JPS61133049A - Objective lens drive device - Google Patents

Abstract

PURPOSE:To obtain a stable objective lens drive device whose drive in focusing and tracking directions is free of sircumferential disturbances from four directions by coinciding the center gravity of a movable part in focusing and tracking directions with a fulcrum from each drive force center and a fixed part. CONSTITUTION:A lens holder 2 for holding a lens 1 and a count weight of the same weight as the movable part of said holder 2 are supported by pivot plates 4a and 4b having four pivot receiving parts each, while the pivot receiving parts 42a and 42b in the vicinity of the center gravity of the pivot plate are supported by pivots 9a and 9b fixed to a base 10, and accordingly the lens holder 2 and the count weight 3 are balanced with the pivots 9a and 9b as a fulcrum. A movement in the tracking direction attains a rotary movement by magnetic circuits 8a and 8b with a total movable part center gravity G0, namely, the fulcrum from the base 10, as a center. In terms of the focusing direction, the center gravity g1 point of the lens holder 2 is driven in the focus direction, and simultaneously the center gravity g2 point of the count weight 3 is driven in the direction reverse to the lens holder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an objective lens driving device for an apparatus for optically writing or reading information.

Conventional technology objective lens drive devices have problems such as focus deviation due to vertical movement of warped disk-shaped recording media such as CO/BACT disks,
In order to correct tracking deviation due to eccentricity, etc., the objective lens is adjusted in two directions: in the focus direction and in the tracking direction.
A conventional objective lens driving device of this type, as shown in, for example, Japanese Unexamined Patent Publication No. 58-64649, had a structure as shown in FIG. 4. FIG. 4 is a perspective view of a conventional objective lens driving device, FIG. 6 (8) is a plan view of the main part thereof, and FIG. 5 (CB) is a front view of the main part.

4 and 6, first, the leaf springs 15a to 16d
The main body supported by the main body is driven in the tracking direction by the magnetic circuits 16a, 16b and the tracking coil 13, and in the focusing direction by the magnetic circuits 18a, 16b and the focusing coil 14. When driven in the tracking direction, the movement of the two magnetic circuits 16a, 1 with respect to the center of gravity G of the movable part as shown in FIG.
Driving force T1 by 6b. T2 works, and the dotted line shows leaf spring 15.
It moves in the tracking direction supported by the deflection of the tracking leaf spring portions a and 15b.

Similarly, when driving in the focus direction, the driving force F is applied from the two magnetic circuits to the center of gravity G of Hitoshi's moving part (see Fig. 5).
1. F2 works, and it moves in the focusing direction as shown by the dotted line, supported by the deflection of the focusing leaf spring portion of the leaf spring.

The entire objective lens driving device is access-driven by a motor in the access direction (same direction as the tracking direction) shown by arrow S on the recording medium.

Problems to be Solved by the Invention However, with such a structure, the object lens 11 swings in the tracking direction due to movement in the access direction during high-speed access required for data transfer. That is, in FIG. 6(8), an inertial force T3 due to the access drive acts on the center of gravity G of the movable part, and the objective lens 11 is driven in the tracking direction as in the case of driving in the trunking direction.

Also, in response to disturbances in the vertical direction (same direction as the focus direction), inertia force T3 acts on the center of gravity G of the movable part in FIG. Driven.

As mentioned above, the objective lens drive device itself is vertical.

Since it is susceptible to left and right disturbances, the current situation is that it is necessary to separately provide a structure for absorbing the disturbances in the system in which the objective lens driving device is mounted.

Therefore, the present invention provides a stable objective lens driving device that is not affected by vertical and horizontal disturbances in driving in the focus and tracking directions.

Means for solving the problems and technical means of the present invention for solving the problems are:
The center of gravity of the movable part in the focusing direction and tracking direction,
The center of each driving force and the support point from the fixed part are made to coincide with each other, and disturbances are supported by the support system fixed part.

Effect: With the above-described configuration, the present invention aligns the center of gravity of the movable part in the focusing direction and the tracking direction with the center of each driving force and the support point from the fixed part, so that the movement in the seven orifice directions and the tracking direction is controlled by each movable part. The center of gravity of the part, i.e., the point of support from the fixed part, is rotated, and the position of the center of gravity does not change even when it is moved, and it is free from disturbances in the vertical direction (same direction as the focusing direction) and horizontal direction (same direction as the tracking direction). In contrast, it is supported by the support system fixing part.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

Fig. 1 (A is a plan view of the objective lens driving device in one embodiment of the present invention, Fig. 1) is a front view of the same, Fig. 2 (8) is an enlarged plan view of the same main part, Fig. 2 CB) is an enlarged vertical cross-sectional view of the same main part.

In FIGS. 1 and 2, 1 is an objective lens (hereinafter referred to as a lens), 2 is a lens holder that holds the lens 1, and the lens 1 and the lens holder 2 constitute a movable part. a
a and 4b have the movable part at one end and the count weight 3 facing the movable part at the other end by pivots 9a and 9b,
The count weight 3 and the pivot plates 4a and 4b are rotatably connected and connected within a plane including the optical axis passing through the lens 1 and a straight line connecting the centers of gravity of the movable part and the count weight 3.
A plurality of pivot plates 4a and 4b pass through the center of gravity of all movable parts including the center of gravity on a straight line parallel to the optical axis. a pivot support fixed to a rotatably supporting base 1o, 8a to 8cf″i
The movable part, a magnetic circuit for focusing that drives the center of gravity of the count weight 3 in the focus direction, and especially 8
8d also has the function of a magnetic circuit for tracking that drives the movable part and the count weight 3 in the tracking direction in a rotational motion about the center of gravity of all the movable parts.

The operation of this embodiment will be explained below. First, the lens holder 2 holding the lens 1 and the count weight 3 having the same weight as its movable part are connected to a sufficiently rigid pivot plate 4a.
, ab are supported as shown in FIG. 2 (5), and the pivot receiving parts 42a and a2b near the center of gravity of the pivot plate are supported by the pivots 9a and 9blC fixed to the base 1o. ), the balance weight 2 and count weight 3 are balanced like a seesaw using pivots 9a and 9b as fulcrums.

Movement in the tracking direction is caused by the magnetic circuit 8&.

8d is the center of gravity G of all moving parts, as shown in FIG.

In other words, it is a rotational movement centered on the support point from the base 10. Even if a disturbance in the tracking direction such as high-speed access is applied, the force exerted by the disturbance on the movable part is all applied to the center of gravity 00, so the center of gravity is fixed to the base 10 by the support system, so it is fixed. If the movable part is strong enough, it will be equivalent to having no disturbance effect on the movable part.

In addition, in the focus direction, the center of gravity g1 of the lens holder 2 is driven in the focus direction by magnetic circuits sa and sb, and at the same time, the center of gravity 92 of the count weight 3 is driven in the opposite direction to the lens holder by magnetic circuits 8c and 8d. do. Overall, as shown in Figure 3 (B), the center of gravity of all movable parts G
This is a rotational motion centered on 0. Even if a vertical disturbance is applied, all the force applied to the movable part will be applied to the 60 points of the entire movable center of gravity. At this time, pivot sa from above and below on a perpendicular line L (center of gravity line) to the focus direction passing through 60 points of all movable centers of gravity.
, 9b, and pivots) 9a and 9b are fixed to the base 1o, so if the fixed part is strong enough, it is equivalent to having no influence of disturbance on the movable part.

In this embodiment, a return mechanism for returning to the position of the driving light in the focus and tracking directions is not shown for convenience, but it goes without saying that an elastic body such as a spring may be provided.

Effects of the Invention The present invention makes the center of gravity of the movable part in the focus direction and the tracking direction of the objective lens drive device coincide with the center of each driving force and the support point from the fixed part, so that the movement in the focus direction and the tracking direction is controlled by each movable part. By rotating around the center of gravity, that is, the support point, the fixed part of the support system supports against disturbances in the vertical direction (in the same direction as the focus direction) and in the lateral direction (in the same direction as the tracking direction). Therefore, even if the objective lens driving device is caused by external disturbances as described above at the movable center, the driving in the focus direction and tracking direction is not affected at all, so the design of the system on which the objective lens driving device is mounted can be easily designed. It can be accomplished.

[Brief explanation of drawings]

Fig. 1 (8) is a plan view of an objective lens drive device according to an embodiment of the present invention, Fig. 1 (B) is a front view of the same objective lens drive device, and Fig. 2 (5) is an enlarged plan view of the same main part. Fig. 42) is an enlarged vertical sectional view of the same main part, Fig. 3 (5) is a plan view of the main part showing the function of the objective lens, Fig. 3 (middle of Fig. 42) is a front view of the main part,
The figure is a perspective view showing a conventional objective lens drive device, and Fig. 5 (
5) is a plan view of the same main part, and FIG. 5 (to) is a front view of the same main part. 1-...Register/z, 2...Lens holder, 3
・・・・・・Kara/Twait, 4a, 4b・・・・
Pivot plate, 5a, 5b... Focusing coil, 6... Tracking coil, 7...
Pivot receiver, 8a-8d...magnetic circuit, 9a, 9b...
...Pivot, 10...Base. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig.
ｰr-Attack Figure 3

Claims (4)

[Claims] (1) The objective lens of a device that optically writes or reads information on a recording medium is set in a direction perpendicular to the surface of the recording medium, that is, in the optical axis direction (hereinafter referred to as the focus direction).
Radial direction perpendicular to the optical axis (hereinafter referred to as tracking direction)
an objective lens drive device that drives a first movable part including the objective lens and a lens holder; a first movable part at one end and a second movable part facing the first movable part at the other end; The two movable parts are each rotatably connected by a pivot or the like within a plane that includes an optical axis passing through the objective lens and a straight line connecting each center of gravity of the first and second movable parts, and perpendicular to the optical axis. two sufficiently rigid first supports parallel to a plane; a base provided parallel to the first supports; and the first and second supports.
The first support body is moved in the focusing direction and the tracking direction by a plurality of pivots or pins on a straight line passing through the center of gravity of all movable parts including the movable part and the first support body and parallel to the optical axis. a second support fixed to the base that rotatably supports the center of gravity of all the movable parts; and one or more supports that drive the center of gravity of the first and second movable parts in the focus direction. A magnetic circuit for focusing, and one or more magnetic circuits for tracking that drive the first and second movable parts in the tracking direction in a rotational motion about the center of gravity of all the movable parts. Characteristic objective lens drive device. (2) The two parallel first supports are positioned equidistantly across a plane that includes a straight line connecting each center of gravity of the first and second movable parts and is perpendicular to the optical axis. An objective lens driving device according to claim 1. (3) A plane that connects the first support body and the first and second movable parts and is perpendicular to a straight line that includes the optical axis and connects the centers of gravity of the first and second movable parts is the outer wall of the first movable part. and a straight line that is parallel to the optical axis and passes through the center of gravity of the second movable section, and is perpendicular to the straight line that connects the centers of gravity of the first and second movable sections. 3. The objective lens driving device according to claim 2, wherein the objective lens driving device is connected to each other on a straight line intersecting an outer wall of the objective lens driving device. (4) The objective lens driving device according to claim 2 or 3, characterized in that a focusing magnetic circuit is used in combination with a tracking magnetic circuit.