JPH01182939A - Actuator for optical head - Google Patents

Abstract

PURPOSE:To reduce the weight of a driven part as much as possible and to increase the accessing speed of an optical head by providing respective means to drive an optical lens in the both a focusing direction and a tracking direction. CONSTITUTION:An intermediate supporting body to have a balance weight 4, a lens supporting body 6 to carry on objective lens 7 and supported parallel- movably in a focusing direction to the intermediate supporting body, a means to support the intermediate supporting part tiltably on a center-of-gravity line parallel in the focusing direction, and the means to drive the lens supporting body 6 in the both focusing direction and a tracking direction are provided. Thus, an optical head is stabilized to an impact, and a settling time is shortened. Besides, since the weight of a movable part at a time when the objective lens 7 is moved in the focusing direction is reduced, a moving speed is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] <Industrial Application Field> The present invention relates to an actuator for driving an objective lens in an optical head used in an optical disk drive or the like in both focusing and tracking directions.

<Prior Art> Actuators for optical heads used in optical disk drives and the like include linear movement actuators in which an objective lens is supported movably in the focusing direction and the tracking direction by a leaf spring, etc.; −
A shaft sliding type actuator using a voice coil type linear motor as disclosed in Japanese Patent No. 271632 is generally used.

<Problems to be Solved by the Invention> However, in the conventional linear movement type actuator, the objective lens is supported on a cantilever, and the balance thereof is not taken into consideration. Therefore, for example, when moving the optical head in the radial direction (coarse feed) in an optical disk drive, the objective lens becomes unstable due to impact, and the stabilization time becomes longer. Access speeds tended to be slow.

Regarding the shaft sliding type actuator, one has been proposed in which a balance weight is provided on the side opposite to the objective lens via the sliding shaft, considering the stability against the above-mentioned impact.
For example, see Japanese Patent Application Laid-Open No. 60-125942), since the entire movable part is heavy, a large amount of force is required especially to drive the objective lens in the focusing direction, which may reduce the access speed or cause the lens to move. The magnetic circuit and the like that drive in the focusing direction sometimes become larger.

In addition, shaft sliding type actuators have problems with machining workability because the sliding contact part needs to be machined with high precision.
Furthermore, there is also the problem that the sliding contact portion is susceptible to changes in temperature and humidity, dirt, and the like.

A main object of the present invention is to provide an actuator for an optical head in which the part driven by the actuator is made as light as possible and the access speed of the optical head is improved.

[Structure of the Invention] <Means for Solving the Problems> According to the present invention, such an object is an actuator for an optical head for driving an objective lens in an optical head in both focusing and tracking directions,
an intermediate support having a balance weight; a lens support supporting the objective lens so as to be movable in a focusing direction with respect to the intermediate support; and a focusing direction of the lens support and the intermediate support. To provide an actuator for an optical head, comprising means for tiltably supporting the intermediate support on a center of gravity line parallel to the center of gravity, and means for driving the lens support in both focusing and tracking directions. This is achieved by

In this way, the optical head is stabilized against impact and the settling time is shortened. Furthermore, the moving speed of the objective lens in the focusing direction is increased because the weight of the movable part is reduced.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 show a first embodiment of an actuator according to the invention.

This actuator consists of fixed base 1 and fixed base 1.
An intermediate support body consisting of an arm 3 and a balance weight 4 supported by a hinge 2 so as to be tiltable in the tracking direction, and a link mechanism 5 parallel to the balance weight 4.
It has a lens support 6 supported via a lens support 6, a focusing drive coil 10 and a tracking drive coil 11 that are integrally fixed to the support, and a magnetic unit 12 that supplies magnetic flux to these coils. There is.

An objective lens 7 is supported on a lens support part 8 at the tip of the lens support body 6 .

The focusing drive coil 10 is wound around a pair of coil holding parts 9 each having a C-shaped cross section and formed at symmetrical positions on the lens support 6 around axes parallel to the optical axis. Further, two pairs of tracking drive coils 11 are attached to the outer surface of the focusing drive coil 10, one pair each.

The parallel link mechanism 5 includes hinges 17 and 18 that allow the base ends of the pair of parallel links 15 and 16 to be tilted in the focusing direction, that is, in the y direction shown in FIG. 2 with respect to the balance weight 4.
The free end is hinged to the lens support 6 via hinges 19 and 20 which can be tilted in the y direction as described above, and the lens support 6 is tilted in the focusing direction with respect to the balance weight 4. It is supported so that it can be moved in parallel.

The tracking hinge 2 is provided on the center of gravity of the movable portion including the lens support 6, the parallel link mechanism 5, the balance weight 4, and the arm 3, which is parallel to the focusing direction. Therefore, this movable part is balanced around the hinge 2, and the head is stabilized in the event of an impact when, for example, the actuator, ie, the optical head, is roughly fed in the radial direction of the optical disc, so the settling time is shortened. Access speed is improved. Moreover, by providing the hinge 2 on the center of gravity of the movable part, it is also possible to prevent an uneven load from being applied to the hinge 2.

Here, the hinges 17 to 2\, 0 in the parallel link mechanism 5 and the tracking hinge 2 are made of thin synthetic resin material, so that there is no play in the hinge parts, and A spring action is also obtained which maintains the lens support in a neutral position to a certain extent.

The magnetic unit 12 is connected to the coil 10 on the fixed base 1 side.
．． A pair of yokes 13 are provided at positions corresponding to the magnetic units 11 and have a yoke 13 having a C-shaped cross section and a permanent magnet 14 fixed inside the yoke. The coil 10.11 is fed into the gap 12a and penetrates the part of the coil 10.11 that protrudes into its interior. In particular, as best shown in FIG. 2, the coil 10
The outer side 10a of the coil 11 and one section 11a extending in the vertical direction of the coil 11 are placed within the parallel magnetic flux formed by the magnetic unit 12.

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

When both focusing drive coils 10 are energized, the outer sides 10a of the coils 10 are both driven in the same direction up and down, since the magnetic flux distributions co-supplied by both magnetic units 12 are symmetrical to each other. Then, the objective lens 7 is moved in parallel with the lens support 6 in the y direction, that is, in the focusing direction, by the parallel link mechanism 5. At this time, the parallel link machine′! Since the balance weight 4 and arm 3 on the base end side of a5 do not move, the portion that moves in the focusing direction is lighter than that of the conventional type.

Next, when the tracking drive coil 11 is energized, an effective force is generated only in the section 11a of the coil 11, so by appropriately selecting the direction of the current supplied to each coil 11, the hinge 2 can be used as a fulcrum. The balance weight 4 side and the lens support body 6 side rotate in opposite directions,
The objective lens 7 moves in the X direction shown in FIG. 2, that is, in the tracking direction.

FIG. 3 is a partial perspective view corresponding to FIG. 1 showing a second embodiment based on the present invention, and the same parts as in the first embodiment are denoted by the same reference numerals. Detailed explanation will be omitted.

In this embodiment, a leaf spring 22 is provided between the fixed base 1 and the arm 3 instead of providing the hinge 2 in the first embodiment. Further, instead of providing the parallel link mechanism 5 consisting of parallel links and hinges in the first embodiment, two parallel leaf springs 23 and 24 are provided. Therefore, compared to the first embodiment, a more reliable spring action for holding the objective lens 7 in the neutral position can be obtained. Other than that, the operation and effect of the second embodiment are the same as those of the first embodiment.

[Effects of the Invention] As described above, according to the present invention, by balancing the movable parts, the optical head is stabilized against impact, the settling time is shortened, and the objective lens is moved in the focusing direction. The moving speed is faster because the moving parts are lighter. Therefore, it is possible to increase the access speed, and in particular, it is possible to make the magnetic circuit for focusing as small and lightweight as possible. From the above, the effect of improving actuator performance is extremely large.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing a first embodiment of an actuator for an optical head according to the present invention. FIG. 2 is a perspective view of the embodiment shown in FIG. 1.゛Third
The figure shows the second actuator for an optical head based on the present invention.
FIG. 2 is a partial perspective view similar to FIG. 1 showing an embodiment of the invention. 1...Fixed base 2...Hinge 3...Arm 4...Balance weight 5...Parallel link mechanism 6...Lens support 7...Objective lens
8...Lens support part 9...Coil holding part 10...Focusing drive coil 10a...Side 11...Tracking drive coil

Claims (1)

[Scope of Claims] An actuator for an optical head for driving an objective lens in an optical head in both focusing and tracking directions, comprising: an intermediate support having a balance weight; a head support supported to be movable parallel to the focusing direction relative to the body; and means for tiltably supporting the intermediate support on a center of gravity line parallel to the focusing direction of the lens support and the intermediate support. An actuator for an optical head, comprising: means for driving the lens support in both focusing and tracking directions.