JPS6251039A - Driving device for optical system - Google Patents

Abstract

PURPOSE:To hold cavity between a tracking coil and a magnetic body member at a regulated level and to prevent magnetic flux form changing by forming a plane facing with the tracking coil of the magnetic body member faced with the tracking coil so as to correspond to the rotating radius of the tracking coil. CONSTITUTION:An opposite plane 15a to the tracking coil 5 of a yoke 15 of recessed shape is formed so as to correspond to the rotating radius of the tracking coil 5, enabling the cavity between the tracking coil 5 and the yoke 15 to be held constantly at a regulated level even in the turning of an optical system holding body 1 (coil 5). Thereby, a tracking control in an optical system can be performed with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical system drive device, and particularly to an optical disk device,
The present invention relates to an optical system drive device that focuses a light beam onto a recording medium in an optical information storage device such as a magneto-optical disk device or a digital audio device.

(Prior Art) As a conventional optical system driving device, for example, an optical system driving device for an optical disk device, an optical system driving device having a structure shown in FIG. 2 is known. That is, the disc-shaped optical system holder 1 has:
An objective lens 2 and a balancer 3 are installed in a straight line as an optical system around the bearing hole 1&. 4 is a focusing coil arranged on the outer peripheral surface of the optical system holder l, and 5 is a tracking coil arranged opposite to the outer peripheral surface in the same direction as the objective lens 2, the bearing hole 1m, and the balancer 3. It is. Reference numeral 6 denotes a base, and on the base 6 there is a support, a shaft 7 as the center, a permanent magnet 8 and yokes 9, 10 as magnetic members for focusing, and a permanent magnet 11 as a magnetic member for tracking. The yokes 12 are arranged opposite to each other. Then, the support shaft 7 of the base 6 is passed through the bearing hole 1a of the optical system holder 1, and the support shaft 7 is rotatably rotated.
Moreover, it is supported slidably along the support shaft 7.

In the optical system drive device configured in this way, first,
The driving of the objective lens 2 in the optical axis direction, that is, the focusing control, is composed of a coil 4 disposed on the outer peripheral surface of the optical system holder 1, a permanent magnet 8 and yokes 9, 10 disposed opposite to the base 6. This is done using a magnetic circuit. The optical system holder 1 can be slid in the direction of the support shaft 7 (in the direction of the optical axis of the objective lens 2) by the driving force of the magnetic circuit, thereby controlling the focusing of the objective lens 2. Next, objective lens 2
The driving in the direction perpendicular to the optical axis of the optical system, that is, tracking control, is composed of a coil 5 facing the outer peripheral surface of the optical system holder 1, and a permanent magnet 11 and a yoke 12 facing the base 6. This is done by a magnetic circuit. Furthermore, the optical system holder 1 can be rotated about the support shaft 7 by the magnetic circuit, and the tracking control of the objective lens 2 can be performed.

(Problems to be Solved by the Invention) However, as shown in FIG. is formed into a circular arc shape in accordance with the shape of the outer peripheral surface of the optical system holder 1. Since the surface 11& of the tracking permanent magnet 11 disposed opposite to the base 6 facing the tracking coil 5 is a flat surface, when the optical system holder 1 rotates, the coil 5 and the permanent magnet 11 The difference occurs in the space between. When the knob and coil 5 are in a resting state (solid line),
If the air gap between the coil 5 and the permanent magnet 11 when it rotates (dotted line) is Hl r Hl, then H, (H,
become. Therefore, depending on the position of the coil 5, even if a constant current is passed through the coil 5, the magnetic field changes, causing a difference in the generated driving force.
This has the disadvantage that tracking control of the objective lens 2 is difficult and errors are likely to occur.

The present invention has been made to solve these conventional problems, and it is an object of the present invention to provide an optical system driving device that can perform tracking control of an optical system with high precision.

(Means for Solving the Problems) As a means for solving the above problems, the present invention provides tracking and focusing coils disposed on the outer peripheral surface of a movably supported optical system holder. In an optical system drive device that is disposed in a magnetic circuit constituted by a magnetic member and drives the optical system holder by energizing the coil, the magnetic member for tracking faces the tracking coil. The gist is that the surface facing the coil is formed to correspond to the radius of rotation of the tracking coil.

(Example) Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 is a perspective view showing essential parts of an optical system driving device showing an embodiment of the present invention. Incidentally, the same members as those in the conventional example are given the same reference numerals and their explanations will be omitted.

In this figure, reference numeral 1 denotes a disc-shaped optical system holder, and as in the conventional example, the optical system holder 1 has an objective lens 2, an i+, a lancer 3, and are installed in a straight line. 4 is a focusing coil, and 5 is a tracking coil. A magnetic circuit is constructed by fixing permanent magnets 14 and concave yokes 15 to both sides of an inwardly inclined yoke 13 as a magnetic member so as to face the tracking coil 5 on the base 6. There is. Here, the concave yoke 1
5, a surface 15m facing the tracking coil 5;
is formed to correspond to the rotation radius of the tracking coil 5, and is formed to correspond to the rotation radius of the tracking coil 5, and the optical system holder 1 (coil 5)
Even if the tracking coil 5 rotates, the gap between the tracking coil 5 and the yoke 15 can be kept constant. Although not shown in the figure, a yoke 13 is similarly formed on the base 6 facing the other tracking coil 5.
．． 15 and a permanent magnet 14 are arranged, and furthermore, K, a permanent magnet 8, and a yoke 9.
Magnetic circuits consisting of 10 are arranged oppositely on the base 6.

Further, although this embodiment is an example in which the optical system drive device of the present invention is applied to an optical system drive device of an optical disk device, the optical system drive device according to the present invention can also be applied to an optical information storage device such as a magneto-optical disk device or a digital audio device. This is clear.Furthermore, in the above-mentioned embodiment, the case where only the objective lens is driven has been explained, but the present invention is not limited to this, but can also be applied to the case where the entire optical system including the light source etc. is driven. is possible.

(Effects of the Invention) As explained above, in the optical system drive device according to the present invention, the surface of the magnetic member facing the tracking coil that faces the tracking coil corresponds to the radius of rotation of the tracking coil. By forming it in such a manner, the gap between the tracking coil and the magnetic member can be maintained constant, and the magnetic field can be prevented from changing. Therefore, the driving force for rotating the optical system holder can be kept constant, and tracking control can be performed with high precision, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing main parts of an optical system driving device according to the present invention, FIG. 2 is a schematic diagram showing a conventional optical system driving device, and FIG. 3 is a main part of the optical system driving device. FIG. 1... Optical system holder, 2... Objective lens, 4...
Focusing coil, 5... Tracking coil, 6... Base, 13.15... Yoke, 14 River permanent magnet, tSa... surface.

Claims (1)

[Claims] A tracking and focusing coil disposed on the outer circumferential surface of a movably supported optical system holder is arranged in a magnetic circuit made of a magnetic member, and the optical system is held by energizing the coil. In an optical system drive device for driving a body, a surface of the magnetic member facing the tracking coil that faces the tracking coil is formed to correspond to a radius of rotation of the tracking coil. Characteristic optical system drive device.