WD2 are preferably different from the viewpoint of improving the off-axis characteristics of the objective optical element.

  As shown in FIG. 22, the single objective optical element OL1 of the present invention for the first optical disc and the second optical disc and the objective optical for another optical disc (for example, the third optical disc and / or the fourth optical disc). A lens unit in which the element OL2 is integrally formed may be used. As shown in FIG. 22, the integrally formed lens unit is a case where the first objective optical element OL1 and the second objective optical element OL2 are fused (for example, the first objective optical element). And a second objective optical element as shown in FIG. 23 or FIG. 24, as well as a lens unit having a second objective optical element by integral molding by injection molding). The optical elements may be integrated by molding separately, and then fitting, adhering or engaging with each other.

  FIG. 23 shows an example of a lens unit in which the first objective optical element and the second objective optical element are engaged and integrally formed. The second objective optical element OL2 made of plastic forms an opening HOL having a stepped portion ST in the rectangular plate-shaped flange portion FL2, and the flange portion FL1 is held by the stepped portion ST in the opening HOL. In this way, the first objective optical element OL1 made of glass or plastic of the present invention is assembled from the optical axis direction and integrated by adhesion or the like, and the first objective optical element OL1 and the second objective optical element are integrated. A lens unit OE in which OL2 is arranged in parallel is formed.

  FIG. 24 shows another example of a lens unit in which a first objective optical element and a second objective optical element are engaged and integrally formed. The second objective optical element OL2 made of plastic forms a cutout CT having a stepped portion ST in the rectangular plate-like flange portion FL2, and the flanged portion FL1 is held by the stepped portion ST2 in the cutout CT2. In this way, the first objective optical element OL1 made of glass or plastic of the present invention is assembled from the direction orthogonal to the optical axis and integrated by adhesion or the like, and the first objective optical element OL1 and the second objective optical are integrated. A lens unit OE in which the elements OL2 are arranged in parallel is formed.

  As shown in FIG. 25, the flange portion FL1 of the first objective optical element OL1 may be supported on the upper surface of the flange portion FL2 without forming a step in the opening HOL or the notch CT2. Alternatively, although not shown, the first objective optical element OL1 made of glass or plastic and the second objective optical element OL2 made of plastic may be integrated by assembling to a holding member which is a separate member. good. In any case, it is preferable that the holding member has an opening, and the objective lens unit is fitted therein.

The first light beam may be incident on the objective optical element as parallel light, or may be incident on the objective optical element as divergent light or convergent light. Preferably, the magnification m1 of the first light beam incident on the objective optical element is expressed by the following formula (11),
−0.02 <m1 <0.02 (11)
Is to satisfy.

On the other hand, when the first light flux is incident on the objective optical element as diverging light, the magnification m1 of the first light flux incident on the objective optical element is expressed by the following equation (12):
-0.10 <m1 <0.00 (12)
It is preferable to satisfy.

In order to make the sine condition compatible in both recording and / or reproduction of the first optical disk and recording and / or reproduction of the second optical disk, it is preferable to satisfy the following conditional expression (13).
m11 <m12 (13)
M11 represents the magnification of the first light beam incident on the objective optical element during recording and / or reproduction of the first optical disk, and m12 represents the first magnification during recording and / or reproduction of the second optical disk. The magnification of the incident light beam to the objective optical element is shown.

  For example, when recording and / or reproducing the first optical disk, the first light beam is incident on the objective optical element as infinite parallel light, and when recording and / or reproducing the second optical disk, the first light beam is finitely focused on the objective optical element. As an example, a preferred embodiment is a mode in which the light is incident.

  When the light beam is incident on the objective optical element at an oblique incidence of 0.5 ° during recording and / or reproduction of the second optical disc, if the wavefront aberration is 25 mλ rms or more, the divergent light or convergent light is used as the objective. When entering the optical element, it becomes easy to make a shadow, and it is easy to adversely affect the performance of the focused spot. Therefore, it is preferable to satisfy m11 = m12 = 0.

  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 for guiding toward the head, a spindle motor for rotating 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, with a simple and low-cost configuration, without using a complicated mechanism for BD and HD, it is compatible with one objective optical element of BD and HD that uses the same light beam at low cost. In addition, it is possible to provide an optical pickup device and an objective optical element with high light utilization efficiency.

It is sectional drawing of an example of the objective optical element OE which concerns on this invention. It is a figure which shows schematically the structure of the optical pick-up apparatus which concerns on this invention. FIG. 5A is an aberration diagram when an objective optical element optimized for BD is used. It is an aberration diagram (a)-(b) at the time of using an example of the objective optical element which concerns on this invention. FIG. 6 is aberration diagrams (a) to (b) when another example of the objective optical element according to the present invention is used. FIG. 6 is aberration diagrams (a) to (b) when another example of the objective optical element according to the present invention is used. FIG. 6 is aberration diagrams (a) to (b) when another example of the objective optical element according to the present invention is used. FIG. 6 is aberration diagrams (a) to (b) when another example of the objective optical element according to the present invention is used. It is sectional drawing of an example of the objective optical element which concerns on this invention. It is sectional drawing of an example of the objective optical element which concerns on this invention. It is the schematic at the time of seeing an example of the objective optical element which concerns on this invention from an optical axis direction. It is the schematic at the time of seeing an example of the objective optical element which concerns on this invention from an optical axis direction. It is sectional drawing of an example of the objective optical element which concerns on this invention. It is a part of sectional drawing of an example of the objective optical element which concerns on this invention. It is sectional drawing of an example of the objective optical element which concerns on this invention. It is sectional drawing of an example of the objective optical element which concerns on this invention. It is sectional drawing of an example of the objective optical element which concerns on this invention. It is sectional drawing of an example of the objective optical element which concerns on this invention. It is a graph which shows the relationship between the value of a side lobe and the number of area divisions. It is sectional drawing of an example of the objective optical element which concerns on this invention. It is sectional drawing of an example of the objective optical element which concerns on this invention. It is sectional drawing of an example of the lens unit which concerns on this invention. It is a schematic perspective view of an example of the lens unit which concerns on this invention. It is a schematic perspective view of an example of the lens unit which concerns on this invention. It is a part of sectional drawing of an example of the lens unit which concerns on this invention.

Explanation of symbols

A1 1st area A2 2nd area L1 1st optical element L2 2nd optical element BA BD exclusive area HA HD exclusive area OA Optical axis CS Correction surface HE Frame body OE Objective optical element S1 1st optical surface S2 2nd optical surface PU1 Optical pickup device LD Blue-violet semiconductor laser AC Biaxial actuator PBS Polarizing prism CL Collimating lens PL1 Protection substrate PL2 Protection substrate RL1 Information recording surface RL2 Information recording surface QWP λ / 4 wavelength plate

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 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 present invention is not limited to the present embodiment.

  The optical pickup device PU1 includes an objective optical element OE, a λ / 4 wavelength plate QWP, a collimator lens CL, a polarizing prism PBS, 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. In this drawing, an example having the first optical element and the second optical element is shown as the objective optical element OE, but instead of this objective optical element, a single objective optical as shown in FIG. An element may be used.

  The objective optical element OE is an optical element having the flat plate-like first optical element L1 which is the correction element shown in FIG. 1 and the second optical element L2 of the aspherical lens.

  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 polarizing prism PBS, converted into a parallel light beam by the collimator lens CL, and then linearly generated by the quarter-wave plate QWP. Polarized light is converted into circularly polarized light, its beam diameter is regulated by a diaphragm (not shown), and a spot formed on the information recording surface RL1 of the BD via the protective substrate PL1 having a thickness of 0.0875 mm by the objective optical element OE. Become.

  At this time, the light beam that has passed through the BD dedicated area BA and the second area A2 of the first area A1 of the first optical element L1 is condensed on the information recording surface of the BD by the second optical element to form a spot, The light beam that has passed through the HD exclusive area HA of the first area A1 of the first optical element L1 does not form a condensed spot on the information recording surface of the BD. If a single objective optical element as shown in FIG. 9 is used as the objective optical element, the light beam that has passed through the first area BD dedicated area BA1 and the second area BA2 is projected onto the information recording surface of the BD. A light beam that is condensed to form a spot and passes through the HD dedicated area HA does not form a condensed spot on the information recording surface of the BD.

  The reflected light beam modulated by the information pits on the information recording surface RL1 passes through the objective optical element OE and the aperture again, and then is converted from circularly polarized light to linearly polarized light by the quarter wave plate QWP, and converged by the collimating lens CL. After being reflected by the polarizing prism PBS, the light is converged on the light receiving surface of the light receiving element PD by the sensor lens SL. Then, 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 objective optical element OE by the biaxial actuator AC.

  Next, a case where HD recording / reproduction is performed 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 polarizing prism PBS, converted into a parallel light beam by the collimator lens CL, and then linearly generated by the quarter-wave plate QWP. Polarized light is converted into circularly polarized light, its beam diameter is regulated by a diaphragm (not shown), and a spot formed on the information recording surface RL2 of the HD via the protective substrate PL2 having a thickness of 0.6 mm by the objective optical element OE Become.

  At this time, the first light beam that has passed through the HD dedicated area HA of the first area A1 of the first optical element L1 is condensed on the information recording surface of the HD by the second optical element to form a spot. The first light flux that has passed through the BD dedicated area BA and the second area of the first area A1 of the element does not form a condensed spot on the HD information recording surface. When a single objective optical element as shown in FIG. 9 is used as the objective optical element, the light beam that has passed through the HD dedicated area HA is condensed on the HD information recording surface to form a spot. A light beam that has passed through one area of the BD-dedicated area BA1 and the second area BA2 does not form a condensed spot on the HD information recording surface.

The reflected light beam modulated by the information pits on the information recording surface RL2 is transmitted again through the objective optical element OE and the aperture, and then converted from circularly polarized light to linearly polarized light by the quarter wave plate QWP, and converged by the collimating lens CL. After being reflected by the polarizing prism PBS, the light is converged on the light receiving surface of the light receiving element PD by the sensor lens SL. Then, by using the output signal of the light receiving element PD, the objective optical element OE is focused or tracked by the biaxial actuator AC, whereby the information recorded on the HD can be read.
(Example)
Next, examples that can be used in the above-described embodiment will be described. Examples 1 to 5 are single-lens objective optical elements. Among them, Examples 1 to 3 are examples in which the working distance of BD is equal to the working distance of HD, and Example 4 is an example in which the working distance of BD is different from the working distance of HD. Among Examples 1 to 4, Example 1 is an example of a four-wheel zone, Example 2 is an example of a five-wheel zone, Example 3 is an example of a six-wheel zone, and Example 4 is It is an example of a three-ring zone. Examples 5 and 6 are examples having a first optical element on the light source side and a second optical element on the optical disk side. In the following embodiments, the first optical disc is BD and the second optical disc is HD.

In the following tables, ri is the radius of curvature, di is the position in the optical axis direction from the i-th surface to the (i + 1) -th surface, and ni is 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 expressed using E (for example, 2.5 × E−3). In addition, 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 mathematical formulas obtained by substituting the coefficients 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 conical coefficient, Ai is an aspherical coefficient, h is a height from the optical axis, and r is a paraxial radius of curvature. It is.
Example 1
In the first embodiment, the center area including the optical axis is the second optical disk dedicated area, and from there toward the outside in the optical axis orthogonal direction, the first optical disk dedicated area, the second optical disk dedicated area, This is a four-band structure in which a first optical disc dedicated area, which is two areas, is provided. All the areas have an aspheric shape, the two dedicated areas for the first optical disc have the same aspheric shape, and the two dedicated areas for the second optical disc also have the same aspheric shape, The first optical disk dedicated area and the second optical disk dedicated area have different aspherical shapes. FIG. 15 shows the lens shape and the light collection state for each of BD and HD. FIG. 15A shows a condensing state for BD, and FIG. 15B shows a condensing state for HD. In this example, the level difference in the optical axis direction is also suppressed.

  Tables 1 to 3 show lens data of Example 1.

(Example 2)
In Example 2, the most central area including the optical axis is the first optical disk dedicated area, and from there toward the outside in the direction orthogonal to the optical axis, the second optical disk dedicated area, the first optical disk dedicated area, and the second optical disk in order. This is a five-band structure in which a dedicated area and a first optical disk dedicated area as a second area are provided. All the regions have an aspheric shape, the three first optical disc dedicated regions have the same aspheric shape, and the two second optical disc dedicated regions also have the same aspheric shape, The first optical disk dedicated area and the second optical disk dedicated area have different aspherical shapes. FIG. 16 shows the lens shape and the light collection state for each of BD and HD. FIG. 16A shows a light collection state for BD, and FIG. 16B shows a light collection state for HD. Also in this example, the level difference in the optical axis direction is suppressed.

  Tables 4 to 6 show lens data of Example 2.

(Example 3)
In the third embodiment, the center area including the optical axis is the second optical disk dedicated area, and from there toward the outside in the direction orthogonal to the optical axis, the first optical disk dedicated area, the second optical disk dedicated area, and the first optical disk in order. This is a six-band structure in which a dedicated area, a second optical disk dedicated area, and a first optical disk dedicated area as the second area are provided. All the regions have an aspheric shape, the three first optical disc dedicated regions have the same aspheric shape, and the three second optical disc dedicated regions also have the same aspheric shape, The first optical disk dedicated area and the second optical disk dedicated area have different aspherical shapes. FIG. 17 shows the lens shape and the light collection state for each of BD and HD. FIG. 17A shows a condensing state for BD, and FIG. 17B shows a condensing state for HD. In this example as well, the level difference in the optical axis direction is suppressed.

  Tables 7 to 9 show lens data of Example 3.

Example 4
In the fourth embodiment, the most central area including the optical axis is the first optical disk dedicated area, and from there toward the outside in the direction orthogonal to the optical axis, the second optical disk dedicated area and the second area are sequentially dedicated to the first optical disk. It is a structure of a three-ring zone provided with a region. All the areas have an aspheric shape, and the two first optical disc dedicated areas have the same aspheric shape. In addition, the working distance in BD is different from the working distance in HD. FIG. 18 shows the lens shape and the light collection state for each of BD and HD. FIG. 18A shows a condensing state for BD, and FIG. 18B shows a condensing state for HD.

  Tables 10 to 12 show lens data of Example 4.

In Example 4 in which the working distance when using BD is different from the working distance when using HD, a simulation was performed at an incident angle of 0.5 degree of light flux when using HD, and the value of wavefront aberration was 0.0908 λrms. ing. Therefore, it can be seen that the wavefront aberration value of the obliquely incident light beam becomes smaller and the off-axis characteristics become better when the working distance when using BD is different from the working distance when using HD.

  FIG. 19 is a graph showing the relationship between the number of zones and the side lobe values in Examples 1 to 3. Table 13 below lists the number of zones and side lobe values. As can be seen from FIG. 19 and Table 13, the value of the side lobe decreases as the number of ring zones increases, and the case where the number of ring zones is 5 or 6 is particularly preferable. Increasing the number of rings more than this has little effect on the side lobe value, but increases the number of rings, making manufacturing difficult, so from the viewpoint of balance between ease of manufacturing and good side lobe Shows that the number of ring zones is preferably 5 or 6.

  Table 14 shows a summary of spec data such as focal length, spot diameter, Strehl ratio, and side lobe in Examples 1 to 4.

(Example 5)
The fifth embodiment includes a first optical element that is a correction element and a second optical element that is an aspheric lens. In the correction element, the most central area including the optical axis is a second optical disk dedicated area (inner second optical disk area), and from there toward the outside in the direction orthogonal to the optical axis, the first optical disk dedicated area (inner first optical disk area). An optical disk area), a second optical disk dedicated area (outer second optical disk area), and a second optical disk dedicated area (outer first optical disk area). The first optical disk dedicated area has an aspherical afocal design for both the inner first optical disk area and the outer first optical disk area, and the second optical disk dedicated area has the inner second optical disk area and the outer second optical disk. Both regions have an aspheric shape. Further, the optical surface on the light source side is provided with an inclined surface between the inner first optical disc region and the outer second optical disc region. On the other hand, on the optical surface on the optical disc side, an inclined surface is provided between the inner second optical disc region and the inner first optical disc region.

  Tables 15 to 16 show lens data of Example 5. On the optical surface on the light source side of the correction element, the 2-1 surface is the inner second optical disc region, the 2-2 surface is the inner first optical disc region, the 2-3 surface is the inclined surface, and the 4-2 surface is the outer second optical disc region. , 2-5 is the outer first optical disc area. On the other hand, on the optical surface of the correction element on the optical disc side, the 3-1 surface is the inner second optical disc region, the 2-2 surface is the inclined surface, the 3-3 surface is the inner first optical disc region, and the 3-4 surface is the outer second surface. The optical disc area, surface 3-5, is the outer first optical disc area.

(Example 6)
The sixth embodiment includes a first optical element that is a correction element and a second optical element that is an aspheric lens. In the correction element, the most central area including the optical axis is a second optical disk dedicated area (inner second optical disk area), and from there toward the outside in the direction orthogonal to the optical axis, the first optical disk dedicated area (inner first optical disk area). An optical disk area), a second optical disk dedicated area (outer second optical disk area), and a second optical disk dedicated area (outer second optical disk area). The first optical disk dedicated area has an aspherical afocal design for both the inner first optical disk area and the outer first optical disk area, and the second optical disk dedicated area has the inner second optical disk area and the outer second optical disk. Both regions have an aspheric shape. Further, the optical surface on the light source side is provided with an inclined surface between the inner first optical disc region and the outer second optical disc region. On the other hand, on the optical surface on the optical disc side, an inclined surface is provided between the inner second optical disc region and the inner first optical disc region. Schematic diagrams of this objective optical element are shown in FIGS. FIG. 20 is a diagram showing a condensing state when BD is used as the first optical disc, and FIG. 21 is a diagram showing a condensing state when HD is used as the second optical disc.

  Tables 17 to 18 show lens data of Example 6. On the optical surface on the light source side of the correction element, the 2-1 surface is the inner second optical disc region, the 2-2 surface is the inner first optical disc region, the 2-3 surface is the inclined surface, and the 4-2 surface is the outer second optical disc region. , 2-5 is the outer first optical disc area. On the other hand, on the optical surface of the correction element on the optical disc side, the 3-1 surface is the inner second optical disc region, the 2-2 surface is the inclined surface, the 3-3 surface is the inner first optical disc region, and the 3-4 surface is the outer second surface. The optical disc area, surface 3-5, is the outer first optical disc area.

Table 19 summarizes data such as focal lengths of the fifth and sixth embodiments.

Claims (30)

A condensing optical system having a first light source that emits a first light flux having a wavelength of λ1 (380 nm <λ1 <450 nm) and an objective optical element for condensing the first light flux on an information recording surface of an optical disc; ,
Information is recorded and / or reproduced by condensing the first light flux on an information recording surface of a first optical disc having a protective layer having a thickness t1, and the first light flux has a thickness t2 (t1 <t2). In an optical pickup device for recording and / or reproducing information by focusing on the information recording surface of a second optical disc having a protective layer of
The objective optical element is divided into at least a first region including the optical axis and a second region around the first region,
The first light flux that has passed through the first area is used for recording and / or reproduction of the first optical disk and the second optical disk, and the first light flux that has passed through the second area is Used for recording and / or playback,
The condensing optical system has a correction surface in a region corresponding to the first region of the objective optical element,
The optical pickup device, wherein the correction surface is divided into a plurality of concentric regions centered on the optical axis by a step. In the plurality of regions of the correction surface,
The passed first light beam is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disk, and the passed first light beam is collected on the information recording surface of the second optical disk. A first optical disc dedicated area that does not light;
The passed first light beam is not condensed on the information recording surface of the first optical disc, and the passed first light beam can record and / or reproduce information on the information recording surface of the second optical disc. 2. The optical pickup device according to claim 1, further comprising a second optical disc dedicated area for focusing. The first optical disc is a BD and the second optical disc is an HD;
3. The optical pickup device according to claim 2, wherein the area closest to the center including the optical axis of the objective optical element is the area dedicated to the second optical disk.   In the plurality of regions of the correction surface, the passed first light beam is condensed on the information recording surface of the first optical disc, and the passed first light beam is also reflected on the information recording surface of the second optical disc. The optical pickup device according to any one of claims 1 to 3, wherein a condensing region is included. The objective optical element is composed of a single lens,
The optical pickup device according to any one of claims 1 to 4, wherein the objective optical element has the correction surface. The sum Δ of the coding lengths of all the steps provided on the optical surface of the objective optical element in the optical axis direction (the sign is the optical path in the region closer to the optical axis of each step than the region on the far side) The optical pickup device according to any one of claims 1 to 5, characterized in that:
0.1mm ≦ Δ ≦ 1.0mm The objective optical element has a first optical element and a second optical element,
The optical pickup device according to any one of claims 1 to 4, wherein the first optical element has the correction surface.   8. The optical pickup device according to claim 7, wherein the first optical element is a flat element, and the second optical element is an aspherical lens. The step amount of the step on the correction surface is a step amount that gives an optical path difference of a times the wavelength λ1 to the first light flux. An optical pickup device according to claim 1.
However, a is a positive integer other than 0. The step amount of the step on the correction surface is a step amount that gives an optical path difference of b times the wavelength λ1 to the first light flux. An optical pickup device according to claim 1.
However, b is 0 or a positive integer + x, and x is 0.4 or more and 0.6 or less. The step amount of the step on the correction surface is a step amount that gives an optical path difference c times the wavelength λ1 to the first light flux. An optical pickup device according to claim 1.
However, c is 0 or a positive integer + y, and y is greater than 0, less than 0.4, greater than 0.6, and less than 1.   12. The objective optical element according to any one of claims 1 to 11, wherein the objective optical element has a ring zone of 3 or more and 10 or less in combination of the first region and the second region. Optical pickup device.   The optical pickup device according to claim 12, wherein the objective optical element has a ring zone of 5 or more and 10 or less in total of the first region and the second region.   The working distance of the objective optical element during recording and / or reproduction of the first optical disc is different from the working distance of the objective optical element during recording and / or reproduction of the second optical disc. The optical pickup device according to any one of ranges 1 to 13. The working distance WD1 of the objective optical element at the time of recording and / or reproduction of the first optical disc and the working distance WD2 of the objective optical element at the time of recording and / or reproduction of the second optical disc satisfy the following conditional expressions: The optical pickup device according to claim 14, wherein the optical pickup device satisfies the condition.
-0.36mm ≤ WD1-WD2 ≤ 0.17mm A condensing optical system having a first light source that emits a first light flux having a wavelength of λ1 (380 nm <λ1 <450 nm) and an objective optical element for condensing the first light flux on an information recording surface of an optical disc; ,
Information is recorded and / or reproduced by condensing the first light flux on an information recording surface of a first optical disc having a protective layer having a thickness t1, and the first light flux has a thickness t2 (t1 <t2). In an objective optical element used for an optical pickup device for recording and / or reproducing information by focusing on an information recording surface of a second optical disc having a protective layer of
The objective optical element is divided into at least a first region including the optical axis and a second region around the first region,
The first light flux that has passed through the first area is used for recording and / or reproduction of the first optical disk and the second optical disk, and the first light flux that has passed through the second area is Used for recording and / or playback,
The objective optical element has a correction surface in a region corresponding to the first region of the objective optical element,
The objective optical element, wherein the correction surface is divided into a plurality of concentric regions centered on the optical axis by a step. In the plurality of regions of the correction surface,
The passed first light beam is condensed so that information can be recorded and / or reproduced on the information recording surface of the first optical disk, and the passed first light beam is collected on the information recording surface of the second optical disk. A first optical disc dedicated area that does not light;
The passed first light beam is not condensed on the information recording surface of the first optical disc, and the passed first light beam can record and / or reproduce information on the information recording surface of the second optical disc. 17. The objective optical element according to claim 16, further comprising a second optical disc dedicated area for focusing. The first optical disc is a BD and the second optical disc is an HD;
18. The objective optical element according to claim 17, wherein the area closest to the center including the optical axis of the objective optical element is the area dedicated to the second optical disc.   In the plurality of regions of the correction surface, the passed first light beam is condensed on the information recording surface of the first optical disc, and the passed first light beam is also reflected on the information recording surface of the second optical disc. The objective optical element according to any one of claims 16 to 18, wherein a condensing region is included. The objective optical element is composed of a single lens,
The objective optical element according to any one of claims 16 to 19, wherein the objective optical element has the correction surface. The sum Δ of the coding lengths of all the steps provided on the optical surface of the objective optical element in the optical axis direction (the sign is the optical path in the region closer to the optical axis of each step than the region on the far side) 21. The objective optical element according to any one of claims 16 to 20, characterized in that:
0.1mm ≦ Δ ≦ 1.0mm The objective optical element has a first optical element and a second optical element,
The objective optical element according to any one of claims 16 to 19, wherein the first optical element has the correction surface.   The objective optical element according to claim 22, wherein the first optical element is a flat element, and the second optical element is an aspheric lens. 24. The step according to any one of claims 16 to 23, wherein the step amount of the step on the correction surface is a step amount that gives an optical path difference a times the wavelength λ1 to the first light flux. An objective optical element according to any one of the above.
However, a is a positive integer other than 0. 24. The step according to any one of claims 16 to 23, wherein the step amount of the step on the correction surface is a step amount that gives an optical path difference of b times the wavelength λ1 to the first light flux. An objective optical element according to any one of the above.
However, b is 0 or a positive integer + x, and x is 0.4 or more and 0.6 or less. 24. The step according to any one of claims 16 to 23, wherein the step amount of the step on the correction surface is a step amount that gives an optical path difference c times the wavelength λ1 to the first light flux. An objective optical element according to any one of the above.
However, c is 0 or a positive integer + y, and y is greater than 0, less than 0.4, greater than 0.6, and less than 1.   27. The objective optical element according to any one of claims 16 to 26, wherein the objective optical element has a ring zone of 3 or more and 10 or less in total of the first region and the second region. Objective optical element.   28. The objective optical element according to claim 27, wherein the objective optical element has a ring zone of 5 or more and 10 or less in total of the first region and the second region.   The working distance of the objective optical element during recording and / or reproduction of the first optical disc is different from the working distance of the objective optical element during recording and / or reproduction of the second optical disc. The objective optical element according to any one of ranges 16 to 28. The working distance WD1 of the objective optical element at the time of recording and / or reproduction of the first optical disc and the working distance WD2 of the objective optical element at the time of recording and / or reproduction of the second optical disc satisfy the following conditional expressions: 30. The objective optical element according to claim 29, wherein the objective optical element is satisfied.
-0.36mm ≤ WD1-WD2 ≤ 0.17mm