JPH05144040A - Objective lens drive device - Google Patents

Abstract

PURPOSE:To realize a high speed access by supporting the actuator of the objective lens movably in a tracking direction with a support means and correcting the positional shift of the actuator. CONSTITUTION:A required drive quantity is generated by the workings of a DC current impresses to coils 4 and 4 and the magnetic flux of a magnetic circuit and when an actuator 1 is moved along yokes 8 and 8, the movement toward the tracking direction is allowed in the condition that parallel leaf springs are 2A and 2B are deflected and the actuator 1 is supported. In this case, the actuator 1 is given an elastic force so as to draw the circular locus of a movement by the deflections of the leaf springs 2A and 2B of a parallel linkage mechanism, a positional shift is generated in the right and left directions of an optical axis, but the optical axis is parallely moved right and left as much as the positional shift by the correction optical system and thus, an optical spot is correctly formed by the laser light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an objective lens driving device in a magneto-optical or optical information recording device.

[0002]

2. Description of the Related Art Conventionally, the above-described objective lens driving device has an objective lens for a light spot when a disc-shaped recording medium is irradiated with laser light to optically record information. The actuator of the objective lens is held along the guide rail so that the tracking control is performed in the radial direction of the recording medium, and the movement can be controlled in the seek direction and the tracking direction by an appropriate driving force.

Here, in order to speed up the information recording apparatus, it is necessary to reduce the weight of the movable portion of the optical head.
As much as possible, the actuator side optical system element of the objective lens, the movable part of the tracking and focusing control system,
It has been reduced and simplified. In order to further reduce the weight, a new configuration has been proposed in which a fine tracking function element is not mounted on the movable part side by using a galvano mirror, as is known in academic conferences and the like.

[0004]

However, even in the information recording apparatus employing the galvano mirror as described above, the objective lens driving device includes an actuator for driving the objective lens in the focus direction and a seek direction for the actuator. It required a carriage to move to, and the weight saving was not achieved yet.

Therefore, the present inventor first abolished the carriage and supported the actuator by a parallel link mechanism composed of a leaf spring, thereby permitting movement of the actuator in the entire movement region in the seek direction. Proposes a composition. However, in this method, because of the structural reason, the movement locus becomes an arc shape, so that the laser light may deviate from the optical axis of the objective lens, and the light intensity on the recording surface of the recording medium may become insufficient.

[0006]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned circumstances. It is possible to achieve high-speed access, is sufficiently lightweight, and even if the actuator is displaced, it can be moved in a non-movable part. It is an object of the present invention to provide an objective lens driving device which can be corrected by an optical correction means.

[0007]

Therefore, according to the present invention,
In an objective lens driving device configured to perform tracking control of an objective lens for a light spot in the radial direction of the recording medium when optically recording information by irradiating a disc-shaped recording medium with laser light. The actuator of the objective lens includes a tracking coil for moving in the tracking direction, and a focusing coil for focusing the objective lens on a recording surface of the recording medium, and an optical axis of the objective lens. Equipped with a mirror for refracting the laser beam toward and the optical path of the laser beam, a position sensor is arranged so as to surround the mirror at the entrance of the optical path, and the laser beam is parallelized based on the output of the position sensor. Equipped with a moving correction optical system.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. In the figure, reference numeral 1 is an objective lens 7 and a laser beam provided from a light source (for example, a semiconductor laser) of a fixed optical system (indicated by reference numeral 15 in the figure) is directed to the objective lens 7 and reflected. An actuator having a mirror 16 for returning light. Tracking coils 4 and 4 are attached to the left and right of the actuator 1,
The coils 4 and 4 surround the inner yokes 8 and 8 extending parallel to the tracking direction (seek direction). A focusing coil 5 is provided on each side of the coil 4.
Is attached. Outer yokes 10 and 10 parallel to the inner yokes 8 and 8 are connected at both ends thereof, and magnets 11 and 11 are attached to the outer yokes 10 and 10 so as to face the inner yokes. A required magnetic circuit is configured so that the magnetic flux, which is mounted, acts perpendicularly to the coils 4 and 4.

The actuator 1 is supported by a parallel link mechanism 2 arranged on one side of its moving direction. The parallel link mechanism connects the punched leaf springs 2A, 2A and 2B, 2B and the base ends of the leaf springs 2A, 2A and 2B, 2B extending in the moving direction, that is, the direction orthogonal to the longitudinal direction of the inner yoke 8. It is composed of a supporting member 3 for supporting, and the tip ends thereof are connected and fixed to the upper and lower surfaces of the actuator 1. The support member 3 is fixed to a chassis (not shown) of the device or the like.

The optical axis of the laser light from the fixed optical system is
The mirror 16 is parallel to the inner and outer yokes.
It is bent at a right angle through and is directed in the direction of the objective lens 7 (that is, in the direction perpendicular to the disk surface of the recording medium). Therefore, the actuator 1 is formed with optical paths 1A and 1B for guiding the laser light.

The output light from the fixed optical system is located on the optical path directed to the mirror 16, and a correction optical system is provided there. In this embodiment, the correction optical system is a yoke 1 that is arranged in parallel on the left and right sides of the optical axis.
3 and 13, a parallel plate glass 11 having both end faces parallel to each other, which intersects the optical axis, and coils 12 and 12 attached to the parallel plate glass 11 so as to surround the inner yoke portions of the yokes 13 and 13. The magnets 14 and 14 are arranged along the yokes 13 and 13 so that the magnetic flux crosses the coils 12 and 12. The parallel flat plate glass 11 is preferably supported so as to be rotatable around a support shaft perpendicular to the optical axis. Then, as shown in FIG. 2, the parallel plate glass 11 is tilted left and right with respect to the optical axis by the value of the current flowing through the coils 12 and 12, and the central optical axis of the laser beam directed to the actuator 1 is parallel left and right. You can slide to.

On the front surface of the actuator 1 facing the fixed optical system, the optical path 1A is surrounded by 4
The annular position sensor 6 having the divided light receiving portions 6a to 6d is attached, and the peripheral portion (circular 17 in this embodiment) of the light flux of the laser light is projected. For this reason, when the actuator 1 is laterally displaced with respect to the optical axis, a difference in the amount of received light occurs between the light receiving portions 6c and 6d,
The value of the generated electric signal is different. These electric signals are compared in the comparison operation circuit shown in FIG. That is, in the above-mentioned comparison operation circuit, the output signal of the light receiving portion 6c is output by the amplifier 21, and the output signal of the light receiving portion 6d is output by the amplifier 2.
It is amplified by 2 and is applied to the comparator 23 to obtain the difference signal. Then, the drive signal obtained from this signal is fed back to the correction optical system. It should be noted that even if the actuator 1 is vertically displaced, the light receiving portions 6a, 6
It is checked by the difference in the amount of received light of b.

As is apparent from the figure, the DC current applied to the coils 4 and 4 and the magnetic flux of the magnetic circuit generate a required driving force, and the required driving force is generated along the inner yokes 8 and 8. When the actuator 1 is moved, the parallel leaf springs 2A and 2B are bent to allow movement in the tracking direction while supporting the actuator 1. In this case, the actuator 1 receives an elastic force so as to draw an arc-shaped motion locus due to the bending of the leaf springs 2A and 2B of the parallel link mechanism and causes a positional shift in the left-right direction of the optical axis. The correction optical system functions as described above, and the optical axis is moved in parallel in the left-right direction by an amount commensurate with the positional deviation.
A light spot can be correctly formed on the disk surface of the recording medium through the center of the.

[0014]

As described above, the present invention is constructed such that the actuator of the objective lens is supported by an appropriate supporting means so as to be movable in the tracking direction. Even if the optical axis of the objective lens may shift, the correction optical system is used to correct the positional deviation of the actuator brought by the supporting means, so that the conventional carriage is not necessary and the conventional apparatus can be used. Compared with the weight saving, it is possible to realize high-speed access without lowering the accuracy of recording and reproducing.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part showing an embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a vertical sectional front view of the same.

FIG. 4 is a front view of a sensor for detecting a displacement of an actuator according to the present invention.

FIG. 5 is a comparison circuit diagram of a signal from the sensor.

[Explanation of symbols]

 1 Actuator 1A, 1B Optical path 2A, 2B Leaf spring 3 Support member 4, 5 Coil 6 Sensor 7 Objective lens 8 Inner yoke 9 Magnet 10 Outer yoke 11 Parallel plate glass 12 Coil 13 York 14 Magnet 15 Fixed optical system

Claims (2)

[Claims] 1. When a disc-shaped recording medium is irradiated with laser light to optically record information, an objective lens for a light spot is tracking-controlled in a radial direction of the recording medium. In the objective lens driving device, the actuator of the objective lens includes a tracking coil for moving in the tracking direction, and a focusing coil for focusing the objective lens on the recording surface of the recording medium. A mirror for refracting laser light toward the optical axis of the objective lens and an optical path of the laser light are provided, and a position sensor is disposed so as to surround the mirror at the entrance of the optical path. The objective lens driving device is equipped with a correction optical system for parallelly moving the laser light. 2. The position sensor is composed of a light receiving element divided into four regions of up, down, left and right, and for detecting up and down displacement and left and right displacement with respect to the optical axis of the laser light. 2. The apparatus according to claim 1, further comprising a comparison circuit for comparing outputs of the respective light receiving elements, and the output is used to drive the correction optical system to translate the optical axis of the laser light in parallel. Objective lens driving device.