JPH09288837A - Optical pickup and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly perform recording and reproducing of an optical disk even when the optical disk is of any system having different disk substrates in thickness. SOLUTION: The optical pickup has two semiconductor laser elements 21a and 21b for emitting light beams having different wavelengths respectively as a light source, and a hologram 28 for leading the light beams to a signal recording surface of the optical disk is formed to have such a phase depth as not a multiple of integer of a 1st wavelength of the light from one semiconductor laser element but a multiple of integer of a 2nd wavelength of the light from the other semiconductor laser element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of types of optical discs having different disc substrate thicknesses, irradiates the surface of a rotating optical disc with light, and detects return light. It is about.

[0002]

2. Description of the Related Art Conventionally, an optical pickup for reproducing an optical disc is constructed as shown in FIG.
In FIG. 10, the optical pickup 1 includes a semiconductor laser element 2, a collimator lens 3, a grating 4, a beam splitter 5, an objective lens 6, a multi-lens 7 and a photodetector 8.

According to the optical pickup 1 having such a configuration, the light beam emitted from the semiconductor laser element 2 is
After being converted into parallel light by the collimator lens 3 and divided into a main beam and a side beam by the grating 4, the light is reflected by the reflecting surface of the beam splitter 5 and is on the signal recording surface of the optical disc D via the objective lens 5. It converges to one point.

The return light beam reflected by the signal recording surface of the optical disc D enters the beam splitter 5 again via the objective lens 6. Here, the return light beam passes through the beam splitter 5 and enters the light receiving portion of the photodetector 8 via the multilens 7. As a result, the photodetector 8
The information recorded on the signal recording surface of the optical disc D is reproduced based on the detection signal output from the optical disc D.

[0005]

By the way, in recent years, optical discs have been highly densified as an auxiliary storage device for computers and a package medium for audio / image information and the like. There is a method of making the numerical aperture NA of the objective lens larger than the numerical aperture NA of the objective lens in the conventional optical pickup for a compact disc and using a short light source wavelength to make the beam spot small in diameter. There is a problem in that the allowable range for the tilt of the optical disc is reduced when the value is increased.

An optical disc has a predetermined disc substrate thickness (generally, 1.2 in the case of a compact disc or the like).
Since a signal recording surface is provided via a (mm) transparent substrate, when the optical disc is tilted with respect to the optical axis of the objective lens of the optical pickup, wavefront aberration occurs and a reproduction signal (RF) is generated. It will have an impact. At this time, regarding the wavefront aberration, the third-order coma aberration that is proportional to the cube of the numerical aperture and the square of the skew angle θ and that is inversely proportional to the wavelength is dominant. Therefore, an optical disc provided with a transparent substrate made of polycarbonate or the like that is mass-produced at low cost has a skew angle θ of, for example, plus or minus 0.5 to plus or minus 1 degree. Optical disk 6 from laser element 2
The converging spots to become asymmetrical, and intersymbol interference increases remarkably, and accurate reproduction of the RF signal cannot be performed.

Therefore, paying attention to the fact that the third-order coma aberration is proportional to the disc substrate thickness of the optical disc, the third-order coma aberration is remarkably reduced by setting the disc substrate thickness to, for example, 0.6 mm. It is possible to In this case, as an optical disc, two standards having different characteristics, that is, the disc substrate is relatively thick (for example, 1.2).
mm and those having a relatively thin disk substrate (for example, 0.6 mm) are mixed.

Here, for example, when a parallel flat plate having a thickness t is inserted in the optical path, the thickness t and the numerical aperture NA are t
Spherical aberration proportional to × (NA) ⁴ occurs. From this point of view, the objective lens of the optical pickup is designed to cancel this spherical aberration. By the way, if the disc substrate thickness is different, the spherical aberration is also different. Therefore, an objective lens corresponding to an optical disc having one standard, for example, a disc substrate thickness of 0.6 mm, is used, and the other standard, for example, a compact disc substrate thickness of 1.2 mm. When an optical disc such as a disc, a write-once optical disc, or a magneto-optical disc is played back, spherical aberration occurs due to the difference in the disc substrate thickness, so that the tolerance of the disc substrate thickness error that the optical pickup can handle is greatly increased. Will be exceeded.
Therefore, since a signal can be correctly detected from the returned light from the optical disc, there is a problem that a conventional optical pickup cannot reproduce a plurality of types of optical discs having different disc substrate thicknesses.

Therefore, it is possible to use a hologram that generates a wavefront that cancels the above-mentioned spherical aberration. For example, the first-order optical disc having the disc substrate thickness t1 is reproduced by the 0th-order light of the hologram, and the second-type optical disc having the disc substrate thickness t2 is reproduced by the primary light. A method compatible with a plurality of different types of optical discs is also possible. In this method, the primary light is lost when reproducing the first type optical disc, and the 0th order light is lost when reproducing the second type optical disc.
There is a problem that it is not suitable for a recordable optical disk device that requires high optical power.

In view of the above points, the present invention is to provide an optical pickup and an optical disk device which can properly perform recording and reproduction of an optical disk of any type having different disk substrate thicknesses. Has an aim.

[0011]

According to the present invention, the above object is to provide a light source for emitting a light beam, and an objective lens for irradiating the light beam from the light source so as to converge the light beam onto a signal recording surface of an optical disk. A light separating means arranged between the light source and the objective lens; a light detecting means for receiving a return light beam from the signal recording surface of the optical disk separated by the light separating means; And a hologram having a lens effect disposed in the optical path between the two semiconductor laser elements that emit light beams having different wavelengths as the light source, and the hologram is one of the semiconductors. The optical pitch is formed so as to have a phase depth that is not an integral multiple of the first wavelength of the light from the laser element and an integral multiple of the second wavelength of the light from the other semiconductor laser element. By the up, it is achieved.

According to the above arrangement, the hologram arranged between the light source and the optical disk has a phase depth which is not an integral multiple of the first wavelength of the light from one of the semiconductor laser elements. , Acts as a hologram only for the light of the first wavelength, and because the phase depth is an integral multiple of the second wavelength of the light from the other semiconductor laser element, the second light is directly It will be transparent.

Thus, for example, in the case of the first type of optical disc having a relatively thick disc substrate, the hologram acts as a lens for the light from one of the semiconductor laser elements, so that the spherical aberration of the disc substrate is reduced. Will be corrected. Therefore, the light beam from the light source is correctly focused on the signal recording surface of the optical disc through the hologram, and the return light from the signal recording surface of the optical disc is
It is incident on the light detection means.

Further, for example, in the case of the second type of optical disk having a relatively thin disk substrate, the hologram does not act on the light from the other semiconductor laser element, and the signal recording of the optical disk is performed through the objective lens. Reach the surface. Therefore, the light beam from the light source passes through the hologram as it is and is correctly focused on the signal recording surface of the optical disc.
The return light from the signal recording surface of the optical disc enters the light detecting means. Thus, the optimum signal reproduction is always performed regardless of the optical disc having any disc substrate thickness.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
The embodiments described below are preferable specific examples of the present invention, and therefore, various technically preferable limitations are given,
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows the configuration of an optical disk device incorporating an embodiment of an optical pickup according to the present invention. In FIG. 1, an optical disc device 10 includes a spindle motor 12 as a drive unit that rotationally drives an optical disc 11, an optical pickup 13, and a feed motor 14 as a drive unit. Here, the spindle motor 12 is driven and controlled by the system controller 16 and the servo control circuit 18, and is rotated at a predetermined rotation speed. As the optical disk 11, a plurality of types of optical disks can be selected and reproduced. For example, as the optical disc, a phase change type optical disc, a compact disc (CD), or the like can be reproduced.

Further, the optical pickup 13 irradiates the signal recording surface of the rotating optical disk 11 with light, and based on the signal from the signal demodulator and error correction circuit (ECC) 17, returns it to return light. Based on this, a reproduction signal is output.
As a result, the recording signal demodulated by the signal demodulator is error-corrected via the error correction circuit 17. The error-corrected recording signal is transmitted to the interface 1 when the optical disk device 10 is for data storage of a computer.
It is sent via 9 to an external computer or the like. As a result, the external computer or the like can receive the signal recorded on the optical disc 11 as a reproduction signal. When the optical disk device 10 is for audio, the error-corrected recording signal is converted from digital to analog by the D / A converter of the D / A and A / D converter 20, as indicated by the dotted line. And is output as an audio signal.

A feed motor 14 for moving the optical pickup 11 to a predetermined track on the optical disc 11 is connected to the optical pickup 13. The servo control circuit 18 controls the spindle motor 12 and the feed motor 14, and controls the focusing direction and the tracking direction of a biaxial actuator (not shown) that holds the objective lens of the optical pickup 13.

FIG. 2 shows a preferred embodiment of the optical pickup according to the present invention. In FIG. 2, the optical pickup 13 includes a semiconductor laser element 21 as a light source,
Between the collimator lens 22, the grating 23 as the diffraction element, the beam splitter 24 as the light separating means, the objective lens 25, the multi-lens 26 and the photodetector 27 as the light detecting means, and between the beam splitter 24 and the objective lens 25. The hologram 28 disposed in the optical path.

The semiconductor laser device 21 is a light emitting device utilizing recombination light emission of a semiconductor and is used as a light source. The light beam emitted from the semiconductor laser device 21 is
It is guided to the collimator lens 22. In this case, the semiconductor laser device 21, as shown in FIG. 3, has two light emitting portions 21a and 21b configured to emit light of different wavelengths.
It has. That is, the light emitting unit 21a has, for example, the wavelength λ1.
= Infrared laser for generating light of about 780 nm,
The light emitting unit 21b is a red laser that emits light with a wavelength λ2 = 635 nm.

Two semiconductor laser devices 21a and 21b having different oscillation modes are arranged on a substrate 21c made of an insulator such as silicon or aluminum nitride or a conductor such as copper, as shown in FIG. By arranging them side by side and mounting them, the semiconductor laser device 21 having a hybrid structure for emitting lights of different wavelengths can be easily constructed. The semiconductor laser device 21 shown in FIG. 3 has a hybrid structure, but the present invention is not limited to this, and the semiconductor laser devices 21a and 21a having a hybrid structure are provided.
You may make it arrange two b.

The collimator lens 22 is a convex lens and converts the light beam from the semiconductor laser element 21 into parallel light.

The grating 23 is a diffraction grating, and splits the parallel light from the collimator lens 22 into at least three light beams of a main beam of 0th order light and side beams of plus or minus 1st order light. To do.

The beam splitter 24 is arranged with its reflecting surface 24a serving as a half mirror tilted by 45 degrees with respect to the optical axis. The light beam from the semiconductor laser element 21 and the signal recording surface of the optical disk D are arranged in the beam splitter 24. Separate the return light from. That is, the light beam from the semiconductor laser device 21 is reflected by the reflecting surface 24 a of the beam splitter 24, and the return light is transmitted through the beam splitter 24.

The objective lens 25 is a convex lens, and the semiconductor laser device 21 reflected by the beam splitter 24.
The light beam from is focused on a desired track on the signal recording surface of the rotationally driven optical disc D. In this case, the objective lens 25 is designed so that, for an optical disc having a relatively thin disc substrate, the spherical aberration when the light beam passes through the disc substrate is corrected. Further, the objective lens 25 is supported by a biaxial actuator (not shown) so as to be movable in biaxial directions, that is, in a tracking direction and a focusing direction.

The multi-lens 26 is, for example, a cylindrical lens, which converges the return light beam which has passed through the beam splitter 24 to the photodetector 27 and which is non-incident with respect to the incident light in order to detect the focus error signal. It is designed to add point aberration.

The photodetector 27 is configured to have a light receiving portion for each return light beam that has passed through the beam splitter 24.

As shown in FIG. 4A, the hologram 28 is constructed as a diffraction grating type element having a hologram pattern formed in a concentric ring shape so as to have a lens effect. Here, in the hologram pattern of the hologram 28, the phase depth is not an integral multiple of the wavelength λ1 of the light beam of the one semiconductor laser element 21a, and an integral multiple of the wavelength λ2 of the light beam of the other semiconductor laser element 21b. Is set as follows. Specifically, the hologram 28 is shown in the partially enlarged sectional view of FIG. In the figure, letting the refractive index n, the wavelength λ, and the refractive index of air be 1 for light respectively passing through the region A and the region B of the hologram 28, the position of {(n-1) d} / λ There is a phase difference. Where (n-
1) Since d is the phase depth and {(n-1) d} / λ is not an integer of λ1, the light beam of the semiconductor laser element 21a is subjected to the hologram effect when passing through the hologram 28. On the other hand, when {(n-1) d} / λ is an integer of the wavelength λ2 of the light beam of the semiconductor laser element 21b, the light beam of the semiconductor laser element 21b does not undergo the hologram effect when passing through the hologram 28.

As a result, the hologram 28 having such a structure acts as a hologram when the wavelength of the incident light is λ1 and allows the hologram 28 to pass therethrough when the wavelength of the incident light is λ2. Acts like.

Therefore, for example, the light having the first wavelength λ1 from the light emitting portion 21a is converted into the primary light by the action of the hologram 28 as a lens, as shown in FIG. 5B. Via, it is correctly focused on the signal recording surface of the optical disc D1 having a relatively thick disc substrate. The light having the second wavelength λ2 from the light emitting portion 21b passes through the hologram 28 as it is, as shown in FIG. 5A, and the 0th-order light thereof passes through the objective lens 25 and the disc substrate. The optical disc D2 having a relatively thin thickness is correctly focused on the signal recording surface.

Optical pickup 13 according to the present embodiment
The following is a description of a case where the optical disk (for example, a compact disk) D1 having the above-described relatively thick disk substrate thickness of 1.2 mm is first reproduced.
In this case, the semiconductor laser element 21a of the semiconductor laser element 21 emits light.

As a result, the light beam having the wavelength λ1 from the semiconductor laser device 21a is emitted by the collimator lens 22.
Is converted into parallel light by the beam splitter 23, and is split into a main beam and a side beam by the grating 23, and then is reflected by the reflecting surface 24a of the beam splitter 24.
The optical disc D1 is irradiated with the light through the objective lens 8 and the objective lens 25. At this time, the hologram 28 acts as a hologram with respect to the light of the first wavelength λ1 from the semiconductor laser element 21a, and thus the spherical aberration is corrected for the objective lens 25 for an optical disc having a relatively thin disc substrate.
On the other hand, the spherical aberration is corrected for the optical disc D1 having a relatively thick disc substrate. This allows
The light beam will be correctly focused on the signal recording surface of the optical disc D1.

The return light from the optical disk D1 again passes through the objective lens 25 and the hologram 28, the beam splitter 24, and then converges on the photodetector 27 via the multi-lens 26. As a result, the recording signal of the optical disc D1 is reproduced based on the detection signal of the photodetector 27. In this case, the light converged on the signal recording surface of the optical disc D1 is only the primary light of the light beam from the semiconductor laser element 21a that has passed through the hologram 28 and is used, for example, only for reproduction.

Next, a relatively thin disk substrate thickness of 0.6 m
When reproducing the optical disc D2 of m, the semiconductor laser element 21b of the semiconductor laser elements 21 emits light.

As a result, the light beam having the wavelength λ2 from the semiconductor laser device 21b is collimated by the collimator lens 22.
Is converted into parallel light by the beam splitter 23, and is split into a main beam and a side beam by the grating 23, and then is reflected by the reflecting surface 24a of the beam splitter 24.
It is irradiated onto the optical disc D2 via the objective lens 8 and the objective lens 25. At this time, the light having the second wavelength λ2 from the semiconductor laser device 21b passes through the hologram 28 as it is, so that the light beam is correctly transmitted to the signal recording surface of the optical disc D2 based on the spherical aberration of the objective lens 25. It will converge.

The return light from the optical disk D2 again passes through the objective lens 25 and the hologram 28 and further through the beam splitter 24, and then converges on the photodetector 27 via the multi-lens 26. Thereby, the photodetector 2
Based on the detection signal of 7, the recording signal of the optical disc D2 is reproduced. In this case, the light emitted to the optical disc D2 is the 0th-order light of the light beam from the semiconductor laser element 21b that has passed through the hologram 28.
Since 8 does not act as a hologram, almost 100% of the light beam from the semiconductor laser device 21b is used. Therefore, since the light amount loss of the semiconductor laser element 21b which is the light source is extremely small,
For example, it will be used for recording and reproduction.

6 to 9 show the optical pickup 1 described above.
3 shows a configuration example of the photodetector 27 in No. 3. First,
In the first configuration example of the photodetector shown in FIG. 6, the photodetector 30 is configured so that the focus error signal is detected by the astigmatism method and the tracking error signal is detected by the three-spot method. ing. That is, in FIG. 6, the photodetector 30 includes the semiconductor laser elements 21a and 21a.
b is a configuration used when the optical discs D are arranged in the radial direction, and the light receiving portion A is divided into four vertically and horizontally in the center with respect to the tangential direction.
A set of light-receiving parts 31, 32, which is composed of B, C, D and light-receiving parts E, F arranged on both sides thereof (upper and lower in the drawing).
Are provided side by side in the radial direction in which the semiconductor laser elements 21a and 21b are aligned.

As a result, when the optical beam from the semiconductor laser element 21a is applied to the optical disc D1, the returned light from the optical disc D1 is received by the set 31 of the light receiving units, and the light receiving units A, B, and The side beams enter C and D, and the side beams enter the light receiving portions E and F on both sides. Further, when the optical beam from the semiconductor laser element 21b is applied to the optical disc D2, the return light from the optical disc D2 is received by the set 32 of the light receiving units, and the main beam is received by the central light receiving units A, B, C and D. Also, the side beams are incident on the light receiving portions E and F on both sides.

The photodetector 33 shown in FIG. 7 has a structure used when the semiconductor laser elements 21 are arranged in the direction of 45 degrees between the radial direction and the tangential direction of the optical disk D. With respect to the tangential direction, from the light receiving portions A, B, C, D disposed in the center and divided into four vertically and horizontally, and the light receiving portions E, F disposed on both sides (oblique in the drawing) thereof. A set of light receiving parts 34,
Two sets of 35 are arranged side by side in the direction in which the semiconductor laser elements 21a and 21b are arranged. In this case, the light receiving portions A, B, C, D at the center are divided in a direction parallel to the direction in which the semiconductor laser elements 21a, 21b are arranged and a direction perpendicular thereto.

As a result, when the optical beam from the semiconductor laser device 21a is applied to the optical disc D1, the return light from the optical disc D1 is received by the set 34 of the light receiving units, and the light receiving units A, B, and The side beams enter C and D, and the side beams enter the light receiving portions E and F on both sides. Further, when the optical beam from the semiconductor laser device 21b is applied to the optical disc D2, the return light from the optical disc D2 is received by the light receiving unit set 35, and the main beam is transmitted to the central light receiving units A, B, C and D. Also, the side beams are incident on the light receiving portions E and F on both sides.

The photodetector 36 shown in FIG. 8 is used when the semiconductor laser elements 21 are arranged in the tangential direction of the optical disc D, and is arranged at the center in the tangential direction. A set of light receiving portions 37, 38, which is composed of light receiving portions A, B, C, D divided into four vertically and horizontally and light receiving portions E, F arranged on both sides (left and right in the drawing) of the semiconductor, Two sets of the laser elements 21a and 21b are arranged side by side in the tangential direction. As a result, when the optical beam from the semiconductor laser device 21a is applied to the optical disc D1, the optical disc D1
In the set 37 of the light receiving portions, the return light from the main beam enters the central light receiving portions A, B, C, D, and the side beams enter the light receiving portions E, F on both sides. Also,
The optical beam emitted from the semiconductor laser device 21b is the optical disc D.
When it is irradiated on the optical disc 2, the return light from the optical disc D2 is
In the set 38 of light receiving parts, the main beam is incident on the central light receiving parts A, B, C and D, and the side beam is incident on the light receiving parts E and F on both sides.

In the photodetectors 30 and 33, the focus error signal FCS and the tracking error signal T
RK, when the signals from the respective light receiving portions A, B, C, D, E and F are Sa, Sb, Sc, Sd, Se and Sf, respectively,

[Equation 1]

[Equation 2] Given in.

The photodetector 39 shown in FIG. 9 is another structure used when the semiconductor laser elements 21 are aligned in the tangential direction of the optical disc D, and corresponds to the semiconductor laser element 21a. , With respect to the tangential direction, the light receiving portions A, B, C, D are divided into four vertically and horizontally at the center, and the light receiving portions E, F are provided on both sides (left and right in the drawing) of the light receiving portions. It has a first set 40 of light receiving parts. Then, the semiconductor laser device 21b
In the tangential direction, the light receiving portions A1, B1, C1, which are arranged in the center and are divided into four vertically and horizontally.
There is provided a second set 41 of light receiving portions, which includes D1 and light receiving portions E1 and F1 arranged on both sides (left and right in the drawing) thereof.

The set 40 of the first and second light receiving portions,
Two sets 41 are provided side by side in the tangential direction in which the semiconductor laser elements 21a and 21b are arranged side by side, and the light receiving section F in the first set 40 and the light receiving section E1 in the second set 41 are the same one. The light receiving unit is configured to be shared. As a result, the length of the entire photodetector 39 in the tangential direction is determined by the photodetector 3 of FIG.
Compared with 6, the configuration will be shorter. As a result, when the optical beam from the semiconductor laser device 21a is applied to the optical disc D1, the return light from the optical disc D1 is received by the set of light receiving units 40, and the main beam is received at the central light receiving units A, B, C and D. In addition, the side beams are incident on the light receiving portions E and F on both sides.

When the optical beam from the semiconductor laser device 21b is applied to the optical disc D2, the optical disc D
With respect to the return light from 2, the main beam is incident on the central light receiving portions A1, B1, C1, D1 and the side beam is incident on the light receiving portions F (E1), F1 on both sides in the light receiving portion set 41. become.

In the photodetector 39, the focus error signal FCS1 and tracking error signal TRK1 from the semiconductor laser element 21a are sent to the respective light receiving portions A, B, and
The signals from C, D, E, F, A1, B1, C1, D1, and F1 are respectively sent to Sa, Sb, Sc, Sd, Se, Sf,
When Sa1, Sb1, Sc1, Sd1, Sf1 are set,

(Equation 3)

(Equation 4) As a result, the focus error signal FCS2 and the tracking error signal T generated by the semiconductor laser element 21b
RK2 is

(Equation 5)

(Equation 6) Will be given by

Although the hologram 28 is disposed between the beam splitter 24 and the objective lens 25 in the above embodiment, the invention is not limited to this, and the hologram 28 is disposed between the semiconductor laser element 21 which is the light source and the optical disk D. It suffices if it is arranged in the optical path of. Further, the semiconductor laser device 21 is not limited to the configuration shown in FIG. 3, and other arbitrary arrangement is possible.

Further, in the above-described embodiment, the semiconductor laser elements 21a and 21b, which are the two light emitting portions of the semiconductor laser element 21, are arranged in the tangential direction, the radial direction or the intermediate direction thereof, which corresponds to this. ,
Each of the photodetectors 30, 33, 36, 39 is provided with a set of light receiving portions thereof, but is not limited to this, and the semiconductor laser element 21 which is two light emitting portions of the semiconductor laser element 21 is not limited to this.
It is obvious that a and 21b are arranged in an arbitrary direction, and each light emitting portion of the photodetector may be arranged correspondingly.

Further, in the above embodiment, the optical disc has a disc substrate thickness of 1.2 mm and 0.6 m.
In the case of m, the hologram 28 transmits the light beam or acts as a hologram so that the light beams are converged on the signal recording surfaces of the optical disc having a relatively thin disc substrate thickness and the optical disc having a relatively thick disc substrate thickness. However, the present invention is not limited to this, and the present invention can be applied, for example, when reproducing a bonded optical disk in which two substrates are bonded and a normal optical disk.

[0050]

As described above, according to the present invention, it is possible to provide an optical pickup for an optical disc reproducing apparatus which can properly reproduce an optical disc regardless of the type of optical disc having a different disc substrate thickness. become.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical disc device incorporating an embodiment of an optical pickup according to the present invention.

FIG. 2 is a schematic side view showing a configuration of an optical pickup in the optical disk device of FIG.

3A and 3B are a plan view and a side view showing a configuration example of a semiconductor laser element in the optical pickup of FIG.

4 is a plan view showing a configuration of a hologram in the optical pickup of FIG.

5 is a schematic side view showing a converged state of the holograms of FIG. 4 with respect to optical disks of different kinds having different disk substrate thicknesses.

6 is a plan view showing a first configuration example of a photodetector in the optical pickup of FIG.

FIG. 7 is a plan view showing a second configuration example of a photodetector in the optical pickup of FIG.

FIG. 8 is a plan view showing a third configuration example of the photodetector in the optical pickup of FIG.

9 is a plan view showing a fourth configuration example of the photodetector in the optical pickup of FIG.

FIG. 10 is a schematic perspective view showing an example of a conventional optical pickup.

[Explanation of symbols]

10 ... Optical disk device, 11 ... Optical disk, 1
2 ... Spindle motor, 13 ... Optical pickup, 14 ... Feed motor, 15 ... Magnetic head, 1
6 ... System controller, 17 ... Signal demodulator and ECC, 18 ... Servo control circuit, 19 ... Interface, 20 ... D / A, A / D converter, 2
1, 21a, 21b ... Semiconductor laser device, 22 ...
・ Collimator lens, 23 ... Grating, 24
... Beam splitter, 25 ... Objective lens, 26
... Multi-lens, 27 ... Photodetector, 28 ...
Hologram, 30, 33, 36, 39 ... Photodetector,
31, 32, 34, 35, 37, 38, 40, 41 ...
・ Set the light receiving part.

Claims (3)

[Claims] 1. A light source that emits a light beam, an objective lens that irradiates the light beam from the light source so that the light beam converges on a signal recording surface of an optical disc, and a light disposed between the light source and the objective lens. Separation means, light detection means for receiving a return light beam from the signal recording surface of the optical disk separated by the light separation means, and hologram having a lens effect arranged in the optical path between the light source and the optical disk. And having, as the light source, two semiconductor laser elements that emit light beams having different wavelengths, and the hologram is an integer multiple of the first wavelength of light from one of the semiconductor laser elements. And an optical pickup which is formed so as to have a phase depth which is an integral multiple of a second wavelength of light from the other semiconductor laser device. 2. A diffraction element for dividing a light beam from each of the semiconductor laser elements into at least three light beams, and one side from each of the semiconductor laser elements divided by the diffraction element. The optical pickup according to claim 1, wherein the beam is detected by the same light receiving section of the light detecting means. 3. Driving means for rotating the optical disc, and light irradiating the optical disc through an objective lens, and returning light from the signal recording surface from the optical disc is detected by the light detecting means through the objective lens. An optical pickup, a means for supporting the objective lens so as to be movable in two axial directions, a signal processing circuit for generating a reproduction signal based on a detection signal from the light detection means, and a detection signal from the light detection means, A servo circuit for moving the objective lens of the optical pickup in two axial directions, wherein the optical pickup converges the light source for emitting a light beam and the light beam from the light source onto the signal recording surface of the optical disc. An objective lens for irradiating an object, a light separating means arranged between the light source and the objective lens, and a signal recording surface of an optical disk separated by the light separating means. And a hologram having a lens effect arranged in the optical path between the light source and the optical disc, the light detecting means for receiving the return light beam from Having two semiconductor laser elements to emit, and the hologram is not an integral multiple of the first wavelength of the light from one semiconductor laser element, and the second wavelength of the light from the other semiconductor laser element An optical disk device formed so as to have a phase depth that is an integral multiple.