JPS62245534A - Optical system driver - Google Patents

Abstract

PURPOSE:To attain the focusing control with high accuracy by constituting a support of two parallel plates provided in optical axis direction made of a rigid body, and of a rubber elastic body gripping both ends of the plates. CONSTITUTION:In driving an objective lens 12 in the focus direction A-A', an external force is caused in the focus direction A-A' by the magnetic interaction between the magnetic field caused by supplying a current to focusing coils 18a, 18b and the magnetic field caused by magnets 34a, 34b to the lens holder 10 and the external force is received by a support S. Since the support S consists of upper/lower plates 32a, 32b and upper/lower rubber members 33a, 33b, 33c, 33d having the elasticity gripping the plates 32a, 32b respectively, a parallel link mechanism is constituted of lens holder 10 - plates 33a, 32a, 33c, - bearing 16 - plates 33b, 32b, 33b and the lens holder 10 is moved in the focus direction A-A' while keeping in parallel with the bearing 16.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical system drive device in an optical information recording/reproducing device such as an optical disk device.

(Prior art and its problems) Generally, an optical disk in an optical information recording/reproducing device such as an optical disk device has a width of about 1 to 2 μm and a length of 1 to 3 μm.
An information trunk consisting of a row of about m information pits is formed in a spiral shape or a concentric circle shape.

- To reproduce information from such an optical disk, first a laser beam is focused into a minute spot using an optical system such as an objective lens, and while the optical disk is rotated, the focused laser beam is used to reproduce the information on the optical disk. The track is irradiated, and the information focus row is scanned by this beam spot. Next, a photodetector detects changes in the intensity of reflected or transmitted light irradiated onto the optical disk surface to reproduce a signal.

As mentioned above, the information focus of an optical disc is extremely small.
In order to accurately reproduce information, it is important that the light beam spot always accurately follow the information track (tracking) and always accurately focus on the information track (focusing). For this reason, optical disk devices generally use tracking control to correct positional deviations of the light beam spot caused by eccentricity of the optical disk, and focusing control to correct defocusing caused by warping of the optical disk. It is being done. A method for realizing such tracking control and focusing control is to hold the objective lens with a support having elasticity, and to eliminate the deviation based on the detection signal of the positional deviation and defocusing of the light beam spot. A method is generally used in which the objective lens is driven in this manner.

FIG. 2 shows a conventional objective lens driving device using the method described in 1.

In the same figure, 10 is a lens holder for holding the objective lens 12, and this lens holder IO has a pair of metal leaf springs 14a, 14 facing each other while maintaining a horizontal plane.
It is supported by a bearing 16 via b. Lens holder 1
On the side of 0, a pair of focusing coils 18a, 1
8b and tracking coils 20a and 20b are arranged to face each other.

On the other hand, the bearing 1 [; is provided with a rotating shaft 22 whose lower end is fixed to a base 24 in the same direction as the optical axis of the objective lens 12.
4a, 14b and the lens holder 10 are integrated into the base 2.
4, it is possible to swing in the horizontal direction. Further, 26 is a neutral position holder, which allows the objective lens 12 to maintain a neutral position with respect to the base 24.

In the conventional objective lens drive device configured in this way, the coils 18a, 18b, and 20a.

When a current is applied to 20b, the coils 18a, 18b.

Due to the interaction due to electromagnetic force generated by a magnetic circuit (not shown) consisting of a magnet and a yoke provided at opposing positions of the plates 20a and 20b, the plate springs 14a and 14b are deformed in the optical axis direction, and the optical axis is Focusing control and tracking control of the objective lens 12 attached to the lens holder 10 can be performed by swinging around the rotation axis 22 in a direction perpendicular to the above direction.

However, in such a conventional objective lens driving device, the lens holder 10 and the leaf springs 14a, 14b are
Since the main resonant frequency and higher-order resonant frequencies exist in the holding section H, the coils 18a, 18b, 20a
, 20b to perform focusing control, resonance occurs in agreement with the resonant frequency of the holding portion H, making it difficult to perform highly accurate control. In addition, since the leaf springs 14a and 14b are made of metal, they have a small damping rate, and if the frequency of the coil drive current matches the resonant frequency of the holding part H and causes resonance, the resonance will increase, making it difficult to perform high-precision focusing control. It was becoming more difficult to do so.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and is designed to reduce the resonance of the objective lens holding portion caused by the frequency of the coil drive current, which is seen in conventional objective lens drive devices. An object of the present invention is to provide an optical system drive device that can perform highly accurate focusing control.

(Means for Solving the Problems) According to the present invention, the above-mentioned objects include an optical system holder having an optical system, and an optical system holder fixed on a base and provided parallel to the optical axis of the optical system. In the optical system drive device, the optical system drive device includes a bearing mounted to be swingable around a rotation axis, and a support part for supporting the optical system holder on the bearing, wherein the support part is made of a rigid body and extends in the optical axis direction. This is achieved by an optical system driving device characterized by comprising two mutually parallel plates arranged side by side, and a rubber-like elastic body gripping both ends of each plate.

(Example) Hereinafter, details of the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the optical system driving device of the present invention, and members having the same functions as in FIGS. 2 and 3 are given the same reference numerals.

In the figure, reference numeral 24 denotes a base, and a rotating shaft 22 is attached to the base 24 in a direction perpendicular to the base surface, that is, in the focus direction A-A'. It is attached so that it can swing in a direction perpendicular to the direction AA', that is, in the tracking direction BB'. A support part S is provided for the (ijl1 song) of the bearing 16, and the bearing 1
On the opposite side of 6 is a lens holder 1 on which an objective lens 12 is attached so that the optical axis is in the focus direction 1i188'.
0 is attached.

The support part S includes two rigid plates, an upper plate 32a and a lower plate 321), and each of the two plates 32a and 32b*:1. 1. It consists of upper rubber parts 4433a, 33c and lower rubber members 33b, 33d, which are molded from Y-shaped rubber elastic bodies, and the two plates are perpendicular to the optical axis of the objective lens 12. They are arranged so that they face each other while maintaining their faces.

On the other hand, two focusing coils 18a are provided on the side surface of the lens holder 10 at a position opposite to the support portion S.

18b and two trunking coils 20a.

20b are arranged at symmetrical positions.

Further, 26 is a neutral position holder, which allows the objective lens 12 to maintain a neutral position with respect to the base 24.

Next, the operation of this embodiment will be explained with reference to FIGS. 1, 5, 6, and 7. FIG. 5(a) shows the coils 18a, 18b, 20a, 20b.
FIG.
FIG. 5 (bl is a side view thereof. FIG. 6 is a diagram for explaining the relationship of the magnetic circuit to the coil.

FIG. 7(al) is a side view of the device in this embodiment, and FIG. 7(b) is a side view when the support portion of the device is deformed by receiving external force.

In FIG. 5, the magnetic circuit M consists of a yoke 36 and magnets 34a, 34b, 34c, and 34d provided at symmetrical positions on the yoke 36 in the left, right, top, and bottom, respectively.
The coil 18 a is located at the position of these magnets shown by the dashed line in the figure.
, 18b, 20a, and 20b are arranged.

First, when driving the objective lens 12 in the tracking direction BB', the trunking coil 2
A magnetic field generated by applying a current to 0a, 20b in any suitable direction shown by arrow C and magnets 34a, 34
An external force is generated on the lens holder 10 in the tracking direction BB' due to the magnetic interaction with the magnetic field generated by b. This external force causes the lens holder 0 to swing around the rotation axis 22, allowing tracking control of the objective lens 12.

Next, when driving the objective lens 12 in the focusing direction A-A', the current is generated by applying a current to the focusing coils 18a and 18b in any suitable direction shown by the arrow B, as shown in FIG. Magnetic field and magnet 34
Due to the magnetic interaction with the magnetic field generated by a and 34b, an external force is generated on the lens holder 10 in the focus direction AA', and at the same time, the support portion S receives this external force. In this case, as shown in FIG. 7(t)1, the support portion S consists of upper and lower plates 32a, 32b made of a rigid body and these plates 32a.

Since it is composed of upper and lower rubber members 33a, 33b, 33c, and 33d each having elasticity to grip the lens holder row upper rubber member 33a and lower plate body 32a, a part of the rubber member 33C is attached to the bearing. 16-lower part'-N, :) old A'33b-lower plate rest 32b-lower rubber part 331) constitute a parallel link mechanism, and the lens holder 10 is kept parallel to the bearing 16. It moves in the focus direction AA'.

Therefore, during focusing control, lens holder 1
0 moves in the focus direction AA', the optical axis I of the objective lens 12 is always parallel to the bearing 16, and the optical axis of the objective lens 12 does not tilt. Also, upper and lower rubber members 33a, 33b, 33c.

33d is molded from a rubber material, so the coil 18
Even if resonance occurs in the lens holder 10 and the support part S when performing focusing control by applying current to , elasticity, viscoelasticity, etc. can be effectively suppressed and absorbed, so that the accuracy of focusing control can be improved. Further, in the present invention, since the support part is made of a rigid body except for the bearing and the attachment part to the holder, there is little expansion and contraction in the direction perpendicular to the optical axis, and there is an advantage that the optical axis is less likely to tilt.

In this embodiment, the optical system is limited to the objective lens, but the present invention can also be applied to the case where the entire optical system including the light source and the like is driven.

In addition, although this embodiment shows an example in which it is applied to an optical system drive device of an optical disk device, it can also be applied to a shape detection device, a laser processing machine, etc.
It can also be applied to other optical instruments.

(Effects of the Invention) As explained above, according to the optical system driving device of the present invention, the resonance of the optical system holding portion due to the frequency of the driving current of the coil is reduced during focusing control, and the optical axis tilt of the optical system is reduced. Since it is possible to eliminate the error and prevent malfunctions in focusing control, it is possible to achieve high accuracy in focusing control.

[Brief explanation of drawings]

1 is a perspective view showing an embodiment of the optical system drive device of the present invention, FIG. 2 is a perspective view of the optical system drive device in a conventional example, FIG. 3Fa) is a front view of the magnetic circuit, Figures (bl is a side view thereof, Figure 4 is a diagram for explaining the positional relationship between the magnetic circuit and the coil, and Figures 5 (ta+) and (b) are side views of the optical system drive device shown in Figure 1. 1. 10... Lens holder, 12... Objective lens, 16
...Bearing, 24...Base, 32a...Upper plate,
32b...Lower plate body, 33a, 33c...Upper rubber member, 33b, 33d...Lower rubber member, S...Support part. Agent Patent Attorney Jo Taira Yamashita Figure 5 (b)

Claims (1)

[Claims] an optical system holder having an optical system; a bearing fixed on a base and swingably mounted around a rotation axis provided parallel to the optical axis of the optical system; and the optical system holder. and a support section for supporting the bearing on the bearing, wherein the support section is composed of two mutually parallel plates made of a rigid body and arranged side by side in the optical axis direction, and both ends of each of these plates. and a rubber-like elastic body that grips the optical system drive device.