JP2006277854A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup in which the vibration characteristics for vibration from the outside of the optical pickup is made proper and the reliability is high. <P>SOLUTION: In the optical pickup performing writing and reading of information for an optical disk using an objective lens, a support center and centroid in-disk plane of the optical disk are made to coincide inside the objective lens. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical pickup provided in an optical disc apparatus that reads information recorded on a recording surface of an optical disc or records information on an optical disc.

  An optical disk apparatus that records information on a disk-shaped recording medium or reads and reproduces recorded information can record a relatively large amount of information on the disk, and the medium is also rigid and easy to handle. Therefore, it is used as an external recording device of a computer or a video / audio recording device.

  In an optical pickup of an optical disc apparatus, laser light emitted from a laser light emitting element is condensed by an objective lens and irradiated onto the optical disc, and reflected light from the optical disc passes through the objective lens and enters a photodetector to record information. Playback is performed. The objective lens is driven with high accuracy in a focusing direction, which is a direction approaching or moving away from the optical disk surface, and a tracking direction, which is a radial direction of the optical disk, by driving means using electromagnetic force. The optical pickup is coarsely moved in the tracking direction, which is the radial direction of the optical disk, using a gear or the like.

  An example of such a conventional structure of an optical pickup is described in Patent Document 1. In this publication, the positional relationship between the support part of the optical pickup and the barycentric line of the optical pickup parallel to the track is shown.

Japanese Patent Laid-Open No. 8-212723 (page 3-8, FIG. 17)

  Vibrations from the outside of the optical pickup include vibrations in the focusing direction, the tracking direction, and the three translational directions parallel to the track and the rotational directions of the respective axes. The place most affected by the vibration is an objective lens driving device supported so as to be movable. The objective lens drive device has a mechanism that can normally follow the focusing direction and the tracking direction, and the two directions of vibration in the translation direction can be followed by the objective lens drive device, and the direction parallel to the remaining one-way track is also the disc. Since it is in the same direction as rotation, there is no influence from external vibration. On the other hand, the rotation direction of each axis is a direction in which the rotation direction around the focusing direction is replaced with the translation in the substantially tracking direction so that the objective lens driving device can follow. However, the other two rotation directions (the rotation direction with the tracking direction as the axis and the rotation direction with the direction parallel to the tracking as the axis) are factors that cause distortion of the focal point and spot by the objective lens, that is, deterioration of optical characteristics, It is necessary to reduce vibration due to signal degradation and malfunction. However, the optical pickup described in Patent Document 1 describes only the rotation direction with one direction parallel to the track as an axis, and does not consider the vibration in the rotation direction with the tracking direction as an axis. In conventional optical pickups, most of the optical components are arranged in the pickup housing in the direction of the feed axis or guide axis from the objective lens, and the position of the objective lens is offset from the support center. Is likely to occur. This optical axis misalignment may cause signal degradation and malfunction of the disk drive device.

  The present invention has been made in view of the above-mentioned problems of the prior art, and the object thereof is to improve the vibration characteristics against vibration from the outside of the optical pickup, provide a highly reliable optical pickup, and use the same. An object of the present invention is to provide a high-quality optical disc apparatus.

In order to achieve the above object, the present invention is configured as follows.
In an optical pickup that reads and writes information from and to an optical disk using an objective lens, the optical pickup has a support center in the disk surface of the optical pickup that matches the objective lens.
Further, the optical pickup is configured such that the center of gravity in the disc surface of the optical pickup coincides with the objective lens.
Further, the optical pickup is configured such that the support center and the center of gravity of the optical pickup coincide with each other in the objective lens.

According to the present invention, the objective lens is positioned at a neutral position for vibration in any direction by matching the support center and the center of gravity of the optical pickup within the objective lens against vibration from the outside. Therefore, the optical axis shift of the lens hardly occurs. As a result, a highly reliable optical pickup without causing signal degradation and malfunction can be obtained, and a high-quality optical disc apparatus using the same can be provided.

  An embodiment of an optical pickup according to the present invention will be described with reference to the drawings.

  First, the optical disk device 110 on which the optical pickup 100 is mounted will be described with reference to the block diagram of FIG. The optical disk device 110 includes a spindle motor 112 that rotates the optical disk 111, an optical pickup 100 that reads information from the optical disk 111, and a controller 113 that controls them. The optical pickup 100 includes optical components such as the objective lens 1 and objective lens driving means.

  The disk rotation control circuit 114 connected to the controller 113 receives a command from the controller 113 and rotates the spindle motor 112 on which the optical disk 111 is mounted. In addition, the feed control circuit 115 connected to the controller 113 moves the optical pickup 100 in the radial direction of the optical disc 111 in response to a command from the controller 113.

The laser light of the laser light emitting element 51 mounted on the optical pickup 100 is condensed on the optical disk 111 by the objective lens 1. The condensed laser light is reflected by the optical disk 111, passes through the objective lens 1, and enters the photodetector 53. The detection signal 116 obtained by the photodetector 53 is sent to the servo signal detection circuit 117 and the reproduction signal detection circuit 118. A servo signal is generated based on the detection signal 116 sent to the servo signal detection circuit 117 and input to the actuator drive circuit 119.
The actuator drive circuit 119 inputs a drive signal to a focusing coil or tracking coil (not shown) of the optical pickup, and controls the objective lens 1 for positioning.
On the other hand, a reproduction signal is generated from the detection signal 116 input to the reproduction signal detection circuit 118, and information on the optical disc 111 is reproduced.

Details of the optical pickup 100 shown in FIG. 5 will be described below.
FIG. 1 is a perspective view of an optical pickup 100 of the present invention. In the figure, the z direction is a focusing direction for moving the objective lens 1 toward or away from the optical disk surface along the optical axis of the objective lens 1, and the y direction is a tracking direction for operating the objective lens 1 in the radial direction of the optical disk. . A direction orthogonal to both the y direction and the z direction is defined as an x direction.

  The objective lens 1 is mounted on the upper surface of the holder 2, and a permanent magnet 6 is attached to the side surface of the holder 2 facing the x direction. Optical components such as a laser light emitting element 51 and a photodetector 53 (not shown) are mounted inside the holder 2. The movable part 11 including the objective lens 1 and the holder 2 is supported with respect to the fixed part 8 by support members 7 a, 7 b, 7 c, and 7 d disposed on both side surfaces facing the tracking direction of the holder 2.

  The focusing coils 3a and 3b and the tracking coils 4a and 4b are attached to the yokes 5a and 5b, and are separated from the permanent magnets 6a and 6b of the movable portion 11.

  The operation of the movable part 11 will be described. When a drive current as a drive signal is applied from the actuator drive circuit 119 shown in FIG. 5 to the focusing coils 3a and 3b or the tracking coils 4a and 4b, an electromagnetic force is generated by the interaction with the permanent magnets 6a and 6b. The movable part 11 is driven in the focusing direction or the tracking direction. A component constituted by a magnetic circuit including the movable portion 11, the focusing coils 3a and 3b, the tracking coils 4a and 4b, and a component that supports the movable portion 11 is referred to as an objective lens driving device.

  The movable portion 11 is mounted on a pickup housing 101 that is a component part of the optical pickup 100. The optical pickup 100 is supported by a feed shaft 31 provided with a gear or the like so as to be movable in the tracking direction and a guide shaft 32 provided in parallel with the feed shaft 31. The feed shaft is provided with support portions 21a and 21b having a bearing function at two locations, and the guide shaft 32 is provided with a support portion 22 having a bearing function at one location.

  The support portions 21a, 21b, and 22 of the optical pickup 100 will be described with reference to FIG. A support center 33 in the plane parallel to the disc surface (in the xy plane) determined by the support portions 21 a, 21 b, and 22 of the optical pickup 100 is in the objective lens 1. The center of gravity 34 in the xy plane of the optical pickup 100 is in the objective lens 1.

  In the case of a low frequency, the vibration from the outside of the optical pickup 100 appears with respect to the resultant force applied to the support center 33 determined by the support portions 21a, 21b, and 22 up to several tens of Hz. At this time, if the support center 33 of the optical pickup 100 and the support center 35 of the movable portion 11 are separated from each other, a moment with the distance 41 between the arms as an arm is generated. This moment may cause the objective lens 1 to tilt and cause an optical axis shift, resulting in signal deterioration and malfunction of the disk drive device 110. Therefore, in this embodiment, the support center 33 of the optical pickup 100 is provided in the objective lens 1 so that the support center 33 of the optical pickup 100 and the support center 35 of the movable portion 11 substantially coincide. As a result, the length of the moment arm is reduced, the moment is suppressed, and unnecessary vibration can be eliminated. Here, since the support center 35 of the movable part 11 in the xy plane is often coincident with the objective lens center, the support center 35 of the movable part 11 described above may be used as the objective lens center.

  Further, the vibration from the outside of the optical pickup 100 appears for the resultant force applied to the center of gravity 34 of the optical pickup 100 in the case of a high frequency, here, several tens of Hz or more. At this time, if the center of gravity 34 of the optical pickup 100 and the center of gravity 36 of the movable part 11 are separated from each other, a moment with the distance 42 between the two as an arm is generated. This moment may cause the objective lens 1 to tilt and cause an optical axis shift, resulting in signal deterioration and malfunction of the disk drive device 110. Therefore, in this embodiment, the center of gravity 34 of the optical pickup 100 is provided in the objective lens 1 so that the center of gravity 34 of the optical pickup 100 and the center of gravity 36 of the movable portion 11 substantially coincide. As a result, the length of the moment arm is reduced, the moment is suppressed, and unnecessary vibration can be eliminated. Here, since the center of gravity 36 of the movable part 11 in the xy plane often coincides with the center of the objective lens, the center of gravity 36 of the movable part 11 described above may be used as the center of the objective lens.

  Although the above description is limited to the xy plane, unnecessary vibration is obtained by making the support center 33 and the center of gravity 34 of the optical pickup 100 coincide with the support center 35 and the center of gravity 36 of the movable part 11 for all of the yz plane and the zx plane. Thus, the optical pickup 100 has good vibration characteristics with no vibration.

  Here, the configuration of the movable portion 11 for arranging the support center 33 and the center of gravity 34 of the optical pickup 100 at predetermined positions will be described with reference to FIGS.

  FIG. 3 shows the arrangement of the optical components in the movable part 11. FIG. 3A shows the movable part 11 with the laser light emitting element 51, the half mirror 52, the objective lens 1 and the photodetector 53 mounted thereon, and the optical system is optically connected. This is a finite optical system using divergent light and focused light. Optical components such as a collimator lens that changes divergent light into parallel light by not using parallel light are omitted, and the minimum component structure is achieved. As a result, the number of parts can be reduced and the cost can be reduced.

  Even when the objective lens 1 is operated in the tracking direction in order to follow the eccentricity of the disk 111 by mounting all the optical components on the movable portion 11, the positions of the laser light emitting element 51, the objective lens 1 and the photodetector 53 are not affected. Is always constant, it is possible to suppress a decrease in light utilization efficiency and an optical axis shift.

  (B) is a structure in which a mirror 54 having a reflecting surface is mounted in addition to the component parts of (a), and the distance in the z direction of the movable portion 11 is shortened by folding the optical path toward the objective lens 1 side. By folding the optical path by the reflection mirror 54, the movable part 11 is downsized. FIG. 6 shows a side view of FIG. At this time, if the angle 55 between the reflecting surface of the reflecting mirror 54 and the surface of the disk 111 is set to 20 degrees to 30 degrees, the photodetector 53 can be disposed beside the objective lens 1, and the efficiency for reducing the size is best.

  FIG. 4 shows the movable part 11 on which the optical component shown in FIG. 3 is mounted. 4A shows the structure of the movable part 11 used in FIG. 3A. The objective lens 1 is mounted on the upper surface of the holder 2, and the permanent magnets 6a and 6b are mounted on the side surfaces of the holder 2 facing the x direction. Is attached. On the holder 2, optical components such as a laser light emitting element 51, a photodetector 53 (not shown), and a half mirror 52 are mounted.

  4 (b) shows the structure of the movable part 11 used in FIG. 3 (b). The objective lens 1 is mounted on the upper surface of the holder 2, and the permanent magnets 6a and 6b are mounted on the side surfaces of the holder 2 facing the x direction. Is attached. On the holder 2, optical components such as a laser light emitting element 51, a photodetector 53, a half mirror 52 and a reflection mirror 54 (not shown) are mounted. At that time, by using the reflecting mirror 54 to dispose the laser light emitting element 51 and the photodetector 53, which are heat generating components, on the disk side, it is possible to effectively use the rotational flow by the disk and improve the heat dissipation. It has a structure.

  Optical components other than the conventional objective lens 1 are arranged in the pickup housing and are arranged so as to be biased to one side from the objective lens. Here, by adopting the configuration of the movable portion 11, the optical components can be centrally arranged around the objective lens 1 to simplify the structure of the pickup housing 101, and the structure and arrangement of the support portions 21a, 21b, and 22 can be simplified. The support center 33 and the center of gravity 34 of the optical pickup 100 can be disposed in the objective lens 1.

  The present invention can be applied to an optical pickup of an optical disc.

It is a perspective view of the Example of the optical pick-up concerning this invention. It is explanatory drawing of the relationship between the support position of the optical pick-up shown in FIG. 1, and a gravity center. It is optical component arrangement | positioning explanatory drawing of the movable part shown in FIG. It is explanatory drawing of the movable part shown in FIG. 1 is a block diagram of an embodiment of an optical disc apparatus according to the present invention. It is a side view of optical component arrangement | positioning of the movable part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Objective lens, 2 ... Holder, 7a, 7b, 7c, 7d ... Support member, 11 ... Movable part, 21a, 21b, 22 ... Support part, 31 ... Feed shaft 32 ... guide shaft, 33 ... support center, 34 ... center of gravity, 35 ... support center, 36 ... center of gravity, 41, 42 ... distance, 51 ... laser emitting element, 52 ... Half mirror, 53 ... Photo detector, 54 ... Mirror, 55 ... Angle, 100 ... Optical pickup, 110 ... Optical disk device

Claims (4)

  In an optical pickup that reads and writes information from and to an optical disk using an objective lens, the support center of the optical pickup with respect to the feed axis and the guide axis that guides the optical pickup in the radial direction of the optical disk is in a plane parallel to the optical disk surface. An optical pickup characterized by being placed in an objective lens   An optical pickup that reads and writes information from and to an optical disk using an objective lens, wherein the center of gravity of the optical pickup is arranged in the objective lens in a plane parallel to the optical disk surface.   In an optical pickup that reads and writes information from and to an optical disk using an objective lens, the support center of the optical pickup and the center of gravity of the optical pickup with respect to the feed shaft and guide shaft that guide the optical pickup in the radial direction of the optical disk are An optical pickup characterized by being placed in a lens.   In an optical pickup that reads and writes information from and to an optical disk using an objective lens, an objective lens driving device that integrally drives optical components is used, and the angle formed by the reflecting surface of the reflecting mirror and the optical disk surface is changed from 20 degrees to 30 degrees. An optical pickup characterized by being arranged.

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