JPH01235041A - Optical head actuator - Google Patents

Abstract

PURPOSE:To improve the follow-up performance of the servo gain and light spots to the surface waving and the eccentricity of an information recording medium by using a permanent magnet to an objective lens holder. CONSTITUTION:An objective lens holder 2 is made of a magnet of a manganese aluminum alloy, etc., and at the same time magnetized with its cylindrical upper part turned to the polarity in the axial line direction of an optical axis. While the flinge part of the holder 2 is magnetized in the radius direction set around the optical axis for the focusing control purpose. Thus it is possible to improve the follow-up performance of the servo gain and light spots to the surface waving and the eccentricity of an information recording medium in both focusing and tracking directions.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an optical head of an optical recording/reproducing device that condenses a light beam emitted from a light source such as a semiconductor laser onto an information recording medium to record and reproduce information. This relates to an actuator for use.

2. Description of the Related Art A conventional actuator for an optical head has a structure as shown in FIG. 3, for example.

In other words, objective lens holder 2' that holds objective lens 1'
is provided rotatably around the support shaft 11' and slidably in the axial direction of the support shaft.

Further, the objective lens 1' is disposed at a position shifted by a predetermined distance from the objective lens holder 2' so as to have an optical axis substantially parallel to the supporting axis. Further, a focusing control coil 6' is provided on the outer periphery of the objective lens holder 2', and a tracking control coil 5' is provided on the outer periphery thereof. 6' and 6' are magnets 1 oa and 1 on both coils.
It is located in a magnetic field consisting of ob and bay 79'.

With the above configuration, the out-of-focus of the light spot with respect to the information recording medium surface and the track deviation of the light spot with respect to the track on the information recording medium surface are detected, and the objective lens 1' is adjusted according to the detected amount of defocus and track deviation. controlling the position.

Problems to be Solved by the Invention However, with such a structure, the objective lens 1'
, objective lens holder 2', bearing 3', balancer 4
′, damper holding pin 7′, focusing control coil 6′, and tracking control coil 6′ have low servo gain when moving in the focusing direction and the tracking direction, and the light spot is not directed to the information recording medium. There was a problem in that the performance of following surface runout and eccentricity was poor. This is due to the following reasons.

In other words, this is because the rigidity of the movable part composed of the above-mentioned parts is low, and the high-order resonance frequencies of the movable part in the focusing direction and the tracking direction are low.

Therefore, the present invention aims to increase the servo gain when the movable part moves in the focusing direction and the tracking direction, and improve the performance of making the optical spot follow the surface runout and eccentricity of the information recording medium.

Means for solving the problems and technical means of the present invention for solving the above problems are as follows:
The objective lens holder is made of a permanent magnet.

action The effect of this technical means is as follows.

That is, by forming the objective lens holder with a permanent magnet, the number of components of the movable part can be reduced, and the rigidity of the movable part can be made higher than in the conventional example by simplifying the shape of the movable part and making the material thereof.

As a result, the high-order resonance frequency of the movable part in the focusing and tracking directions increases, making it possible to increase the servo gain and improving the ability of the optical spot to follow the surface runout and eccentricity of the information recording medium. .

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

In FIG. 1, an objective lens 1 is attached to a cylindrical objective lens holder 2 having a flange at the bottom. 4 supported by and located diagonally to the base 6.
It is attached to the book pillar A with screws 7a to 7d.

The focusing control coil 3 is connected to the objective lens holder 2.
The tracking control coils 42L and 4b are attached to the base 5 so as to be located under the boxwood part.
The damper 6 is attached to the top of a pair of columns B located between the columns.

The details of the objective lens holder 2 are shown in FIG. That is, the objective lens holder 2 is formed using a magnet such as a manganese-aluminum alloy, and the objective lens holder 2
The upper part of the cylinder is magnetized with the polarity oriented in the axial direction of the optical axis for tracking control, and the collar part is magnetized in the radial direction about the optical axis for focusing control.

Next, the operation of the configuration of this embodiment will be explained.

The movable part consisting of the objective lens 1 and the objective lens holder 2 has a cylindrical shape with a flange and is made of a manganese-aluminum alloy, which dramatically improves the rigidity and makes it movable. The higher-order resonance frequency of the part increases.

As a result, the servo gains in the focusing direction and the tracking direction are increased, and the performance of making the optical spot follow the surface runout and eccentricity of the information recording medium can be improved.

Effects of the Invention In the present invention, the rigidity of the movable part is increased by forming the objective lens holder with a magnet, so the higher-order resonance frequency of the movable part increases, which reduces surface runout in the focusing and tracking directions.

It is possible to have highly accurate tracking performance for eccentricity.

Furthermore, since the higher-order resonance frequencies in the focusing direction and the tracking direction become higher, it is possible to widen the frequency band that can be tracked.

In addition, in the embodiment, the movable part includes a focusing control coil,
Since the tracking control coil is also used as the objective lens holder, the wiring from the coil will not be cut, and the number of parts can be reduced9, making the main body smaller and lighter.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an actuator for an optical head according to an embodiment of the present invention, FIG. 2 is a sectional view of the same embodiment, and FIG.
The figure is a perspective view of a conventional actuator for an optical head. 1...Objective lens, 2...Objective lens. Figure 3

Claims (1)

[Claims] An actuator for an optical head in which an objective lens holder that holds an objective lens and moves the objective lens in directions perpendicular and parallel to the optical axis of an optical system is formed of a permanent magnet.