JPS62102435A - Optical system driving device - Google Patents

Abstract

PURPOSE:To form a magnetic circuit in the vicinity of a bearing and to make an optical holding body smaller in size and weight by insuring the optical system holding body against a cylindrical shape and inserting the bearing of the optical holding body into a supporting axis firmly fixed on a base stand. CONSTITUTION:The bearing 10 is installed on the objective lens holding body 7 of an optical system driving device, and in the vicinity of the bearing 10 an objective lens 1 and a fixed pin 8 are fitted. Simultaneously a focus coil 6 is wound on the outer periphery of the bearing 10, and tracking coils 2a and 2b are arranged on the outer peripheral part of the holding body 7. A supporting axis 3 made of a ferromagnetic body is installed on the base stand 9, and permanent magnets 5a and 5b are fitted at a position facing the coils 2a and 2b on the outer periphery of the base stand 9, thereby forming a magnetic circuit. The bearing 10 of the holding body 7 is inserted into the supporting axis 3 of the holding stand 9 through a neutral point holding rubber 4. And the holding body 7 is not made in a cylindrical shape, and the optical system driving device is miniaturized in lightweight. Furthermore the following performance in focus and tracking operations can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical system drive device, and in particular to a support shaft fixed to a base and an optical system holder inserted into the support shaft via a bearing. The present invention relates to an optical system driving device having a focusing coil fixed to the optical system holder, and a magnetic circuit that forms a magnetic field entirely across the focusing coil.

[Conventional technology]

As a conventional optical system drive device, an objective lens drive device for an optical information recording/reproducing device will be described with reference to FIG.

FIG. 2 is a perspective view of a conventional objective lens driving device. In FIG. 2, the objective lens holder 28 is mounted via a bearing.
It is inserted into a support shaft 26 fixed to the base 21, and an Fj objective lens 23 and a lens 29 having approximately the same weight as this objective lens 23 are attached near the support shaft 26. . Furthermore, a neutral point holding member (not shown) is attached below this weight 929. A focusing coil 24 is wound around the outer periphery of the objective lens holder 28, and a tracking coil 25b and a tracking coil 25a (not shown) are disposed on the focusing coil 24.
(With respect to the support shaft 26, it is attached at a position opposite to the tracking coil 25b). Permanent magnets 27 a + 27 b forming opposing magnetic poles near the outer and inner peripheries of the objective lens holder 28 are fixed to the base 21 so as to face the focusing coil 24 , and are also used for tracking. Coil 25m
, 25b, permanent magnets 22m and 22b are attached near the outer periphery of the objective lens holder 28 so as to face the permanent magnets 22m and 25b.

Force, X coil 24 and tracking coil 2
The objective lens holder 28 is caused to slide up and down about the support shaft 26 by the electromagnetic force generated by the current flowing through the coils 5m and 25b and the magnetic field formed for each coil.
Rotated left and right.

[Problem that the invention seeks to solve]

However, in the objective lens driving device, since the focusing coil 24 is wound around the outer circumference of the objective lens holder 28, the moment of inertia becomes large, which becomes an obstacle to improving the tracking performance of the tracking control. Further, since the objective lens holder 28 itself generates heavy noise, it becomes an obstacle to improving the follow-up performance of focus control.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical system drive device that has good optical system tracking performance, is lightweight, and is compact.

[Means for solving problems]

In other words, the above problem is caused by the support shaft fixed to the base,
an optical system holder inserted into the support shaft of the lens via a bearing;
A focusing coil fixed to this optical system holder,
and a magnetic circuit that forms a magnetic field across the focusing coil. This problem is solved by the optical system driving device of the present invention, which has a 5r% characteristic by providing a circuit forming means.

[For production]

The optical system drive device of the present invention has a focusing coil wound in gold around a bearing, and a magnetic circuit forming means is provided in the vicinity of the front row bearing to face the focusing coil, and the magnetic field generated by the magnetic circuit and the focusing coil are connected to each other. Focus control is performed by vertically sliding the optical system holder using electromagnetic force generated by the flowing current. That is, since focus control is performed by electromagnetic force acting on a bearing, the optical system holder can be made compact in shape and light in weight.

Furthermore, if the support shaft is made of a ferromagnetic material, it is possible to provide a high magnetic flux density υ with respect to the focusing coil and to further increase the distribution electromagnetic force.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Note that an objective lens driving device of an optical information recording/reproducing device will be explained as an optical system driving device of the present invention.

FIG. 1 is a developed perspective view of an embodiment of the objective lens driving device of the present invention.

In FIG. 1, the objective lens holder 7 has a bearing 10, and a focusing coil 6 is wound around the outer circumference of the bearing 10. An objective lens 1 and a fixing pin 8 are attached near the bearing 10, and rectangular tracking coils 2m and 2b are attached to the outer periphery of the objective lens holder 7.
is installed. The objective lens holder 7 is inserted into the support shaft 3 fixed to the base 9 via the bearing 1°.

A cylindrical permanent magnet 5a is fixed around the support shaft 3 so as to be coaxial with the support shaft 3 as a magnetic circuit forming means, and when the bearing 10 is inserted into the support shaft 3, it is wound around the bearing 10. The focusing coil 6 thus formed faces the cylindrical permanent magnet 511. The objective lens holder 7 is slid in the vertical direction (B B' direction) about the support shaft 3 by the electromagnetic force generated by the current flowing through the focusing coil 6 and the magnetic field formed by the permanent magnet 5a. That is, focus control is performed.

Furthermore, if the support shaft 3 is made of a ferromagnetic material, the support shaft 3 becomes a magnetic pole facing the permanent magnet 5C, increasing the magnetic flux density and making it possible to obtain a larger electromagnetic force. Further, if the base 9 is a yoke, the loss of magnetic flux between the permanent magnet 5 and the support shaft 3 can be reduced.

As the magnetic circuit forming means, not only a permanent magnet but also a cylindrical yoke fixed on the permanent magnet may be opposed to the total focusing coil 6.

Also, the base 9 is equipped with a tracking coil of 2 m.

Permanent magnets 5a and 5b are fixed near the outer wall of the objective lens holder 7, opposite to the permanent magnets 2b. The current flowing through the tracking coils 2m, 2b and the permanent magnets 5m, 5
The p objective lens holder 7 is moved in the left-right direction (A
' A direction). That is, tracking control is performed.

The neutral point is maintained by a neutral point holding rubber 4 fixed to the base 9. The fixing pin 8 is inserted into the hole of the neutral point holding rubber 4, and the objective lens holder 7 can be rotated left and right and slid up and down within the holding range.

According to the above embodiment of the present invention, since there is no need to wind a focusing coil around the outer periphery, there is no need to make the objective lens holder 7 cylindrical, and the weight can be reduced, so that focus control can be easily followed. Since performance can be improved and the moment of inertia can be reduced, the follow-up performance of tracking control can also be improved at the same time. In addition, since the inner circumferential portion of the permanent magnet 511 faces the entire outer circumferential portion of the focusing coil, it contributes to the entire focus control of the focusing coil and can operate efficiently.

Furthermore, if the support shaft 3 is made of a ferromagnetic material, a high magnetic flux density can be achieved and focus pursuit performance can be further improved.

〔Effect of the invention〕

As described above in detail, according to the optical system drive device of the present invention, there is no need for the optical system holder to have a cylindrical shape or the like, and the optical system holder can be made co-impact and lightweight. As a result, the follow-up performance of the focus control and tracking control of the optical system can be completely improved. Furthermore, if the support shaft is made of a ferromagnetic material, it is possible to achieve a high magnetic flux density and further improve the pursuit performance of focus control.

[Brief explanation of drawings]

FIG. 1 is a developed perspective view of an embodiment of the objective lens driving device of the present invention. FIG. 2 is a perspective view of a conventional objective lens driving device. 1... Objective lens, 2m, 2b... Tracking coil, 3... Support shaft, 4... Neutral point holding rubber, 5
&. 5b, 5... Permanent magnet, 6... Focusing coil, 10... Bearing. Agent Patent Attorney Minoru Yamashita Children Figure 1 Figure 2

Claims (2)

[Claims] (1) A support shaft fixed to the base, an optical system holder inserted into this support shaft via a bearing, a focusing coil fixed to this optical system holder, and a coil that crosses this focusing coil. In the optical system drive device having a magnetic circuit for forming a magnetic field, the focusing coil is wound around the bearing, and a magnetic circuit forming means is provided in the vicinity of the bearing so as to face the focusing coil. An optical system drive device characterized by: (2) The optical system drive device according to claim 1, wherein the support shaft is made of a ferromagnetic material.