JPS60182524A - Objective lens actuator - Google Patents

Abstract

PURPOSE:To decrease the retrieving time and to improve the record/reproduction accuracy by providing a control coil which shifts a lens in the direction opposite to the shift direction of an objective lens and preventing the vibration of the lens. CONSTITUTION:A tracking coil control coil 17 which is shifted to the right from the center of an objective lens 5 is provided to a yoke 15. While a coil 18 of the left side is provided to a yoke 16. Therefore a lens 5 is shifted toward C when coils 17 and 18 are energized toward arrow heads A and B and vice versa with energization of opposite directions. Thus the tracking is carried out. If the lens 5 is turned to the right side, the electromagnetic force is large in the direction F of the coil 17 and small in the direction G of the coil 18 respectively. Thus the lens 5 tries to return to its neutral point and prevents the vibration due to the force of inertia of the lens 5. This decreases the retrieving time after the lens vibration is stopped and improves the record/reproduction accuracy.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an objective lens actuator for an optical disk device;
In particular, it relates to a tracking control mechanism for an objective lens.

[Prior art]

FIG. 1 is a simplified diagram showing the configuration of an optical disk device. In the figure, 1 is an optical head containing a semiconductor laser light source, various lenses, etc., 2 is an objective lens actuator consisting of a drive mechanism for the objective lens provided in the optical head 1, and 3 is a disk with an information trunk on its surface. . The optical head 1 is moved in the radial direction of the disk 3 by a motor (not shown) so that the objective lens of an objective lens actuator 2 faces a desired information track on the disk 3. The objective lens actuator 2 drives, within its movable range, an objective lens that condenses the light from the semiconductor laser to a diameter of approximately 1 μm, and irradiates the information 1-rank with the light from the semiconductor laser. As a result, information is recorded and reproduced. The objective lens actuator 2 is conventionally constructed as shown in FIG. In the figure, 3 is a housing, 4 is a hollow cylinder forming a path for semiconductor laser light, and 5 is an objective lens. The objective lens 5 is loaded into a lens barrel 6 and held by a leaf spring 7 whose one end is fixed to the lower part of the hollow cylinder 4 so as to have a constant distance from the inner wall of the hollow cylinder 4.

Furthermore, the hollow cylinder 4 is held by a temporary spring 8 fixed to the housing 3. In the gap surrounded by the housing 3, the hollow cylinder 4, and the plate spring 8, there are a magnet 9 and a yoke lO fixed to the housing 3, and a coil 11 fixed to the hollow cylinder 4.
is provided. By energizing the coil 11, the hollow cylinder 4 held by the plate springs 8 moves in its axial direction due to the action of electromagnetic force, and the objective lens 5 can be moved in the direction of the optical axis of the semiconductor laser. Using this mechanism, focus control can be performed to focus the objective lens 5 on the disk 3. On the other hand, rod-shaped magnets 12 with the same polarity are arranged on both sides facing the temporary spring 7 in correspondence with the objective lens 5 held by the leaf spring 7.
A rod-shaped yoke 14 is provided around which a coil 13 is wound to bridge mutually identical poles. When the coils 13 are energized in the directions of arrows A and B, the objective lens 5 acts on the lens barrel 6 (moves in the direction of arrow C due to electromagnetic force). Also, when the coils 13 are energized in the opposite direction, they can be moved in the opposite direction. By using this mechanism to move the objective lens 5 in a direction perpendicular to the optical axis of the semiconductor laser and in the radial direction of the disk 3, tracking control for searching the information trunk on the disk 3 can be performed.However, the above-mentioned tracking Only information trunks located within the movable range of the objective lens 5 can be searched by control, and if the desired information track is not within the movable range, the optical head 1 itself must be moved before tracking control is performed. Become.

This movement of the optical head 1 is performed at high speed in order to shorten the search time.

However, according to the conventional objective lens actuator 2 configured as described above, when the optical head 1 stops after moving at high speed, an inertial force acts on the objective lens 5 and the lens barrel 6. When it stops, the objective lens 5 vibrates due to the inertial force and the elasticity of the spring 7.The vibration does not stop immediately, so tracking control cannot be performed for a while, the search time becomes longer, and recording and This has the disadvantage that the accuracy of reproduction is reduced.

[Summary of the invention]

The present invention eliminates the above-mentioned drawbacks by providing coils for tracking control that are displaced in directions opposite to each other with respect to the direction of movement of the objective lens. This will be explained in detail below using examples.

[Embodiments of the invention]

FIG. 3 is a simplified configuration diagram showing one embodiment of a tracking control mechanism for an objective lens actuator according to the present invention.

Components that are the same as those in FIG. 2 are designated by the same reference numerals. In the figure, 15 is a yoke that bridges the N poles of the magnets 12 and 12, and 16 is a yoke that bridges the S poles thereof. York 15
A coil 17 is provided on the yoke 16, displaced to the right in the figure from the center, which is the neutral position of the objective lens, and a coil 18 is provided on the yoke 16, displaced from the center to the left in the figure. When the coils 17 and 18 are energized in the directions of arrows A and B, the objective lens 5 moves in the direction of arrow C due to electromagnetic force.
Furthermore, when the current is applied in the opposite direction, it can be moved in the opposite direction to the above, and normal tracking control can be performed. Next, the operation of this mechanism when tracking control is not applied, that is, when the optical head 1 is moving, will be explained with reference to FIG.

The coils 17 and 18 are oriented so that the electromagnetic force acts in the direction opposite to the displacement of the coil, that is, in the direction of arrows F and G.

Electrify in the E direction. Note that the lengths of arrows F and G represent the magnitude of the action of electromagnetic force. Figure 4 (at is when the objective lens 5 is located at the neutral point, and the electromagnetic force of the coils 17 and 18 acts on the objective lens 5 with the same magnitude and in the opposite direction, maintaining the objective lens 5 at the neutral point. Fig. 4 fb) shows a case where the objective lens 5 moves to the right in the figure due to inertia force and stops.The electromagnetic force acting on the objective lens 5 is increased in the direction of arrow F due to the coil 17, and The direction of arrow G becomes smaller. Therefore, a force acts on the objective lens 5 to return it to the neutral point. Figure 4 (C1 shows the case where the objective lens 5 moves to the left in the figure and stops, and a force that tries to return to the neutral point acts as in the above case.The above action acts more strongly as the displacement of the objective lens 5 becomes larger, so it is due to inertial force. It works to reduce the displacement of the objective lens 5 and the amplitude of the vibration caused by the elasticity of the plate springs 7, and the vibration can be stopped quickly.In this way, the objective lens 5 comes to rest at the neutral point in a short time. It is possible to quickly move on to the next trunking control.

〔Effect of the invention〕

As explained above, according to the objective lens actuator according to the present invention, by providing tracking control coils that are displaced in directions opposite to each other with respect to the moving direction of the objective lens, trunking can be controlled in a short time after stopping the optical head. This has the effect of shortening the search time and improving the accuracy of recording and playback.

[Brief explanation of the drawing]

Figure 1 is a simplified configuration diagram showing an example of an optical disk device;
The figure is a simplified configuration diagram showing an example of a conventional objective lens actuator, and FIGS. 3 and 4 are simplified configuration diagrams showing an example of a tracking control mechanism for an objective lens actuator according to the present invention. ■...Optical head, 2...Objective lens actuator, 3...D, frame, 5...Objective lens, 6...
Lens barrel, 12...Magnet, 15°16...Yoke, 17.18...Coil. Note that the same reference numerals are used for the middle part of the figure or corresponding parts.

Claims (1)

[Claims] A tracking control mechanism includes an objective lens elastically supported to be movable in the radial direction of an optical disk, and a coil opposing the objective lens, and the position of the objective lens can be adjusted by the electromagnetic force of the coil. In the objective lens actuator equipped with the above-mentioned objective lens actuator, both of the coils are displaced in the movement direction of the objective lens and in mutually opposite directions, centering on the neutral position of the objective lens, and the objective lens is moved from each coil toward the neutral position. An objective lens actuator characterized in that it generates an electromagnetic force that exerts force on the objective lens, and prevents vibrations occurring in the objective lens.