JPH10293937A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record and reproduce optical disks different in transparent substrate thickness by one convergent optical system by changing a position of a light source so that a distance (WD) from a final diffractive surface to the transparent substrate of a first optical information recording medium becomes equal to the distance from the final diffractive surface to the translucent substrate of a second optical information recording medium when the second optical information recording medium is recorded/reproduced. SOLUTION: A first semiconductor laser 11 and a second semiconductor laser 12 are arranged so that the WD when a first optical disk is recorded/ reproduced becomes nearly equal to the WD when a second optical disk is recorded/reproduced. Thus, the necessity that an objective lens 16 is moved to a position different from the time when the first optical disk is recorded/ reproduced when the second optical disk is recorded/reproduced is eliminated. Further, a divergent degree revised by a divergent degree revision optical element 13 is constituted so that the divergent degree for luminous flux emitted from the second semiconductor laser 12 is made smaller than the divergent degree for the luminous flux emitted from the first semiconductor laser 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light converging optical system for condensing a light beam emitted from a light source onto an information recording surface via a transparent substrate of an optical information recording medium, and recording or recording information on the information recording surface. The present invention relates to an optical pickup device for reproducing (recording / reproducing) information on a recording surface, in particular, as an optical information recording medium, a first optical information recording medium having a transparent substrate having a thickness of t1 and a transparent substrate having a thickness of t2 (where , T2 ≠ t1), and the recording / reproducing of the first optical information recording medium has a wavelength λ.
The present invention relates to an optical pickup device using a first light source and a second light source having a wavelength λ2 (λ2 ≠ λ1) for recording / reproducing on / from a second optical information recording medium.

[0002]

2. Description of the Related Art Various optical information recording media (hereinafter, also referred to as optical discs) have been put into practical use as high-density, large-capacity recording media. Among them, an optical disk (hereinafter, also referred to as a CD) called a compact disk uses a condensing optical system having a numerical aperture of about 0.45 to 0.5 when the light source wavelength is 780 (nm) to 830 (nm). The recorded music signal is reproduced by the used optical pickup device. At this time, the light beam emitted from the light source is narrowed down to a spot having almost diffraction-limited performance on the information recording surface through a transparent substrate having a thickness of t2 = 1.2 (mm) made of polycarbonate by a condensing optical system. . Note that C
On the side opposite to the transparent substrate of 1.2 (mm) with respect to the information recording surface of D, a protective layer having a role of protecting an extremely thin information recording surface whose thickness can be substantially ignored compared to the transparent substrate is provided. Is provided.

In recent years, various optical information recording media having different sizes (diameters), substrate thicknesses, information recording densities, and recording / reproducing principles have been put into practical use one after another. Among them, an optical disk (hereinafter, also referred to as a DVD) called a digital video disk has a storage capacity that is about seven times as large as a CD, even in the case of a single-sided type.

Therefore, for recording / reproducing DVDs, a light-condensing optical system having a light source wavelength of 600 (nm) to 700 (nm) and a numerical aperture of about 0.55 to 0.7 is used. An optical pickup device is required. In the case of DVD, the thickness of the transparent substrate is t1 = 0.6 (mm).
DVDs include a single-sided type and a double-sided type. In both cases, a (transparent) substrate having a thickness of 0.6 (mm) is attached to both sides of the information recording surface.

[0005] CDs have already been produced and sold in large quantities, and it is desired that future optical pickup devices for recording / reproducing multimedia can reproduce not only DVDs but also CDs.

However, when considering an optical pickup device that can reproduce not only DVDs but also CDs,
A large spherical aberration occurs between the DVD and the CD because the thickness of the transparent substrate is different. For this reason, when trying to reproduce DVDs and CDs, special measures are required, and several methods have been proposed.

One is to propose an optical pickup device which prepares two types of light condensing optical systems, one for DVD and one for CD, and uses them by switching according to the optical disk to be reproduced.
However, this method requires two types of condensing optical systems and requires a mechanism for switching between them, which is problematic in terms of cost and accuracy.

[0008] Therefore, one condensing optical system, DVD and C
A proposal to reproduce D is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-55.
As described in JP-A-363-363, by optimizing the size of the two light sources and the aperture, the image spots of both DVD and CD have a wavefront aberration of 0.01λ (rm).
s) There has been proposed an optical pickup device arranged as follows.

[0009]

However, in the optical pickup device described in Japanese Patent Application Laid-Open No. 8-55363, the wavefront aberration of the imaging spot of both DVD and CD is simply 0.01λ (rms) or less. The light source is arranged in such a manner that the distance from the final refraction surface, which is the refraction surface closest to the optical information recording medium of the light-collecting optical system, to the transparent substrate of the optical disk (hereinafter, also referred to as working distance, WD). Not considered. If the WD is different between the case of DVD and the case of CD, when reproducing at least one of the optical disks, the drive current is always supplied to the actuator for moving the objective lens of the focusing optical system for focusing. It is necessary to keep it flowing. For this reason, there is a problem that power consumption must be increased. Also,
In order to earn the necessary moving distance for focusing,
There is a problem that the actuator becomes larger than a case where the actuator is dedicated to DVD or CD.

It is an object of the present invention to provide an optical pickup device which enables recording / reproducing of an optical disk having a different transparent substrate thickness with one condensing optical system, and which is compact and consumes less power.

[0011]

The above object can be attained by the following constitution.

(1) A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system including a plurality of refraction surfaces, and information is recorded or recorded on the information recording surface. An optical pickup device for reproducing (recording / reproducing) information on an information recording surface, wherein as the optical information recording medium, a first optical information recording medium having a transparent substrate having a thickness of t1 (mm) and a thickness of a transparent substrate are provided. Is t2 (mm) (where t2 ≠ t
In the optical pickup device using the second optical information recording medium of 1), the final refraction which is the refraction surface closest to the optical information recording medium of the condensing optical system when recording / reproducing the first optical information recording medium. The distance from the surface to the transparent substrate of the first optical information recording medium and the distance from the final refraction surface to the transparent substrate of the second optical information recording medium when recording / reproducing the second optical information recording medium are substantially equal. An optical pickup device wherein the position of the light source is changed so as to be equal.

(2) A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system comprising a plurality of refraction surfaces, and information is recorded or recorded on the information recording surface. An optical pickup device for reproducing (recording / reproducing) information on an information recording surface, wherein as the optical information recording medium, a first optical information recording medium having a transparent substrate having a thickness of t1 (mm) and a thickness of a transparent substrate are provided. Is t2 (mm) (where t2 ≠ t
1) In the optical pickup device using the second optical information recording medium, a first light source that emits a light beam of wavelength λ1 for recording / reproducing the first optical information recording medium and a second optical information are used as the light sources. Wavelength λ for recording / reproducing a recording medium
A second light source that emits a second light beam, and a distance from a final refraction surface, which is a refraction surface closest to the optical information recording medium of the condensing optical system, to a transparent substrate of the first optical information recording medium; An optical pickup device, wherein the first light source and the second light source are arranged such that a distance from the final refraction surface to a transparent substrate of the second optical information recording medium is substantially equal.

(3) The light-converging optical system has a divergence changing optical element fixed to the optical pickup device for changing a divergence of a light beam emitted from the light source, and a divergence changing optical element. The optical pickup device according to (1) or (2), further comprising: an objective optical element that focuses the changed light beam on an information recording surface of the optical information recording medium.

(4) The divergence of the luminous flux emitted from the light source changed by the divergence changing means at the time of recording / reproducing of the first optical information recording medium is t2> t1,
The optical pickup device according to (3), wherein the divergence of the light beam emitted from the light source, which is changed by the divergence changing unit during recording / reproducing of the second optical information recording medium, is smaller.

(5) The light beam emitted from the light source, which is changed by the divergence changing means at the time of recording / reproducing on the first optical information recording medium, becomes parallel light. Optical pickup device.

(6) The imaging magnification of the condensing optical system with respect to the light beam emitted from the light source during recording / reproduction on the first optical information recording medium is m1, and the recording magnification / reproduction on the second optical information recording medium is performed. The imaging magnification of the light-collecting optical system with respect to the light beam emitted from the light source is m2, the focal length of the light-collecting optical system is f (mm), and the wavelength of the light source during recording / reproducing of the first optical information recording medium. Assuming that the refractive index of the transparent substrate of the first optical information recording medium is n1, and the refractive index of the transparent substrate of the second optical information recording medium with respect to the wavelength of the light source during recording / reproducing of the second optical information recording medium is n2, | m2-m1) f-t1 / n1 + t2 / n2 | <0.
The optical pickup device according to any one of (1) to (5), wherein a condition of 25 (mm) is satisfied.

(7) | (m2-m1) f-t1 / n1
The optical pickup device according to (6), wherein a condition of + t2 / n2 | <0.15 (mm) is satisfied.

(8) At least one refracting surface of the condensing optical system is divided into a plurality of divided surfaces concentrically with the optical axis. An optical pickup device according to any one of the above.

(9) At least one of the objective optical elements
The two refracting surfaces include a first division surface near the optical axis, a second division surface outside the first division surface, and a third division surface outside the second division surface, and the first optical information recording. When recording / reproducing a medium, the luminous flux emitted from the first light source mainly includes:
When recording / reproducing a second optical information recording medium using a light beam that has passed through the first division surface and the third division surface, the light beam emitted from the second light source mainly includes the first division light. The optical pickup device according to any one of (2) to (6), wherein a light beam that has passed through the surface and the second division surface is used.

(10) The objective optical element has a plurality of divided surfaces at least one surface of which is divided concentrically with the optical axis, and at the time of recording / reproducing of the first optical information recording medium, Of the light beams emitted from the light source, the light beams passing through the first division surface near the optical axis and the third division surface outside the first division surface form an image at substantially the same image forming position, and The light beam passing through the second division surface between the surface and the third division surface forms an image at an imaging position different from the imaging position of the light beam passing through the first division surface and the third division surface. The optical pickup device according to any one of (3) to (7) and (9), wherein:

(11) The objective optical element has a plurality of divided surfaces at least one surface of which is divided concentrically with the optical axis, and at the time of recording / reproducing of the second optical information recording medium, Of the luminous flux emitted from the light source, of the luminous flux passing through the first division surface near the optical axis, the position where the light beam passing near the optical axis forms an image, and the first division surface in the direction orthogonal to the optical axis. (3) to (7), wherein a light beam passing through a second division surface outside the first division surface is imaged between a position where a light beam passing through the end portion forms an image.
(9) The optical pickup device according to any one of (10) and (10).

(12) When the required numerical aperture on the optical information recording medium side of the objective optical element required for recording / reproducing the second optical information recording medium is NA2, the objective optical element has a required numerical aperture. (3)-(7), (9)-(11), wherein at least two aperture positions near the numerical aperture corresponding to NA2, the spherical aberration is changed discontinuously. Optical pickup device.

(13) When the smallest numerical aperture among the at least two aperture positions is NAL and the largest numerical aperture is NAH, the objective optical element has a numerical aperture NA.
The optical pickup device according to (12), wherein L and numerical aperture NAH are changed discontinuously in opposite directions.

(14) At the time of recording / reproducing of the second optical information recording medium, a light beam emitted from the light source passes through the light condensing optical system and is condensed on the information recording surface of the second optical information recording medium. The objective optical element is characterized in that the spherical aberration between the numerical apertures NAL and NAH has the same sign as the spherical aberration of the other numerical apertures (13).
An optical pickup device according to item 1.

(15) When the required numerical aperture on the optical information recording medium side of the objective optical element required for recording / reproducing the second optical information recording medium is NA2, the objective optical element has a required numerical aperture. Any one of (3) to (7) and (9) to (11), wherein a phase difference is provided between at least two aperture positions near a numerical aperture corresponding to NA2.
An optical pickup device according to any one of the above.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments, an optical pickup device 10 described below has a plurality of optical information recording media (hereinafter, also referred to as optical disks) 20 having different thicknesses of transparent substrates 21. Of the optical disc 20
Reproduction (recording information on the information recording surface 22 of the optical disc 20 or reproducing information on the information recording surface 22 is called recording / reproduction.
Playback). As the plurality of optical discs 20, a first optical disc having a transparent substrate thickness t1 and a second optical disc having a thickness t2 different from the transparent substrate thickness t1 of the first optical disc will be described.
Further, the necessary numerical aperture on the optical disk side of a condensing optical system (described later) required for recording / reproducing the first optical disk is set to N.
A1, and the required numerical aperture on the optical disk side of the condensing optical system required for recording / reproducing the second optical disk is NA2 (in the following description, the first optical disk has a higher density of information recording than the second optical disk. Since it is a medium, NA1> NA
2).

In the following description, DVD (including DVD)
-RAM) refers to the first optical disc, in which case the thickness t1 of the transparent substrate is 0.6 mm (DVDs are of a single-sided type and a double-sided type, both of which have thicknesses on both sides of the information recording surface). The thickness of the DVD itself is 1.2 mm because the transparent substrate of the thickness t1 is stuck, and the CD (including CD-R) refers to the second optical disc. In this case, t2 = 1.2 mm ( That is, t1 <t2).

(First Embodiment) A first embodiment will be described. FIG. 1 is a schematic configuration diagram of the optical pickup device 10. In FIG. 1, a DVD is shown as a first optical disk above the optical axis and a CD as a second optical disk below. In the optical pickup device 10, the optical disk 20 has a surface opposite to the information recording surface 22 of the transparent substrate 21 (a surface close to the objective lens 16).
Is placed on a tray (not shown) with reference to.

In the optical pickup device 10 of the present embodiment, the first semiconductor laser 11 as the first light source is used as the light source.
(Wavelength λ = 610 nm to 670 nm) and the second semiconductor laser 12 (wavelength λ = 740 nm to 870 n) as the second light source
m). The first semiconductor laser 11 has a first
The second semiconductor laser 12 is a light source used when recording / reproducing on / from the optical disk, and the second semiconductor laser 12 is a light source used when recording / reproducing on / from the second optical disk. The arrangement of the first semiconductor laser 11 and the second semiconductor laser 12 will be described later in detail. Also, in FIG. 1, the stop 17 out of the luminous flux emitted from the first semiconductor laser 11
The outermost light beam narrowed down by a (described later) is shown by a two-dot chain line, and the outermost light beam of the light beam emitted from the second semiconductor laser 12 that is narrowed down by the stop 17 is shown by a one-dot chain line.

The combining means 19 is a means capable of combining the light beam emitted from the first semiconductor laser 11 and the light beam emitted from the second semiconductor laser 12. In the present embodiment, a dichroic prism 19 is used. The synthesizing unit 19 converts the light beam emitted from the first semiconductor laser 11 or the light beam emitted from the second semiconductor laser 12 via one condensing optical system described later.
These are means for making the optical paths on the optical axis the same (almost the same) so as to converge them on the first optical disk or the second optical disk, respectively. Further, the synthesizing means 19 converts a light beam emitted from the first semiconductor laser 11 and reflected from the information recording surface of the first optical disk and a light beam emitted from the second semiconductor laser 12 and reflected from the information recording surface of the second optical disk. These are also means for leading to first light detecting means 31 and second light detecting means 32, respectively, which will be described later. In the present embodiment, the first optical disc and the second optical disc are exclusively recorded / reproduced by the synthesizing means 19 in order to record / reproduce them exclusively.
The light beam emitted from the semiconductor laser 11 and the light beam emitted from the second semiconductor laser 12 are not actually combined.

The condensing optical system includes a light source (the first semiconductor laser 1).
This is a means for converging a light beam emitted from the first or second semiconductor laser 12) on the information recording surface 22 via the transparent substrate 21 of the optical disc 20 to form a spot. The condensing optical system includes a first semiconductor laser 11 and a second
A divergence changing optical element 13 for changing the divergence of the light beam emitted from the semiconductor laser 12, and a divergence changing optical element 13
And an objective optical element 16 for condensing the light flux whose divergence has been changed on the information recording surface 22 of the optical disc 20. More specifically, in the present embodiment, as the divergence degree changing optical element 13, a collimator lens 13 that converts a light beam emitted from the first semiconductor laser 11 into parallel light (which may be substantially parallel) and a collimator lens 13 are used. An objective lens 16 for condensing the luminous flux.

As described above, in the present embodiment, recording / reproducing of a plurality of optical discs is performed using one condensing optical system, so that the optical pickup device 10 can be realized with a low-cost and simple structure. .

In the present embodiment, a so-called infinite condensing optical system using a collimator lens 13 and an objective lens 16 as a converging optical system for the light beam emitted from the first semiconductor laser 11 is used. Although it is a system, there is no collimator lens 13 and only the objective lens 16 for directly condensing divergent light from the light source, a so-called finite condensing optical system or a divergence from the first semiconductor laser 11 as a divergence changing optical element 13 A so-called quasi-finite system including a lens that reduces the degree of divergence of light or a lens that changes (coupling) a light beam from the first semiconductor laser 11 into convergent light and an objective lens that condenses the light beam through this lens. A condensing optical system may be used.

In the focusing optical system, the light flux is set to a numerical aperture N.
An aperture 17 for limiting the numerical aperture to A1 is provided. In the present embodiment, the aperture 17 fixes the numerical aperture so as to limit the light flux emitted from the first semiconductor laser 11 to the numerical aperture corresponding to the numerical aperture NA1, does not require an extra mechanism, and reduces cost. Can be realized, but the second
At the time of recording / reproducing on the optical disk, the numerical aperture of the stop 17 may be variable so that the light beam emitted from the second semiconductor laser 12 is limited to the numerical aperture corresponding to the numerical aperture NA2.

The change means 25 and 26 change the light path of the light beam reflected from the information recording surface to a light path different from the light path of the light beam emitted from the light source (the first semiconductor laser 11 and the second semiconductor laser 12, respectively). Means. That is, the changing units 25 and 26 are provided between the changing units 25 and 26 and the optical disk, to reflect the optical path of the light beam emitted from the light source (the first semiconductor laser 11 and the second semiconductor laser 12) and from the information recording surface of the optical disk. This is means for making the optical path of the light beam the same. In the present embodiment, the changing means 25 is constituted by the polarization beam splitter 25, and changes the optical path of the light beam reflected from the information recording surface of the first optical disc without changing the optical path of the light beam emitted from the first semiconductor laser 11. It is changed so as to guide the light to the light detecting means 31. Change means 2
Reference numeral 6 denotes a parallel plane plate (half mirror) 26, and the optical path of the light beam emitted from the second semiconductor laser 12 is changed so as to be guided to the second optical disk, and the optical path of the light beam reflected from the information recording surface of the second optical disk. Is guided to the light detecting means 32 described later without being changed. In the changing means 25 and 26, the optical path to be changed may not be changed as in the present embodiment, but either one may be changed or both may be changed.

The light detecting means 31 and 32 include the changing means 25,
26, an optical disk (a first optical disk,
It is means for detecting a light beam reflected from the information recording surface of the second optical disc). By the light detecting means 31 and 32,
A change in the light amount distribution of the light beam reflected from the information recording surface is detected, and a focus error signal, a tracking error signal, and a reproduction signal (information) are read by an arithmetic circuit (not shown).

In this embodiment, since the focus error signal is obtained by using the astigmatism method, the light detecting means 3
Before astigmatism 1 and 32, the astigmatism generating elements 27 and 26 (in the present embodiment, the astigmatism generating element 27 is constituted by a cylindrical lens, and the element changing means 26 also serves as the astigmatism generating element. The focus error signal is not an astigmatism method, but a knife edge method (including Foucault method), a phase difference detection (DPD) method, a spot size detection (SSD) method, etc. It can be detected by various known methods. The tracking error signal can also be detected by various known methods such as a three-beam method, a phase difference detection (DPD) method, a push bull method, and a wobbling method.

The two-dimensional actuator 15 is means for moving the objective lens 16 and is used for focusing control for moving the objective lens 16 to a predetermined position (focusing and tracking) based on a focus error signal obtained by an arithmetic circuit. And tracking control for moving the objective lens 16 to a predetermined position (track following) based on a track error signal.

Next, such an optical pickup device 1 will be described.
0, recording / reproducing of the first optical disc will be described.

A light beam (indicated by a two-dot chain line in FIG. 1) emitted from the first semiconductor laser 11 passes through the polarizing beam splitter 25, and the optical path is bent by the dichroic prism 19 toward the condensing optical system, so that the light is collected. Light enters the optical system. The divergence of the light beam emitted from the first semiconductor laser 11 and incident on the condensing optical system is changed by the collimator lens 13, that is, the light beam is changed to a parallel light beam in the present embodiment. The luminous flux whose divergence has been changed in parallel by the collimator lens 13 is stopped down by the stop 17,
The light is focused on the information recording surface by the objective lens 16 via the transparent substrate of the first optical disc. When recording is performed on the first optical disk, recording is performed using the focused beam spot.

Then, the light beam reflected by the information recording surface is again condensed by an optical system (objective lens 16, collimator lens 1).
3), the optical path is changed by the dichroic prism 19 and the polarizing beam splitter 25, and astigmatism is given by the cylindrical lens 27.
Incident on 1. Then, when reproducing the first optical disk, a reproduction signal of the information recorded on the first optical disk is obtained using the signal output from the light detecting means 31. Further, a change in the light amount distribution due to a change in the spot shape on the light detecting means 31 is detected, and a focus error signal and a tracking error signal are obtained. The objective lens 16 is moved by the two-dimensional actuator (for focusing control) 15 based on the obtained focus error signal so that the light beam emitted from the first semiconductor laser 11 forms an image on the information recording surface of the first optical disc. Let it. The objective lens 16 is moved by the two-dimensional actuator (for tracking control) 15 based on the obtained tracking error signal so that the light beam emitted from the first semiconductor laser 11 forms an image on a predetermined track of the first optical disc. Move.

In this manner, information is recorded on the information recording surface of the first optical disk or information is reproduced on the information recording surface of the first optical disk.

Similarly, when recording / reproducing the second optical disk, the light beam (indicated by the one-dot chain line in FIG. 1) emitted from the second semiconductor laser 12 is bent by the parallel plane plate 26 so that the dichroic prism 19 The light passes through the collimator lens 13 (stopped by the stop 17) and the objective lens 16 and is focused on the information recording surface via the transparent substrate of the second optical disc. The light beam reflected by the information recording surface again passes through the condensing optical system (the objective lens 16 and the collimator lens 13) and the dichroic prism 19, is given astigmatism by the plane-parallel plate 26, and Incident on. Then, a reproduction signal, a focus error signal, and a tracking error signal are obtained by using the signal output from the light detection means 32. The objective lens 16 is moved by the two-dimensional actuator (for focusing control) 15 based on the obtained focus error signal so that the light beam emitted from the second semiconductor laser 12 forms an image on the information recording surface of the second optical disc. Let it. Also,
The objective lens 16 is moved by the two-dimensional actuator (for tracking control) 15 based on the obtained tracking error signal so that the light beam emitted from the second semiconductor laser 12 forms an image on a predetermined track of the second optical disc. .

In this manner, information is recorded on the information recording surface of the second optical disk or information is reproduced on the information recording surface of the second optical disk.

Incidentally, the optical pickup device 10
When trying to record / reproduce the second optical disk with (one condensing optical system), the thickness of the transparent substrate is different between the first optical disk and the second optical disk. When the information is placed with reference to the surface opposite to the recording surface (the surface close to the objective lens 16), the position of the information recording surface of the first optical disk is different from the position of the information recording surface of the second optical disk. Therefore, when the position of the second semiconductor laser 12 is arranged at a position equivalent to the position of the first semiconductor laser 11, the light is emitted from the second semiconductor laser 12 (although, of course, the thickness of the transparent substrate is different). In order for the light beam to converge on the information recording surface of the second optical disc via the converging optical system, a current always flows through the two-dimensional actuator (for focusing control) 15 and the objective lens 1
It is necessary to move the position 6 to a position different from the position at the time of recording / reproducing of the first optical disk.

In other words, the distance from the final refraction surface (in this embodiment, the surface of the objective lens 16 on the optical disk side), which is the refraction surface closest to the optical information recording medium, of the condensing optical system to the transparent substrate of the optical disk. (Working distance,
WD) when recording / reproducing the first optical disc,
It is necessary to apply an offset to the two-dimensional actuator 15 so as to differ from the time of recording / reproducing of the second optical disk, so that the power consumption has to be increased, and the objective lens 16 by the two-dimensional actuator 15 is correspondingly increased. Therefore, the two-dimensional actuator 15 must be large. When the first optical disk is a DVD and the second optical disk is a CD, the thickness of the DVD (# 1.
2 mm, DVD has a thickness of 0.6 (m) on both sides of the information recording surface.
m), and the thickness of the CD (ＣＤ1.2 mm) is equal, so the same problem occurs even if the tray position (reference surface) is on the opposite side.

Therefore, in the present embodiment, the second semiconductor laser 12 and the second semiconductor laser 12 are arranged such that WD when recording / reproducing the second optical disk is substantially equal to WD when recording / reproducing the first optical disk. I do. That is, the first semiconductor laser 11 and the second semiconductor laser 12 are arranged such that the WD when recording / reproducing the first optical disc and the WD when recording / reproducing the second optical disc are substantially equal. Thus, in the present embodiment, it is not necessary to move the objective lens 16 to a position different from that for recording / reproducing on the first optical disc when recording / reproducing on the second optical disc, and the power consumption is small and the compact optical pickup is used. Device.

It is to be noted that a case where the WD when recording / reproducing the first optical disk and the WD when recording / reproducing the second optical disk are equal to each other means that the objective lens 16 originally moves in the optical axis direction for focusing. Therefore, a value within the range of ± 0.2 mm or less corresponds to “substantially equal” in the present invention.

As described above, the first semiconductor laser 11 and the second
By arranging the semiconductor laser 12 and the divergence changing optical element 13 in the present embodiment, the divergence of the light emitted from the first semiconductor laser 11 is changed to a collimator lens that changes the divergence to a parallel light. Worked,
The luminous flux emitted from the second semiconductor laser 12 has a function of simply changing the divergence (it does not function as a collimator lens). More specifically, the divergence changed by the divergence changing optical element 13 is smaller for the light beam emitted from the second semiconductor laser 12 than for the light beam emitted from the first semiconductor laser 11. I do. In particular, in the present embodiment, NA1
> NA2, the divergence changing optical element 13 causes the first
It is preferable that the light beam emitted from the semiconductor laser 11 is a parallel light beam. In this case, the light beam emitted from the second semiconductor laser 12 is a divergent light beam as shown in FIG.

Further, regarding the arrangement of the first semiconductor laser 11 and the second semiconductor laser 12, the imaging magnification of the condensing optical system with respect to the light beam emitted from the first semiconductor laser 11 during recording / reproducing of the first optical disk is changed. m1, the imaging magnification of the condensing optical system for the light beam emitted from the second semiconductor laser 12 during recording / reproduction on the second optical disc is m2,
The focal length of the condensing optical system is f (mm), the refractive index of the transparent substrate of the first optical disk with respect to the wavelength λ1 of the first semiconductor laser 11 is n1, and the transparent substrate of the second optical disk with respect to the wavelength λ2 of the second semiconductor laser 12 is n. Assuming that the refractive index is n2, | (m2-m1) f−t1 / n1 + t2 / n2 | <0.
It is preferable to satisfy the condition of 25 (mm). By satisfying this condition, it is possible to reduce the power consumption without flowing an extra drive current to the two-dimensional actuator (for focusing control) 15.

Further, in order not to increase the size of the two-dimensional actuator 15, | (m2-m1) ft-1 / n1
More preferably, the condition of + t2 / n2 | <0.15 (mm) is satisfied.

(Second Embodiment) Next, a second embodiment will be described with reference to FIG. In the first embodiment, the first semiconductor laser 11 and the second semiconductor laser 12 are used as light sources.
Although the problem was solved by arranging the semiconductor lasers 11 and 12 as described above using this method, in the present embodiment, the problem is solved using only the first semiconductor laser 11 as a light source. . That is, in the first embodiment, the light source and the light detecting means corresponding to the first optical disk and the second optical disk are provided, but the first optical disk and the second optical disk are respectively supported. In the present embodiment, 1
The same reference numerals are given to the same functions, functions, and members as those of the first embodiment in the one light source 11 and the one light detecting means 31, and the description thereof will be omitted except as described below. is there.

In the present embodiment, the first semiconductor laser 11, which is the first light source, the light detecting means 31, and the parallel means which also serves as the changing means 25 and the astigmatism generating element 27 in the first embodiment described above. The flat plates 25 and 27 and the unit 4
It is integrated as 1. And this unit 41
Is provided so as to be movable by the moving means 40.
Further, since the first optical disk and the second optical disk are recorded / reproduced using one light source, the second semiconductor laser 12, the synthesizing means 19, the parallel flat plate 26,
The light detecting means 32 is omitted.

When recording / reproducing the first optical disk, the light beam emitted from the first semiconductor laser 11 (in FIG.
The light path is bent by the parallel plane plates 25 and 27, converted into a parallel light beam by the collimator lens 13, stopped down by the stop 17, and recorded on the information recording surface by the objective lens 16 via the transparent substrate of the first optical disk. Focused on top. Then, the light beam reflected on the information recording surface is again condensed optical system (objective lens 16, collimator lens 13)
Is transmitted through the plane, and astigmatism is imparted by the parallel plane plates 25 and 27, and is incident on the light detecting means 31. Then, a reproduction signal, a focus error signal, and a tracking error signal are obtained using the signal output from the light detection means 31. The objective lens 16 is moved by the two-dimensional actuator (for focusing control) 15 based on the obtained focus error signal so that the light beam emitted from the first semiconductor laser 11 forms an image on the information recording surface of the first optical disc. Let it. The objective lens 16 is moved by the two-dimensional actuator (for tracking control) 15 based on the obtained tracking error signal so that the light beam emitted from the first semiconductor laser 11 forms an image on a predetermined track of the first optical disc. Move.

When recording / reproducing the second optical disk with the optical pickup device 10, the unit 41 is moved by the moving means 40 so that the WD is equal to the WD when recording / reproducing the first optical disk (FIG. 2). At the position indicated by the broken line). Then, recording / reproducing of the second optical disk is performed in the same manner as described above. In FIG. 2, the dashed line indicates the stop 1 of the light beam emitted from the first semiconductor laser 11 when recording / reproducing the second optical disc.
7 (described later) shows the outermost light beam focused. As described above, in the present embodiment, the objective lens 16 is moved to a position different from that during recording / reproduction on the first optical disk during recording / reproduction on the second optical disk (the two-dimensional actuator 15).
, No power consumption,
It becomes a compact optical pickup device.

The divergence changing optical element 13 for recording / reproducing the first optical disk is a collimator lens which changes the divergence of the light beam emitted from the first semiconductor laser 11 to produce a parallel light beam. It has a function of only changing the divergence (it does not function as a collimator lens). More specifically, the divergence changed by the divergence changing optical element 13 is smaller when recording / reproducing the second second optical disc than when recording / reproducing the first optical disc. In particular, in the present embodiment,
Since NA1> NA2, when recording / reproducing the first optical disk, it is preferable that the light beam emitted from the first semiconductor laser 11 by the divergence degree changing optical element 13 be a parallel light beam. In this case, the divergence changing optical element 13 converts the light beam emitted from the first semiconductor laser 11 into a divergent light beam as shown in FIG.

Further, regarding the arrangement of the first semiconductor laser 11 and the second semiconductor laser 12, the imaging magnification of the condensing optical system with respect to the light beam emitted from the first semiconductor laser 11 during recording / reproducing of the first optical disk is changed. m1, the imaging magnification of the condensing optical system for the light beam emitted from the second semiconductor laser 12 during recording / reproduction on the second optical disc is m2,
The focal length of the condensing optical system is f (mm), the refractive index of the transparent substrate of the first optical disk with respect to the wavelength λ1 of the first semiconductor laser 11 is n1, and the transparent substrate of the second optical disk with respect to the wavelength λ2 of the second semiconductor laser 12 is n. Assuming that the refractive index is n2, | (m2-m1) f−t1 / n1 + t2 / n2 | <0.
It is preferable to satisfy the condition of 25 (mm). By satisfying this condition, it is possible to reduce the power consumption without flowing an extra drive current to the two-dimensional actuator (for focusing control) 15.

Further, in order not to increase the size of the two-dimensional actuator 15, | (m2-m1) ft-1 / n1
More preferably, the condition of + t2 / n2 | <0.15 (mm) is satisfied.

(Preferred Example of Objective Lens) Next, the objective lens 16 suitably used in the optical pickup device 10 according to the first and second embodiments will be described with reference to FIG. FIG. 3A is a diagram schematically showing a state in which a light beam passing through the objective lens 16 forms an image on the first optical disc during recording / reproducing on the first optical disc, and FIG.
3 is a view of the objective lens 16 viewed from the light source side, and FIG.
FIG. 4C is a diagram schematically showing a state in which a light beam passing through the objective lens 16 forms an image on the second optical disk during recording / reproduction on the second optical disk.

In this embodiment, the objective lens 16 is a convex lens having a positive refractive power, in which both the refracting surface S1 on the light source side and the refracting surface S2 (final refracting surface) on the optical disk side have an aspherical shape. The refraction surface S1 of the objective lens 16 is constituted by a plurality of (three in this example) first division surfaces Sd1 to third division surfaces Sd3 concentrically with the optical axis, and a boundary is formed between the division surfaces Sd1 and Sd2. ing.

When recording / reproducing the first optical disc (see FIG. 3A), the objective lens 16 in this embodiment
The first passing through the first division surface Sd1 and the third division surface Sd3
The light beam and the third light beam (light beam indicated by oblique lines) form an image at substantially the same image forming position (the information recording surface 22 of the first optical disk). At this time, the second light flux (the light flux indicated by the broken line) passing through the second division surface Sd2 forms an image at an image formation position different from the image formation position of the first and third light fluxes (that is, the first optical disk). No image is formed on the information recording surface 22). Therefore, at the time of recording / reproducing on the first optical disk, the first light beam and the third light beam converge on the information recording surface 22 of the first optical disk to form a beam spot, which is reflected and detected by the light detecting means 30. Then, as described above, the focus error signal, the track error signal, and the reproduction signal (information) are read.

When recording / reproducing the second optical disk (see FIG. 3 (c)), the first light flux (shown by oblique lines rising to the right) and the second light flux (shown by oblique lines falling to the right). )
Form an image at substantially the same image forming position (on the information recording surface of the second optical disc). At this time, the third light flux (shown partly by a broken line) is generated as a flare. Therefore, the second
On the information recording surface 22 of the optical disk, a nucleus is mainly formed by the first and second light beams, and a beam spot shape is formed around the nucleus where a flare is generated by the third light beam. .

In other words, the objective lens 1 of the present embodiment
Reference numeral 6 denotes a first light beam passing near the optical axis having a small numerical aperture.
It is used for recording / reproduction of all optical discs that can be recorded / reproduced, and is divided so as to correspond to each optical disc that reproduces a light flux passing outside the first division surface, and each divided light flux is applied to each optical disc (this embodiment). In the embodiment, the first and second optical disks are used for recording / reproduction. At this time, the luminous flux used for recording / reproducing the optical disc (first optical disc) having the larger required numerical aperture is the first of the divided luminous fluxes.
The light beam is separated from the light beam (third light beam).

FIG. 4 is a diagram of spherical aberration on the information recording surface for explaining the function of the objective lens 16.
It will be described based on. FIG. 4A is a diagram schematically showing a spherical aberration diagram when passing through a transparent substrate having a thickness t1 during DVD recording / reproduction, and FIG. 4B is a diagram illustrating the thickness during CD recording / reproduction. It is the figure which showed typically the spherical aberration figure at the time of passing through the transparent substrate of t2. The vertical axis indicates the numerical aperture corresponding to the numerical aperture on the optical disk side (final refraction surface S2) of the condensing optical system. Also, the numerical aperture NAL in the figure
Is the position closest to the optical axis in the second divided surface Sd2, and corresponds to the boundary between the first divided surface Sd1 and the second divided surface Sd2, and the numerical aperture NAH is This is the position farthest from the axis, and corresponds to the boundary between the second divided surface Sd2 and the third divided surface Sd3.

As shown in FIG.
At the time of reproduction, the first divided surface Sd1 and the third divided surface Sd
The light beams passing through No. 3 form an image at substantially the same image forming position, and the light beams passing through the second division surface Sd2 are formed at a position different from the image forming position. Further, as shown in FIG. 4B, of the light beams passing through the first division surface Sd1,
The second position between the position where the light beam passing near the optical axis forms an image and the position where the light beam passing through the end of the first divided surface Sd1 that is separated from the optical axis in a direction perpendicular to the optical axis is formed. Division surface Sd2
The rays passing through are imaged.

According to the objective lens 16 of this embodiment, the spherical aberration changes discontinuously at at least two aperture positions (two in this embodiment) near the numerical aperture corresponding to the required numerical aperture NA2. The direction that changes discontinuously is a small numerical aperture NAL (a position closest to the optical axis in the second divided surface Sd2 and corresponds to a boundary between the first divided surface Sd1 and the second divided surface Sd2) and a large value. Numerical aperture NAH (second division surface Sd2
Are farthest from the optical axis, and correspond to the boundary between the second divided surface Sd2 and the third divided surface Sd3).

In the objective lens 16 of this example, spherical aberration originally occurs on the under side (FIG. 4B). Therefore, when viewed from a small numerical aperture to a large numerical aperture, the numerical aperture N
In the AL, the spherical aberration changes discontinuously in the positive direction, and in the numerical aperture NAH, the spherical aberration changes discontinuously in the negative direction. Accordingly, it is possible to detect the light beams reflected from the DVD having the thin transparent substrate t1 and the CD having the thick transparent substrate t2 thick. Here, “the spherical aberration changes discontinuously” means that a sudden change in the spherical aberration is observed when viewed in a spherical aberration diagram.

Further, looking at the spherical aberration diagram at the time of recording / reproducing a CD (FIG. 4B), it can be seen from the numerical aperture NAL to the numerical aperture NAH.
Spherical aberration during the other numerical aperture (from the optical axis to the numerical aperture NAL,
The spherical aberration is the same as the spherical aberration of the numerical aperture NAH to the required numerical aperture NA1 (in this embodiment, both are on the over side). This further improves the focus error signal.

As described above, according to the objective lens 16 of the present embodiment, the light beam (the first light beam) passing through the first divided surface Sd1 near the optical axis.
The light flux) is used for recording / reproduction on the first optical disc and the recording / reproduction on the second optical disc, and the light flux (second light flux) passing through the second division surface Sd2 outside the first division surface Sd1 is mainly the second optical disc. Of the second division surface Sd2
The light beam (third light beam) passing through the outermost third division surface Sd3 has a shape mainly used for recording / reproducing of the first optical disc.

Here, the meaning of the word “mainly” means that in the case of a light beam passing through the second division surface Sd2, the third division surface Sd
In a state in which the light beam passing through the third division surface Sd3 is not shielded, the light beam passing through the third division surface Sd3 is converted to the energy of the core portion at the position where the center intensity of the beam spot formed on the light detection means 30 is maximized. It means that the energy ratio of the nucleus at the position where the center intensity of the beam spot becomes maximum in the light-shielded state ("nuclear energy in the light-shielded state" / "nuclear energy in the light-shielded state") is in the range of 60% to 100%. ing. Similarly, in the case of a light beam passing through the third division surface Sd3, the energy ratio of the light-shielded core to the light-shielded state of the second division surface Sd2 (“light-shielded nuclear energy” / “non-light-shielded nuclear energy”) )
Is in the range of 60% to 100%.
In order to simply measure the energy ratio, in each case, the peak intensity Ip at the position where the center intensity of the beam spot is maximum, and the beam diameter Dp (the intensity is e ^{−2 with} respect to the center intensity). Is determined at the position where
Since the shape of the beam at the core is almost constant, Ip
XDp may be obtained and compared.

In this example, the division surfaces Sd1 to Sd3 are provided on the refraction surface S1 on the light source side of the objective lens 16, but may be provided on the refraction surface S2 on the optical disk side. (The divergence changing optical element 13, the synthesizing means 19, the changing means 25, 26, etc.), or may be provided as a separate element.

In the present embodiment, the first division surface Sd
Steps are provided at the boundaries of the first to third divided surfaces Sd3,
A step may be provided only at one of the boundaries, and the connection may be made at a surface having a predetermined radius of curvature instead of the step.

In this example, the objective lens 16 is
As shown in (a), the second divided surface Sd2 has an aspherical shape, but may be formed of a hologram (or Fresnel). When the second division surface Sd2 is formed by a hologram, one of the light beams divided into the 0th-order light and the 1st-order light is used for recording / reproduction on the first optical disk, and the other is used for recording / reproduction on the second optical disk. Use. At this time, it is preferable that the light amount of the light beam used for recording / reproducing on the second optical disk is larger than the light amount of the light beam used for recording / reproducing on the first optical disk. Further, in the present example, the second division surface Sd2 is provided in a ring (circle) shape concentric with the optical axis. However, the present invention is not limited to this, and the second division surface Sd2 may be provided in a concentric elliptical shape or an interrupted ring shape.
Further, in the present embodiment, the configuration is such that spherical aberration is given to the second division surface Sd2, but instead or in addition to this, a phase difference is provided, that is, the phase of the light beam passing through the second division surface Sd2 is changed. May be shifted from the phase of the light beam passing through the first divided surface Sd1 and the third divided surface Sd3.

[0075]

Embodiments of the present invention will be described below. This example is an example of the first embodiment described above.
DVD (transparent substrate thickness t1 =
0.6 mm, a required numerical aperture NA1 = 0.60 (wavelength λ of the first semiconductor laser 11 = 635 nm), and a CD (transparent substrate thickness t2 = 1.2 m) as the second optical disk.
m, required numerical aperture NA2 = 0.45 (λ = 780n)
m)) will be used.

Table 1 shows the lens data.

[0077]

[Table 1]

In Table 1, the emission points of the first and second semiconductor lasers are defined as the zeroth plane, and the light emission points of the first and second semiconductor lasers are set in accordance with the light traveling direction.
From here, the i-th is shown, and up to the information recording surface of the optical disk (however, changing means 25 and 26 and synthesizing means 19
The first and second surfaces are divergence changing optical elements 13 and the fourth and fifth surfaces are objective optical elements 16). R is the radius of curvature of the plane intersecting the optical axis, d
Is the distance between the i-th surface and the (i + 1) -th surface,
n represents the refractive index at the wavelength of the light beam of the semiconductor laser to be used. Incidentally, the sign indicates that the traveling direction of light is positive.

The focal length f of the divergence changing optical element 13 is f =
16.0 (mm) Focal length of the objective optical element 16 f = 2.64 (mm) Focal length of the focusing optical system f = 3.43 (mm) Focusing optics for the light beam emitted from the first semiconductor laser 11 The imaging magnification m1 of the system is −1 / 6.06. The imaging magnification m2 of the light-converging optical system with respect to the light beam emitted from the second semiconductor laser 12 is −1 / 3.65.

Table 2 shows the data of the aspherical surface of the above-mentioned surfaces using the aspherical surface.

[0081]

[Table 2]

The expression of the aspherical surface is as follows.

[0083]

(Equation 1)

It is assumed that Here, X is the axis in the optical axis direction, H is the axis in the direction perpendicular to the optical axis, and the traveling direction of light is positive. K is the conic coefficient, Aj is the aspheric coefficient, and Pj is the power of the aspheric surface.

FIG. 5 is a diagram showing spherical aberration on the information recording surface when recording / reproducing a DVD (a) and when recording / reproducing a CD (b). FIG. 6 shows a relative intensity distribution chart of a condensed spot having the best spot shape at the time of DVD recording / reproduction (a) and at the time of CD recording / reproduction (b).

According to the present embodiment, good recording / reproduction can be performed for both DVD and CD, the WDs are the same for both DVD and CD, and the two-dimensional actuator 15 does not need extra power consumption as a bias. Therefore, it is not necessary to extend the movable range of the objective optical element 16 to be moved, and the apparatus becomes compact.

[0087]

As described in detail above, according to the present invention,
It is possible to provide an optical pickup device that enables recording / reproducing of optical disks having different transparent substrate thicknesses with one condensing optical system, has a simple structure having mutual compatibility, is compact, and has low power consumption.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical pickup device.

FIG. 2 is a schematic configuration diagram of an optical pickup device according to a second embodiment.

FIG. 3 is a diagram showing an objective lens suitably used for an optical pickup device.

FIG. 4 is a diagram of spherical aberration on an information recording surface for explaining a function of an objective lens.

FIG. 5 is a diagram of spherical aberration on the information recording surface of the example.

FIG. 6 is a relative intensity distribution diagram of a converging spot having the best spot shape in the embodiment.

[Explanation of symbols]

 Reference Signs List 10 optical pickup device 11 first light source 12 second light source 13 divergence changing optical element 15 two-dimensional actuator 16 objective optical element 17 stop 19 combining means 20 optical disk 21 transparent substrate 22 information recording surface 25, 26 changing means 31, 32 light detection Means 40 Transportation

Claims (15)

[Claims] 1. A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system comprising a plurality of refraction surfaces, and information is recorded or recorded on the information recording surface. An optical pickup device for reproducing (recording / reproducing) information on a recording surface, wherein the optical information recording medium has a first optical information recording medium having a thickness of t1 (mm) and a thickness of a transparent substrate. In the optical pickup device using the second optical information recording medium of t2 (mm) (where t2 ≠ t1), the most optical information of the condensing optical system when recording / reproducing the first optical information recording medium is used. The distance from the final refraction surface, which is the refraction surface on the recording medium side, to the transparent substrate of the first optical information recording medium;
The position of the light source is changed so that the distance from the final refraction surface to the transparent substrate of the second optical information recording medium when recording / reproducing the second optical information recording medium is substantially equal. Optical pickup device. 2. A light beam emitted from a light source is condensed on an information recording surface via a transparent substrate of an optical information recording medium by a condensing optical system comprising a plurality of refraction surfaces, and information is recorded on the information recording surface or the information is recorded on the information recording surface. An optical pickup device for reproducing (recording / reproducing) information on a recording surface, wherein the optical information recording medium has a first optical information recording medium having a thickness of t1 (mm) and a thickness of a transparent substrate. In the optical pickup device using the second optical information recording medium of t2 (mm) (where t2 ≠ t1), a light beam of wavelength λ1 is emitted as the light source for recording / reproducing the first optical information recording medium. And a second light source that emits a light beam of wavelength λ2 for recording / reproducing on / from the second optical information recording medium. Transparency of the first optical information recording medium from a certain final refractive surface The first light source and the second light source are arranged so that a distance to a substrate and a distance from the final refraction surface to a transparent substrate of the second optical information recording medium are substantially equal. Pickup device. 3. A divergence changing optical element fixed to the optical pickup device for changing a divergence of a light beam emitted from the light source, wherein the divergence is changed by a divergence changing optical element. Luminous flux
The optical pickup device according to claim 1, further comprising: an objective optical element that focuses light on an information recording surface of the optical information recording medium. 4. The divergence of a light beam emitted from the light source, which is changed by the divergence changing means during recording / reproducing of the first optical information recording medium, is t2> t1, and the second optical information recording medium is 4. The optical pickup device according to claim 3, wherein the divergence of the light beam emitted from the light source changed by the divergence changing unit at the time of recording / reproducing is smaller than the divergence. 5. The light beam emitted from the light source, which is changed by the divergence changing means during recording / reproducing of the first optical information recording medium, becomes parallel light. Optical pickup device. 6. The imaging magnification of the converging optical system with respect to a light beam emitted from the light source at the time of recording / reproducing on the first optical information recording medium is m1, and the imaging magnification at the time of recording / reproducing on the second optical information recording medium is improved. The imaging magnification of the light-collecting optical system with respect to the light beam emitted from the light source is m2, the focal length of the light-collecting optical system is f (mm), and the focal length of the light-collecting optical system is f / mm. Assuming that the refractive index of the transparent substrate of the first optical information recording medium is n1, and the refractive index of the transparent substrate of the second optical information recording medium with respect to the wavelength of the light source during recording / reproducing of the second optical information recording medium is n2, | (m2 −m1) f−t1 / n1 + t2 / n2 | <0.
The optical pickup device according to any one of claims 1 to 5, wherein a condition of 25 (mm) is satisfied. 7. | (m2−m1) f−t1 / n1 + t2
The optical pickup device according to claim 6, wherein a condition of /n2|<0.15 (mm) is satisfied. 8. The light-collecting optical system according to claim 1, wherein at least one refracting surface of the condensing optical system is divided into a plurality of divided surfaces concentrically with the optical axis. Optical pickup device. 9. The at least one refraction surface of the objective optical element includes a first division surface near an optical axis, a second division surface outside the first division surface, and a second division surface outside the second division surface. When recording / reproducing the first optical information recording medium, the light beam mainly passing through the first divided surface and the third divided surface among the light beams emitted from the first light source is provided. When recording / reproducing the second optical information recording medium, it is preferable to use mainly the light beam that has passed through the first split surface and the second split surface among the light beams emitted from the second light source. The optical pickup device according to any one of claims 2 to 6, wherein: 10. The objective optical element has a plurality of divided surfaces having at least one surface divided concentrically with an optical axis, and the light source is used when recording / reproducing a first optical information recording medium. Of the light beams emitted from the first split surface near the optical axis and the third split surface outside the first split surface, form an image at substantially the same image forming position, and the first split surface And the third
The light beam passing through the second split surface between the split surface and the split surface is imaged at an image forming position different from the image forming position of the light beam passing through the first split surface and the third split surface. The optical pickup device according to any one of claims 3 to 7, 9, wherein 11. The objective optical element has a plurality of divided surfaces at least one surface of which is divided concentrically with an optical axis, and the light source is used when recording / reproducing a second optical information recording medium. Of the luminous flux passing through the first division surface near the optical axis among the luminous fluxes emitted from the optical axis, the position where a light beam passing near the optical axis forms an image, and the end of the first division surface in a direction orthogonal to the optical axis. The light beam passing through the second division surface outside the first division surface forms an image between the position where the light beam passing through the portion forms an image. The optical pickup device according to any one of the above. 12. When the required numerical aperture of the objective optical element on the optical information recording medium side required for recording / reproducing the second optical information recording medium is NA2, the objective optical element has a required numerical aperture of NA2. The spherical aberration is changed discontinuously at at least two aperture positions near a numerical aperture corresponding to the following:
2. The optical pickup device according to any one of 1. 13. The minimum numerical aperture of the at least two aperture positions is NAL, and the maximum numerical aperture is N.
13. The optical pickup device according to claim 12, wherein, when AH is set, the numerical aperture NAL and the numerical aperture NAH are discontinuously changed in directions opposite to each other. 14. When recording / reproducing a second optical information recording medium, a light beam emitted from the light source passes through the condensing optical system and converges on an information recording surface of the second optical information recording medium. 14. The optical pickup according to claim 13, wherein the objective optical element has a spherical aberration between a numerical aperture NAL and a numerical aperture NAH having the same sign as a spherical aberration of another numerical aperture. apparatus. 15. When the required numerical aperture on the optical information recording medium side of the objective optical element required for recording / reproducing the second optical information recording medium is NA2, the objective optical element has a required numerical aperture NA2. The optical pickup device according to any one of claims 3 to 7, and 9 to 11, wherein a phase difference is provided between at least two aperture positions near a numerical aperture corresponding to (1).