JPH0917017A - Optical pickup device - Google Patents

Abstract

(57) [Summary] [Structure] The track pitch of the optical disc 1 on which the disc discriminating circuit 4 is mounted is detected, and a detection output indicating that the mounted optical disc is an optical disc with a narrow track pitch, or a wide track pitch is provided. The detection output indicating the optical disc is supplied to the diffraction grating drive unit 17.
The diffraction grating drive unit 17 determines that each side beam, which is radiated by being deviated by a predetermined amount toward the outer peripheral side and the inner peripheral side of the disc with respect to the recording track, in accordance with the detection output from the disc discriminating circuit 4. By rotating the diffraction grating 18 so as to rotate by a predetermined amount about the main beam with which the center of the beam is irradiated, it is possible to detect a tracking error by the three-spot method for each optical disk having a different track pitch. [Effect] It is possible to record and reproduce two types of optical disks having different track pitches.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device suitable for use in a device adopting an optical reading system such as an optical disk reproducing device, an optical disk recording / reproducing device, and an optical disk recording / reproducing device, and particularly, it has a different track pitch. The present invention relates to an optical pickup device capable of selectively reproducing two types of optical recording media.

[0002]

2. Description of the Related Art Conventionally, an optical disk reproducing apparatus for reproducing a reproduction-only optical disk is known. When the reproduction is started, this optical disk reproducing apparatus drives the laser diode to emit light and emits a laser beam. This laser beam is a zero-order main beam and ± 1
It is divided into two side beams, which are the next beams, into three beams, and the polarized beam splitter is irradiated with the beams. Most of the laser beams are, for example, P-polarized component light, and the polarization beam splitter reflects the P-polarized component light and the S-polarized component in the polarization direction orthogonal to the P-polarized component light. It has the property of transmitting the light of. Therefore, the laser beam emitted to the polarization beam splitter is reflected by the polarization beam splitter, collimated by the collimator lens, and incident on the objective lens. The objective lens converges the incident laser beam into a beam spot having a predetermined diameter and irradiates the optical disc with the converged laser beam. At this time, the main beam is irradiated so that the center of the beam and the center of the recording track coincide with each other, and the side beam of the + 1st-order light is displaced from the recording track by, for example, ¼ track on the outer peripheral side. The side beam of the −1st-order light that is emitted is emitted to the recording track at a position shifted to the inner peripheral side by a quarter track. The diffraction grating has a spectral characteristic such that each beam is in such an irradiation state.

Next, when each beam is irradiated onto the optical disk in this manner, reflected light of each beam is generated. Each of the reflected lights is incident on the polarization beam splitter via the objective lens and the collimator lens. In other words, the optical path of the laser beam of the P-polarized component is reflected by the optical disk, and the optical path is inverted, and is incident on the polarization beam splitter as reflected light of the S-polarized component. As described above, the polarization beam splitter has the property of transmitting the light of the S polarization component. Therefore, each reflected light that has entered the polarization beam splitter passes through the polarization beam splitter and is applied to the photodetector. The photodetector is composed of a first photodetector that receives the reflected light of the main beam and second and third photodetectors that receive the reflected lights of the ± first-order lights.
The first photodetector is a four-division photodetector having light-receiving regions A to D that are radially divided into four equal parts about the optical axis of the reflected light of the received main beam, and in each of the light-receiving regions A to D. A light amount detection signal corresponding to the light amount of the received reflected light is formed, and these are supplied to the signal processing system and the focus control system. The signal processing system reproduces and outputs the RF signal indicating the recording data recorded on the optical disc by adding all the light amount detection signals from the light receiving regions A to D. Further, the focus control system performs addition processing on each light amount detection signal from each light receiving area A and light receiving area C located on the diagonal line and addition processing on each light amount detection signal from each light receiving area B and light receiving area D. ,
By detecting the difference between these added signals, a focus error by the so-called astigmatism method is detected, and the focus of the optical pickup is controlled according to this focus error. Further, the second and third photodetectors receive the reflected light of + primary light and the reflected light of −primary light, respectively,
A light amount detection signal corresponding to the light amount of each reflected light is supplied to the tracking control system. The tracking control system detects a tracking error by the so-called three-spot method by detecting the difference between the light amount detection signals, and controls the tracking of the optical pickup according to the tracking error. As a result, it is possible to reproduce the record data recorded on the optical disk in a state where the laser beam is always in focus and the main beam accurately traces the recording track.

[0004]

In order to record high-definition image data such as still images and moving images in recent years, there has been a demand for higher density optical discs, and in response to this demand, the track pitch should be narrowed. Has developed an optical disc with higher density. In addition, in such a device that reproduces a high-density disc, it is preferable that a conventional normal-density optical disc can also be reproduced in order to improve versatility.

However, in order to record / reproduce information on / from the optical disk, it is necessary to perform accurate tracking control. As described above, in the tracking error detection by the three-spot method, it is necessary to irradiate each side beam by deviating by a predetermined amount with respect to a recording track. When the positional relationship of the beams is adjusted, the positional relationship of the side beams is deviated with respect to an optical disc of normal density having a wide track pitch. Therefore, with respect to an optical disc having a wide track pitch and a normal density, the positional relationship of each side beam is deviated, and the amplitude of the detected tracking error signal is reduced to make it difficult to perform accurate tracking error control. There was a problem that interfered with the recording and reproduction of. Due to such a situation, there is a problem that the conventional normal density optical disk cannot be reproduced by the device for recording and reproducing the high density disk.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an optical pickup device capable of recording / reproducing a plurality of types of optical disks having different track pitches.

[0007]

An optical pickup device according to the present invention irradiates an optical recording medium with a spectroscopic means for splitting light emitted from a light source into a plurality of beams and for emitting the light split by the spectroscopic means. Irradiating means. When the optical recording medium is the first optical recording medium, the first light and the second light of the dispersed light are inside and outside the recording track of the first optical recording medium. The optical recording medium has a track pitch narrower than that of the first optical recording medium.
In the case of the optical recording medium, the first light and the second light of the dispersed light are displaced by a predetermined amount to the inside and the outside of the recording track of the second optical recording medium. As described above, by rotating the spectroscopic means by a predetermined amount,
It has an irradiation position variable control means for variably controlling the irradiation position of the second light. Then, of the reflected lights generated by irradiating the optical recording medium with the lights dispersed by the above-mentioned spectroscopic means, at least the respective reflected lights of the first light and the second light are received and received. It has a light receiving means for outputting a light amount detection signal according to each reflected light.

[0008]

In the optical pickup device according to the present invention, the first and second lights dispersed by the spectroscopic means are distributed to the inside and outside of each recording track of the first and second optical recording media having different track pitches. The irradiation position variable control means controls the rotation of the spectroscopic means so that the irradiation is performed by deviating by a predetermined amount.
The irradiation position of the second light is variably controlled.

[0009]

Embodiments of the optical pickup device according to the present invention will now be described in detail with reference to the drawings. The optical pickup device according to the present invention can be applied to an optical disc reproducing device for reproducing recorded data recorded on an optical disc 1 as shown in FIG. The optical disk reproducing apparatus according to the first embodiment is, for example, a first optical disk having a diameter of 12 cm, a substrate thickness of 1.2 mm and a track pitch of 1.6 μm, and a diameter of 12 cm, a substrate thickness of 0.6 mm and a track pitch of 0.84 μm. Both optical disks of the second optical disk can be reproduced.

That is, the optical disc reproducing apparatus according to the first embodiment includes an optical system 2 for irradiating the optical disc 1 with a laser beam and outputting a light amount detection signal corresponding to the light amount of the reflected light, and the optical system 2 described above. The detection system 3 that forms and outputs the tracking error signal, the focus error signal, and the sum signal (RF signal) based on the light amount detection signal, and the type (track pitch) of the optical disc 1 based on the light amount detection signal. The disc discriminating circuit 4 and the diffraction grating driving unit 1 for controlling the rotation of the diffraction grating 18 provided in the optical system 2 according to the discriminating result of the disc discriminating circuit 4.
7.

The optical system 2 is a shaft sliding type optical system as shown in FIGS. 2 and 3, the movable portion 20 is composed of a bobbin 20A and a holder 20B which are made of a non-magnetic material. At the center position of the holding body 20B, a tubular bearing portion 21 fitted and inserted in the axial direction is provided. On the outer peripheral surface of the bobbin 20A, a focus coil 22 for moving the movable portion 20 in the focus direction (perpendicular to the disk plate surface) forms a ring centered on the bearing portion 21. Is wound like. Further, on the surface of the focus coil 22, two sets of tracking coils 23A and 23B for closely moving the focus coil 22 and moving the movable part 20 in the tracking direction (the radial direction of the disk) are provided, respectively. This tracking coil 23A, 23
B has its winding axis direction orthogonal to the winding axis direction of the focus coil 22, and is provided so as to form a total of four rings on the outer peripheral surface of the bobbin 20A.

Next, a support shaft 29 having a length corresponding to the thickness of the optical system 2 is penetratingly provided at the center of the optical system 2. Further, the support shaft 29 is attached to the holding body 20B.
A stepped hole 37 parallel to the central axis of the support shaft 29 is formed at a position eccentric with respect to. This hole 37
Is provided with a lens barrel 25, and inside the lens barrel 25,
Objective lens 7, quarter wave plate 26, collimator lens 2
7 and the polarization beam splitter 6 are arranged in a line so that their optical axes coincide with each other. The bobbin 20A is provided between the photodetector 8 whose detection surface is directed to the polarization beam splitter 6 side, and the semiconductor laser 5 and the polarization beam splitter 6 described below.
A diffraction grating 18 is provided which divides the laser beam from the semiconductor laser 5 into three and irradiates the polarized beam splitter 6 with the laser beam.

As shown in FIG. 1, the photodetector 8 has first to third light receiving portions 9 at positions where it receives the respective reflected lights of the laser beam divided into three by the diffraction grating 18.
It is a three-divided photodetector formed by arranging 10 to 10. The first photodetector 9 is a photodetector that receives the reflected light of the main beam (zero-order light) of the laser beam divided into three by the diffraction grating 18, and the light receiving region thereof is the reflected light of the received main beam. Radially divided into four equal parts around the optical axis of
It is a light receiving area D). The boundary between the light receiving area A and the light receiving area B and the boundary between the light receiving area C and the light receiving area D are divided so as to coincide with the track direction of the optical disc 1. The second photodetector 10 and the third photodetector 11 are respectively provided at positions where the reflected light of each side beam (± first-order light) of the laser beam divided into three by the diffraction grating 18 is received, There is one light receiving area (light receiving area E and light receiving area F).

Next, a semiconductor laser 5 which is a laser light source
Is substantially symmetrical in weight with respect to the optical components of the objective lens 7, the quarter-wave plate 26, the collimator lens 27, and the polarization beam splitter 6 arranged in a line,
The bobbin 20A is provided. Further, as shown in FIG. 4, the support shaft 29 is provided with a hole 34 serving as an optical path of the laser beam from the semiconductor laser 5, and the laser beam from the semiconductor laser 5 passes through the hole 34. The polarized beam splitter 6 is irradiated. The bearing portion 2 formed integrally with the holder 20B
1 also has a hole 35 serving as an optical path of a laser beam at a position corresponding to the hole 34 of the support shaft 29.

The movable portion 20 thus constructed has the support shaft 2 fixed to the center of the fixed yoke 28 made of a magnetic material.
9 is guided and inserted into the center hole of the bearing portion 21 so that it can be slidably rotated. That is, the movable part 20
Are supported slidably in the axial direction of the support shaft 29 and rotatably around the shaft. Further, on the lower surface of the fixed yoke 28, an annular permanent magnet 30 centered on the support shaft 29 is closely fixed. A first yoke portion 32 having a protruding piece portion 31 is fixed to the lower end surface of the permanent magnet 30. Further, the fixed yoke 28 is provided with a second yoke portion 33 which is arranged inside the bobbin 20A so as to face the protruding piece portion 31 of the first yoke portion 32. A magnetic circuit is constituted by the fixed yoke 28, the permanent magnet 30, the first yoke portion 32, and the second yoke portion 33, and the magnetic gap between the first yoke portion 32 and the second yoke portion 33 is formed. A focus coil 22 and tracking coils 23A and 23B are provided inside. Further, the fixed yoke 28 has a lens barrel 25 held by the holder 20B.
A hole 37 having a diameter larger than the outer diameter of the lens barrel is bored, and the upper end of the lens barrel 25 is guided and inserted into the hole 37.

Next, the detection system 3 shown in FIG. 1 compares the light amount detection signal from the second photodetector 10 in the photodetector 8 and the light amount detection signal from the third photodetector 11 and uses the three-spot method. It has a comparator 12 which forms and outputs a tracking error signal. In addition, the detection system 3 includes an adder 13 that adds the light amount detection signal from the light receiving region A and the light amount detection signal from the light receiving region C of the first photodetector 9 that is a four-division photodetector, and the light amount from the light receiving region B. An adder 14 for adding the detection signal and the light amount detection signal from the light receiving area D
And a comparator 15 for comparing and processing the added signal from the adder 13 and the added signal from the adder 14 to form and output a focus error signal by a so-called astigmatism method. Then, the detection system 3 includes the adders 1
Addition processing is performed on each addition output from 3 and 14, and a sum signal (RF
It has an adder 16 for forming and outputting a signal).

Next, the relationship between the diffraction grating 18 and the diffraction grating driving section 17 provided in the optical system 2 is shown in FIG.
(A). In FIG. 6 (a), the diffraction grating 18 has a substantially disc shape, and has a gear portion 18a along its outer peripheral portion. The diffraction grating drive unit 17 includes the rotating shaft 4 of the stepping motor 40.
0a is a rotary gear 41 having a diameter smaller than that of the diffraction grating 18.
Is provided. The gear portion 41a of the rotary gear 41 is arranged so as to mesh with the gear portion 18a of the diffraction grating 18. Stepping motor 4
0 is rotationally driven according to the type of the optical disc 1 discriminated by the disc discriminating circuit 4, and the rotational force of the stepping motor 40 is transmitted to the diffraction grating 18 via the gear portions 41a and 18a. The diffraction grating 1
8 is rotated by a predetermined amount.

Next, the operation of the optical disk reproducing apparatus according to the first embodiment of the present invention having the above structure will be described. First, in FIG. 3, when the optical disk 1 is mounted on the optical disk reproducing apparatus and reproduction is started, a laser beam is emitted from the semiconductor laser 5. The laser beam emitted from the semiconductor laser 5 is divided into three by a diffraction grating 18 into a main beam which is a zero-order light and two side beams which are ± first-order lights, and are incident on a polarization beam splitter 6. The polarization beam splitter 6 has a property of reflecting, for example, light of a P-polarized component and transmitting light of an S-polarized component in a polarization direction orthogonal to the light of the P-polarized component.
On the other hand, the laser beam from the semiconductor laser 5 is
Most are P-polarized components. Therefore, the polarization beam splitter 6 substantially totally reflects the laser beam from the semiconductor laser 5. The laser beam reflected by the polarization beam splitter 6 is collimated by the collimator lens 27 and is circularly polarized by the quarter-wave plate 26. Then, it is converged by the objective lens 7 so as to form a predetermined beam spot, and is irradiated onto the surface of the optical disc 1.

Next, by irradiating the optical disk 1 with the laser beam in this manner, reflected light of each of the laser beams is generated. This reflected light passes through the same optical path as the optical path of the laser beam, but has a traveling direction opposite to the traveling direction of the laser beam. Therefore, the reflected light is collimated by the objective lens 7 and linearly polarized by the quarter-wave plate 26 to be an S-polarized component whose polarization direction is orthogonal to that of the P-polarized component, resulting in a polarized beam. It is incident on the splitter 6. As described above, the polarization beam splitter 6 has a characteristic of reflecting the P-polarized component and transmitting the S-polarized component. Therefore, the reflected light incident on the polarization beam splitter 6 passes through the polarization beam splitter 6 and is applied to the photodetector 8.

Specifically, of the reflected lights corresponding to the three-divided laser beams, the reflected light of the main beam is applied to the first photodetector 9 in the photodetector 8, and the side beam of the + primary light The reflected light is applied to the second photodetector 10, and the reflected light of the side beam of the −1st order light is applied to the third photodetector 11.
The second photodetector 10 forms a light amount detection signal corresponding to the light amount of the reflected light of the side beam of the + primary light received, and supplies this to the comparator 12. Further, the third photodetector 11 forms a light amount detection signal corresponding to the light amount of the reflected light of the received −first-order light side beam, and supplies this to the comparator 12. The comparator 12 compares the light amount detection signal from the second photodetector 10 and the light amount detection signal from the third photodetector 11 to form a tracking error signal by the so-called 3-spot method, and outputs the tracking error signal. It is supplied to a servo control system (not shown) via 19a.

Further, the first photodetector 9 forms a light amount detection signal corresponding to the light amount of the reflected light of the main beam received in the light receiving regions A and C, and supplies them to the adder 13 and at the same time receives the light. A light amount detection signal corresponding to the light amount of the reflected light of the main beam received in the region B and the light receiving region D is formed, and these are supplied to the adder 14. The adders 13 and 14 perform addition processing on the supplied light amount detection signals and supply them to the comparator 15 and the adder 16, respectively. The comparator 15 forms a focus error signal by a so-called astigmatism method by comparing the added outputs of the adders 13 and 14, and outputs the focus error signal.
It is supplied to the servo control system via b. Further, the adder 16 reproduces an RF signal which is recording data by performing an addition process on each addition output of each of the adders 13 and 14, and supplies this to an unillustrated data processing system via an output terminal 19c. To do.

The servo control system forms a tracking control signal for making the tracking error zero based on the tracking error signal, and the tracking control signal is used for the tracking coil of the shaft sliding type optical system 2 shown in FIGS. 23A, 2
3B respectively. Further, the servo control system forms a focus control signal for making the focus error zero based on the focus error signal, and supplies this to the focus coil 22 of the optical system 2.

The tracking control signal is a current whose level and polarity are changed according to the tracking error. When this current flows through the tracking coils 23A and 23B, the tracking coils 23A and 23B are fed.
B is from the magnetic field in the magnetic gap formed between the projecting piece portion 31 of the first yoke portion 32 and the second yoke portion 33,
A force that induces a rightward or leftward rotation around the support shaft 29 is received, and in response to this, the movable portion 20 causes the support shaft 2 to move.
It rotates rightward or leftward about 9 as a center. At this time, since the lens barrel 25 is provided so as to be eccentric with respect to the central axis of the movable portion 20, the optical axis of the lens barrel 25, that is, the optical axis of the objective lens 7 crosses the recording track of the optical disc 1 ( (The direction of arrow t or arrow t'in FIG. 2)
Then, the tracking control is performed.

The focus control signal is a current whose level and polarity are varied according to the focus error. When this current flows through the focus coil 22, the focus coil 22 causes the first yoke portion 32 to move. The magnetic field in the magnetic gap formed between the second yoke portion 33 and the second yoke portion 33 receives a force in the direction along the support shaft 29, and accordingly the movable portion 20 moves upward or downward along the support shaft 29. Move to. As a result, the objective lens 7, the 1/4 wavelength plate 26, which is housed in the lens barrel 25 provided in the holder 20B,
The collimator lens 27 and the polarization beam splitter 6 fixed to the holder 20B move as a whole while maintaining their respective positional relationships, and the objective lens 7 moves up and down in the direction perpendicular to the surface of the optical disc 1. Focus control is performed.

When the focus control signal is supplied to the focus coil 22 and the tracking control signal is supplied to the tracking coils 23A and 23B, the above focus control and tracking control are performed simultaneously. There is.

In such a shaft-sliding type optical system 2, each optical component forming an optical path from the laser beam from the semiconductor laser 5 back and forth through the objective lens 7 to the photodetector 8 is movable in common. Since it is fixed to the portion 20, it is possible to prevent the inconvenience that the relative positional relationship between the optical members changes due to the focus control and the tracking control. Further, since the lenses can be used at the best points of the initially positioned lenses at all times, they can be used with stable optical characteristics and the optical field of view can be expanded to infinity. Further, it is possible to eliminate the need for aberration removal and reduce the lens cost.

Since the axial lengths of the support shaft 29 and the bearing portion 21 in the axial direction can be set to the length corresponding to the thickness of the optical system 2, the movable portion 20 can be slidably rotated with respect to the support shaft 29. Can be stabilized. For this reason, it is possible to prevent the movable portion 20 from being caught during the sliding rotation, and it is possible to perform highly accurate focus control and tracking control. Further, the semiconductor laser 5 and the optical lens system including the objective lens 7, the quarter-wave plate 26, the collimator lens 27, the polarization beam splitter 6 and the like about the support shaft 29 are arranged at positions substantially symmetrical in weight. Therefore, the weight of the movable part 20 can be balanced,
It is possible to perform stable axial sliding and rotation around the axis.

Here, as described above, the optical disk reproducing apparatus detects the tracking error by the 3-spot method. When the tracking error is detected by the three-spot method, the main beam is irradiated so that the center of the beam and the center of the recording track coincide with each other, and the side beam of + 1st order light is applied to the recording track.
For example, irradiate the position shifted to the outer peripheral side by 1/4 track,
It is necessary to irradiate the side beam of the −1st-order light on the recording track at a position shifted to the inner circumference side by ¼ track. However, as shown in FIGS. 5A and 5B, since the track pitch of the first optical disk and the track pitch of the second optical disk are different, the spectral characteristic of the diffraction grating 18 is wide (1. 6 μm) If the first optical disc is adjusted so that tracking error can be detected by the three-spot method, the irradiation position of each side beam will be shifted with respect to the second optical disc having a narrow track pitch (0.84 μm). Tracking error detection by the 3-spot method becomes impossible. For this reason, in the optical disk reproducing apparatus, the disk discriminating circuit 4 shown in FIG. 1 is used for the type of the optical disk (track pitch) loaded in the optical disk reproducing apparatus before the reproduction as described above.
And the diffraction grating drive unit 17 rotates the diffraction grating by a predetermined amount according to the detection result, so that tracking error detection by the three-spot method can be performed on the first and second optical disks. The irradiation position is adjusted.

That is, in FIG. 1, the disc discriminating circuit 4 irradiates the optical disc 1 mounted in the optical disc reproducing apparatus with a laser beam and detects the reflectance.
The second optical disc with a track pitch of 0.84 μm
The density is higher than that of the first optical disc having a track pitch of 1.6 μm, and the reflectance of the second optical disc is lower than that of the first optical disc. Therefore, the disc discriminating circuit 4 detects whether the optical disc mounted in the optical disc reproducing apparatus is the first optical disc or the second optical disc by detecting the reflectance. Then, the detection output which is a pulsed signal is supplied to the stepping motor 40 of the diffraction grating drive unit 17 shown in FIG. As a result, the stepping motor 4
A rotary gear 4 having a rotational force of 0 on the rotary shaft 40a.
It is transmitted to the diffraction grating 18 via the first gear portion 41 a and the gear portion 18 a of the diffraction grating 18. Then, for example, when the mounted optical disk is the first optical disk having a wide track pitch, the diffraction grating 18 is rotationally driven in the direction A in FIG. 6A, and the mounted optical disk is the second optical disk having a narrow track pitch. In the case of an optical disc, B in FIG.
The diffraction grating 18 is rotationally driven in the direction. Thereby, as shown in FIGS. 5A and 5B, the side beams irradiated on the optical disk can be rotated about the main beam. Therefore, when the second optical disc having a narrow track pitch is mounted on the optical disc reproducing apparatus, each side beam is deviated by 1/4 track to the inner and outer circumference sides of the disc as shown in FIG. When the first optical disc having a wide track pitch is mounted, each side beam is moved to the inner and outer peripheral sides of the disc as shown in FIG. 5B. Irradiation can be performed with a deviation of four tracks.

The rotation control of the diffraction grating 18 is performed based on the rotation position detection by the rotation angle sensor (resolver). This resolver is based on the stepping motor 4 described above.
2 stator coils 90 around 0 rotor coil
By arranging at an angle of 4 degrees and supplying an alternating voltage of a predetermined frequency to the rotor coil, the amplitude output of the induced voltage obtained from the stator coil according to the angular displacement of the rotor is detected as a mechanical rotation angle. It is a thing. This resolver
Since it is possible to detect the rotational position of the stepping motor 40 with a resolution higher than the number of poles, the stepping motor 40 is configured to subtly rotate the diffraction grating 18 and variably control the irradiation position of each side beam by using the resolver.
It is possible to enable fine rotation control. Further, the rotation control of the diffraction grating 18 is adjusted by the rotation control of the stepping motor 40 as well as the size of each gear of the gear portion 18a of the diffraction grating 18 and the gear portion 41a of the rotary gear 41. , Stepping motor 4
0 is in the A direction or B direction, for example, 1 of each gear
When it is driven to rotate by the number of teeth, each side beam is irradiated to the above-mentioned optimum position on the first optical disk, or
Each side beam is irradiated to the above-mentioned optimum position on the optical disc.

When the tracking error is detected by the three-spot method, unless each side beam is displaced by a predetermined amount with respect to the recording track, the amplitude of the tracking error signal due to the phase shift between the side beams decreases. However, this hinders accurate tracking error detection.
The optical disk reproducing apparatus rotates the diffraction grating 18 in accordance with the track pitch of the optical disk to be reproduced, so that the optical disk reproducing apparatus reproduces 3 times for both the first optical disk having a wide track pitch and the second optical disk having a narrow track pitch. Each side beam can be irradiated so that tracking error can be detected by the spot method. Therefore, it is possible to reproduce both the first and second optical disks.

As described above, the amount of rotation of the diffraction grating 18 is a minute amount. Therefore, the gear portion 18a provided on the diffraction grating 18 does not need to be provided over the entire outer peripheral portion, and the rotary gear 41 provided on the stepping motor 40 is not necessary.
The gear portion 41a may be provided only at a meshing portion. However, by providing the gear portion 18a over the entire outer peripheral portion of the diffraction grating 18, the stepping motor 4
A tracking error signal obtained by rotationally driving 0 to vary the irradiation position of each side beam is fed back to, for example, a rotation control circuit, and the rotation control circuit rotates the stepping motor 40 so that the tracking error becomes zero. It is possible to control the rotation control of the diffraction grating 18 in a phase locked loop (PLL) manner.

Next, a second embodiment of the optical disk reproducing apparatus to which the optical pickup device according to the present invention is applied will be described. In the optical disk reproducing apparatus according to the first embodiment described above, the rotary gear 41 provided on the stepping motor 40 is used.
Although the gear portion 41a of the optical disc and the gear portion 18a of the diffraction grating 18 are directly meshed with each other, in the optical disc reproducing apparatus according to the second embodiment, as shown in FIG. 41a is meshed with the slide gear 42 provided with the gear portion 42a to control the rotation of the diffraction grating 18. The optical disc reproducing apparatus according to the second embodiment has the same configuration as the optical disc reproducing apparatus according to the first embodiment described above except for such a mechanism system. Therefore, the optical disc reproducing apparatus according to the second embodiment is the same. In the description of the reproducing apparatus, the description of this mechanical system will be referred to, and the detailed description of the other parts will be omitted.

That is, in the optical disc reproducing apparatus according to the second embodiment, when the optical disc is mounted, the disc discriminating circuit 4 detects the type of the mounted optical disc based on the reflectance of the optical disc, and outputs this detection output. According to FIG.
The stepping motor 40 shown in (b) is rotationally driven.
As a result, the rotational force of the stepping motor 40 is transmitted to the slide gear 42, and the slide gear 42 slides in the C direction or D direction in the figure. Then, by sliding the slide gear 42 as described above, the slide gear 4
The diffraction grating 18 having the gear portion 18a meshed with the second gear portion 42a is rotationally driven to optimally irradiate each side beam onto the first optical disc or the second optical disc as described above. Therefore, also in the optical disc reproducing apparatus according to the second embodiment, the same effect as that of the optical disc reproducing apparatus according to the first embodiment can be obtained.

In the above description of each embodiment, the tracking error is detected by the 3-spot method.
This may be a method that uses at least each side beam, and other methods such as a differential push-pull method (DPP method) can be used. In this case, as the photodetector 8, a first photodetector that is a four-division photodetector that receives the reflected light of the main beam and a second photodetector that is a two-division photodetector that receives the reflected light of the side beam of the + 1st order light, A third photodetector which is a two-divided photodetector that receives the reflected light of the side beam of the −1st-order light is provided. The second and third photodetectors are respectively arranged in a direction orthogonal to the track direction of the disk by a straight line passing through the optical axis of the reflected light of the side beam of the + 1st order light or the reflected light of the side beam of the -1st order light received respectively. Divide into two equal parts. Then, the light amount detection signals from the light receiving regions of the first photodetector are A to D, and the light amount detection signals from the second and third photodetectors are E to H, respectively, and the DPP shown in the following formula 1 is obtained. A tracking error signal is formed by the modulo calculation.

Tracking error signal = [(A + C)-(B +
D)]-K [(E-F) + (G-H) / 2] ... (Equation 1)
K: Coefficient for correcting the light amount difference between the main beam and the side beam With this, the same effect as that of the optical disc reproducing apparatus according to each of the above-described embodiments can be obtained.

Further, in the description of the above-mentioned embodiments, a shaft sliding type optical system is used as the optical system 2. However, this is an optical system of a biaxial device cantilevered by a plurality of elastic supports. May be used.

In the above description of each embodiment, the disc discrimination circuit 4 detects the reflectance of the disc to detect the type of the optical disc loaded in the optical disc reproducing apparatus. Information indicating the type of the disc may be recorded on a second optical disc having a narrow track pitch, and when this information is reproduced, a tracking error signal for the second optical disc may be selected and output. . Alternatively, the disc pitch is detected by detecting the track pitch based on the reflected light, and the disc discrimination is performed by using the astigmatism method with the second and third photodetectors for the side beams as four-division photodetectors. Any method can be used as long as it can discriminate the type of the disc. Even if such automatic discrimination is not performed, the user recognizes the type of the disc (track pitch), and accordingly rotates the diffraction grating 18 manually to adjust the irradiation position of each side beam. May be.

Finally, in the above description of each embodiment, the optical pickup device according to the present invention is applied to a read-only optical disc reproducing device. This applies to optical cards, optical tapes, etc. in addition to optical discs. Recording on an optical recording medium,
It can be applied to any device that reproduces, and the track pitch of the first optical disc is 1.6 μm.
The track pitch of the second optical disk has been described by giving a specific numerical value such as 0.84 μm, but this is merely an example, and various modifications are possible within a range not departing from the technical idea of the present invention. Of course, it is possible.

[0040]

The optical pickup device according to the present invention can record and reproduce a plurality of types of optical discs having different track pitches. Therefore, since it is possible to record and reproduce without selecting a disc,
The versatility of equipment to which the optical pickup device is applied can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment in which an optical pickup device according to the present invention is applied to a reproduction-only optical disc reproduction device.

FIG. 2 is a top view of a shaft-sliding type optical system provided in the optical disc reproducing apparatus according to the first embodiment.

FIG. 3 is a sectional view of the shaft sliding type optical system.

FIG. 4 is a cross-sectional view of a hole portion of a support shaft of the shaft sliding type optical system.

FIG. 5 is a schematic diagram for explaining two types of optical disks having different track pitches that are reproduced by the optical disk reproducing apparatus according to the above-described embodiment.

FIG. 6 is a diagram showing a rotation control mechanism of a diffraction grating provided in the optical disc reproducing apparatus in the embodiment.

[Explanation of symbols]

 1 Optical Disk 2 Optical System 3 Tracking Error Detection System 4 Disk Discrimination Circuit 5 Semiconductor Laser 6 Polarizing Beam Splitter 7 Objective Lens 8 Photodetector 9 First Photodetector 10 Second Photodetector 11 Third Photodetector 12, 15 Comparator 13, 14 , 16 adder

Claims (2)

[Claims] 1. A spectroscopic unit that splits light emitted from a light source into a plurality of beams, and an irradiation unit that irradiates the optical recording medium with the light beams split by the spectroscopic unit, respectively. In the case of a recording medium, the first light and the second light of the dispersed light are radiated while being deviated by a predetermined amount to the inside and the outside of the recording track of the first optical recording medium. In addition, when the optical recording medium is the second optical recording medium having a narrower track pitch than the first optical recording medium, the first light and the second light of the split light are Is rotated by a predetermined amount so that the inside and the outside of the recording track of the second optical recording medium are displaced by a predetermined amount, respectively, and the irradiation positions of the first and second lights are rotated. Irradiation position variable control means for variably controlling the Of the reflected light generated by irradiating the optical recording medium with the reflected light, at least the reflected light of the first light and the reflected light of the second light are respectively received, and the light amount corresponding to the received reflected light is received. An optical pickup device having a light receiving unit for outputting a detection signal. 2. A medium discriminating means for detecting whether the optical recording medium is the first optical recording medium or the second optical recording medium having a track pitch narrower than that of the first optical recording medium. 2. The optical pickup device according to claim 1, wherein the irradiation position variable control means controls the rotation of the spectroscopic means according to a detection output from the medium discriminating means.