JPH09198679A - Two-axis actuator and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-axis actuator and an optical disk device which can change over an objective lens to cope with any system of optical disk and are also advantageous in structure to be formed small in size. SOLUTION: This device is provided with a lens holder 33 which holds an objective lens so that it can slide along the supporting shaft and also can rock around the supporting shaft and which holds an objective lens 25 so that the optical axis becomes parallel with the supporting shaft, a coil for focusing and a magnet 35 for tracking, and a magnet for focusing and magnet 39 for tracking which are fixedly arranged to face these ones. Here, the lens holder 33 maintains objective lenses 26a and 26b which are on concyclic positions having different angles to the supporting shaft and cope with different types of optical disks, and an objective lens 26b of a smaller diameter is arranged in the inner circumference of the optical disk, and, further, each objective lens is inserted in the optical path by rocking of the lens holder around the supporting shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxial actuator for recording and / or reproducing information on a compact disc (CD), a CD-ROM, a magneto-optical disc (hereinafter referred to as "optical disc"), and an optical disc device. In particular, the present invention relates to a biaxial actuator and an optical disc device that are capable of reproducing a plurality of types of optical discs.

[0002]

2. Description of the Related Art Conventionally, an optical pickup for reproducing an optical disk has, for example, a semiconductor laser element as a light emitting means, an objective lens for irradiating the optical disk with light from the semiconductor laser element, and the objective lens for biaxial directions. A biaxial actuator that holds it movably, a photodetector that detects the return light from the optical disk, and a servo circuit that drives and controls the biaxial actuator in the focusing direction and the tracking direction based on the detection signal of the photodetector. It consists of

Here, the biaxial actuator is, for example, a lens holder that is supported so as to be movable in the axial direction and rotatable about the support shaft extending perpendicularly to the signal recording surface of the optical disc. And an objective lens in which the optical axis is held parallel to the support axis at a position eccentric from the support axis of the lens holder, and a biaxial base to which the support axis is attached. Further, in the biaxial actuator, a focusing coil is wound around a cylindrical outer peripheral surface of the lens holder, and a pair of tracking coils are attached to opposite sides of the outer surface of the focusing coil. On the other hand, on the biaxial base, a pair of yokes made of a magnetic material is arranged so as to face the focusing coil and the tracking coil.

According to the optical pickup having such a structure, a driving voltage controlled by tracking servo and focus servo from a servo circuit is supplied to each coil from the outside, so that each coil is generated. The generated magnetic flux interacts with the magnetic flux of the yoke made of a magnetic material, so that the lens holder rotates around the support shaft and slides along the support shaft.
As a result, the objective lens, which is held eccentrically from the center of the lens holder, is moved appropriately in the tracking direction by moving in the tangential direction by the rotation of the lens holder, and by the sliding of the lens holder. By moving in the axial direction, it can be moved appropriately in the focusing direction. As a result, the return light from the optical disc forms a spot on the light receiving surface of the photodetector accurately, and the reproduction signal of the optical disc is detected based on the detection signal from the photodetector.

[0005]

By the way, the density of optical discs has been increased as an auxiliary storage device for computers and a package medium for audio / image information.
In order to achieve this high density, the numerical aperture N of the objective lens is
There is a method of making A larger than the numerical aperture NA of the objective lens in the conventional optical pickup for compact discs, but if the numerical aperture NA is made large, there is a problem that the allowable range for the tilt of the optical disc decreases.

In addition, an optical disk usually has a predetermined disk substrate thickness (generally, in the case of a compact disk or the like,
Since a signal recording surface is provided via a transparent substrate of 1.2 mm), when the optical disc is tilted with respect to the optical axis of the objective lens of the optical pickup, wavefront aberration occurs and a reproduction signal (RF Signal) will be adversely affected. At this time, regarding the wavefront aberration, the cube of the numerical aperture and the skew angle θ
The third-order coma aberration that occurs in proportion to the power of 1 is dominant. Therefore, an optical disc provided with a transparent substrate made of polycarbonate or the like, which is mass-produced at low cost, has a skew angle θ of, for example, plus or minus 0.5 to plus or minus 1 degree, so that the optical pickup is irradiated by the wavefront aberration. The image forming spot on the signal recording surface of the optical disc based on the optical beam becomes asymmetric, and intersymbol interference significantly increases, so that accurate reproduction of the RF signal cannot be performed.

Therefore, paying attention to the fact that the third-order coma aberration is proportional to the disc substrate thickness of the optical disc, the third-order coma aberration is halved by reducing the disc substrate thickness by half to 0.6 mm. It is possible to In this case, as an optical disc, two standards having different characteristics,
That is, the disk substrate thickness is relatively thick (for example, 1.2 mm)
And a disk substrate having a relatively small thickness (for example, 0.6
mm) are mixed.

Here, for example, when a parallel flat plate having a thickness t is inserted in the optical path, the thickness t and the numerical aperture NA are t
Since spherical aberration occurs in proportion to × (NA) 4, the objective lens is designed to cancel this spherical aberration. By the way, if the disk substrate thickness is different, the spherical aberration is also different.
Using an objective lens corresponding to a 6 mm optical disc,
When trying to reproduce an optical disc such as a compact disc having a disc substrate thickness of 1.2 mm, a write-once optical disc, a magneto-optical disc, etc., the above-mentioned fourth-order spherical aberration occurs due to the difference in the disc substrate thickness. The tolerance of the disc substrate thickness error that the pickup can deal with is greatly exceeded. Therefore, there is a problem that a signal cannot be correctly detected from the return light from the optical disk.

Thus, the conventional biaxial actuator has a problem that it is impossible to reproduce a plurality of optical discs of different formats.

In view of the above points, the present invention is advantageous in that any type of optical disc can be reproduced correctly by switching to a corresponding objective lens and can be made particularly small. An object of the present invention is to provide a biaxial actuator and an optical disk device having different structures.

[0011]

According to the present invention, the above-mentioned object is supported so as to be slidable along a supporting shaft and swingable around the supporting shaft, and the optical axis is supported by the supporting shaft. A lens holder that holds the objective lens in parallel, a focusing coil and a tracking coil attached to the lens holder, and the focusing coil and the tracking coil are fixedly arranged so as to face each other. A focusing magnet and a tracking magnet are provided, and the lens holder holds an objective lens corresponding to a plurality of different types of optical discs at different angular positions on the same circumference with respect to the support shaft. The small-diameter objective lens is placed on the inner circumference side of the optical disc, and further swings around the support axis of the lens holder. More was configured to the objective lens is inserted in the optical path, the biaxial actuator is achieved.

According to the above arrangement, the lens holder of the biaxial actuator is swung around the support shaft by the interaction of the tracking coil and the tracking magnet, so that one of the objective lenses can be used. A lens is inserted in the optical path. As a result, the objective lens corresponding to the optical disc on which the signal is to be reproduced is used. Therefore, the light beam from the light source is correctly imaged on the signal recording surface of the optical disc through the objective lens, and the return light from the signal recording surface of the optical disc is
By entering the photodetector, optimum signal reproduction is performed for each of a plurality of different types of optical discs.

Further, among the objective lenses, the objective lens having a small diameter is arranged on the inner peripheral side of the optical disc,
The swing range of the lens holder at the time of switching each objective lens is set closer to the inner circumference side of the optical disc.
That is, even if the swinging range of the lens holder is closer to the rotation driving means such as a spindle motor that drives the optical disk, mutual interference is avoided. Therefore, even if the rotation driving means becomes large, the swinging of the lens holder for switching the objective lens is not hindered, the objective lens can be reliably switched, and the entire size can be reduced. become.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS.
The embodiment described below is a preferred specific example of the present invention, and thus various technically preferable limitations are added. However, the scope of the present invention particularly limits the present invention in the following description. The embodiment is not limited to these embodiments unless otherwise stated.

FIG. 1 shows an embodiment of an optical disk device incorporating a biaxial actuator according to the present invention. In FIG. 1, an optical disk device 10 includes a spindle motor 12 as a driving unit that rotationally drives an optical disk 11, and an optical pickup 13. here,
The spindle motor 12 is driven and controlled by an optical disk drive controller 14 and is rotated at a predetermined rotation speed. Further, the optical pickup 13 irradiates the signal recording surface of the rotating optical disc 11 with light to record a signal, or detects a return light from the signal recording surface in order to detect a return light. A reproduction signal based on the returning light is output to 15.

As a result, the recording signal demodulated by the signal demodulator 15 is error-corrected via the error correction circuit 16 and sent to an external computer or the like via the interface 17. Thus, an external computer or the like can receive a signal recorded on the optical disk 11 as a reproduction signal.

The optical pickup 13 is connected to a head access control section 18 for moving a predetermined recording track on the optical disk 11 by a track jump or the like. Further, at the moved predetermined position, a servo circuit 19 for moving the objective lens in the focusing direction and the tracking direction is connected to a biaxial actuator (described later) that holds the objective lens of the optical pickup 13. There is.

FIG. 2 shows an optical pickup incorporated in the optical disk device 10. In FIG.
The optical pickup 20 includes a semiconductor laser element 21 as a light source, a grating 22 as a light splitting means, a beam splitter 23 as a light splitting means, a raising mirror 24 as an optical path bending means, a collimator lens 25,
It is composed of an objective lens 26 and a photodetector 27, and a biaxial actuator 30 for moving the objective lens 26 in biaxial directions.

The semiconductor laser element 21 is a light emitting element utilizing recombination light emission of a semiconductor, and is used as a light source. The light beam emitted from the semiconductor laser device 21 is
It is guided to the grating 22.

Grating 22 as a light splitting means
Is a diffraction grating that diffracts incident light, and separates the light beam emitted from the semiconductor laser element 21 into at least three light beams of a main beam composed of 0th-order diffracted light and a side beam composed of plus / minus 1st-order diffracted light. Used to

The beam splitter 23 is arranged with its reflection surface inclined by 45 degrees with respect to the optical axis, and separates the light beam from the grating 22 and the return light from the signal recording surface of the optical disk 11. That is, the light beam from the semiconductor laser device 21 is reflected by the reflecting surface 23 a of the beam splitter 23, and the return light is the beam splitter 23.
Through.

As shown in FIGS. 3 and 4, the rising mirror 24 is an optical path bending mirror, which reflects the light beam reflected by the beam splitter 23 upward and returns from the optical disk 11. Reflects light horizontally.

In this case, the raising mirror 24 is selected and arranged so that its tilt direction forms an angle of 45 degrees with the track direction (tangential direction) of the optical disk 11.

As shown in FIGS. 3 and 4, the collimator lens 25 is a convex lens and converts the light beam reflected by the rising mirror 24 into parallel light. In this case, the collimator lens 25 is arranged in the optical path bent by the rising mirror 24, that is, in the optical path perpendicular to the signal recording surface of the optical disc. As a result, the distance between the beam splitter 23 and the rising mirror 24 is selected to be relatively short, and the biaxial actuator 30, the optical pickup 20 and the optical disk device 10 are made compact. Further, since the collimator lens 25 is arranged between the objective lens 26 and the rising mirror 24, the support shaft 32 is formed to be relatively long, and the lens holder 33 is stably held. It will be.

Further, as shown in FIG. 5, the collimator lens 25 has a side edge on the side of the support shaft 32 cut as shown by a chain line 25a, and the support shaft 32 and a focus lens arranged around the support shaft 32 are cut. It does not interfere with the coil 34, the focusing yoke 36, and the focusing magnet 37. Since such a cut 25a has a sufficient length of the collimator lens 25 in the track direction of the optical disc 11, it has almost no influence on tracking servo and the like.

As shown in FIGS. 3 and 4, the objective lens 26 is a convex lens, and images the parallel light from the collimator lens 25 on a desired track on the signal recording surface of the optical disc 11 which is rotationally driven. Let

Here, the objective lens 26 is movably supported in a biaxial direction, that is, a focusing direction and a tracking direction by a biaxial actuator 30 of a shaft sliding type, and is compatible with two different types of optical disks. Two objective lenses 26a, 26b designed to
And the biaxial actuator 30 as described below.
It is supported by a lens holder which is a movable part of so as to be selectively inserted into the optical path.

The photodetector 27 is configured to have a light receiving portion for the return light beam that has passed through the beam splitter 23.

The semiconductor laser device 21, the grating 22, the beam splitter 23, the raising mirror 24, the collimator lens 25 and the photodetector 27 are fixedly arranged on a biaxial base 31 which is a fixed portion of the biaxial actuator 30. ing.

7 and 8 show the structure of the biaxial actuator 30. 7 and 8, the biaxial actuator 30 is skew-adjusted and attached to an optical base 29 that is supported by the optical pickup 20 of FIG. 2 so as to be movable in the radial direction of the optical disk 11 along a guide 28. The shaft base 31, the support shaft 32 extending perpendicularly to the signal recording surface of the optical disk 11 on the biaxial base 31, and the support shaft 32 being movable in the axial direction and rotatable about the shaft. A substantially oval or rectangular lens holder 33 that is supported, and two objective lenses 26a whose optical axes are held parallel to the support axis at a predetermined distance from the rotation axis of the lens holder and at different angular positions.
26b is included.

Here, the objective lens 26a is, for example, a lens having a relatively large numerical aperture NA (for example, NA = 0.6) for a high-density optical disc (second type optical disc), and is an ordinary optical disc ( A first type of optical disc,
For example, the numerical aperture for a CD is relatively small (NA = 0.3
8) The diameter is formed larger than the objective lens 26b. The objective lens 26b having a relatively small diameter is used for the optical disc 1
1 is disposed on the rotation center side (inner peripheral side). As a result, the swing range of the lens holder 33 at the time of switching between the objective lenses 26a and 26b is set closer to the inner circumference side of the optical disc. That is, even if the swing range of the lens holder 33 is closer to the spindle motor 12 that rotationally drives the optical disk 11, mutual interference is avoided. Therefore, the spindle motor 12
Is large, the swing of the lens holder 33 for switching the objective lens is not hindered, and conversely, the swing range of the lens holder 33 is relative to the rotation center of the optical disc 11. The closer it is, the smaller the whole is constructed.

Further, the lens holder 33 is shown in FIG.
As shown in FIG. 1, a concentric cylindrical focusing coil 34 is attached to the lower side of the focusing coil 34, and a pair of tracking coils 35 and 35 are attached to end surfaces on the opposite sides of the rotation axis. There is. On the other hand, on the biaxial base 31 of the biaxial actuator 30, there are provided a pair of focusing yokes 36, 36 arranged so as to face the focusing coil 34 on the opposite sides from the outside. , A pair of focusing magnets 37, 37 attached to the inside thereof, and a tracking yoke 38 disposed so as to face the tracking coils 35, 35 from the outside, respectively.
38, and a pair of tracking magnets 39, 39 mounted inside thereof.

The focusing coil 34 is disposed relatively close to the peripheral surface of the support shaft 32, separately from the tracking coil 35. As a result, the focusing coil 34 is formed by winding a wire made of a conductor into a small diameter in the horizontal direction, so that the entire diameter is small. Correspondingly,
The focus yoke 36 and the magnet 37 are also close to the support shaft 32. As a result, the focusing coil 34 can be made compact as a whole and the effective conductor length can be increased.

The tracking magnet 39 is also used.
Are configured so that the polarities are opposite to each other with respect to the left and right from the center in the axial direction. For example, as shown in FIG. 9, the tracking magnet 39 has a support shaft 3
Regarding No. 2, the S pole 39a and the N pole 39b are arranged clockwise.

Further, on both sides in the circumferential direction of the tracking coil 35, magnetic bodies, such as iron pieces 40 and 41, extending in the axial direction (direction along the magnetization boundary of the tracking magnet 39) are attached. . As a result, one of the iron pieces 40 or 41 is attracted so as to face the boundary 39c between the two poles 39a and 39b of the tracking magnet 39, so that the lens holder 33 is moved to the first objective lens 26a. Is inserted into the optical path at the first midpoint position or the second objective lens 2
6b is moved to a second midpoint position where it is inserted in the optical path. Note that, in FIG. 7, the lens holder 33 is shown to be located between the first midpoint position and the second midpoint position.

Thus, when the objective lens 26a is inserted in the optical path, the iron piece 41 faces the boundary 39c between the two magnetic poles 39a and 39b of the facing tracking magnet 39, as shown in FIG. As a result, the lens holder 33 is at the first midpoint position, and the magnetic flux flows as indicated by the arrow, so that the lens holder 33 is held at the first midpoint position. Here, when a driving current is applied to the tracking coil 35, the lens holder 33 is swung around the support shaft 32 with the first midpoint position as a reference, so that the objective lens 26a moves. The tracking is performed by moving in the tracking direction which is substantially the tangential direction.

When a reverse current is applied to the tracking coil 35, the magnetic field generated in the tracking coil 35 repels the magnetic pole 39a of the tracking magnet 39, as shown in FIG. The tracking coil 35 moves so as to face the magnetic pole 39b. As a result, the iron piece 40 on the opposite side faces the boundary 39c between the magnetic poles 39a and 39b of the tracking magnet 39, the lens holder 33 is moved to the second midpoint position, and the objective lens 26b is in the optical path. Will be inserted into.

FIG. 11 is a block diagram showing a configuration for such midpoint position switching. In FIG. 11, the disc discriminating unit 63 discriminates whether the set optical disc is the above-mentioned first-type optical disc or the above-mentioned second-type optical disc. The photodetector 27 is connected to the disc determination unit 63. The disc discriminating unit 63 is connected to the midpoint switching signal output unit 65 and the tracking error signal arithmetic circuit 62. The midpoint switching signal output unit 65 and the tracking signal calculation circuit 62 are connected to the driving unit 61 of the objective lens. The objective lens drive unit 61 is a driver, and each tracking coil 35,
35.

This tracking error signal calculation circuit 6
2 and the objective lens driving unit 61 are a tracking servo circuit and are a part of the servo circuit 19 of FIG. The disc discriminating unit 63 obtains the ID reading result of the optical disc set at that time from, for example, the photodetector 27, and
It is determined whether the optical disc of the second type or the optical disc of the second type. Alternatively, the disc discriminating unit 63 may use the photodetector 2
The type of the optical disc is discriminated by obtaining a detection result based on the difference in the amount of light reflection due to the difference in the substrate thickness of the set optical discs by using 7 or another photodetector. Further, the photodetector 27 measures the number of tracks for a fixed distance in the radial direction of the optical disc set at that time,
The measurement result is output to the disc discriminating unit 63. Based on this, the disc discriminating unit 63 discriminates the disc. The disc discriminating unit 63 outputs the discrimination result to the midpoint switching signal output unit 65.

Further, without automatically discriminating the type of the optical disc set at that time, the user selects an operator as the selection unit 63, and the information regarding the type of the optical disc set by the user at that time is displayed as the middle point. It is also possible to output to the switching signal output unit 65. The midpoint switching signal output unit 65 is provided for the objective lens 2 depending on the type of optical disc.
In order to switch between 6a and 26b, the objective lens drive unit 61
Output the signal. The objective lens drive unit 61 applies a predetermined current or voltage to each of the tracking coils 35, 35.
Is applied to switch the objective lens.

In this case, the tracking coils 35, 3 correspond to the respective midpoint positions to which the objective lens should be moved.
The current or voltage value supplied to 5 is fixed. These current and voltage values are used when tracking servo is performed.
Based on the output from the tracking error signal calculation circuit 62, the objective lens driving unit 61 causes the tracking coils 3
It is larger than the current or voltage value given to 5, 35. As a result, each of the tracking coils 35, 35 is moved by a distance larger than the tracking stroke to switch the middle position. The discrimination result of the disc discriminating unit 63 is also given to the tracking error signal arithmetic circuit 62. As a result, the tracking error signal calculation circuit 62 calculates the tracking error signal according to the type of the optical disc, that is, one of the tracking error signal by the three-spot method and the tracking error signal by the phase comparison method, and calculates the objective lens. It is designed to be given to the drive unit 61.

The optical disk device 10 incorporating the biaxial actuator according to this embodiment is configured as described above and operates as follows. First, for example, when reproducing a high density optical disc (second type optical disc), the lens holder 33 is at the first midpoint position as shown in FIG. 2, and the objective lens 26a is in the optical path. The iron piece 41, which is inserted into the lens holder 33 and is attached to the lens holder 33, faces the boundary 39c of the tracking magnet 39. Here, the spindle motor 12 of the optical disc device 10 is rotated, so that the optical disc 11 is rotationally driven. And the optical pickup 2
0 is moved in the radial direction of the optical disk 11 along the guide 28, so that the optical axis of the objective lens 26a is
Access is performed by moving the optical disk 11 to a desired track position.

In this state, in the optical pickup 20, the light beam from the semiconductor laser element 21 is split into three light beams by the grating 22 and then reflected by the reflecting surface 23a of the beam splitter 23 to stand up. It is reflected toward the optical disk 11 by the raising mirror 24. Furthermore, the light beam is converted into parallel light by the collimator lens 25, and passes through the objective lens 26a to the optical disk 11.
An image is formed on the signal recording surface of. At this time, the objective lens 26a
Thus, the numerical aperture is appropriately set to, for example, NA = 0.6 corresponding to the high density optical disc, and the light beam is correctly imaged on the signal recording surface of the optical disc 11. The return light from the optical disk 11 is again the objective lens 26a, the collimator lens 25, and the raising mirror 24.
Through the beam splitter 23, and the photodetector 2
Image at 7. As a result, the recording signal of the optical disc 11 is reproduced based on the detection signal of the photodetector 27.

At this time, the tracking error signal and the focusing error signal are detected by the signal demodulator 15 from the detection signal from the photodetector 27, and the servo circuit 19 via the optical disk drive controller 14
Focusing coil 34 and tracking coil 35
Servo control the drive current to. Accordingly, by controlling the drive current of the focusing coil 35, the magnetic field generated in the focusing coil 35 acts on the magnetic fields of the focusing magnet 37 and the focusing coil 36, so that the lens holder 33 is attached to the support shaft 32. Along with that, the movement is adjusted in the focusing direction to perform focusing. Further, the magnetic field generated in the tracking coil 35 acts on the magnetic field generated by the tracking magnet 39 and the tracking yoke 38, so that the lens holder 33 moves around the support shaft 32 with reference to the first midpoint position. The swing is adjusted, and the objective lens 26
Tracking is performed by moving and adjusting a in the tracking direction, which is substantially a tangential direction.

Next, for example, when reproducing an ordinary optical disk (first type optical disk, for example, CD), a reverse current is applied to the tracking coil 35, and as described above, the lens holder 33. So that the other iron piece 40 attached to the lens holder 33 faces the boundary 39c of the tracking coil 39,
It is rotated around the support shaft 32 and moved to the second midpoint position. As a result, the objective lens 26b is inserted in the optical path. As described above, the optical disc to be reproduced is determined by reading the ID of the optical disc, detecting the amount of reflected light due to the difference in substrate thickness, or measuring the number of tracks at a constant radial distance. Due to
Although the objective lens is switched, the objective lens may be switched by a manual switch operation. Here, similarly, the spindle motor 12 of the optical disk device 10 rotates, and the optical disk 11 is rotationally driven. Then, the optical pickup 20 is guided by the guide 28.
The optical axis of the objective lens 26b is moved to a desired track position of the optical disk 11 by being moved in the radial direction of the optical disk 11 along the path, and thus access is performed.

In this state, the optical beam from the semiconductor laser element 21 is split by the grating 22 into three optical beams by the optical pickup 20, and then reflected by the reflecting surface 23a of the beam splitter 23 to stand up. It is reflected toward the optical disk 11 by the raising mirror 24. Further, the light beam is converted into parallel light by the collimator lens 25, and passes through the objective lens 26b to the optical disk 11.
An image is formed on the signal recording surface of. At this time, the objective lens 26b
Thus, the numerical aperture is appropriately set to, for example, NA = 0.38 corresponding to a normal optical disk, and the light beam is correctly imaged on the signal recording surface of the optical disk 11. The return light from the optical disk 11 is again the objective lens 26b, the collimator lens 25, and the raising mirror 24.
Through the beam splitter 23, and the photodetector 2
Image at 7. As a result, the recording signal of the optical disc 11 is reproduced based on the detection signal of the photodetector 27.

At this time, the tracking error signal and the focusing error signal are detected by the signal demodulator 15 from the detection signal from the photodetector 27, and the servo circuit 19 is transmitted via the optical disk drive controller 14 to the servo circuit 19.
Focusing coil 34 and tracking coil 35
Servo control the drive current to. Accordingly, by controlling the drive current of the focusing coil 35, the magnetic field generated in the focusing coil 35 acts on the magnetic fields of the focusing magnet 37 and the focusing coil 36, so that the lens holder 33 is attached to the support shaft 32. Along with that, the movement is adjusted in the focusing direction to perform focusing. Further, the magnetic field generated in the tracking coil 35 acts on the magnetic field generated by the tracking magnet 39 and the tracking yoke 38, so that the lens holder 33 moves around the support shaft 32 with reference to the second midpoint position. The swing is adjusted, and the objective lens 26
Tracking is performed by moving and adjusting a in the tracking direction, which is substantially a tangential direction.

As described above, in the above embodiment, the lens holder of the biaxial actuator is swung around the support shaft, so that one of the plurality of objective lenses is inserted into the optical path. Then, an objective lens corresponding to the optical disc on which the signal is to be reproduced is used. As a result, the light beam from the light source is correctly imaged on the signal recording surface of the optical disc through the objective lens,
When the return light from the signal recording surface of the optical disc enters the photodetector, optimum signal reproduction is performed for a plurality of different types of optical discs.

Here, in the insertion operation of each objective lens into the optical path, the lens holder swings around the support shaft due to the interaction between the tracking coil provided in the lens holder and the tracking magnet fixedly arranged. It is done by being done. Further, among the objective lenses, the small-diameter objective lens is arranged on the inner circumference side of the optical disc, so that the swinging range of the lens holder when switching between the objective lenses is closer to the inner circumference side of the optical disc. Is set. That is, even if the swinging range of the lens holder is closer to the rotation driving means of the optical disc, mutual interference is avoided. Therefore, even if the rotation driving means becomes large, the swinging of the lens holder for switching the objective lens is not hindered, the objective lens can be reliably switched, and the entire size can be reduced. become.

The optical disk device 1 according to the above embodiment.
In the 0 and biaxial actuators 30, the magnetic pole 39a of the tracking magnet 39 is set to the S pole and the magnetic pole 39b is set to the N pole, but the polarities may be reversed. In this case, if the direction of the current flowing through the tracking coil 35 is reversed, the lens holder 33 similarly performs tracking at the first midpoint position and the second midpoint position. Further, in the optical disk device 10 and the biaxial actuator 30 according to the above-described embodiment, the lens holder 33 has two objective lenses 26a and 26b.
However, the present invention is not limited to this, and three or more objective lenses are held, and each objective lens is selectively inserted into the optical path by the interaction between the tracking coil 35 and the tracking magnet 39. Obviously, you may choose to do so.

[0051]

As described above, according to the present invention, any type of optical disc can be switched to a corresponding objective lens, and the biaxial type having a structure particularly suitable for downsizing can be used. It is possible to provide an actuator and an optical disk device using the actuator.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of an optical disk device incorporating a biaxial actuator according to the present invention.

FIG. 2 is a plan view showing a configuration of an optical pickup in the optical disc device of FIG.

FIG. 3 is a vertical cross-sectional view taken along the optical path from the semiconductor laser element to the raising mirror, the collimator lens, and the objective lens in the optical pickup of FIG.

4 is a sectional view of a biaxial actuator in the optical pickup of FIG.

5 is a plan view showing an optical system in the optical pickup of FIG.

6 is a side view showing an optical system in the optical pickup of FIG.

7 is a perspective view of a biaxial actuator in the optical pickup of FIG.

FIG. 8 is an exploded perspective view of the biaxial actuator of FIG.

9 is a schematic plan view showing a magnetic circuit at a first midpoint position of a lens holder in the biaxial actuator of FIG.

10 is a schematic plan view showing a state when the lens holder in the biaxial actuator of FIG. 7 is moved from a first midpoint position to a second midpoint position.

11 is a block diagram showing an electrical configuration for switching the midpoint position of the lens holder in the biaxial actuator of FIG.

[Brief description of reference numerals]

 10 Optical Disc Device 11 Optical Disc 12 Spindle Motor 13 Optical Pickup 14 Optical Disc Drive Controller 15 Signal Demodulator 16 Error Correction Circuit 17 Interface 18 Head Access Control Section 20 Optical Pickup 21 Semiconductor Laser Element 22 Grating 23 Beam Splitter 24 Standing Mirror 25 Collimator Lens 26 , 26a, 26b Objective lens 27 Photodetector 28 Guide 29 Optical base 30 Biaxial actuator 31 Biaxial base 32 Support shaft 33 Lens holder 34 Focus coil 35 Tracking coil 36 Focus yoke 37 Focus magnet 38 Tracking yoke 39 Tracking magnets 39a, 39b Magnetic poles 40, 41 Iron pieces

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yutaka Sugawara 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (2)

[Claims] 1. A lens holder, which is slidably supported along a support shaft and swingably around the support shaft, and holds an objective lens so that an optical axis thereof is parallel to the support shaft. The lens holder includes a focusing coil and a tracking coil attached to the lens holder, and a focusing magnet and a tracking magnet fixedly arranged so as to face the focusing coil and the tracking coil, respectively. However, it holds a plurality of objective lenses for different types of optical discs at different angular positions on the same circumference with respect to the support shaft, and the objective lens with the smaller diameter is placed on the inner circumference side of the optical disc. And further, by swinging around the support axis of the lens holder,
A biaxial actuator characterized in that each objective lens is inserted in the optical path. 2. A drive unit for rotating and driving the optical disc, and a rotating optical disc is irradiated with light through an objective lens, and return light from a signal recording surface of the optical disc is detected by a photodetector through the objective lens. Optical pickup, a biaxial actuator that movably supports the objective lens in two axial directions, a signal processing circuit that generates a reproduction signal based on the detection signal from the photodetector, and a detection signal from the photodetector. And a servo circuit for moving the objective lens of the optical pickup in two axial directions, the biaxial actuator being supported slidably along the supporting shaft and swingable around the supporting shaft. The lens holder that holds the objective lens so that the optical axis is parallel to the support axis, and the focusing coil and the transformer attached to the lens holder. A king coil and a focus magnet and a tracking magnet, which are fixedly arranged so as to face the focus coil and the tracking coil, respectively, are provided, and the lens holder is on the same circumference with respect to the support shaft. It holds a plurality of objective lenses corresponding to different types of optical discs at different angular positions, and the objective lens with the smaller diameter is placed on the inner circumference side of the optical disc. By swinging around
An optical disk device characterized in that each objective lens is inserted in the optical path.