JP2005078735A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disc apparatus capable of accurately correcting a spherical aberration of a beam spot generated when passing through a protective layer of an optical disc in a small and thin shape.
A collimator lens 17 that corrects spherical aberration of a beam spot, a lens holding member 33 that holds the collimator lens 17, a drive motor 29 that drives the collimator lens 17, and a driving force of the drive motor 29 are transmitted to the lens holding member 33. And a collimator driving member 30. Further, the rotation axis of the motor 29 is arranged in parallel with the moving direction of the optical pickup 5. First, the collimator lens 17 is moved in the direction of the optical axis by driving the drive motor 29 from the initial position, the amplitude of the information reproduction signal is detected during the movement, and the position where the amplitude is maximized is the correction position of the collimator lens. And
[Selection] Figure 1

Description

  The present invention relates to an optical disc apparatus for recording information on an optical disc or reproducing recorded information, and more particularly to a technique for correcting spherical aberration of a beam spot caused by a thickness error of a protective substrate of an optical disc.

  In recent years, for example, in the field of recording or reproducing information signals using an optical disc as an information recording medium, development of a small and large-capacity optical disc apparatus has progressed in order to handle high-definition still images and moving images. It is out. The optical disc apparatus includes an optical pickup for forming a beam spot on the information recording surface of the optical disc. In this optical pickup, it is known that spherical aberration occurs when a light beam emitted from a light source passes through a transparent protective substrate layer that protects the information recording layer.

  Therefore, for example, in Japanese Patent Application Laid-Open No. 2003-45068, a knife holder is provided on a lens holder that holds a lens for correcting spherical aberration, and the knife edge is engaged with a feed screw provided on a rotation shaft of a stepping motor. Thus, an apparatus for correcting spherical aberration has been proposed (see Patent Document 1).

In JP-A-11-259906, rotation of a motor is transmitted to a collimator lens holder by a gear mechanism, and the collimator lens held by the lens holder is moved in the optical axis direction to correct spherical aberration. An apparatus has been proposed (see Patent Document 2).
JP 200345068 A JP-A-11-259906

  In Patent Document 1, since the rotation axis of the stepping motor that drives the lens group that corrects the spherical aberration and the optical axis that enters the lens group are arranged in parallel, the light of the spherical aberration correction lens group of the optical pickup is arranged. There is a problem that the width in the direction perpendicular to the axis becomes large and the optical pickup becomes large.

  Moreover, in the thing of patent document 2, the rotating shaft of the stepping motor which drives a collimator lens, and the optical axis which injects into a collimator lens are arrange | positioned in parallel, Moreover, rotation of a motor is carried out through a complicated gear mechanism, and a collimator lens holder Therefore, there is a problem that not only the structure of the optical pickup is complicated but also the width of the collimator lens in the direction perpendicular to the optical axis becomes large, and the optical pickup becomes large.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an optical disc apparatus having a simple structure, small and thin, and capable of correcting spherical aberration.

  In order to achieve the above object, the present invention provides an optical disc apparatus having an optical pickup for recording or reproducing information on an optical disc and moving means for moving the optical pickup in a radial direction of the optical disc. An optical element that corrects the spherical aberration, a holding member that holds the optical element, a motor that drives the optical element, and a driving member that transmits the driving force of the motor to the holding member. The rotation axis is arranged in parallel to the moving direction of the optical pickup.

  According to the present invention, since the rotation axis of the motor is arranged in parallel to the moving direction of the optical pickup, the width of the spherical aberration correcting optical element does not increase in the direction perpendicular to the optical axis direction. The spherical aberration of the beam spot can be corrected with high accuracy without increasing the size.

  Next, the best mode for carrying out the invention will be described in detail with reference to the drawings. FIG. 1 is a plan view showing an embodiment of an optical disk apparatus according to the present invention. In FIG. 1, 1 is an optical disk as an information recording medium, and 2 is a turntable on which an optical disk 1 is placed. The turntable 2 is provided on the front end side of a spindle motor 4 installed on a chassis 3 which is a substrate of a mechanism part of the apparatus.

  Reference numeral 5 denotes an optical pickup that irradiates the optical disk 1 with a light beam to record or read information signals. The optical pickup 5 uses an optical disk 5 as a guide means with a guide shaft 7 supported by guide shaft support members 6a and 6b provided in the chassis 3 and a lead screw 9 rotatably supported by the lead screw support members 8a and 8b. It moves in the disk radial direction (X direction in the figure) along the recording surface 1.

  At this time, the rack gear 10 attached to the back surface of the optical pickup 5 so as to extend in a direction perpendicular to the disk radial direction and the lead screw 9 are engaged with each other, and the driving force of the traverse motor 11 is reduced to the lead screw via the reduction gears 12a to 12d. The optical pickup 5 moves in the radial direction of the optical disc 1 by rotating the lead screw 9 by driving the traverse motor 11. Further, a U-shaped protruding portion is provided at one end of the optical pickup 5, and the protruding portion engages with the guide shaft 7 as shown in FIG. 4 so that the optical pickup 5 can slide.

  FIG. 2 is a sectional view of the optical pickup 5 as viewed from the direction AA ′ in FIG. 3 is a plan view of the initial position of the spherical correction element driving mechanism, FIG. 4 is a side view of FIG. 3, FIG. 5 is a plan view after the movement of the spherical correction element driving mechanism, and FIG. An exploded perspective view of the correction element drive mechanism 14 is shown.

  First, as shown in FIG. 2, the optical pickup 5 has a semiconductor laser 16 as a light source mounted on an optical base 15 serving as a base. The optical axis of the semiconductor laser 16 is parallel to the disk surface, passes through an optical system component (not shown), passes through a collimator lens 17 that is a spherical aberration correction element, and is further reflected by the mirror 18 in the direction perpendicular to the optical disk 1. The Thereafter, the light is focused on the recording surface of the optical disc 1 through the objective lens 19. The optical pickup 5 includes an actuator unit 13 that drives the objective lens 19 and a spherical aberration correction element driving mechanism 14 that drives the collimator lens 17.

  As shown in FIG. 6, the actuator unit 13 has an objective lens 19 and a lens holder 20 that holds the objective lens 19, and the lens holder 20 is wound and fixed in parallel to the optical axis direction of the objective lens. The coil 21 and a pair of tracking coils 22 wound in a direction perpendicular to the focusing coil axis are fixed to the side surface of the focusing coil 21.

  The lens holder 20 is supported by four wire members 23 a to 23 d, and the other end of each wire member is fixedly supported by the support member 24. The support member 24 is attached to a yoke 25 that serves as a base of the actuator unit 13. The yoke 25 constitutes a base, but a part of the base may be a yoke, and the material of the base may be different from the material of the yoke. Here, the wire members 23a to 23d, the support member 24, and the yoke 25 serve as a support for supporting the lens holder 20 in the focusing direction (optical axis direction of the objective lens) and the tracking direction (radial direction of the optical disk).

  As shown in FIG. 2, the yoke 25 is provided with a permanent magnet 26 a inside the focusing coil 21, a permanent magnet 26 b is provided at a position facing the tracking coil 22, and opposed yoke parts 27 a and 27 b are provided on the back side. ing. The focusing coil 21, the tracking coil 22, the permanent magnets 26a and 26b, and the opposing yokes 27a and 27b constitute a magnetic circuit, and the focusing coil 21 and the tracking coil 20 are coupled with wire members 23a to 23d made of a conductive material. Then, by energizing each coil, the entire lens holder 20 including the objective lens 19 moves in the focusing direction and the tracking direction.

  That is, when a current is passed through the focusing coil 21, the force that moves the entire lens holder 20 in the focusing direction, that is, in the direction perpendicular to the optical disc 1, in relation to the magnetic field generated by the permanent magnet 27 a inserted inside the focusing coil 21. Will occur. When a current is passed through the tracking coil 22, the entire lens holder 20 is moved in the focusing direction, that is, in the radial direction of the optical disc 1 in relation to the magnetic field generated by the permanent magnet 27 b provided at a position facing the tracking coil 22. Force to generate. The yoke 25 is provided with four sections 28 that are bonded and fixed to the optical base 15.

  As shown in FIG. 6, the spherical aberration correction element driving mechanism 14 includes a driving motor 29 on the optical base 15 and a collimator driving member 30 on the side surface of the optical base 15. Further, a worm gear 31 is provided at the front end side of the drive motor 29, and the worm gear 31 meshes with a helical gear 30 a provided on the collimator drive member 30. The collimator driving member 30 is rotatably supported by a bearing portion 32 provided on the optical base 15.

  The collimator lens 17 is held by a lens holding member 33, and the lens holding member 33 is guided by two guide shafts 34 provided on the optical base 15 in the optical axis direction (Y direction in the figure) of the collimator lens 17. It is movable. The lens holding member 33 is provided with a rack portion 35 and meshes with a worm gear 30 b provided on the collimator driving member 30. Further, the optical base 15 is provided with a photo interrupter 36 as a position sensor, and the position of the lens holding member 33 (that is, the optical axis direction of the collimator lens 17 in the optical axis direction of the collimator lens 17 by inserting / removing the shielding plate 37 provided on the lens holding member 33) Position).

  Next, the operation of the spherical aberration correction element driving mechanism 14 of the present embodiment will be described. First, the spherical aberration correction element driving mechanism 14 is used for correcting spherical aberration caused by the thickness error of the cover layer of the optical disc 1. That is, the collimator lens 17 can be moved in the optical axis direction, and the light beam incident on the objective lens 19 diverges from parallel light or converges to cause spherical aberration in the light beam emitted from the objective lens 19. Correction is made by canceling out the spherical aberration caused by the thickness error. In this control method, the collimator lens 17 is moved a predetermined distance from the reference position, the amplitude of the information reproduction signal is detected while the collimator lens 17 is moving, and the point at which the reproduction signal amplitude is maximum is set as the correction position of the collimator lens 17.

  More specifically, FIG. 3 shows a state in which the lens holding member 33 is at the reference position where the shielding plate 37 is inserted into the photo interrupter 36. In this state, when the drive motor 29 that is a drive source is rotated, the rotational force is transmitted to the collimator drive member 30. The rotation of the collimator driving member 30 is transmitted to the rack portion 35 of the lens holding member 33, and the lens holding member 33 moves in the optical axis direction of the collimator lens 17 using the guide shaft 34 as a guide. At this time, the lens holding member 33 is engaged with the guide shaft 34 through the hole 33a and the engaging portion 33b, and the optical axis of the collimator lens 17 is inclined or the center position is shifted due to the movement of the lens holding member 33. Never do.

  A stepping motor is used as the drive motor 29, and a motor drive circuit (not shown) supplies predetermined pulses to the motor 29 while counting pulses from a reference position based on control of a control circuit (not shown). FIG. 5 shows a state after supplying a predetermined pulse. During the movement, predetermined information on the optical disc 1 is reproduced by a reproduction circuit (not shown), and the amplitude of the information reproduction signal is detected by a detection circuit (not shown). The above-described control circuit monitors the reproduction signal amplitude, and reversely rotates the drive motor 29 to a position where the reproduction signal amplitude is maximized. In this way, the spherical aberration due to the thickness error of the optical disc 1 is corrected by moving the collimator lens 17 to the optimum position where the reproduction signal amplitude is maximized. The reproduction information of the optical disc 1 is not limited.

  Here, when the reference position is detected using the photo interrupter 36, the light emitting element incorporated in the photo interrupter 36 when the shielding plate 37 provided on the lens holding member 33 enters the detection groove of the photo interrupter 36. And the light receiving element are shielded. When the photo interrupter 36 is shielded, no pulse signal is output from the motor drive circuit (not shown) to the drive motor 29, so that the reference position detection is completed at that time, and the position is set as the reference position as described above. The position of the lens holding member 33 is adjusted. Therefore, it is not necessary to apply an extra load to the drive motor 29, and the reference position can be detected in a short time and with low power consumption. Such spherical aberration correction by the spherical aberration correction mechanism 14 is performed when the power is turned on or the optical disk 1 is replaced.

  In the present embodiment, a stepping motor is used as the drive motor 29, the rotation axis of the drive motor 29 is arranged in parallel with the moving direction of the optical pickup 5, and the collimator drive member 30 is arranged on the side surface of the optical base 15. doing. At this time, the drive motor 29 is substantially the same as the thickness of the optical base 15 as shown in FIG. The collimator driving member 30 is a simple bar-shaped metal member having a shaft threaded as shown in FIGS. 3, 5, 6, etc., and this also does not exceed the thickness of the optical base 15. Is converted into a translational movement of the lens holding member 33 to transmit a driving force.

  By arranging the drive motor 29 and the collimator drive member 30 in this manner, the thickness of the optical base 15 is not increased, and the width of the optical pickup 1 in the radial direction of the optical disk 1 is set to the width of the collimator drive member 30. Since only an increase is required, even if the optical pickup 5 moves to the outer peripheral side of the optical disc 1, it does not protrude from the chassis 3 and the optical disc apparatus does not increase in size.

  Further, the rack portion 35 of the lens holding member 33 is engaged with the worm gear 30 b of the collimator driving member 30. The rack portion 35 is made of resin and has elasticity, and is in contact with the worm gear 30b without a gap. 3 to 5, the collimator driving member 30 has a spherical shaft end 30c biased by a leaf spring 38 in the Y direction in the figure. Therefore, the lens holding member 33 can hold the position of the collimator lens 17 with high accuracy without rattling in the optical axis direction. In addition, a small stepping motor is used as the drive motor 29, so the step angle is large. However, since two worm gears can be used to reduce the pitch, the reduction ratio can be increased, and the collimator lens position can be increased. The accuracy can be controlled, and the spherical aberration can be accurately corrected.

It is a top view which shows one Embodiment of the optical disk apparatus of this invention. It is sectional drawing in the AA of FIG. It is a top view which shows the initial position of a spherical aberration correction element drive mechanism. FIG. 4 is a side view of FIG. 3. It is a top view which shows the position after a predetermined pulse supply of a spherical aberration correction element drive mechanism. It is a disassembled perspective view of an optical pick-up.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Turntable 3 Chassis 4 Spindle motor 5 Optical pick-up 6a, 6b Guide shaft support member 7 Guide shaft 8a, 8b Lead screw support member 9 Lead screw 10 Rack gear 11 Traverse motor 12a-12d Reduction gear 13 Actuator unit 14 Spherical aberration correction Element drive mechanism 15 Optical base 16 Semiconductor laser 17 Collimator lens 18 Mirror 19 Objective lens 20 Lens holder 21 Focusing coil 22 Tracking coil 23a-23d Wire member 24 Support member 25 Yoke 26a, 26b Permanent magnet 27a, 27b Opposing yoke 28 Intersection 29 Drive motor 30 Collimator drive member 30a Lotus gear 30b Worm gear 30c Shaft end 31 Worm gear 32 Bearing portion 33 Lens holding member 33a Hole portion 33b Engagement portion 34 Guide shaft 35 Rack portion 36 Photo interrupter 37 Shield plate 38 Plate spring

Claims (4)

In an optical disc apparatus having an optical pickup for recording or reproducing information on an optical disc and a moving means for moving the optical pickup in the radial direction of the optical disc, the optical pickup has an optical element for correcting spherical aberration of a beam spot, and A holding member that holds the optical element; a motor that drives the optical element; and a driving member that transmits a driving force of the motor to the holding member. A rotation axis of the motor is parallel to a moving direction of the optical pickup. An optical disc apparatus characterized by being arranged. The optical disk apparatus according to claim 1, wherein the driving member is disposed on a side surface of the optical pickup in a direction perpendicular to a rotation axis of the motor. The optical disk apparatus according to claim 1, wherein the driving member is a rotating shaft provided with a worm gear. 2. The optical disc apparatus according to claim 1, wherein an optical axis of the optical element is perpendicular to a moving direction of the optical pickup.

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