JP3380942B2 - Optical pickup device for multilayer optical disc - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layered optical disc in which a plurality of information signal layers which are signal recording areas are laminated, for example, a multi-layer optical disc in which information signals are recorded by pits, a multi-layer magneto-optical disc in which information signals are magneto-optically recorded, The present invention relates to a reproducing apparatus for recording / reproducing information signals from each information signal layer of the multilayer optical disk, a recording apparatus, and an optical pickup apparatus for a multilayer optical disk suitable for use in the recording / reproducing apparatus.

[0002]

2. Description of the Related Art A conventional optical pickup device includes a laser diode, which is a light source, and a collimator lens, a diffraction grating, a polarization beam splitter, and an objective lens, which are provided between the laser diode and the optical disk so that their optical axes coincide with each other. It is configured with. In addition, this optical pickup device has a photodetector that receives a laser beam (hereinafter, referred to as a reflected beam) reflected from an optical disc through a polarization beam splitter, and an optical axis between the photodetector and the polarization beam splitter. The focusing lens is provided so as to be matched with each other.

In this optical pickup device, a laser beam emitted from a laser diode is focused and irradiated on a signal recording area of an optical disc through a polarization beam splitter, an objective lens and the like. Then, the reflected beam from the optical disc through the polarization beam splitter is received by the photodetector to read and reproduce the information signal of the optical disc.

In this optical pickup device, when reading and reproducing the information signal of the optical disc, the focus control for adjusting the focus of the objective lens by the astigmatism method and the signal recording area of the optical disc by the three-spot (three-beam) method are performed. Tracking control is performed to track and adjust the objective lens by following the signal track.

[0005]

By the way, the optical disc is required to have a high recording density of information signals, and a multi-layer optical disc in which a plurality of information signal layers which are signal recording areas are laminated is proposed.

This multi-layer optical disc includes, for example, a two-layer optical disc in which two information signal layers, which are information signal recording areas, are superposed. Two-layer optical disc 2
0 is generally a polycarbonate (P
C), a disk substrate 20C made of a transparent synthetic resin material such as polymethylmethacrylate (PMMA)
And the first formed on the main surface of the disk substrate 20C.
Information signal layer 20A, and a spacer layer 20D formed of a transparent resin material on the first information signal layer 20A.
And a second information signal layer 20B formed by being superposed on the first information signal layer 20A via a spacer layer 20D.
And a protective layer 20E formed on the second information signal layer 20B so as to protect the second information signal layer 20B mechanically and chemically.

The double-layer optical disc 20 is shown in FIG.
, The second information signal layer 20B superposed on the first information signal layer 20A by the optical pickup device.
The laser beam 25 emitted from the laser diode is transmitted through the first information signal layer 20A and applied to the second information signal layer 20B when the information signal is read and reproduced.

In the conventional optical pickup device, when reading and reproducing the information signal from the first information signal layer 20A of the two-layer optical disk 20, as shown in FIG. 7A, the first information signal layer 20A is irradiated. The second information signal layer 20B which is not the target of reading the information signal is transmitted through the first information signal layer 20A in the process of being irradiated with the generated laser beam 25 on the first information signal layer 20A. Is also irradiated.

Therefore, in the optical pickup device, the photodetector 23 is irradiated with the reflected beam 25A from the first information signal layer 20A of the two-layer optical disc 20 with the objective lens 21 focused, and the objective lens 21 is also included.
The reflected beam 25B (hereinafter, referred to as stray light of the reflected beam) enlarged by defocusing is also emitted from the second information signal layer 20B which is not focused. That is, the optical pickup device includes the focusing lens 2
2 onto the photodetector 23 via the reflected beam 25
A and stray light 25B of the reflected beam spread to the outer peripheral side of the reflected beam 25A are concentrically emitted.

Similarly, when the optical pickup device reads and reproduces the information signal from the second information signal layer 20B of the two-layer optical disc 20, as shown in FIG.
Of the laser beam 25 applied to the information signal layer 20B of
In the process of irradiating the second information signal layer 20B, the first information signal layer 20 not targeted for reading the information signal.
A is also irradiated.

Therefore, in the optical pickup device, the photodetector 23 is irradiated with the reflected beam 25A reflected from the second information signal layer 20B of the two-layer optical disc 20 in which the objective lens 21 is focused, and the objective lens is also irradiated. 21 unfocused first information signal layer 2
Stray light 25B, which is a reflected beam enlarged from 0A by defocusing, is also emitted.

By the way, when the optical pickup device reads and reproduces the information signal of the multi-layered optical disc, the signal recording area of the multi-layered optical disc has, for example, scratches, dust, etc. Occur. Therefore, the optical pickup device has a problem in that the objective lens 21 is defocused from the information signal layer of the multilayer optical disc on which the objective lens 21 is focused, and the objective lens 21 is focused on another information signal layer.

When the optical pickup device detects which information signal layer of the multilayer optical disk the focus of the objective lens 21 is focused on, a focus error caused by focusing control performed for reading the information signal of the information signal layer is detected. Based on the signal, the focused information signal layer is detected.

That is, in this optical pickup device, focusing control is performed so that the objective lens 21 is once focused on one of the information signal layers of the multilayer optical disk, and then the focused information signal layer is detected. There is a problem that you cannot do it.

Therefore, when the focused information signal layer is defocused from another information signal layer, the optical pickup device once reads the information signal from the defocused information signal layer. By performing the reproduction, the defocused information signal layer must be detected.

For this reason, this optical pickup device has a problem that when a focal point is deviated, a necessary information signal cannot be read and reproduced during the time required for the correcting operation for correcting the deviated focal point.

Therefore, the present invention provides an optical pickup device for a multi-layer optical disc, which makes it possible to detect the focused information signal layer of the multi-layer optical disc and to rapidly perform the reading / reproducing operation of a desired information signal. The purpose is to provide.

[0018]

In order to achieve the above-mentioned object, the present invention is an optical pickup device for a multilayer optical disc in which a plurality of information signal layers on which desired information signals are recorded are laminated. Then, the objective lens provided so as to focus on any one of the plurality of information signal layers and the astigmatism generating means for generating astigmatism in the reflected beam from the optical disc are orthogonal to each other. A first light amount detection signal is output by calculating a received light amount of the reflected beam received in the first to fourth light receiving regions, which has first to fourth light receiving regions divided into four by a dividing line. The first to fourth identification detectors provided on the extension of the diagonal lines of the first to fourth light receiving regions, and the first to fourth identification detectors. The reflected light received by Second light receiving means for outputting a second light amount detection signal by calculating the received light amount of the beam; control means for controlling the focus of the objective lens based on the first light amount detection signal; And a detection means for detecting the information signal layer on which the objective lens is focused, based on the light amount detection signal of 2. Here, the reflected beam from the information signal layer which is out of focus among the plurality of information signal layers of the multilayer optical disk is the reflected beam from the signal recording layer which is not the target of reading and reproducing the information signal. , Stray light for the reflected beam from the information signal layer that is the target of reading and reproducing the information signal.

Further, each of the light receiving regions is radially divided into four around the optical axis of the reflected beam from the information signal layer which is currently focused, and the reflected beam is received by each of the light receiving regions. The photodetector has a four-division photodetector, and each light-receiving region of the light-receiving means is provided at an outer peripheral portion of each light-receiving region of the four-division photodetector.

Further, the four-division photo detector is
Each of the light receiving regions of the light receiving means is formed in a substantially L shape, and each of the substantially L shaped light receiving regions has an inner bending point which is a diagonal line of the four-divided photodetector. Are provided so as to respectively be located on the extended lines and surround each light receiving region of the four-division photo detector.

[0021]

In the optical pickup device for a multilayer optical disc according to the present invention having the above-mentioned structure, when the information signal is read from each of the information signal layers of the multilayer optical disc and reproduced, the astigmatism generating means operates from the information signal layer of the multilayer optical disc. The astigmatism is generated in the reflected beam of, and the reflected beam from the astigmatism generating means is received by the light receiving means.

By the way, the reflected beam from the information signal layer which is not focused changes the form on the light receiving surface of the light receiving means as the information signal layer of the multilayer optical disc to be reflected changes. Therefore, in the optical pickup device for a multilayer optical disc, the detection means focuses the objective lens on the basis of the amount of light received by the light receiving means in response to the change in the form of the reflected beam from the information signal layer that is not focused. The information signal layer that is present is detected.

That is, in this optical pickup device for a multilayer optical disk, the light receiving means receives the reflected beam from the information signal layer of the multilayer optical disk in which the light receiving means is not focused, thereby detecting the respective light amounts from the respective light receiving areas of the light receiving means. Based on the signal, it is possible at any time for the detection means to detect the information signal layer in which the objective lens is in focus.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical pickup device 1 for a multilayer optical disk according to an embodiment for reading and reproducing a two-layer optical disk as a multilayer optical disk in a specific embodiment of the present invention will be described below with reference to FIG.
~ It demonstrates with reference to FIG. The optical pickup device 1 for a multilayer optical disc performs tracking control by the three-spot method and focusing control by the astigmatism method.

Optical pickup device 1 for multilayer optical disk
Is a laser diode 2 which is a light source, as shown in FIG.
6, the laser diode 26 and the two-layer optical disc 20
, And a collimator lens 27, a diffraction grating 28, and a polarization beam splitter (P
BS) 29, a quarter-wave plate 30, and an objective lens 31. The optical pickup device 1 for a multilayer optical disc includes a photodetector 34 that receives a reflected beam from the double-layer optical disc 20, and the photodetector 3.
A focusing lens 32 and a cylindrical lens 33, which are provided between the polarization beam splitter 4 and the polarization beam splitter 29 with their optical axes aligned with each other, are provided.

As shown in FIG. 2, the photodetector 34 includes a main beam detector 10, first side beam detectors 11 and second side beam detectors 12 provided at both side ends of the main beam detector 10, respectively. A first identification detector 13A to a fourth identification detector 13D provided on the outer periphery of the main beam detector 10, and a detector connected and wired to the first identification detector 13A to the fourth identification detector 13D. It is composed of 18 and.

The main beam detector 10 has a first light receiving region 10A to a fourth light receiving region 10D whose light receiving regions are radially centered on the optical axis of the reflected beam with which the light receiving surface is irradiated.
A substantially rectangular four-divided photodetector divided into four equal parts is used. First side beam detector 11
In the second side beam detector 12, the light receiving area is divided into the first light receiving areas 11A and 12A and the second light receiving areas 11B and 12B by a straight line passing through the optical axis of the reflected beam with which the light receiving surface is irradiated. A divided two-part photo detector is used. Then, the first side beam detector 11 and the second side beam detector 12
Are provided outside the stray light 14 of the main beam with which the main beam detector 10 is irradiated.

In the first identification detector 13A to the fourth identification detector 13D, each light receiving region is formed in a substantially L shape. In each of the L-shaped light receiving regions, the inner bending point is located on the extension of the diagonal line of the main beam detector 10, and the first light receiving region 10A to the fourth light receiving region 1 of the main beam detector 10 are located.
They are arranged so as to respectively surround 0D.

The detector 18 is, as shown in FIG. 3, a first identification detector 13A to a fourth identification detector 13.
The information signal layer, on which the objective lens 31 is focused, is connected to each D and wired based on each light amount detection signal output to the first identification detector 13A to the fourth identification detector 13D. To detect.

As shown in FIGS. 5A and 5B, the two-layer optical disc 20 read and reproduced as a multilayer optical disc by the optical pickup device 1 for a multilayer optical disc is generally made of polycarbonate (PC) or polymethyl ester. A disk substrate 20C made of a transparent synthetic resin material such as methacrylate (PMMA), and a first information signal layer 20A formed on the main surface of the disk substrate 20C.
And a spacer layer 20D formed of a transparent resin material on the first information signal layer 20A, and a second information signal layer formed on the first information signal layer 20A with the spacer layer 20D interposed therebetween. 20B and a protective layer 20E formed on the second information signal layer 20B so as to mechanically and chemically protect the second information signal layer 20B.

The two-layer optical disc 20 is shown in FIG.
, The second information signal layer 20B superposed on the first information signal layer 20A by the optical pickup device.
The laser beam emitted from the laser diode is transmitted through the first information signal layer 20A and applied to the second information signal layer 20B when the information signal is read.

Regarding the optical pickup device 1 for a multi-layered optical disc constructed as described above, the two-layered optical disc 20
When the information signal is read from the first information signal layer and reproduced, the process of detecting the optical path of the laser beam emitted from the laser diode 26 and the focused information signal layer of the two-layer optical disc 20 will be described with reference to FIG. It will be described with reference to FIG.

First, the laser beam emitted from the laser diode 26 is incident on the collimator lens 27,
The collimator lens 27 converts the divergent light into parallel light and emits it. The laser beam emitted to the collimator lens 27 is incident on the diffraction grating 28.

The diffraction grating 28 divides the incident laser beam into a main beam 7, a first side beam 8 and a second side beam 9 and transmits them. Each beam divided into three by the diffraction grating 28 enters a polarization beam splitter 29 and is transmitted through this polarization beam splitter 29.

Each beam transmitted to the polarization beam splitter 29 is incident on the quarter-wave plate 30, and each beam incident on the quarter-wave plate 30 is converted from linearly polarized light to circularly polarized light and transmitted. To be done. Quarter wave plate 3
Each beam transmitted to 0 is incident on the objective lens 31.

The objective lens 31 collects each incident beam and irradiates the first information signal layer 20A of the two-layer optical disc 20 with it. At this time, the dual-layer optical disc 2
Each beam applied to the 0th first information signal layer 20A is
The first information signal layer 20A is irradiated with the second information signal layer 20A while passing through the first information signal layer 20A.
B is also irradiated.

Each beam applied to the first information signal layer 20A of the two-layer optical disc 20 is reflected from the first information signal layer 20A and also from the second information signal layer 20B. Is reflected. That is, each beam applied to the first information signal layer 20A of the two-layer optical disc 20 is reflected by the first information signal layer 20A on which the objective lens 31 is focused, and the focus of the objective lens 31. The second information signal layer 2 which is not matched
Each reflected beam from 0B is reflected as stray light.

Then, each reflected beam and stray light of each reflected beam enter the objective lens 31, respectively. The objective lens 31 transmits the reflected beams and the stray light of the reflected beams, respectively, and makes them incident on the quarter-wave plate 30. The quarter-wave plate 30 converts each of the incident reflected beams and stray light of each reflected beam from circularly polarized light into linearly polarized light and transmits the linearly polarized light.

The reflected beam and the stray light of each reflected beam transmitted through the quarter-wave plate 30 are polarized beam splitter 2
The light beam is incident on the polarization beam splitter 9, and is reflected and transmitted by the polarization beam splitter 29. Each reflected beam and the stray light of each reflected beam transmitted through the polarization beam splitter 29 are incident on a focusing lens 32, converged by this focusing lens 32 and transmitted.

The reflected beams and the stray light of the reflected beams that have passed through the focusing lens 32 are incident on the cylindrical lens 33. This cylindrical lens 33
Stray light of each reflected beam and each reflected beam incident on
The light is collected and irradiated onto each detector of the photo detector 34.

The main beam detector 10 of the photodetector 34 controls the focusing of the objective lens 31 according to the amount of each received light of the main beam 7 with which the first light receiving area 10A to the fourth light receiving area 10D are irradiated. The main beam detector 10 includes the first light receiving area 10A to the fourth light receiving area 10A.
Assuming that the light amount detection outputs outputted by the light receiving area 10D are E1, E2, E3, and E4, respectively, a so-called focus error signal (FE) indicating the amount of defocus on the surface of the first information signal layer 20A of the two-layer optical disc 20 is displayed. )
Can be obtained by FE = (E1 + E3)-(E2 + E4).

The first side beam detector 11 and the second side beam detector 12 of the photo detector 34 include a first light receiving region 11A and a second light receiving region 11B, a first light receiving region 12A and a second light receiving region 11A. Light receiving area 1
The objective lens 31 is tracking-controlled by the respective received light amounts of the first side beam 8 and the second side beam 9 irradiated on the 2B and 2.

The first side beam detector 11 and the second side beam detector 12 are provided in the first light receiving region 1
1A and the second light receiving area 11B, and the first light receiving area 12
Assuming that the light amount detection outputs outputted by A and the second light receiving region 12B are E5, E6, E7, and E8, respectively, 2
A so-called tracking error signal (TE) indicating the amount of track deviation on the surface of the first information signal layer 20A of the layered optical disc 20 can be obtained by TE = (E5 + E6)-(E7 + E8).

The main beam detector 10, the first side beam detector 11, and the second side beam detector 12 are arranged from the first information signal layer 20A to the main beam 7, the first side beam 8, and the second side beam. The beam 9 and the stray light 14 of the main beam, the stray light of the first side beam and the stray light of the second side beam (not shown) are respectively emitted from the second information signal layer 20B.

The stray light 14 of the main beam with which the main beam detector 10 is irradiated is provided with the first side beam detector 11 and the second main beam detector 12 at a predetermined distance from the main beam detector 10. Therefore, they are not superposed on the first side beam detector 11 and the second side beam detector 12, respectively. In addition, the stray light of the first side beam and the second light
Although not shown, the stray light of the side beam is not superposed on the main beam detector 10.

Further, even if the stray light of the first side beam and the stray light of the second side beam are superposed on the main beam detector 10, the stray light of the intensity is larger than that of the stray light 14 of the main beam. Since it is sufficiently weak, it does not adversely affect the main beam detector 10.

As shown in FIGS. 2 and 3, the optical pickup device 1 for a multilayer optical disk has a spot shape of the stray light 14 of the main beam which is elliptical in order to perform focusing control by the astigmatism method. The main beam stray light 14 is reflected by the first information signal layer 20A or the second information signal layer 20B of the two-layer optical disc 20 and is reflected by the elliptical major axis and minor axis. And change and change.

That is, in the optical pickup device 1 for a multilayer optical disc, as shown in FIGS. 2 and 3, the information signal layer targeted for reading and reproducing the information signal is the second information signal layer of the two-layer optical disc 20. In the case of 20B, the stray light 14 of the main beam is reflected from the first information signal layer 20A (on the side closer to the objective lens 31), and the major axis of the elliptical shape which is the stray light 14 of the main beam is 45 degrees to the right. Inclined.

Also, in the optical pickup device 1 for a multilayer optical disc, as shown in FIGS. 2 and 3, the information signal layer targeted for reading and reproducing the information signal is the first information signal layer of the two-layer optical disc 20. In the case of 20 A, the stray light 14 of the main beam causes the second information signal layer 20 B (objective lens 3
The long axis of the elliptical shape which is the stray light 14 of the main beam is reflected to the left by 45 degrees.

Therefore, the first identification detector 13
In the A to fourth detectors 13D for identification, the amount of light received by each light receiving region changes as the elliptical shape of the stray light 14 of the main beam changes. These first
Identification detectors 13A to 4th identification detector 1
The 3D outputs each light amount detection signal of each light receiving region, and the detector 18 causes the objective lens 3 to output based on each light amount detection signal.
The focused information signal layer of 1 is detected.

The light amount detection outputs of the first identification detector 13A to the fourth identification detector 13D output by the respective light receiving regions are S1, S2, S3 and S4. Then, the detection signal (LS) for detecting the information signal layer of the two-layer optical disc 20 to which the objective lens 31 is focused can be obtained by LS = (S1 + S3) − (S2 + S4).

The optical pickup device 1 for a multilayer optical disc uses the detector 18 to read and reproduce the information signal of the two-layer optical disc 20 as a multilayer optical disc.
The information signal layer on which the objective lens 31 is focused is
If LS> 0, the first information signal layer 20A is detected, and if LS <0, the second information signal layer 20B is detected.

Next, in the optical pickup device 1 for a multilayer optical disc described above, when reading and reproducing a three-layer optical disc (not shown) as a multilayer optical disc, the first identification detector 13A to the fourth identification detector 13D are used.
However, the process of detecting the information signal layer in which the objective lens 31 is focused will be described with reference to FIGS. 4 (A) to 4 (C).

First, when the optical pickup device 1 for a multilayer optical disc reads and reproduces an information signal from the first information signal layer (the side closest to the objective lens 31) of the three-layer optical disc, as shown in FIG. 4 (A). The stray light 14B of the reflected beam from the second information signal layer in which the objective lens 31 is not focused on the first identification detector 13A to the fourth identification detector 13D and the third information signal layer from The stray light 14C of the reflected beam is concentrically superimposed.

Stray light 14B of the reflected beam from the second information signal layer and stray light 1 of the reflected beam from the third information signal layer 1
4C is an elliptical shape whose major axis is inclined 45 degrees to the right. Stray light 14C of the reflected beam from the third information signal layer
Are formed in concentric circles that are spread on the outer peripheral portion of the stray light 14B of the reflected beam from the second information signal layer.

Next, when the optical pickup device 1 for a multilayer optical disc reads and reproduces an information signal from the second information signal layer of a three-layer optical disc, as shown in FIG. 4 (B),
Stray light 14A of a reflected beam from the first information signal layer in which the objective lens 31 is not focused on the first to fourth detectors 13A to 13D and a reflected beam from the third information signal layer Stray light 14C are superposed on each other.

Stray light 1 of the reflected beam from the first information signal
4A has an elliptical shape with the major axis inclined to the left by 45 degrees, and the stray light 14C of the reflected beam from the third information signal layer is
It has an elliptical shape with the major axis inclined to the right by 45 degrees. Stray light 14A of the reflected beam from the first information signal layer intersects stray light 14C of the reflected beam from the third information signal layer.

When the optical pickup device 1 for a multilayer optical disc reads and reproduces an information signal from the third information signal layer (the side farthest from the objective lens 31) of the three-layer optical disc, as shown in FIG. 4C. In addition, the stray light 14A of the reflected beam from the first information signal layer in which the objective lens 31 is not focused on the first identification detector 13A to the fourth identification detector 13D and the second information signal layer from the stray light 14A The stray light 14C of the reflected beam is concentrically superimposed.

Stray light 14A of the reflected beam from the first information signal layer and stray light 1 of the reflected beam from the second information signal layer 1
4B is an elliptical shape whose major axis is inclined to the left by 45 degrees. Stray light 14A of the reflected beam from the first information signal layer
Are formed in concentric circles that are spread on the outer peripheral portion of the stray light 14B of the reflected beam from the second information signal layer.

That is, when the optical pickup device 1 for a multilayer optical disc reads and reproduces an information signal from each information signal layer of the three-layer optical disc, the first identification is performed according to the information signal layer on which the objective lens 31 is focused. Detector 1
The state in which the stray lights 14A, 14B, and 14C of the reflected beams from the respective information signal layers are superimposed on the 3A to fourth identification detectors 13D changes.

Therefore, in the optical pickup device 1 for a multilayer optical disk, the light receiving regions of the first to fourth detectors 13A to 13D output the respective light amount detection signals in accordance with the respective received light amounts, and these The detector 18 detects each light amount detection signal to detect the information signal layer on which the objective lens 31 is focused.

As described above, the optical disc pickup apparatus 1 for a multilayer optical disc according to the embodiment has the first identification detector 1
By providing the third to fourth identification detectors 13D, the information signal layer on which the objective lens 31 is focused can be detected at any time, if necessary.

Therefore, the optical pickup device 1 for a multilayer optical disc is focused on the objective lens 31 due to, for example, scratches and dust on the signal recording area of the multilayer optical disc during reading and reproducing the information signal of the multilayer optical disc. Even if the information signal layer that has been focused is defocused and the other information signal layers are focused, the correction operation for returning the focus to the original information signal layer that was focused can be performed quickly. .

That is, the optical pickup device 1 for a multilayer optical disk can promptly read and reproduce a desired information signal by promptly correcting the focal position even if the focal position of the objective lens 31 is deviated. You can

Although the multilayer optical disk pickup device 1 of the embodiment is provided with the polarization beam splitter 29,
By using a beam splitter instead of the polarization beam splitter 29, the quarter wavelength plate 30 is unnecessary, and the configuration can be simplified.

Further, the pickup device 1 for the multilayer optical disk according to the present embodiment detects the tracking error signal by the three-spot method, but the invention is not limited to the three-spot method. For example, another push-pull method, heterodyne The tracking error signal may be detected by a method or the like.

Further, in the first identification detector 13A to the fourth identification detector 13D, the light receiving regions are arranged in a radial pattern of four.
It may be composed of four equally divided photo detectors. In this case, the optical pickup device 1 for a multilayer optical disk
Is equipped with a beam splitter that splits the reflected beam reflected by the polarization beam splitter 29 into two, and irradiates the main beam detector 10 with one of the reflected beams split by this beam splitter, and splits the reflected beam into the other reflected beam. An astigmatism is generated by the cylindrical lens 33, and the reflected beam is applied to the four-division photodetector.

In addition, the optical pickup device 1 for a multilayer optical disc of the embodiment has the first identification detector 13A to the fourth identification detector 13D having a substantially L-shaped light receiving area.
And a main beam detector 10 having a substantially square shape, the first to fourth identification detectors having a substantially arc-shaped light receiving region, and the first to fourth identification detectors to the fourth identification detector. It may be configured to include a circular main beam detector whose outer peripheral portion is surrounded by a beam detector.

Finally, in the optical pickup device 1 for a multilayer optical disc of the embodiment, the first identification detector 13A to the fourth identification detector 13D are independently provided, but the outer peripheral portion of the main beam detector 10 is provided. Is provided with an identification detector having a substantially rectangular ring-shaped light receiving area, and the light receiving area of the identification detector is divided into four equal parts corresponding to the respective light receiving areas of the main beam detector 10 to obtain the first identification detector 13A. ~ You may comprise the 4th detector 13D for identification.

[0070]

According to the optical pickup device for a multilayer optical disk of the present invention, any one of a plurality of information signal layers is provided.
The objective lens provided so as to focus on the layer, the astigmatism generating means for generating astigmatism in the reflected beam from the optical disk, and the first to fourth light receiving beams divided into four by the dividing lines orthogonal to each other. A first light receiving means having a region for outputting a first light amount detection signal by calculating a received light amount of the reflected beam received by the first to fourth light receiving regions; By having the first to fourth identification detectors provided on the extension of the diagonal line of the light receiving area of the above, and calculating the received light amount of the reflected beam received by the first to fourth identification detectors. Second light receiving means for outputting a second light amount detection signal; control means for controlling the focus of the objective lens based on the first light amount detection signal; and based on the second light amount detection signal, Focus of the above objective lens By having a detecting means for detecting an information signal layer being combined at any time, it is possible to detect the information signal layer which is combined focus if necessary.

Therefore, this optical pickup device for a multilayer optical disc can promptly correct the focus position even if the focused information signal layer is deviated and the other information signal layer is focused. Then, the desired information signal can be quickly read and reproduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical pickup device for a multilayer optical disc according to a first embodiment of the present invention.

FIG. 2 is a schematic plan view showing a photodetector included in the optical pickup device for the multilayer optical disk.

FIG. 3 is a schematic plan view showing a main beam detector of a photodetector included in the optical pickup device for the multilayer optical disk.

FIG. 4 is a schematic plan view showing a main beam detector and an identification detector of a photo detector included in the optical pickup device for the multilayer optical disk.

FIG. 5 is a partially enlarged perspective view showing a two-layer optical disc.

FIG. 6 is a schematic diagram for explaining a state in which a conventional optical pickup device irradiates a two-layer optical disc with a laser beam.

FIG. 7 is a schematic diagram shown for explaining an optical path of a laser beam with which a conventional optical pickup device irradiates a two-layer optical disc.

[Explanation of symbols]

1 Optical Pickup Device for Multilayer Optical Disc 10 Main Beam Detector (Quadrant Photodetector) 18 Detector (Detecting Means) 13A to 13D Identification Detector (Light Receiving Means) 26 Laser Diode (Laser Light Source) 31 Objective Lens 33 Cylindrical Lens (Astigmatism) Generating means)

Continuation of front page (56) Reference JP-A-5-151609 (JP, A) JP-A-4-243024 (JP, A) JP-A-1-96828 (JP, A) JP-A-1-155524 (JP , A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B ^7/ 08-7/22

Claims (2)

(57) [Claims] 1. An optical pickup device for a multi-layer optical disc, wherein a plurality of information signal layers in which desired information signals are recorded are laminated, wherein any one of the plurality of information signal layers is focused. The objective lens provided as described above, astigmatism generating means for generating astigmatism in the reflected beam from the optical disc, and a dividing line orthogonal to each other.
A first light output region, which has divided first to fourth light receiving regions, and outputs a first light amount detection signal by calculating a light receiving light amount of the reflected beam received in the first to fourth light receiving regions. The light receiving means and the first to fourth identification detectors provided on the extension of the diagonal lines of the first to fourth light receiving areas, and the light received by the first to fourth identification detectors. Second light receiving means for outputting a second light amount detection signal by calculating the received light amount of the reflected beam; control means for controlling the focus of the objective lens based on the first light amount detection signal; An optical pickup device for a multilayer optical disc, comprising: a detection unit that detects the information signal layer on which the objective lens is focused based on a second light amount detection signal. 2. The first to fourth light receiving regions are formed in a substantially rectangular shape, and the first to fourth identification detectors are formed in a substantially L shape, and The bending point is located on an extension of a diagonal line of the first to fourth light receiving regions, and is provided so as to surround the first to fourth light receiving regions, respectively. Optical pickup device for multilayer optical disc.