JPH0954961A - Optical pickup for optical disk reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce correctly even an optical disk of any system by providing plural pieces of objective lenses suitable for the optical disks of different kinds and inserting/ejecting them into an optical path according to the kinds of the optical disks. SOLUTION: Two pieces of objective lenses 16, 17 set numerical apertures so as to correct spherical aberration answering to one side of 0.6mm or 1.2mm of a thickness of a protection film 20b when they focus on the signal recording surface 20a of the optical disk 20. Biaxial actuators 18, 19 support respectively the objective lenses 16, 17 drivably in the biaxial directions of focusing and tracking. A slider 28 placing the biaxial actuators 18, 19 is constituted so as to be movable in a plane vertical to an optical axis, and moves so that the optical axis of the suitable objective lens 16 or 17 is inserted selectively into the optical path consisting of a semiconductor laser element 11, a photodetector 15, a beam splitter 13, etc., according to the kinds of the optical disk 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus for reproducing a recording signal by irradiating a surface of a rotating optical disk with light and detecting return light.

[0002]

2. Description of the Related Art Conventionally, for example, an optical disk reproducing apparatus for reproducing an optical disk on which data is digitized and compressed is recorded, in which a light such as a laser beam is emitted from an optical pickup onto the surface of a rotationally driven optical disk. Irradiate. Then, the light receiving element of the optical pickup detects the return light from the surface of the optical disc and reads the signal recorded on the optical disc to generate the reproduction signal of the image data.

[0003]

However, the above-mentioned optical disks have two or more standards having different characteristics, for example, one having only one side configured as a signal recording surface and one having both sides configured as a signal recording surface. Are mixed. In addition, in these standards, the thickness of the substrate forming the optical disk, that is, the thickness of the transparent protective film is, for example, 1.2.
Since there are those with a thickness of 0.6 mm and those with a thickness of 0.6 mm, the allowable range of the error in the thickness of the disc substrate that can be handled by the optical pickup greatly exceeds. Therefore, it is difficult to reproduce the optical discs of both standards with one optical pickup.

Since the disk substrate of the optical disk produces spherical aberration proportional to the thickness of its transparent protective film, the objective lens is designed to cancel this spherical aberration. By the way, when the thickness of the disc substrate is different, the spherical aberration is also different. Therefore, an objective lens corresponding to an optical disc of one standard, for example, a disc substrate thickness of 1.2 mm is used, and the other standard, for example, the disc substrate thickness of 0.6.
When the mm optical disc is used for reproduction, there is a problem that the spherical aberration cannot be canceled by the objective lens, so that the signal cannot be correctly detected from the return light from the optical disc.

Thus, there is a problem that the user needs to reproduce the optical discs of both systems by the optical disc reproducing apparatus dedicated to each system while always being aware of which system.

In view of the above points, the present invention has an object to provide an optical pickup of an optical disk reproducing apparatus, which makes it possible to correctly reproduce an optical disk of any type.

[0007]

According to the present invention, the above-mentioned object is to focus a light source which emits a light beam and a light beam emitted from the light source onto a signal recording surface of a rotationally driven optical disc. An objective lens that irradiates in this manner, a photodetector that receives the return light beam from the signal recording surface of the optical disc through this objective lens, and a plurality of objective lenses that correspond to multiple types of optical discs with different disc substrate thicknesses. A plurality of biaxial actuators for moving the respective objective lenses in the biaxial directions, and a switching means for relatively inserting / removing the objective lenses corresponding to the type of the optical disc to be reproduced into / out of the optical path. Achieved by pickup.

According to the above construction, a plurality of objective lenses having different characteristics designed corresponding to different disc substrate thicknesses of the optical disc are provided, and it is optimal according to the disc substrate thickness of the optical disc to be reproduced. Since various objective lenses are selected and inserted into the optical path by individual biaxial actuators, optimum signal reproduction is always performed for a plurality of types of optical discs having different disc substrate thicknesses.

[0009]

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

FIG. 1 shows a first embodiment of an optical pickup according to the present invention. In FIG. 1, the optical pickup 10 in this case has a non-polarized and infinite optical system, and includes a semiconductor laser element 11 and a grating 1.
2, an optical system A including a beam splitter 13, a collimator lens 14, and a photodetector 15, two objective lenses 16 and 17 selectively inserted into and removed from the optical path of the optical system A, and these objective lenses 16 and It is composed of biaxial actuators 18 and 19 that respectively move and adjust 17 in biaxial directions.

The semiconductor laser device 11 is a light emitting device utilizing recombination light emission of a semiconductor and is used as a light source. The light beam emitted from the semiconductor laser device 11 is
Guided by the grating 12.

The grating 12 is also called a diffraction grating and splits the light beam from the semiconductor laser element 11 into 0th order light and plus / minus 1st order light.

The beam splitter 13 has its reflecting surface 13
a is disposed in a state of being inclined by 45 degrees with respect to the optical axis of the objective lens 15, and separates the light beam emitted from the semiconductor laser element 11 and the return light from the signal recording surface of the optical disc 21. That is, the light beam from the semiconductor laser device 11 is reflected by the reflecting surface 13a of the beam splitter 13,
The return light passes through the beam splitter 13.

The collimator lens 14 is a convex lens and converts the light beam from the semiconductor laser element 11 into parallel light.

The objective lenses 16 and 17 are convex lenses, and when inserted in the optical path, the parallel light beam from the collimator lens 14 is directed onto a desired track on the signal recording surface of the optical disc 18 which is driven to rotate. Form an image.
Further, the objective lenses 16 and 17 are supported by biaxial actuators 18 and 19 so as to be movable in biaxial directions, that is, in the tracking direction perpendicular to the paper surface in FIG. 1 and in the vertical focusing direction.

Here, the objective lenses 16 and 17 are formed so as to correspond to optical disks having different disk substrate thicknesses. For example, the objective lens 16 is for an optical disc having a disc substrate thickness of 1.2 mm, and the objective lens 17 is
Is designed for an optical disc having a disc substrate thickness of 0.6 mm.

That is, the optical disk 20 has, for example, a signal recording surface 20a on which a pit row corresponding to a recording signal is formed on a predetermined track, and a transparent protective film 20b made of synthetic resin covering the surface of the signal recording surface 20a. And have. The light passing through the objective lenses 16 and 17 is the transparent protective film 20b.
To reach the signal recording surface 20a. In this case, the case where the thickness of the transparent protective film 20b is 0.6 mm and 1.
In the case of 2 mm, the spherical aberration given to the transmitted light is different. Therefore, the objective lenses 16 and 17
Has its NA (numerical aperture) determined in advance so that the spherical aberration can be canceled in accordance with the thickness of the corresponding protective film 20b of the optical disc 20.

The light beam with which the signal recording surface 20a of the optical disc 20 is irradiated is again guided to the beam splitter 13 via the objective lens 16 or 17 and the collimator lens 14 as a return light beam. Then, the return light beam that has passed through the beam splitter 13 is incident on the light receiving portion of the photodetector 15.

The photodetector 15 has a light receiving surface capable of receiving the returning light beam. Here, the biaxial actuator 1
Reference numerals 8 and 19 are also called objective lens actuators and are configured symmetrically in the drawing, and as shown in FIG.
A lens holder 21 having the objective lens 16 or 17 attached to the tip thereof, and a coil bobbin 22 attached to the lens holder 21 by adhesion or the like.
And

The lens holder 21 has a pair of elastic supporting members 24, one end of which is fixed to both sides of the lens holder 21 and the other end of which is fixed to the fixed portion 23. It is movably supported in two orthogonal directions, that is, a tracking direction and a focusing direction.

Further, in the illustrated case, the coil bobbin 22 is formed integrally with the lens holder 21, as shown in FIG.
As shown in FIG. 3, a focusing coil 22a formed by winding a wire in a predetermined direction, and a tracking coil 22b formed by winding the wire in a direction orthogonal to the winding direction of the wire of the focusing coil 22a are provided. ing. By energizing the focusing coil 22a and the tracking coil 22b, the magnetic flux generated in each coil interacts with the magnetic flux generated by the yoke 26 attached to the biaxial base 25 and the magnet 27 attached thereto. It has become.

Further, the elastic support member 24 is formed of an elastic body and is fixed between the lens holder 21 and the fixing portion 23 so as to be parallel to each other.

The fixed portion 23 is a biaxial base 25.
Fixed to the two biaxial actuators 1
The biaxial base 25 of 8, 19 includes the objective lens 16 or 1
It is attached to a slider 28 that can move horizontally in the X direction in a plane perpendicular to the optical axis of the optical system A passing through 7.
Therefore, by the horizontal movement of the slider 28, the biaxial actuators 18, 1 for supporting the objective lenses 16, 17 are provided.
9 is moved horizontally. As a result, the objective lens 16 or 17 is selectively inserted into or removed from the optical path of the optical system A.

Optical pickup 1 according to this embodiment
0 is configured as described above, and a case where the optical disk 20 having a disk substrate thickness of 1.2 mm is first reproduced will be described. The optical disc 20 has a disc substrate thickness of 1.2.
In the case of mm, as shown in FIG. 4, by the detection signal from the detection means B for detecting the type of the disc,
Alternatively, the slider 28 is manually moved to insert the objective lens 16 supported by the biaxial actuator 18 into the optical path of the optical system A.

As a result, the light beam from the semiconductor laser element 11 is reflected by the beam splitter 13 via the grating 12, and then the collimator lens 14 is provided.
Then, an image is formed on the signal recording surface of the optical disc 20 via the objective lens 16. At this time, since the objective lens 16 corresponds to a disc substrate thickness of 1.2 mm, the light beam is correctly focused on the signal recording surface of the optical disc 20 by the objective lens 16.

The return light from the optical disk 20 again passes through the beam splitter 13 via the objective lens 16 and the collimator lens 14 and enters the photodetector 15. As a result, the reproduction signal, the focus servo signal, and the tracking servo signal are detected based on the detection signal of the photodetector 15.

Here, the biaxial actuator 18 includes a focusing coil 22 wound around a coil bobbin 22.
The drive currents based on the focus servo signal and the tracking servo signal are supplied to a and the tracking coil 22b, respectively. As a result, the magnetic field of the magnetic circuit formed by the yoke 26 and the magnet 27, the focusing coil 22 a, and the tracking coil 22.
The lens holder 21, that is, the objective lens 16 is driven in the focus direction and the tracking direction by the magnetic field generated from b, and focusing and tracking are performed.

Next, when the optical disk 20 is replaced and the optical disk 20 having a disk substrate thickness of 0.6 mm is loaded, as shown in FIG. 5, a detection signal from the detection means B for detecting the type of the disk is detected. Or manually, the slider 28 is moved to move the biaxial actuator 19
The objective lens 17 supported by is inserted in the optical path of the optical system A.

As a result, the light beam from the semiconductor laser device 11 is reflected by the beam splitter 13 via the grating 12, and then the collimator lens 14 is provided.
Then, an image is formed on the signal recording surface of the optical disc 20 via the objective lens 17. At this time, since the objective lens 17 corresponds to a disc substrate thickness of 0.6 mm, the objective lens 17 correctly images the light beam on the signal recording surface of the optical disc 20.

The return light from the optical disk 20 passes through the beam splitter 13 again through the objective lens 17 and the collimator lens 14, and enters the photodetector 17. As a result, the reproduction signal, the focus servo signal, and the tracking servo signal are detected based on the detection signal of the photodetector 15.

Here, the biaxial actuator 19 includes a focusing coil 22 wound around a coil bobbin 22.
The drive currents based on the focus servo signal and the tracking servo signal are supplied to a and the tracking coil 22b, respectively. As a result, the magnetic field of the magnetic circuit formed by the yoke 26 and the magnet 27, the focusing coil 22 a, and the tracking coil 22.
The lens holder 21, that is, the objective lens 17 is driven in the focus direction and the tracking direction by the magnetic field generated from b, and focusing and tracking are performed.

Thus, whether the optical disc 20 has a disc substrate thickness of 1.2 mm or 0.6 mm, the objective lens 16 or 1 corresponding to the type of the optical disc 20 is used.
By inserting 7 into the optical axis of the optical system A, the signal reproduction of the optical disc 20 is correctly performed.

In this case, the slider 28 is adapted to be horizontally translated in the direction of the arrow X in FIG. 1, but the present invention is not limited to this, and the two biaxial actuators are selectively moved to move the slider 28. Other configurations are possible as long as the two objective lenses supported by the respective biaxial actuators are selectively inserted into and removed from the optical path of the optical system. For example, in the second embodiment of the optical pickup shown in FIG. 6, a slider 29 rotatably supported around a rotation shaft 29a as shown by an arrow Y is provided. The slider 29 is a substantially fan-shaped substrate as shown in the drawing, and has a rotating shaft 29a near its center. In this case, the biaxial actuators 18, 19 with respect to the rotation axis 29a of the slider 29 have the objective lens 1
6 and 17 are arranged at the same radial position. As a result, the objective lenses 16 and 17 are brought to the same position by the swing of the slider 29 and inserted into the optical path of the optical system.

FIG. 7 shows a third embodiment of the optical pickup according to the present invention. In FIG. 7, an optical pickup 30 includes a semiconductor laser element 11, a grating 12, a beam splitter 13, and a collimator lens 14.
And an optical system A including a photodetector 15 and two objective lenses 16 and 17 selectively inserted into and removed from the optical path of the optical system A.
And biaxial actuators 31 and 32 for moving and adjusting the objective lenses 16 and 17 in the biaxial directions, respectively.

In this case, the semiconductor laser element 11, the grating 12 and the beam splitter 1 which constitute the optical system A
3, the collimator lens 14 and the photodetector 15, and the objective lenses 16 and 17 are the optical pickup 10 shown in FIG.
The configuration is the same as that of.

Here, the biaxial actuators 31, 32
Are symmetrically arranged in the drawing, and are respectively shown in FIG.
The biaxial actuators 18 and 19 of the optical pickup 10 shown in FIG. 2 are configured in the same manner, but the fixing portions 23 of both biaxial actuators 31 and 32 are integrally fixed to the optical base 33. ing.

Further, on the optical base 33, a fixed mirror 34 is provided which is inclined downward at an angle of 45 degrees with respect to the optical axis of the objective lens 17 supported by the biaxial actuator 32, and the light of the optical system A. A movable mirror 35 is provided above the axis (that is, the optical axis of the collimator lens 14) so that it can be inserted and removed at an angle of 45 degrees.
The movable mirror 35 automatically or manually based on a detection signal from the detection means B for detecting the type of the disk, for example, is indicated by an arrow Z between the illustrated insertion position and the left retracted position. Is moved in the direction. Then, the movable mirror 35 is moved to the retracted position in the case of reproducing the optical disk 20 having a disk substrate thickness of 1.2 mm, and is inserted as shown in the case of reproducing the optical disk 20 having a disk substrate thickness of 0.6 mm. Brought to position.

The optical pickup 3 constructed in this way
At 0, when reproducing the optical disk 20 having a disk substrate thickness of 1.2 mm, the light beam from the semiconductor laser element 11 is reflected by the beam splitter 13 via the grating 12, and then is collimated by the collimator lens 14 and the objective lens. An image is formed on the signal recording surface of the optical disc 20 via the lens 16. At this time, since the objective lens 16 corresponds to a disc substrate thickness of 1.2 mm, the light beam is correctly focused on the signal recording surface of the optical disc 20 by the objective lens 16.

The return light from the optical disk 20 again passes through the beam splitter 13 via the objective lens 16 and the collimator lens 14 and enters the photodetector 15. As a result, the reproduction signal, the focus servo signal, and the tracking servo signal are detected based on the detection signal of the photodetector 15.

Next, when the optical disc 20 is replaced and the optical disc 20 having a disc substrate thickness of 0.6 mm is loaded, the optical disc 20 is moved by a detection signal from the detection means B for detecting the type of the disc or manually. Mirror 35
Moves to the insertion position shown in the figure, and the optical path of the optical system A is bent by the movable mirror 35 and the fixed mirror 34, so that the objective lens 17 supported by the biaxial actuator 32 is relatively positioned in the optical path. Will be inserted.

As a result, the light beam from the semiconductor laser device 11 is reflected by the beam splitter 13 via the grating 12, and then the collimator lens 14 is provided.
Through the objective lens 17 and then is imaged on the signal recording surface of the optical disc 20. At this time, the objective lens 1
In consideration of the optical path length from the movable mirror 35 to the fixed mirror 34, 7 is designed to correspond to a disk substrate thickness of 0.6 mm. As a result, the light beam is correctly focused on the signal recording surface of the optical disc 20 by the objective lens 17.

The return light from the optical disk 20 passes through the beam splitter 13 again through the objective lens 17, the fixed mirror 34, the movable mirror 35 and the collimator lens 14 and enters the photodetector 17. As a result, the reproduction signal, the focus servo signal, and the tracking servo signal are detected based on the detection signal of the photodetector 15.

In this way, as shown in the first embodiment, when the detection means for discriminating the type of the optical disc to be reproduced and controlling the switching of the switching means is provided, it is used. The player can correctly reproduce the optical disc without being aware of the type of the optical disc to be reproduced.

When the respective biaxial actuators are arranged on the same plane perpendicular to the optical axis and are moved on this plane by the switching means to be inserted into and removed from the optical path, the biaxial actuators Switching of the actuator is easily performed.

Each biaxial actuator is mounted on one substrate movably supported by the switching means, or mounted on one substrate swingably supported by the switching means. In this case, the switching means simply moves or swings the one substrate to move both biaxial actuators, so that the biaxial actuators can be easily switched.

As shown in the second embodiment, the biaxial actuators are fixedly arranged, and the switching means moves the optical path switching mirrors so that the biaxial actuators relatively move the optical paths. When it is inserted and removed, the member moved by the switching means can be lightweight, and the switching means can be made compact.

In the above embodiment, the objective lenses 16 and 17 corresponding to the optical discs having the disc substrate thicknesses of 1.2 mm and 0.6 mm are used.
Is configured to be switched into and out of the optical path, but when the disk substrate thickness is three or more, for example, a plurality of corresponding objective lenses and the objective lenses are moved and adjusted in the biaxial directions. Obviously, the biaxial actuator can be configured for switched use, depending on the type of optical disc to be played.

[0048]

As described above, according to the present invention, it is possible to provide an optical pickup for an optical disk reproducing apparatus, which makes it possible to correctly reproduce an optical disk of any type. Become.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a first embodiment of an optical pickup according to the present invention.

FIG. 2 is an enlarged view showing the configuration of two biaxial actuators in the optical pickup of FIG.

3 is a detailed cross-sectional view of a magnetic circuit unit in the biaxial actuator of FIG.

FIG. 4 is a diagram illustrating a disk substrate thickness 1. of the optical pickup of FIG.
It is a schematic sectional drawing which shows the reproduction | regeneration state in case of 2 mm.

5 is a diagram illustrating a disk substrate thickness of 0.
It is a schematic sectional drawing which shows the reproduction | regeneration state in case of 6 mm.

FIG. 6 is a schematic plan view showing a main part of a second embodiment of an optical pickup according to the present invention.

FIG. 7 is a schematic sectional view showing a first embodiment of an optical pickup according to the present invention.

[Explanation of symbols]

 10 Optical Pickup 11 Semiconductor Laser Element (Light Source) 12 Grating 13 Beam Splitter 14 Collimator Lens 15 Photodetector 16,17 Objective Lens 18,19 Biaxial Actuator 20 Optical Disc 21 Lens Holder 22 Coil Bobbin 23 Fixing Part 24 Elastic Support Member 25 Biaxial Base 26 Yoke 27 Magnet 28 Slider 30 Optical pickup 31, 32 Biaxial actuator 33 Optical base 34 Fixed mirror 35 Movable mirror

Claims (6)

[Claims] 1. A light source for emitting a light beam, an objective lens for irradiating the light beam emitted from the light source so as to focus on a signal recording surface of a rotationally driven optical disk, and an objective lens A photodetector that receives the returning light beam from the signal recording surface of the optical disc, a plurality of objective lenses corresponding to a plurality of types of optical discs with different disc substrate thicknesses, and a plurality of objective lenses that move each objective lens in two axial directions. An optical pickup comprising a biaxial actuator and a switching means for relatively inserting and removing an objective lens corresponding to a type of an optical disc to be reproduced into and out of an optical path. 2. The optical pickup according to claim 1, further comprising detection means for discriminating a type of the optical disc to be reproduced and controlling switching of the switching means. 3. The biaxial actuators are arranged on the same plane perpendicular to the optical axis, and are moved on this plane by a switching means to be inserted into and removed from the optical path. The optical pickup according to claim 1. 4. The optical pickup according to claim 3, wherein each of the biaxial actuators is mounted on one substrate supported by the switching means so as to be movable in parallel. 5. The optical pickup according to claim 3, wherein each of the biaxial actuators is mounted on one substrate that is swingably supported by a switching unit. 6. The biaxial actuators are fixedly arranged, and the switching means moves the optical path switching mirrors so that the biaxial actuators are relatively inserted into and removed from the optical path. The optical pickup according to claim 1.