JP2010135007A - Optical disk apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk which is advantageous to miniaturize. <P>SOLUTION: A main guide shaft 58A guides a moving base 56 in the radial direction of the optical disk 2 in a movable fashion. A supporter 62 for the guide shaft supports the main guide shaft 58A to be revolvable but not movable in the axial direction. A drive 64 for rotating the guide shaft is set in a housing 54 to rotate the main guide shaft 58A. A cam 66 is made revolvable integrally with the main guide shaft 58A, combined movably in the axial direction of the main guide shaft 58A, and further combined movably in the axial direction integrally with the moving base 56. A moving mechanism 70 includes a cam follower 68 for engaging with the cam 66, transfers the motion of the cam follower 68 due to the rotation of the cam 66 to a spherical aberration correction lens 46, and moves the spherical aberration correction lens 46 along a light path L. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that records and reproduces signals on an optical disc.

In recent years, CD (Compact Disc), DVD (Digital Versatile Disc), and BD (Blu-ray Disc) have been put to practical use as recording media for optical disks. Furthermore, the practical use of multilayer optical discs having two or more recording layers is progressing.
In optical pickups that record and / or reproduce information signals on these optical discs, spherical aberration is used to produce the best spot by focusing the light beam on various optical discs and multiple signal recording layers. The amount needs to be adjusted.
As a configuration for adjusting the spherical aberration, it is possible to realize the best spot generation by moving the spherical aberration correction lens by a motor or the like.
For example, as a means for moving the spherical aberration correction lens, a technique has been proposed in which a drive system including a stepping motor and a lead screw is disposed in the optical pickup, and the spherical aberration correction lens is moved using this drive system.
However, the conventional technology has a drawback that the optical pickup is increased in size because the drive system is disposed in the optical pickup.
Thus, a technique has been proposed in which a nut is engaged with a feed screw that drives a moving base on which an optical pickup is mounted, and the spherical aberration correction lens is moved in conjunction with the movement of the nut (see Patent Document 1).
JP 2006-147054 A

However, in the above prior art, a complicated brake mechanism that selectively regulates whether to move the moving base in conjunction with the rotation of the feed screw or to move the spherical aberration correction lens in conjunction with the rotation of the feed screw. Must be provided in the pickup. In addition, it is necessary to provide a drive source such as a motor for driving the brake mechanism in the optical pickup.
For this reason, it is not sufficient to reduce the size of the optical pickup and to reduce the movement space of the optical pickup. Therefore, there is a disadvantage in reducing the size of the optical disk apparatus.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical disc apparatus that is advantageous in reducing the size.

  In order to achieve the above object, an optical disc apparatus according to the present invention includes a housing, an optical disc rotation drive unit that rotationally drives the optical disc, and an optical disk that is rotated by the optical disc rotation drive unit by irradiating the optical beam with the light beam. An optical pickup that records and / or reproduces an information signal with respect to the optical disc, a moving base on which the optical pickup is mounted, and a guide shaft that is supported by the housing and guides the moving base in a radial direction of the optical disc. A moving base drive unit that moves the moving base in the radial direction of the optical disc, a spherical aberration correction lens provided on the optical path of the light beam in the moving base, and the spherical aberration correction lens along the optical path. A spherical aberration correction lens driving unit for moving the spherical aberration compensation lens. The lens drive section includes the guide shaft, a guide shaft support section that is provided on the housing and supports the guide shaft so as to be rotatable and immovable in the axial direction, and a guide shaft rotation driving section that rotates the guide shaft. A cam that is integrally rotatable with the guide shaft and that is movable in the axial direction of the guide shaft, and that is coupled to be movable integrally with the moving base in the axial direction; A moving mechanism that includes a cam follower that engages with a cam and that transmits the movement of the cam follower caused by the rotation of the cam to the spherical aberration correction lens and moves the spherical aberration correction lens along the optical path.

According to the present invention, the spherical aberration correction lens is moved along the optical path via the cam follower by rotating the cam coupled to the moving base and the guide shaft together with the guide shaft.
Therefore, it is not necessary to provide a drive source such as a motor or a complicated brake mechanism in the optical pickup, which is advantageous in reducing the size of the optical disc apparatus.

(Optical disk device 10)
Next, an embodiment of the present invention will be described.
FIG. 1 is a block diagram showing a configuration of an optical disc apparatus 10 according to the present embodiment.
First, the control system of the optical disc apparatus 10 will be briefly described.
As shown in FIG. 1, the optical disc apparatus 10 includes a spindle motor 12, an optical pickup 14, a feed motor 16, a guide shaft rotating motor 6402, and the like.
The optical disc apparatus 10 includes a system controller 18, a servo control unit 20, a signal modulation / demodulation & ECC 22, a signal processing unit 24, an interface 26, a D / A, an A / D converter 30, an audio / visual processing unit 32, and an audio / visual signal. An input / output unit 34, a laser control unit 36, and the like are further provided.
The spindle motor 12 constitutes an optical disk rotation drive unit that rotationally drives the optical disk 2.
Here, the spindle motor 12 is configured to be driven and controlled at a predetermined rotational speed by the system controller 18 and the servo control unit 20.
The optical pickup 14 is mounted on a moving base 56 (FIG. 3) described later.
The feed motor 16 constitutes a moving base drive unit 59 (FIG. 3) that moves the moving base 56 in the radial direction of the optical disc 2.
The guide shaft rotating motor 6402 constitutes a guide shaft rotating drive unit 64 (FIG. 3) that rotates the main guide shaft (FIG. 3).

The optical pickup 14 irradiates the signal recording surface of the optical disc 2 rotating according to instructions from the system controller 18 and the servo control unit 20 with a light beam. Recording and / or reproduction of an information signal (optical signal) with respect to the optical disc 2 is performed by such light irradiation.
The optical pickup 14 is configured to detect various light beams based on the reflected light beam from the signal recording surface of the optical disc 2 and to supply a signal corresponding to each light beam to the signal processing unit 24. Yes.
The signal modulation / demodulation unit and ECC block 22 modulate and demodulate the signal output from the signal processing unit 24 and add an ECC (error correction code).

The signal processing unit 24 is a servo control signal based on a detection signal corresponding to each light beam, that is, a focus error signal, a tracking error signal, an RF signal, a monitor signal (R-OPC signal) necessary for running OPC processing, The ATIP signal and the like necessary for controlling the rotation of the optical disc during recording can be generated.
Various conventionally known methods can be adopted as a method for generating a focus error signal, a tracking error signal, and an RF signal by the optical pickup 14.
Further, predetermined processing such as demodulation and error correction processing based on these signals is performed by the servo control unit 20, the signal modulation unit, the ECC block 22, and the like according to the type of recording medium to be reproduced.
Here, if the recording signal demodulated by the signal modulation unit and the ECC block 22 is, for example, for data storage of a computer, it is sent to an external computer 28 or the like via the interface 26. Accordingly, the external computer 28 and the like are configured to receive a signal recorded on the optical disc 2 as a reproduction signal.

If the recording signal demodulated by the signal modulation unit and the ECC block 22 is for audio / visual use, the digital / analog conversion is performed by the D / A conversion unit of the D / A and A / D converter 30, and the audio / visual conversion is performed. It is supplied to the processing unit 32. The audio / video processing unit 32 performs audio / video signal processing and transmits the audio / video signal to an external imaging / projection device via the audio / visual signal input / output unit 34.
The optical pickup 14 is configured to be moved to a predetermined recording track on the optical disc 2 by the rotation of the feed motor 16 together with the moving base 56.
The servo control unit 20 controls the spindle motor 12, the feed motor 16, and the guide shaft rotating motor 6402.
The servo control unit 20 controls the focusing direction and the tracking direction of the objective lens 50 (FIG. 2) of the optical pickup 14 based on the focus error signal and the tracking error signal, and further controls the radial skew.
The laser controller 36 controls the light emitting element 40 (FIG. 2) of the optical pickup 14.

(Optical pickup 14)
Next, the optical pickup 14 will be described.
FIG. 2 is an explanatory diagram showing the configuration of the optical pickup 14.
As shown in FIG. 2, the optical pickup 14 includes a light emitting element 40, a beam splitter 42, a collimator lens 44, a spherical aberration correction lens 46, a rising mirror 48, an objective lens 50, a light receiving element 52, and the like. .
The optical pickup 14 is mounted on the moving base 56 (FIG. 3). Accordingly, the light emitting element 40, the beam splitter 42, the collimator lens 44, the spherical aberration correction lens 46, the rising mirror 48, the objective lens 50, and the light receiving element 52 are moved. It is attached to the base 56.

The light emitting element 40 is a semiconductor laser, and a light beam (laser light) is emitted from the light emitting element 40.
The beam splitter 42 reflects the light beam emitted from the light emitting element 40 by the separation surface 4202 and guides it to the collimator lens 44, and transmits the reflected light beam of the laser light reflected by the optical disc 2 through the separation surface 4202 to receive the light. Lead to 52.
The collimator lens 44 converts the incident light beam into a parallel light beam.
The light beam incident on the collimator lens 44 via the beam splitter 42 becomes a parallel light flux and enters the objective lens 50 via the rising mirror 48.

The spherical aberration correction lens 46 is a lens for correcting spherical aberration that occurs when the cover layer of the optical disc 2 has a thickness error or the like.
The spherical aberration correction lens 46 is provided on the optical path L of the light beam in the moving base 56 (FIG. 3), and the spherical aberration is corrected by moving along the optical path L.

The raising mirror 48 reflects the light beam emitted from the light emitting element 40 and guides it to the objective lens 50, and guides the reflected light beam reflected by the optical disc 2 to the collimator lens 44.
The objective lens 50 focuses the incident light beam on the recording surface of the optical disc 2 and guides the reflected light beam reflected by the optical disc 2 to the rising mirror 48.

Therefore, the light beam emitted from the light emitting element 40 is reflected by the separation surface 4202 to be converted into a parallel light beam by the collimator lens 44, passed through the spherical aberration correction lens 46, raised by the rising mirror 48, and optical disc by the objective lens 50. 2 is irradiated on the recording surface.
Further, the light beam irradiated on the recording surface of the optical disc 2 is reflected on the recording surface of the optical disc 2 to become a reflected light beam. The reflected light beam is transmitted through the separation surface 4202 through the objective lens 50, the rising mirror 48, the spherical aberration correction lens 46, and the collimator lens 44, and is incident on the light receiving element 52.
In this manner, the information signal is recorded on the optical disc 2 by irradiating the recording surface of the optical disc 2 with the light beam.
Further, when a reflected light beam is incident on the light receiving element 52, each signal such as an RF signal is detected, and an information signal for the optical disc 2 is reproduced.

Next, the main part of the present invention will be described in detail.
FIG. 3 is a bottom view of the optical disk apparatus 10, and FIG.
FIG. 5A is a plan view of the main guide shaft 58A and the guide shaft rotating drive unit 64, FIG. 5B is a view taken in the direction of arrow B in FIG. ) Is a view on arrow D of (A).
6 to 9 are explanatory views of the operation of the cam 66 and the cam follower 68, FIG. 10 is an explanatory view showing a state in which the moving base 56 is positioned on the outer peripheral side of the optical disc 2, and FIG. It is explanatory drawing which shows the state located in.
FIG. 12 is an explanatory diagram of the operation of the cam 66, the cam follower 68, and the spherical aberration correction lens 46.

As shown in FIG. 3, the optical disc apparatus 10 includes a housing 54, a moving base 56, a main guide shaft 58A, a sub guide shaft 58B, a moving base drive unit 59, and a drive for a spherical aberration correction lens of the present invention. A part 60 is further provided.
As shown in FIG. 3, the spherical aberration correction lens driving section 60 includes a main guide shaft 58A, a guide shaft support section 62, a guide shaft rotation driving section 64, a cam 66, and a moving mechanism 70. It consists of
The housing 54 has a plate shape extending along the lower surface of a housing (not shown) of the optical disc apparatus 10, and FIG. 3 shows a state in which the housing 54 is seen through from below the housing.
3, 10, and 11, reference numeral 2 </ b> A denotes a center hole (disc center) of the optical disc 2 attached to a turntable (not shown) of the spindle motor 12.

As shown in FIG. 3, the moving base 56 is disposed on the housing 54.
The main guide shaft 58A and the sub guide shaft 58B are provided in parallel with the radial direction of the optical disc 2 at a distance from each other.
The main guide shaft 58A is supported by the housing 54 and guides the moving base 56 so as to be movable in the radial direction of the optical disc 2, and corresponds to the guide shaft of the present invention.
The guide shaft support portion 62 is provided in the housing 54 and supports the main guide shaft 58A so as to be rotatable and immovable in the axial direction.
In the present embodiment, as shown in FIGS. 5A to 5D, the guide shaft support portion 62 is constituted by two sleeves 6202 that support locations near both ends of the main guide shaft 58A. Each sleeve 6202 is attached to the housing 54 via a mounting member (not shown).
The moving base 56 is provided with two bearing portions 61 spaced apart from each other, and the main guide shaft 58A is inserted into each bearing portion 61 so that the moving base 56 can be moved in the radial direction of the optical disc 2. Is done.
As shown in FIG. 4, a part of the outer peripheral surface of the main guide shaft 58A is cut off by a plane parallel to the central axis of the main guide shaft 58A. Therefore, the main guide shaft 58A is D-cut.

The sub guide shaft 58B is supported by the housing 54 and prevents the movement base 56 from rotating.
More specifically, the moving base 56 is provided with one engaging portion 64, and the engaging base 64 is engaged with the sub guide shaft 58B, so that the moving base 56 moves without shaking in the radial direction of the optical disc 2. Guided as possible.

The moving base drive unit 59 moves the moving base 56 in the radial direction of the optical disc 2.
In the present embodiment, as shown in FIG. 3, the moving base drive unit 59 includes the feed motor 16, a feed screw 5902 that is rotationally driven by the feed motor 16, and a feed screw 5902 provided on the movement base 56. And an internal thread portion 5904 that is screwed together.
Accordingly, when the feed motor 16 rotates forward and backward and the feed screw 5902 rotates, the moving base 56 moves in the radial direction of the optical disc 2 via the female screw portion 5904.

As shown in FIGS. 3 and 5A to 5D, the guide shaft rotating drive unit 64 is provided in the housing 54 and rotates the main guide shaft 58A.
In the present embodiment, guide shaft rotation drive unit 64 is provided on guide shaft rotation motor 6402, first gear 6404 provided on the drive shaft of guide shaft rotation motor 6402, and main guide shaft 58A. The second gear 6406 meshes with the first gear 6404.
Therefore, when the guide shaft rotating motor 6402 rotates forward and backward, the main guide shaft 58A rotates forward and backward via the first gear 6404 and the second gear 6406.
In FIG. 5, reference numeral 6410 denotes an attachment member for attaching the guide shaft rotating motor 6402 to the housing 54.

As shown in FIGS. 10 and 11, the cam 66 is coupled to the main guide shaft 58A so as to be rotatable integrally with the main guide shaft 58A and movable in the axial direction of the main guide shaft 58A. It is movably coupled together.
More specifically, as shown in FIG. 4, the cam 66 has a cam surface 6602 and an insertion hole 6604.
In the cam 66, the main guide shaft 58A is inserted into the insertion hole 6604, whereby the cam 66 is coupled to the main guide shaft 58A so as to be rotatable integrally with the main guide shaft 58A and movable in the axial direction of the main guide shaft 58A.
Also, as shown in FIG. 10, the moving base 56 is provided with two pairs of engagement plates 5620 that can be engaged with both end surfaces of the cam 66, so that the cam 66 extends in the axial direction of the main guide shaft 58A. The moving base 56 is coupled to the moving base 56 so as to move integrally therewith.

As shown in FIG. 3, the moving mechanism 70 includes a cam follower 68 that engages with the cam 66, and transmits the movement of the cam follower 68 due to the rotation of the cam 66 to the spherical aberration correction lens 46, thereby passing the spherical aberration correction lens 46 along the optical path L. To move.
In the present embodiment, the moving mechanism 70 includes a swing lever 72, a lens holder 74, a main guide shaft 76, a sub guide shaft 78, a biasing member 80, and the like in addition to the cam follower 68. ing.

The cam follower 68 is provided on the moving base 56 and engages with the cam surface 6602 of the cam 66.
As shown in FIGS. 4 and 10, the cam follower 68 has a slide plate portion 6802, a guide groove 6804, a cam engagement plate portion 6806, and a lever engagement plate portion 6808.
The slide plate portion 6802 has a substantially rectangular plate shape.
The guide groove 6804 is formed to extend linearly in the longitudinal direction at the center in the width direction of the slide plate portion 6802.
The cam engagement plate portion 6806 is bent from one short side of the slide plate portion 6802 so as to be engageable with the cam surface 6602 of the cam 66.
The lever engaging plate portion 6808 is bent from the other short side of the slide plate portion 6802 and is provided so as to be engageable with a swing lever 72 (FIG. 10) described later.
As shown in FIG. 4, the slide plate portion 6802 is abutted against a guide surface 5610 provided on the moving base 56, and two guide pins 5612 projecting from the guide surface 5610 are inserted into the guide groove 6804. Yes.
Therefore, the cam follower 68 is supported so as to be linearly movable along the guide groove 6804.

As shown in FIGS. 10 and 11, the base end of the swing lever 72 is connected to the moving base 56 via a support shaft 7202 so as to be swingable.
At an intermediate portion in the extending direction of the swing lever 72, an engaging convex portion 7204 that engages with the lever engaging plate portion 6808 is provided so as to project in a direction orthogonal to the extending direction of the swing lever 72.
Therefore, the swing lever 72 swings about the support shaft 7202 due to the movement of the cam follower 68 due to the rotation of the cam 66.
An engaging groove 7206 that engages with the engaging pin 7410 of the lens holder 74 is formed at the tip of the swing lever 72.

As shown in FIGS. 10 and 11, the lens holder 74 holds the spherical aberration correction lens 46 and has two bearing portions 7402 and 7404.
One bearing portion 7402 has an engagement pin 7410 protruding therefrom.

As shown in FIGS. 10 and 11, the main guide shaft 76 and the sub guide shaft 78 extend in parallel with the optical path L at a distance from each other, and both ends thereof are attached to the moving base 56. Yes.
The main guide shaft 76 and the sub guide shaft 78 are inserted into the bearing portions 7402 and 7404 of the lens holder 74, whereby the lens holder 74 moves along the optical path L (along the optical axis of the spherical aberration correction lens 46). Supported as possible.
Therefore, the lens holder 74 is moved along the optical path L by the swing of the swing lever 72.

As shown in FIGS. 10 and 11, the urging member 80 urges the lens holder 74 in one of the optical path L directions (in the direction close to the objective lens 50 in the present embodiment).
In the present embodiment, the urging member 80 is configured by a compression coil spring wound around the outer periphery of the sub guide shaft 78.
The urging force of the urging member 80 is transmitted to the cam follower 68 via the lens holder 74 and the swing lever 72, so that the cam engagement plate portion 6806 is always applied to the cam surface 6602 as shown in FIG. Energized to the state.
Accordingly, as shown in FIGS. 6 to 9, when the cam 66 rotates, the cam follower 68 moves following the cam surface 6602, and the movement of the cam follower 68 is transmitted to the lens holder 74 via the swing lever 72, As a result, the spherical aberration correction lens 46 is moved along the optical path L.

Next, the operation will be described.
As shown in FIGS. 10 and 11, the moving base 56 is moved along the radial direction of the optical disk 2 by the moving base drive unit 59.
As shown by a solid line and a two-dot chain line in FIG. 12, the cam 66 moves integrally with the moving base 56.
As shown in FIGS. 6 to 9, when the main guide shaft 58A is rotated by the guide shaft rotating drive section 64, the cam 66 is rotated.
The cam follower 68 moves following the rotation of the cam 66, the swinging lever 72 swings following the movement of the cam follower 68, and the lens holder 74 is moved following the swinging of the swinging lever 72. The spherical aberration correction lens 46 is moved along the optical path L.
Therefore, the amount of movement of the spherical aberration correction lens 46 along the optical path L is controlled and the spherical aberration is corrected by controlling the rotation amount of the guide shaft rotating motor 6402 by the servo control unit 20.

As described above, according to the present embodiment, the spherical aberration correction lens 46 is moved via the cam follower 68 by rotating the cam 66 coupled to the moving base 56 and the main guide shaft 58A together with the main guide shaft 58A. It was made to move along the optical path L.
Therefore, unlike the prior art, there is no need to provide a drive source such as a motor for moving the spherical aberration correction lens 46 in the optical pickup 14 (movement base 56).
Further, as in the prior art, selectively restricts whether to move the moving base in conjunction with the rotation of the feed screw that moves the optical pickup or to move the spherical aberration correction lens in conjunction with the rotation of the feed screw. No complicated brake mechanism is required.
Therefore, it is not necessary to provide a driving source such as a motor or a brake mechanism in the moving base 56, that is, the optical pickup 14, and the optical pickup 14 can be simplified.
Therefore, it is extremely advantageous in reducing the size of the optical pickup 14 and reducing the moving space of the optical pickup 14, and is advantageous in reducing the size of the optical disc apparatus 10.
Further, since it is not necessary to provide a driving source such as a motor or a brake mechanism in the optical pickup 14, it is advantageous for increasing the degree of freedom in designing the optical pickup 14.

1 is a block diagram showing a configuration of an optical disc device 10 according to the present embodiment. 2 is an explanatory diagram showing a configuration of an optical pickup 14. FIG. 2 is a bottom view of the optical disc apparatus 10. FIG. 4 is a view taken in the direction of arrow A in FIG. (A) is a plan view of the main guide shaft 58A and the guide shaft rotation drive unit 64, (B) is a view from the arrow B in (A), (C) is a view from the arrow C in (A), (D) is from It is D arrow line view of (A). FIG. 6 is an operation explanatory diagram of a cam 66 and a cam follower 68. FIG. 6 is an operation explanatory diagram of a cam 66 and a cam follower 68. FIG. 6 is an operation explanatory diagram of a cam 66 and a cam follower 68. FIG. 6 is an operation explanatory diagram of a cam 66 and a cam follower 68. 4 is an explanatory diagram showing a state in which a moving base 56 is positioned on the outer peripheral side of the optical disc 2. FIG. 4 is an explanatory diagram showing a state in which a moving base 56 is positioned on the inner peripheral side of the optical disc 2. FIG. FIG. 6 is an operation explanatory diagram of a cam 66, a cam follower 68, and a spherical aberration correction lens 46.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Optical disk apparatus, 12 ... Spindle motor, 14 ... Optical pick-up, 46 ... Spherical aberration correction lens, 54 ... Housing, 56 ... Moving base, 58A ... Main guide shaft, 59 ... For moving base Drive unit 60... Spherical aberration correction lens drive unit 62. Guide shaft support unit 64. Guide shaft rotation drive unit 66. Cam cam 68. Cam follower 70.

Claims (4)

A housing;
An optical disk rotating drive unit for rotating the optical disk;
An optical pickup that records and / or reproduces an information signal with respect to the optical disc by irradiating the optical disc rotated by the optical disc rotation drive unit with a light beam;
A moving base on which the optical pickup is mounted;
A guide shaft that is supported by the housing and guides the moving base so as to be movable in a radial direction of the optical disc;
A moving base drive unit for moving the moving base in the radial direction of the optical disc;
A spherical aberration correction lens provided on the optical path of the light beam in the moving base;
A spherical aberration correction lens drive unit that moves the spherical aberration correction lens along the optical path;
The spherical aberration correction lens drive unit is:
The guide shaft;
A guide shaft support that is provided in the housing and supports the guide shaft rotatably and immovably in the axial direction;
A guide shaft rotation drive unit for rotating the guide shaft;
A cam rotatably coupled to the guide shaft and movably coupled in the axial direction of the guide shaft; and further coupled to the movable base in a movable manner in the axial direction;
A moving mechanism that includes a cam follower that engages with the cam and transmits the movement of the cam follower due to rotation of the cam to the spherical aberration correction lens, and moves the spherical aberration correction lens along the optical path;
An optical disc device comprising: The spherical aberration correction lens is supported by a lens holder,
The moving mechanism includes a rocking lever that engages with the cam follower and is rocked by the movement of the cam follower connected to the lens holder to move the lens holder along the optical path. Being
The optical disk device according to claim 1. The moving mechanism includes an urging member that urges the cam follower in a direction to engage the cam.
The biasing member is provided between the lens holder and the moving base.
The optical disk apparatus according to claim 2. The moving base is provided with a pair of engaging plates that can engage with both end faces of the cam,
The coupling between the cam and the moving base is performed by engaging the pair of engagement plates with both end faces of the cam.
The optical disk device according to claim 1.

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