JP3223143B2 - Optical pickup device and optical recording / reproducing device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical pickup device for recording and / or reproducing data on or from a plurality of types of optical discs having different substrate thicknesses and recording methods.

[0002]

2. Description of the Related Art An optical disk having a thickness of about 1.2 mm, such as a CD-ROM, from which information is read using a semiconductor laser is provided. In this type of optical disk, focus servo and tracking servo are performed on a pickup objective lens to irradiate a pit row on a signal recording surface with a laser beam to reproduce a signal. Recently, the recording density for recording a long moving image has been increasing.

[0003] For example, the same 12 cm diameter as a CD-ROM
A DVD standard for recording 4.7 Gbyte information on one side of an optical disc has been proposed. The thickness of a DVD disk is about 0.6 mm, and 9.4 Gbyte information can be recorded on a single disc by bonding both sides. There is also a CD-R as a recordable optical disc having the same diameter, substrate thickness and recording density as a CD.

[0004] Furthermore, it is possible to record a signal magnetically, irradiate the recorded signal with a laser beam, and detect a difference in the angle at which the plane of polarization of the reflected light is rotated by the magneto-optical signal to reproduce the signal. 6.1 Gby in a simple magneto-optical recording medium
Media with a high capacity of te have also been developed. Next time, it is conceivable that these four types of recording media coexist, so a device capable of compatible reproduction of the four types of recording media is required. CD, CD
In the case of -R and DVD, in order to record a signal as a pit row, reproduction is performed by detecting a change in intensity of reflected laser beam on the recording surface of the irradiated laser beam. On the other hand, in the magneto-optical recording medium, in order to magnetically record a signal, reproduction is performed by detecting a difference in an angle at which an irradiated laser beam is rotated on a polarization plane by a magnetic domain. In the case of DVDs and magneto-optical recording media and CDs and CD-Rs, the substrate thickness of the former optical disk is 0.6 mm, and the latter is 1.2 mm.

A technique for reproducing a recording medium having a different substrate thickness with one optical pickup device is disclosed in Japanese Patent Laid-Open No. 5-30.
It is disclosed in Japanese Patent No. 3766. This technology uses an objective lens with a numerical aperture of 0.6 designed to reproduce a high-density disk with a short-wavelength laser beam. This is an apparatus in which an aperture for reducing the effective numerical aperture by blocking the outer peripheral side of the beam is added to the light source side of the objective lens.

Further, as a method of changing the effective numerical aperture of an objective lens for condensing a laser beam by selectively shielding the outer peripheral portion of a laser beam emitted from a semiconductor laser, the applicant has disclosed Japanese Patent Application No. Hei. No. 84307 proposes a method of combining a liquid crystal that selectively rotates a polarization plane of a laser beam and a polarization filter that transmits only a laser beam polarized in a specific direction, and using this method, it is possible to interchangeably reproduce optical disks having different substrate thicknesses. Disclosure technology.

[0007]

However, Japanese Patent Application Laid-Open No. 5-3
In the method disclosed in Japanese Patent Application No. 03766 and Japanese Patent Application No. 8-84307, it is possible to perform compatible reproduction between DVDs having different substrate thicknesses, CDs, and CD-Rs, but to use CDs and CDs having different recording methods.
It is not possible to perform compatible reproduction between a DR, DVD and a magneto-optical recording medium.

Accordingly, the present invention has been made to solve the above problems, and provides an optical pickup device capable of performing recording and / or reproduction on a plurality of types of optical discs having different substrate thicknesses and recording methods. .

[0009]

According to the present invention, there is provided a first laser beam having a first wavelength and a second laser beam having a second wavelength different from the first laser beam. A laser light generating means for selectively generating laser light, and a first or second laser light from the laser light generating means is selectively incident, and shields an outer peripheral portion of the incident first laser light. And a first optical element that diffracts the inner peripheral portion and transmits the incident second laser light as it is, and the laser light passing through the first optical element is incident, and the incident laser light is An objective lens for guiding to the recording surface of the optical disc, a first state in which the reflected light from the recording surface of the optical disc is transmitted as it is, and diffracted light reflected from the recording surface of the optical disc.
A second optical element that is switched to a second state in which a laser beam having a mixture of a polarization component and an S-polarization component, a laser beam having only a P-polarization component, and a laser beam having only an S-polarization component is separated; Light detecting means for receiving laser light via a second optical element, wherein the first laser from the laser light generating means receives the first laser from a recording surface of an optical disk via the first optical element and the objective lens. A first optical disc to be guided to the light detecting means via the second optical element switched to the first state and to be reproduced by the laser beam generating means; Guides the second laser from the optical disc to the recording surface of the optical disk via the first optical element and the objective lens, and switches the reflected light from the recording surface to the first state. Through the element A second optical disc guided to the light recording detecting means and reproduced, and the second laser from the laser light generating means guided to the recording surface of the optical disc via the first optical element and the objective lens, and And selectively reproducing a third optical disc to be reproduced by guiding reflected light from a recording surface to the light detecting means via the second optical element switched to the second state. Optical pickup device.

The present invention also provides a first laser beam having a first wavelength and a first polarization direction and a second laser beam having a second wavelength and a second polarization direction different from the first laser beam. A laser light generating means for selectively generating the laser light, and a first or second laser light from the laser light generating means are selectively incident, and an outer peripheral portion of the incident first laser light is A first optical element that shields light, diffracts an inner peripheral portion, and transmits the incident second laser light as it is;
A laser beam is incident through the optical element, and an objective lens that guides the incident laser beam to the recording surface of the optical disc, and a first lens that directly transmits reflected light from the recording surface of the optical disc.
And the light reflected from the recording surface of the optical disk is diffracted,
A second optical element that is switched to a second state in which a laser beam in which a P-polarized component and an S-polarized component are mixed, a laser beam having only a P-polarized component, and a laser beam having only an S-polarized component are separated; Light detecting means for receiving the laser light via the second optical element, and recording the first laser from the laser light generating means on the optical disk via the first optical element and the objective lens To the recording surface and switch the reflected light from the recording surface to the first state.
A first optical disc guided to the light detecting means through the optical element for reproduction, and the second laser beam from the laser light generating means is supplied to the optical disc through the first optical element and the objective lens. The second light that has been guided to the recording surface and the reflected light from the recording surface has been switched to the first state.
A second optical disc guided to the light detecting means through the optical element for reproduction, and the second laser beam from the laser light generating means is supplied to the optical disc through the first optical element and the objective lens. The second light guided to the recording surface and the reflected light from the recording surface is switched to the second state.
An optical pickup device for selectively reproducing a third optical disk which is guided to the light detecting means via the optical element and reproduced.

Further, in the present invention, the second optical element includes one glass plate on which a transparent electrode is formed in the optical axis direction, and a liquid crystal provided in contact with the transparent electrode of the one glass plate. And another glass plate on which a transparent electrode is formed so as to be in contact with the liquid crystal, wherein a voltage is selectively applied to the transparent electrode according to a recording method of the optical disk. I do.

Further, in the optical pickup device of the present invention, a tracking error signal and a focus error signal are generated by a laser beam having a mixture of a P-polarized component and an S-polarized component detected by the light detecting means. The reproduction signal is generated based on the intensity difference between the laser light having only the P-polarized component and the laser light having only the S-polarized component detected by the method.

Further, the present invention is an optical recording / reproducing apparatus provided with the above optical pickup device.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the rated values and reproduction conditions of CDs, CD-Rs, DVDs, and high-density magneto-optical recording media (hereinafter referred to as "MO-7") to be compatible with the present invention. The substrate thickness of the CD and CD-R is 1.2 (with a tolerance of ± 0.2.
1) mm, the shortest pit length is 0.90 (tolerance ± 0.1)
μm, track pitch 1.6 (tolerance ± 0.1)
m, the reflectivity for a laser beam having a wavelength of 780 nm is 6
0%, and the spot diameter of the laser beam during reproduction is 1.
5 (tolerance ± 0.1) μm, numerical aperture of the objective lens is 0.1
45 (tolerance ± 0.05), and the reproduction laser beam wavelength is 780 (tolerance ± 15) nm. The substrate thickness of the DVD is 0.6 (tolerance ± 0.05) mm, the shortest pit length is 0.40 (tolerance ± 0.1) μm, and the track pitch is 0.74 (tolerance ± 0.01). ) Μm, wavelength 635 nm
Is 70% or more (in the case of a single signal recording surface) or 20 to 40% (in the case of two signal recording surfaces), and the spot diameter of the laser beam at the time of reproduction is 0.9 ( The tolerance is ± 0.5) μm, the numerical aperture of the objective lens is 0.6 (tolerance ± 0.05), and the reproducing laser beam wavelength is 635 (tolerance ± 15) nm. Furthermore, MO
The substrate thickness of −7 is 0.6 (tolerance ± 0.05) mm, the shortest domain length is 0.15 (tolerance ± 0.05) μm, and the track pitch is 0.6 (tolerance ± 0.05). μm, wavelength 6
20-30% reflectivity for 35 nm laser beam
And the spot diameter of the laser beam during reproduction is 0.9.
(Tolerance: ± 0.5) μm, numerical aperture of objective lens is 0.6
(Tolerance ± 0.05), reproduction laser beam wavelength is 63
5 (allowable error ± 15) nm.

CD, CD-R, DVD, and MO-7
FIG. 2 shows the configuration of an optical pickup device 10 that performs compatible playback of data.
Shown in Wavelength 635 emitted from laser light generating means 1
(Tolerance: ± 15, the same applies hereinafter) nm or wavelength 73
The laser beam of 5 nm (tolerance: ± 15, the same applies hereinafter) is half reflected by the half mirror 2, enters the collimator lens 3, is collimated by the collimator lens 3, and is raised by the rising mirror 4. . The raised laser beam is selectively shielded at the outer peripheral portion by the first optical element 5, diffracted at the inner peripheral portion and condensed by the objective lens 7, and is transmitted through the transparent polycarbonate substrate 11 (or 11).
0) through the signal recording surface 11a (or 1
10a). The laser beam reflected by the signal recording surface 11a (or 110a)
(Or 110), returning to the half mirror 2 via the objective lens 7, the first optical element 5, the rising mirror 4, and the collimator lens 3, half of the light is transmitted by the half mirror 2, and the second optical element At 8, the laser beam is selectively diffracted into a laser beam containing only the P-polarized component, a laser beam containing only the S-polarized component, and a laser beam containing both the P-polarized component and the S-polarized component, and detected by the photodetector 9. The objective lens 7
Is the substrate thickness 0.6 (tolerance ± 0.05, the same applies hereinafter) m
Designed for optical discs with a numerical aperture of 0.6
(Allowable error ± 0.05, the same applies hereinafter).

In the present invention, the laser beam generating means 1 comprises a semiconductor laser 1a for generating a laser beam having a wavelength of 635 nm and a semiconductor laser 1b for generating a laser beam having a wavelength of 780 nm.
Is reproduced, the semiconductor laser 1 b
D, when the MO-7 is reproduced, the semiconductor laser 1
a is selectively driven by the laser drive circuit 20. With reference to FIG. 3, mounting of the semiconductor lasers 1a and 1b will be described. FIG. 3 is a view of the laser light generating means 1 as seen from the direction of the half mirror 2. The laser light generating means 1
The optical disk is arranged so that the direction indicated by arrow 31 is the track direction of the optical disk and the direction indicated by arrow 32 is the tracking direction of the optical disk. Further, the laser light generating means 1 has three cuts k1, k2, and k3, and the light emitting points A and B of the semiconductor lasers 1a and 1b are respectively cut off by k.
It is mounted so as to be aligned in the direction of arrow 32 on the line connecting 1-k2. Further, the semiconductor lasers 1a and 1b may be independently formed and mounted on one substrate, or two semiconductor lasers may be formed by growing crystals on one substrate. Further, the distance L between the light emitting points A and B of the semiconductor lasers 1a and 1b is in the range of 100 to 500 μm. When the semiconductor lasers 1a and 1b are formed, the light emitting points A and B may be shifted from the center of the element, and the distance L may be shortened by arranging the two elements in the direction of the arrow 32.

Referring to FIGS. 4, 5, 6, 7, 8, and 9, details of the first optical element 5 will be described. The first optical element 5 includes an outer peripheral portion 5a and an inner peripheral portion 5b, and the outer peripheral portion 5a emits a laser beam having a wavelength of 635 nm.
It has the function of transmitting the entire laser beam as it is, diffracts only the laser beam having a wavelength of 780 nm to the outside of the optical axis, and does not allow the laser beam to enter the objective lens 7. Wavelength 78
The objective lens 7 by diffracting only the laser beam of 0 nm.
It has a function to make it incident on Referring to FIG. 5, the cross-sectional structure of the first optical element 5 is such that the outer peripheral portion 5a has an uneven structure, the inner peripheral portion 5b has a large triangular shape, and a portion corresponding to a triangular slope has a small step-like shape. (See FIG. 5A). In order to diffract a laser beam having a wavelength of 780 nm to the outside of the optical axis, the pitch of the unevenness of the outer peripheral portion 5a is preferably in the range of 8 to 12 μm. It can be easily formed by etching. The cross-sectional structure of the inner peripheral portion 5b is not limited to the structure shown in FIG. 5A, and a structure having a smooth slope as shown in FIG. 5B is suitable.

Referring to FIGS. 6 and 7, the first optical element 5 further preferably has an outer peripheral portion 5a having an uneven structure provided on one surface of the glass. The inner peripheral portion 5b is provided on the other surface different from the surface on which the outer peripheral portion 5a is provided. FIG. 6 in which the outer peripheral portion 5a and the inner peripheral portion 5b are formed on different surfaces,
The structure shown in FIG. 7 facilitates the production of the first optical element 5.

Referring to FIG. 8, the function of the first optical element 5 for a laser beam having a wavelength of 635 nm will be described. The laser beam having a wavelength of 635 nm is not affected at all by the first optical element 5, passes through as it is, enters the objective lens 7, is condensed by the objective lens 7, and has a substrate thickness of 0.6 mm. Focus on the signal recording surface 11a of the optical disc. Referring to FIG.
The function of the first optical element 5 for a laser beam of nm will be described. The portion of the laser beam having a wavelength of 780 nm, which enters the outer peripheral portion 5a, is largely diffracted outside the optical axis by the diffraction grating, and does not enter the objective lens 7. The laser beam incident on the inner peripheral portion 5b is diffracted outward by the triangular shape.
As described above, the light is incident on the objective lens 7 without being greatly diffracted.
Therefore, only the laser beam incident only on the inner peripheral portion 5b of the first optical element 5 reaches the objective lens 7, and is condensed by the objective lens 7 and is focused on the signal recording surface 110a of the optical disk having a substrate thickness of 1.2 mm. Focus. That is, the wavelength 780n
The laser beam of m is substantially shielded from the outer periphery by the first optical element 5, only the inner periphery is diffracted, and the zero-order light LB ₀ and the first-order light LB ₁ enter the objective lens 7. I do.
The first optical element 5 causes diffraction of the inner peripheral portion of the laser beam having a wavelength of 780 nm to generate primary light LB ₁ because the objective lens 7 has a substrate thickness of 0.6 mm.
It is designed for an optical disc, and it is 1.2m thick only by shielding the outer periphery of the laser beam of 780nm wavelength.
This is because the aberration is generated when the light is incident on the m substrate, and this aberration is reduced. Accordingly, the diameter and the diffraction of the inner peripheral portion 5b of the first optical element 5 are reduced so that the effective numerical aperture of the objective lens 7 by the zero-order light LB ₀ and the first-order light LB ₁ generated by the diffraction becomes 0.45. The triangular shape to be raised is determined.

In the description of FIGS. 8 and 9, the optical element in which the outer peripheral portion 5a and the inner peripheral portion 5b are formed on the same surface has been described, but the outer peripheral portion 5a and the inner peripheral portion 5b are different. Needless to say, the same function can be obtained even when formed on the surface. Further, the first optical element 5 is fixed to the objective lens 7 and the actuator 6 and has a structure that moves in conjunction with the objective lens 7.

As described above, the first optical element 5 substantially shields the outer periphery of a laser beam having a wavelength of 780 nm due to the difference in the wavelength of the laser beam.
The laser beam in the inner peripheral portion is diffracted and focused on the signal recording surface 110a of the optical disk having a substrate thickness of 1.2 mm, and the wavelength 63
This is a bifocal optical element that transmits a 5-nm laser beam as it is without causing any diffraction and focuses on the signal recording surface 11a of an optical disk having a substrate thickness of 0.6 mm.

Referring to FIG. 10, the second optical element 8
Will be described in detail. The second optical element 8 is composed of two glass plates 81 and 82 with transparent electrodes rubbed in a certain direction.
To make the rubbing direction parallel so that the TN type liquid crystal 80
Is sandwiched between them. Therefore, when a voltage is not applied to the TN type liquid crystal 80 through the glass plates 81 and 82 with transparent electrodes, the liquid crystal molecules 8 as shown in FIG.
3 are arranged in a direction parallel to the rubbing direction from one glass plate 81 with a transparent electrode to another glass plate 82 with a transparent electrode. As a result, the laser beam 8 polarized in a certain direction
When the light 4 enters the second optical element 8, the laser beam 840 is diffracted by the liquid crystal molecules 83 arranged as described above, and a laser beam 840 in which a P-polarized component and an S-polarized component are mixed, and a laser beam 841 having only a P-polarized component. , And the laser beam 842 having only the S-polarized component is separated and transmitted through the second optical element 8.

On the other hand, when a voltage of 10 V is applied to the TN type liquid crystal 80 through the glass plates 81 and 82 with transparent electrodes, the liquid crystal molecules 80 become two sheets of glass with transparent electrodes as shown in FIG. The arrangement is such that it stands vertically with respect to the directions of 81 and 82. As a result, when the laser beam 84 polarized in a certain direction is incident on the second optical element 8, the laser beam 84 is not diffracted from the liquid crystal molecules 83 and is transmitted as it is. Therefore, the transmitted light is a laser beam 840 in which a P-polarized component and an S-polarized component are mixed.

As described above, the second optical element 8
Is a laser beam 840 in which a P-polarized component and an S-polarized component are mixed by selectively applying a voltage to the TN liquid crystal 80 to selectively diffract an incident laser beam, and a laser beam having only a P-polarized component. 841 and an element having a function of separating and transmitting a laser beam 842 including only an S-polarized component.

The details of the photodetector 9 will be described with reference to FIG. The photodetector 9 is arranged so that the direction indicated by the arrow 190 is the track direction and the direction indicated by the arrow 191 is the tracking direction, and its surface is divided into eight detection areas. That is, CD and CD-R focus error signals and playback signals, DVD focus error signals, tracking error signals and playback signals, and MO
A region 91, B region 92, C region 93, and D region 94 for detecting a focus error signal and a tracking error signal of -7, and E region 95 and F region 96 for detecting a tracking error signal of CD and CD-R. , G-region 97 and H-region 98 for detecting reproduction signals of MO-7. FIG.
0, when the DVD is reproduced, the reflected light on the signal recording surface 11a is not diffracted by the second optical element 8, so that only one laser beam 99 is detected by the photodetector 9. The A region 91, the B region 92, the C region 93, and the D region 94 are irradiated. As a result, the A region 91 and the B region 9
2, the sum [A + B + C + D] of the intensity of the laser beam detected in each of the C region 93 and the D region 94 is detected as a reproduction signal, and the sum [A + C] of the laser beams detected in the A region 91 and the C region 93 ], B area 92 and D area 9
The phase difference [[A + C]-[B + D]] from the sum [B + D] of the laser beams detected in step 4 is detected as a tracking error signal, and the sum of the intensities of the laser beams detected in the area A 91 and the area C 93 [A + C], the sum of the intensities of the laser beams detected in the B area 92 and the D area 94 [B + D]
The difference [[A + C] − [B + D]] is detected as a focus error signal.

When a CD or CD-R is reproduced, three beams are generated in the track direction by a diffraction grating not shown in FIG. 2 and are irradiated on the optical disk, so that the light reflected on the signal recording surface 110a is reflected. Since the three beams are not diffracted in the tracking direction by the second optical element, the laser beam 99 is applied to the photodetector 9 as shown in FIG. , C
In the region 93 and the D region, the laser beam 102
The area 95 is irradiated with the laser beam 103 to the F area. As a result, the A region 91, the B region 92,
The sum [A + B + C + D] of the laser beam intensities detected in each of the C region 93 and the D region 94 is detected as a reproduction signal, and the sum [A + C] of the laser beam intensities detected in the A region 91 and the C region 93 is obtained. ] And the sum [B + D] of the laser beam intensities detected in the B region 92 and the D region 94 [[A + C] − [B + D]] are detected as focus error signals, and the laser detected in the E region 95 The difference [EF] between the beam intensity and the intensity of the laser beam detected in the F region 96 is detected as a tracking error signal.

Further, when the MO-7 is reproduced, the light reflected on the signal recording surface 11a is diffracted in the tracking direction by the second optical element 8, and the P-polarized component and the S-polarized component are mixed. Since the laser beam is separated into a laser beam, a laser beam having only a P-polarized component, and a laser beam having only an S-polarized component, the photodetector 9 includes, as shown in FIG. Beam 99 is A
In the region 91, the B region 92, the C region 93, and the D region,
The laser beam 100 having only the P-polarized component is irradiated on the G region, and the laser beam 101 having only the S-polarized component is irradiated on the H region. As a result, the difference [GH] between the intensity of the laser beam detected in the G region 97 and the intensity of the laser beam detected in the H region is detected as a reproduction signal, and detected in the A region 91 and the D region 94. [A + D] between the sum [A + D] of the laser beam intensities obtained and the sum [B + C] of the laser beam intensities detected in the B region 92 and the C region 93.
− [B + C]] is detected as a tracking error signal, and the sum [A + C] of the laser beam intensities detected in the A region 91 and the C region 93 and the intensity of the laser beam detected in the B region 92 and the D region 94 The difference [[A + C] − [B + D]] from the sum [B + D] is detected as a focus error signal.

With reference to FIG. 11, the operation of reproducing a DVD which is an optical disk having a substrate thickness of 0.6 mm will be described. D
When VD is reproduced, a semiconductor laser 1a that generates a laser beam having a wavelength of 635 nm is selectively driven by a laser driving circuit 20 in an optical reproducing apparatus described later, and 10 V is applied to the second optical element 8 by a liquid crystal driving circuit 21. Is applied. As a result, a half of the laser beam having a wavelength of 635 nm is reflected by the half mirror 2, converted into parallel light by the collimator lens 3, raised by the rising mirror 4, and not diffracted by the first optical element 5, The light is transmitted as it is, condensed by the objective lens 7, and irradiates the signal recording surface 11 a through the substrate 11 of the optical disk. Signal recording surface 11
The spot diameter of the laser beam applied to a is 0.9 (allowable error ± 0.1) μm. The laser beam reflected by the signal recording surface 11a is transmitted to the substrate 11, the objective lens 7, the first
Optical element 5, rising mirror 4, collimator lens 3
The light returns to the half mirror 2 via the optical path, and after half of the light is transmitted, the light passes through the second optical element 8 as it is and is condensed and irradiated on the photodetector 9.

Referring to FIG. 12, MO-recordable and / or reproducible optical disk having a substrate thickness of 0.6 mm is used.
7 will be described. When MO-7 is reproduced, the wavelength of 635 n
The semiconductor laser 1a that generates a laser beam of m is selectively driven, and the liquid crystal driving circuit 21 drives the second optical element 8
No voltage is applied to As a result, a half of the laser beam having a wavelength of 635 nm is reflected by the half mirror 2, converted into parallel light by the collimator lens 3, raised by the rising mirror 4, and not diffracted by the first optical element 5, The light is transmitted as it is, condensed by the objective lens 7, and irradiates the signal recording surface 11 a through the substrate 11 of the optical disk. The spot diameter of the laser beam applied to the signal recording surface 11a is 0.9 (allowable error ± 0.1) μm. The laser beam reflected by the signal recording surface 11a
An objective lens 7, a first optical element 5, a rising mirror 4,
Returning to the half mirror 2 via the collimator lens 3,
After half is transmitted, it is diffracted by the second optical element 8,
A laser beam in which a P-polarized component and an S-polarized component are mixed,
The laser beam is separated into a laser beam having only the polarization component and a laser beam having only the S polarization component, and is condensed and irradiated on the photodetector 9. Then, a tracking error signal and a focus error signal are generated from the laser beam in which the P-polarized component and the S-polarized component detected by the photodetector 9 are mixed, and are used for servo. In addition, P detected by the photodetector 9
A reproduction signal is generated from an intensity difference between the laser beam having only the polarization component and the laser beam having only the S polarization component.

Referring to FIG. 13, the optical disk has a substrate thickness of 1.2 mm. The reproduction operation of a CD or CD-R will be described. When a CD or CD-R is reproduced, the laser driving circuit 20 selectively drives the semiconductor laser 1b that generates a laser beam having a wavelength of 780 nm, and the liquid crystal driving circuit 21 applies a voltage of 10 V to the second optical element 8. Is applied. As a result, a half of the laser beam having a wavelength of 780 nm is reflected by the half mirror 2, is converted into parallel light by the collimator lens 3, is raised by the rising mirror 4, and
The outer peripheral portion is substantially shielded from light by the optical element 5 and only the inner peripheral portion is diffracted and enters the objective lens 7. The laser beam that has entered the objective lens 7 is condensed and passes through the substrate 110 of the optical disk to irradiate the signal recording surface 110a.
The spot diameter of the laser beam applied to the signal recording surface 110a is 1.5 μm (allowable error ± 0.1). The laser beam reflected by the signal recording surface 110a is
An objective lens 7, a first optical element 5, a rising mirror 4,
Returning to the half mirror 2 via the collimator lens 3,
After half of the light is transmitted, the light passes through the second optical element 8 as it is, and is condensed and irradiated on the photodetector 9.

The first optical element 5 substantially shields the outer periphery of the laser beam having a wavelength of 780 nm and diffracts the inner periphery, as shown in FIGS. Not limited to those shown, but may be anything. Referring to FIGS.
The outer peripheral portion 55a may be an optical element 55 composed of a polarizing film 551a, and the inner peripheral portion 55b may be an optical element 55 composed of a wavelength-selective diffraction grating 551b. The diffraction grating of the inner peripheral portion 55b is the same as that described above. The polarizing film is a film that transmits only a laser beam polarized in a specific direction, and in this embodiment, transmits only a laser beam that is polarized in a direction perpendicular to the plane of the drawing. 635 nm wavelength
Is polarized in a direction perpendicular to the plane of the paper, and has a wavelength of 78.
The 0 nm laser beam is polarized in a direction parallel to the paper.
Accordingly, the laser beam having a wavelength of 635 nm
As a result, the outer peripheral portion is not shielded from light and the inner peripheral portion is transmitted without being diffracted. On the other hand, a wavelength of 780 nm
Since the laser beam is polarized in a direction parallel to the plane of the drawing, the outer periphery is shielded by the polarizing film 551a, and the inner periphery is diffracted by the diffraction grating 551b to reach the objective lens 7.

Further, the first optical element 5 is shown in FIGS.
However, the present invention is not limited to those shown in FIGS. The optical element 552 shown in FIGS. 16 and 17 has a polarizing glass 552a on the outer periphery and a diffraction grating 552b on the inner periphery. The diffraction grating 552b is the same as described above. The polarizing glass 552a absorbs only a laser beam of a specific wavelength. The polarizing glass 552a is obtained by elongating silver atoms on the surface of the glass and baking it. The aspect ratio R ₁ / R ₂ of the elongated silver atoms is 1
-5. In the present embodiment, the wavelength 78
The aspect ratio is such that only a laser beam of 0 nm can be absorbed. Therefore, even when the first optical element 552 is used, the laser beam having a wavelength of 635 nm is not shielded from the outer peripheral portion, the inner peripheral portion is transmitted without being diffracted, and reaches the objective lens 7. The laser beam having a wavelength of 780 nm is shielded at the outer periphery and diffracted at the inner periphery to reach the objective lens 7.

In the above description, it has been described that the inner peripheral portion of the first optical element 5 selectively causes a diffraction phenomenon due to the wavelength of the laser beam. However, the present invention is not limited to this. May cause a diffraction phenomenon selectively due to the difference in the polarization plane. That is, in the present embodiment, only a laser beam polarized in a direction parallel to the paper surface may be diffracted, and a laser beam polarized in a direction perpendicular to the paper surface may not be diffracted.

Referring to FIG. 18, DVD and MO-7 having a substrate thickness of 0.6 mm, and CDs and CD-ROMs having a substrate thickness of 1.2 mm
A playback device for compatible playback of R will be described. The objective lens 7 of the optical pickup 10 is controlled so that a signal to be reproduced by the servo mechanism 14 focuses a laser beam on a track formed as a pit row or a domain row.
And the optical disk substrate 11 (or 110)
Then, the light is irradiated onto the signal recording surface 11a (or 110a). The laser beam reflected by the signal recording surface 11a (or 110a) is detected by the photodetector 9 and detected as a reproduction signal. The reproduction signal detected by the photodetector 9 is sent to a preamplifier 12, and after a predetermined amplification, sent to a discrimination circuit 15, an RF demodulation circuit 17 and a servo circuit 13. The servo circuit 13 controls the servo mechanism 14 based on the tracking error signal sent. Further, the discriminating circuit 15 identifies the type of the optical disc mounted on the reproducing apparatus based on the transmitted signal, and sends the identification result to the command circuit 16. The command circuit 16 selectively drives any one of the semiconductor lasers 1a and 1b of the laser beam generating means 1 so as to be compatible with the identified optical disk and selectively applies a voltage to the second optical element. , And issues a command to the control circuit 19 based on the received identification result. The instruction circuit 16 also issues an instruction to the characteristic switching circuit 18 based on the identification result sent to switch to a demodulation circuit suitable for reproducing the identified optical disk. The control circuit 19 selectively drives a semiconductor laser in the optical pickup 10 via a laser drive circuit 20 based on a command from the command circuit 16, and controls the second laser in the optical pickup via a liquid crystal drive circuit 21.
The characteristic switching circuit 18 switches the RF demodulation circuit 16 based on a command from the command circuit 16. As a result, reproduction suitable for the optical disk mounted on the reproduction device can be performed.

In the above, reproduction of CD, CD-R, DVD and MO-7 using the optical pickup 10 has been described.
In R and MO-7, recording can be performed using the optical pickup 10. In this case, in the MO-7, the tracking servo for performing recording can be performed by the same method as the focus servo in the above-described reproduction, but the laser beam is irradiated to change the reflectance of the organic dye. Therefore, in a CD-R on which a signal is recorded, tracking cannot be performed by the three-beam method as in the case of reproduction. In the three-beam method, three beams are emitted in the track direction. However, considering a state in which a signal is recorded by the main beam, one sub-beam emitted forward in the track direction from the main beam has a signal recorded. Since the other sub-beam irradiates the area where no signal is recorded and the other sub-beam irradiates backward in the track direction from the main beam, it irradiates the area where a signal is recorded. This is because the intensity difference of the reflected light from the optical disk cannot be accurately detected. Therefore, when recording a signal on a CD-R, one beam
-R, the reflected light of which is A region 91 and D region out of the laser beam intensities detected in the A region, B region, C region, and D region of the photodetector 9 in FIG. Sum of the intensity of the laser beam detected in the region 94 [A +
D] and the difference [[A + D] − [B +] between the sum [B + C] of the laser beam intensities detected in the B region 92 and the C region 93.
C]] to perform tracking by generating a tracking error signal. The generation of the focus error signal is the same as that described with reference to FIG.

The CD-R, MO-
7, a signal can be recorded. When a signal is recorded on a CD-R, the laser
The semiconductor laser 1b in the laser beam generating means 1 for generating a laser beam of 0 nm is selectively driven, and the recording signal is modulated in a predetermined manner by the encoder 25. Based on the modulation result, the laser drive circuit 20 drives the semiconductor laser 1b.
Blinks and a signal is recorded on the CD-R.

When a signal is recorded on the MO-7, the recording signal is modulated by the encoder 22 in a predetermined manner, and the modulation result is sent to the laser drive circuit 20 and the magnetic head drive circuit 23. The magnetic head drive circuit 23 drives the magnetic head 24 based on the result from the encoder 22, and the magnetic head 24 applies a magnetic field to the MO-7 according to a predetermined modulation method. Further, the laser drive circuit 20 selectively drives the semiconductor laser 1a for generating a laser beam having a wavelength of 635 nm in the laser light generating means 1, and blinks the semiconductor laser 1a based on the recording signal modulated by the encoder 22 in a predetermined method. Let it. As described above, M
A signal is recorded by applying a laser beam and a magnetic field to O-7 based on a recording signal modulated in a predetermined system.

[0043]

According to the present invention, light sources having different wavelengths are used.
Since two semiconductor lasers are used, it is possible to perform compatible reproduction between a thin optical disk and an optical disk having a reflectance of 10% or less for a laser beam having a standard thickness of 635 nm. Further, according to the present invention, the laser beam selectively diffracting the reflected light from the optical disk and mixing a P-polarized component and an S-polarized component, a laser beam having only a P-polarized component,
And separates the laser beam into only S-polarized component,
Compatible reproduction of optical disks with different recording methods is possible.

Further, according to the present invention, the outer peripheral portion is selectively shielded from light due to the difference in the wavelength of the laser beam, and the inner peripheral portion is diffracted to enter the objective lens.
An optical disk having a substrate thickness of 1.2 mm can be reproduced by a laser beam having almost no aberration using an objective lens designed for the purpose. Further, according to the present invention, it is possible to perform compatible playback between a read-only optical disc and a recordable optical disc by using a single optical pickup device, and perform recording on a recordable optical disc.

Further, according to the present invention, since the detection unit of the photodetector is divided into eight, a signal for servo can be generated according to the optical disk mounted on the apparatus.

[Brief description of the drawings]

FIG. 1 is a table showing standard values and reproduction conditions of a CD, a CD-R, a DVD, and a magneto-optical recording medium (MO-7).

FIG. 2 is a diagram showing a configuration of an optical pickup according to the present invention.

FIG. 3 is a diagram illustrating a method of mounting a semiconductor laser according to the present invention.

FIG. 4 is a plan view of a first optical element according to the present invention.

FIG. 5 is a sectional view of a first optical element according to the present invention.

FIG. 6 is another sectional view of the first optical element according to the present invention.

FIG. 7 is still another sectional view of the first optical element according to the present invention.

FIG. 8 is a diagram illustrating a function of a first optical element with respect to a laser beam having a wavelength of 635 nm.

FIG. 9 is a diagram illustrating a function of a first optical element with respect to a laser beam having a wavelength of 780 nm. .

FIG. 10 is a perspective view for explaining a function of a second optical element according to the present invention.

FIG. 11 is a diagram illustrating a DVD reproducing operation.

FIG. 12 is a diagram for explaining a playback operation of MO-7.

FIG. 13 is a diagram for explaining a reproduction operation of a CD and a CD-R.

FIG. 14 is a plan view of another first optical element according to the present invention.

FIG. 15 is a diagram for explaining a function of another first optical element according to the present invention.

FIG. 16 is a plan view of still another first optical element according to the present invention.

FIG. 17 is a diagram illustrating a function of still another first optical element according to the present invention.

FIG. 18 is a block diagram of a recording / reproducing apparatus using an optical pickup according to the present invention.

FIG. 19 is a plan view of a photodetector.

FIG. 20 is a diagram illustrating detection of a reproduction signal, a tracking error signal, and a focus error signal when a DVD is reproduced.

FIG. 21 is a diagram illustrating detection of a reproduction signal, a tracking error signal, and a focus error signal when a CD or CD-R is reproduced.

FIG. 22 is a diagram illustrating detection of a reproduction signal, a tracking error signal, and a focus error signal when reproducing a magneto-optical recording medium (MO-7).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser light generation means 1a, 1b ... Semiconductor laser 2 ... Half mirror 3 ... Collimator lens 4 ... Start-up mirror 5 ... First optical element 6 ... Actuator 7 ... Objective lens 8 ... Second optical element 9 ... Photodetector 10 ... Optical pickup 11, 110 ... Substrate 11a, 110a ... Signal recording surface 12 ... Preamplifier 13 ..Servo circuit 14 ... Cervo mechanism 15 ... Discrimination circuit 16 ... Command circuit 17 ... RF demodulation circuit 18 ... Characteristic switching circuit 19 ... Control circuit 20 ... Laser drive Circuit 21 ... Liquid crystal drive circuit 22, 25 ... Encoder 23 ... Magnetic head drive circuit 24 ... Magnetic head

Continuation of the front page (56) References JP-A-9-54973 (JP, A) JP-A-9-179020 (JP, A) JP-A-9-50648 (JP, A) JP-A-9-211460 (JP, A) JP-A-10-124918 (JP, A) JP-A-10-241179 (JP, A) Registered utility model 3036314 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/12-7/22 G11B 11/105 551

Claims (5)

(57) [Claims] A first laser beam having a first wavelength;
A second laser having a second wavelength different from the first laser light;
Laser light generating means for selectively generating laser light, and first or second laser light from the laser light generating means
Is selectively incident, and the outer periphery of the incident first laser light
Part is shielded and the inner peripheral part is diffracted.
A first optical element that transmits the laser light as it is, and a laser light that passes through the first optical element is incident on the first optical element.
Object lens that guides the emitted laser light to the recording surface of the optical disk
And a second light that transmits reflected light from the recording surface of the optical disc as it is.
Diffraction of the light reflected from the recording surface of the optical disk and the state of 1
A laser beam in which a P-polarized component and an S-polarized component are mixed;
Laser light with only P polarization component and laser with only S polarization component
Second light switched to a second state of separation into light
Photodetector for receiving the academic elements, the laser light through the second optical element
Means, and the first laser from the laser light generating means
Optical disc through the optical element and the objective lens
And the reflected light from the recording surface is directed to the first recording surface.
Through the second optical element switched to the state of
A first optical disc guided to the light recording detection means and reproduced;
The second laser from the laser light generating means to the second laser
Optical disc through the optical element and the objective lens
And the reflected light from the recording surface is directed to the first recording surface.
Through the second optical element switched to the state of
A second optical disc guided to the light recording detecting means and reproduced,
The second laser from the laser light generating means to the second laser
Optical disc through the optical element and the objective lens
And the reflected light from the recording surface is transmitted to the second recording surface.
Through the second optical element switched to the state of
A third optical disc to be guided to the light recording detecting means and reproduced.
Optical pickup device characterized by selective reproduction
Place. 2. A light source having a first wavelength and a first polarization direction.
A first laser beam and a second laser beam different from the first laser beam.
A second laser beam having a wavelength and a second polarization direction.
Laser light generating means for selectively generating, and first or second laser light from the laser light generating means
Is selectively incident, and the outer periphery of the incident first laser light
Part is shielded and the inner peripheral part is diffracted.
A first optical element that transmits the laser light as it is, and a laser light that passes through the first optical element is incident on the first optical element.
Object lens that guides the emitted laser light to the recording surface of the optical disk
And a second light that transmits reflected light from the recording surface of the optical disc as it is.
Diffraction of the light reflected from the recording surface of the optical disk and the state of 1
A laser beam in which a P-polarized component and an S-polarized component are mixed;
Laser light with only P polarization component and laser with only S polarization component
Second light switched to a second state of separation into light
Photodetector for receiving the academic elements, the laser light through the second optical element
Means, and the first laser from the laser light generating means
Optical disc through the optical element and the objective lens
And the reflected light from the recording surface is directed to the first recording surface.
Through the second optical element switched to the state of
A first optical disc guided to the light recording detection means and reproduced;
The second laser from the laser light generating means to the second laser
1 through an optical element and the objective lens.
And guide the reflected light from the recording surface to the
Via the second optical element switched to state 1
A second optical disc guided to the light detecting means and reproduced.
And the second laser from the laser light generating means.
The light beam is transmitted through the first optical element and the objective lens.
Guides the light to the recording surface of the disc and reflects light reflected from the recording surface.
Via the second optical element switched to the second state
Third optical disk which is guided to the light detecting means for reproduction
Optical pickup characterized by selectively reproducing
apparatus. 3. The second optical element includes: one glass plate on which a transparent electrode is formed in an optical axis direction; a liquid crystal provided in contact with the transparent electrode of the one glass plate; And another glass plate on which a transparent electrode is formed so as to be in contact with the optical disk, wherein a voltage is selectively applied to the transparent electrode according to a recording system of the optical disc. Or the optical pickup device according to claim 2. 4. A laser comprising a P-polarized component and an S-polarized component detected by the photodetector, generates a tracking error signal and a focus error signal from the mixed laser beam, and detects only the P-polarized component detected by the photodetector. 4. The optical pickup device according to claim 1, wherein a reproduction signal is generated based on an intensity difference between the light and the laser light having only the S-polarized component. 5. An optical recording / reproducing apparatus comprising the optical pickup device according to claim 1.