JPH01182937A - Objective lens drive device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an objective lens driving device in an optical head used in an optical information recording/reproducing device.

2. Description of the Related Art In recent years, many recording and reproducing devices for video, audio, etc. using optical disks have been announced, and related technologies have also progressed accordingly. In particular, various methods have been proposed for optical pickup, but it is difficult to adjust the position of the optical system.
It is hoped that issues in this area will be resolved. Optical reading devices are known from the prior art, in particular for the purpose of responsively correcting focusing and tracking.
A dimensionally driven mechanism is disclosed in Japanese Patent Application No. 60-293842, and has a structure as shown in FIGS. 4 and 5.

FIG. 4 is a perspective view of a conventional objective lens driving device.
The figure is a sectional view taken along arrow A in FIG. 4.

1001 indicates a focusing direction, and 1002 indicates a tracking direction.

Reference numeral 100 denotes an objective lens, and an objective lens holding member 102 is held so that its front axis is parallel to the focusing direction 1001.
is fixed. A pair of upper and lower elastic members 104 are arranged in two planes perpendicular to the focusing direction 1001, and one end is fixed to the objective lens holding member 102 and the other end is fixed to the rotating member 202. The elastic member 104 is configured as a parallel spring by a thin plate spring arranged so that the section modulus is small in the focusing direction 1001 and the section modulus is large in the tracking direction 1002.

This allows the objective lens holding member 102 to be flexible in the focusing direction 1001 and flexible in the tracking direction 1002.
is strongly supported.

Reference numeral 218 denotes a balancer, which corrects the amount of unbalance with respect to the rotating wheels of the objective lens 100, the rotating member 202, the parallelogram prism 132, etc., and is arranged so that the center of gravity of the movable part is on the rotating axis.

204 is a tracking drive magnetic circuit fixed to a base 208, to which the tracking drive magnet 108 is fixed. A magnetic flux is generated in the magnetic gap of the tracking drive magnetic circuit 204 in a direction parallel to the focusing direction 1001, and by applying a tracking drive signal to the tracking drive coil 116 fixed to the rotating member 202, the magnetic flux is generated in the tracking direction 1002. Drive.

The shaft 206 is fixed to the rotating member 202. axis 206
is supported substantially perpendicularly to the surface of the disk 200 by two bearings 120 and 122 (FIG. 5), which are mounted on an arm housing 212 provided on the base 208 and on the base 208, respectively. Fixed.

In FIG. 5, a parallelogram prism 132 is attached to the shaft 206.
An opening 210 is provided so that the first reflective surface 214 of the shaft 206 can be positioned at the rotation center of the shaft 206, and the opening 210 is connected to a hole 126 provided at the rotation center of the shaft 206. There is.

The laser beam emitted from the fixed optical system 128 passes through the hole 126.
, is totally reflected by the first reflecting surface 214 and the second reflecting surface 216, and is guided to the objective lens 100.

Reference numeral 140 denotes a focus drive magnetic circuit fixed to the base 208, and the gap portion 146 is formed in an arc shape centered on the rotation wheel of the rotation member 202, and a magnetic field is formed in the radial direction of the gap portion 146.

Reference numeral 138 denotes a focus drive coil located in the gap portion 146 and fixed to one end of the objective lens holding member 102. By applying a signal according to the focusing error signal to this focus drive coil 13B, the objective lens 100 is moved in the focusing direction 1001,
The distance from the recording surface of the recording/reproducing disk 200 can be kept constant.

Problem to be Solved by the Invention However, in the above configuration, when the rotating member 202 is to be rotated in the tracking direction 1002, the optical axis of the objective lens 10G is set to the geometric center of rotation of the rotating member 202. If the position is deviated, problems such as an offset in the tracking error signal or, in extreme cases, the inability to obtain a control signal, will occur. Therefore, the relative geometrical position of the optical axis of the objective lens 100 and the rotating member 202 must be adjusted. In the conventional configuration, when moving the objective lens 100, the position must be adjusted by making the elastic member 104 movable. There was a drawback that the optical axis was tilted.

Means for Solving the Problems In order to solve the above problems, the objective lens drive device of the present invention arranges an intermediate member between the rotating member and the elastic member, and adjusts the geometry of the objective lens and the rotating member. This structure prevents deformation of the elastic member and tilting of the optical axis of the objective lens when performing physical position adjustment.

Effect of the Invention With the above-described configuration, the present invention can secure the optical axis with high precision even when the rotating member is driven in the tracking direction, so problems such as offset of the tracking error signal are solved, and the laser beam is It can follow the track with precision. Furthermore, since deformation of the elastic member can be eliminated, the frequency characteristics of the elastic member can be improved, and since the inclination of the optical axis of the objective lens can be reduced, the quality of recorded and reproduced signals can also be improved.

Embodiment An embodiment of the objective lens driving device of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective sectional view showing an example of an objective lens driving device according to the present invention, FIG. 2 is an assembled view of essential parts of the present invention, and FIG. 3 is an assembled view of a rotating member.

In FIGS. 1 and 2, 1001 indicates the focusing direction, and 1002 indicates the tracking direction.

In FIGS. 1 and 2, reference numeral 100 denotes an objective lens, which is fixed to the objective lens holding member 2 so that its optical axis is parallel to the focusing direction 1001.

4 is a pair of upper and lower elastic members, which are aligned in the focusing direction 100
1, one end is fixed to the objective lens holding member 2, and the other end is fixed to the intermediate member 62.

The elastic member 4 is configured as a parallel spring in the focusing direction 1001 by a thin leaf spring arranged so that the section modulus is small in the focusing direction 1001 and the section modulus is large in the tracking direction 1002.

As a result, the objective lens holding member 2 is supported flexibly in the focusing direction 1001 and rigidly in the tracking direction 1002.

44 is a tracking drive magnetic circuit fixed to the base 58, and the tracking drive magnet 8 is fixed thereto. Five bundles are formed in the magnetic gap of the tracking drive magnetic circuit 44 in a direction parallel to the focusing direction 1001. In FIG. 2, by applying a tracking drive signal to the tracking drive coil 16 fixed to the rotation member 52, the rotation member 52 is tracked in a tracking direction 1002.
driven by. At this time, the objective lens 100, the objective lens holding member 2, the rotating member 52, the tracking drive coil 1
The height of the center of gravity of the movable part 6 etc. is approximately the same height as the height at which the tracking drive coil 16 is arranged, and therefore,
The thrust generated is approximately at the same height as the center of gravity of the moving part.

The shaft 6 is fixed to a rotating member 52. The shaft 6 is supported by two bearings 20.22.
is fixed to the tracking drive magnetic circuit 44 fixed to the base 58. Normally, magnetic circuits are made of iron-based materials with a certain degree of thickness in order to reduce leakage magnetic flux, so their rigidity is quite high. Therefore, the resonant frequency of this portion can be made relatively high.

In FIG. 1, the axis 6 has the first parallelogram prism 32
An opening 10 is provided so that the reflective surface 14 of the shaft 6 can be positioned at the center of rotation of the shaft 6, and the opening 10 is connected to a hole 26 provided at the center of rotation of the shaft 6.

The laser beam emitted from the fixed optical system 28 passes through the hole 26, is totally reflected by the first reflecting surface 14 and the second reflecting surface 46, and is guided to the objective lens 100.

40 is a focus drive magnetic circuit fixed to the tracking drive magnetic circuit 44, and the gap portion 48 is a rotating member 52.
It is formed in an arc shape centered on the rotation axis, and a magnetic field is formed in the radial direction.

38 is a focus drive coil located in the gap portion 48 and fixed to one end of the objective lens holding member 2. By applying a signal corresponding to the focusing error signal to the focus drive coil 38, the objective lens 100 is
By moving the lens in the focusing direction 1001, the distance from the recording surface can be kept constant.

An example of the present invention will be explained in detail with reference to FIG.

Both end surfaces 14 of the parallelogram prism 32 (not shown),
The laser beam totally reflected by the objective lens 10
0, but at that time, it is necessary that no error occurs in the relative position between the optical axis of the objective lens 100 and the rotation center of the rotation member 52.

The intermediate member 62 has a fixing hole 64 for being fixed to the rotating member 52, and is fixed to the rotating member 52 by a fixing member 66. The diameter of the fixing hole 64 is slightly larger than the diameter of the fixing member 66, and is approximately equal to the gap between the fixing portion 68 formed on the rotating member 52 and the shoulder portion 70 provided on a part of the intermediate member 62. It is configured to move within a plane.

Furthermore, a through hole 72 is provided in the intermediate member 62 so that one total reflection surface 46 of the parallelogram prism 32 fixed to the rotating member 52 can be positioned directly below the objective lens 100.

The objective lens 100 is created by the apparatus configured as described above.
The relative position between the optical axis of the rotary member 52 and the center of rotation of the rotary member 52 can be adjusted by moving the intermediate member 62. Therefore, during position adjustment, the elastic member 4 can move the optical axis of the objective lens 100 while being fixed to the intermediate member 62, so that the elastic member 4 can be deformed after adjustment. Fixed part 68
Since the flatness machining can be performed with sufficient accuracy, it is possible to eliminate the tilting of the objective lens optical axis after position adjustment.

Effects of the Invention As described above, the present invention fixes the elastic member to the intermediate member,
By fixing the intermediate member to the rotating member after adjusting the position of the objective lens, adjustments can be made without deforming the elastic member or tilting the optical axis of the objective lens, which tend to occur when adjusting the position of the objective lens. The quality of the reproduced signal is improved, the offset of the tracking error signal is eliminated, and the frequency characteristics of the elastic member can also be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective sectional view of an objective lens driving device of the present invention;
2 is an assembled view of the main parts of FIG. 1, FIG. 3 is an assembled view of the rotating member, FIG. 4 is a perspective view of a conventional objective lens drive device, and FIG. FIG. 2... Objective lens holding member, 4... Elastic member, 6... Axis, 8... Tracking drive magnet, 16... Tracking Drive coil, 20.22...Bearing, 38...Focusing drive coil, 52...Rotating member, 6
2...Intermediate member, 64...Fixing hole, 6
6... fixed member, 68... fixed part,
70...Shoulder. Agent's name Patent attorney Toshio Nakao Haka 1 Famous Confectionery 1 Illustration Culm Cane Figure 3

Claims (3)

[Claims] (1) an objective lens; an objective lens holding member that moves integrally with the objective lens; an elastic member having one end fixed to the objective lens holding member and the other end fixed to an intermediate member; a rotating member that rotates around a first optical axis that is parallel to the optical axis, the intermediate member is fixed to the rotating member, and the rotating member rotates from the optical axis to the one axis. an optical path changing means for guiding light to the first
a pair of bearings rotatably supported around an axis of the rotating member; and at least one tracking drive coil that generates torque around the first axis, and the tracking drive coil is configured to rotate the rotating member. The objective lens holding member has a focusing drive coil that is driven in the optical axis direction of the objective lens, and the optical path changing means is arranged in a tracking drive magnetic circuit that has a magnetic gap in the rotation direction of the objective lens. An objective lens driving device that is fixed to a moving member and has two planar reflecting surfaces that are inclined with respect to the optical axis and are arranged parallel to each other and facing each other. (2) The objective lens driving device according to claim (1), wherein the optical path changing means is constituted by one parallelogram prism. (3) The objective lens drive device according to claim (1), wherein the center of gravity of the optical path changing means, the rotating member, and the intermediate member are arranged at approximately the same height as the tracking drive coil.