JPS62205542A - Optical system driving device - Google Patents

Abstract

PURPOSE:To drive an optical system stably and at high accuracy without causing falling of the optical axis by driving the optical system by a needle and bimorph elements provided movably. CONSTITUTION:To drive an objective 108 in focus direction, voltage is applied to bimorph elements 107, 107a, and the elements 107, 107a are bent and moved in the direction of optical axis B by displacement H. Then, the objective 108 attached to the tip of the elements 107, 107a is moved in the direction of optical axis B by an amount H. At this time, as elements 107, 107a are attached parallel and opposite to each other, the objective lens 108 moves in the direction of optical axis B, and falling of optical axis B of the objective 108 does not occur at the time of driving in focus direction. When driving the objective 108 in the direction of tracking, a needle 101 is driven in the direction of axial line A-A' along shafts 105, 106 by magnetic mutual action of a magnetic field generated by applying current to a coil 104 wound on the outer peripheral face of a bearing part 102 and a magnetic field formed by a shaft 105 made of a magnetic substance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical system drive device, and particularly to an optical information recording/reproducing device such as an optical disk device, a magneto-optical disk device, or a digital audio device. This invention relates to an optical system drive device that focuses light onto an information recording medium.

(Prior Art) In general, in an optical information recording/reproducing device such as an optical disk device, in order to read information recorded in the information focus (width 1 to 2 μm, length 1 to 3 μm) of an information recording medium, first, A light beam (usually a laser beam) is focused on a minute spot by an optical system such as an objective lens, and is irradiated onto an information pit. At this time, the reflected light or transmitted light from the information recording medium optically changes depending on the presence or absence of information. By detecting this change with a photodetector, a reproduced signal corresponding to the information focus can be obtained. In the optical information recording/reproducing apparatus described above, it is extremely important that the minute spot of the light beam always accurately scan the upper row of information pins on the information recording medium. To this end, autofocusing is required to correct focal shifts due to warpage of the information recording medium, and autotracking is required to correct irradiation position shifts due to eccentricity of the information recording medium.

As a means for realizing the autofocus function and the autotracking function, a method is known in which the optical system is supported by a spring-like structure and the electromagnetic force generated by a magnetic circuit consisting of a coil and a magnetic member is utilized.

FIG. 4 is a perspective view showing a conventional optical system drive device having an autofocus function and an autotracking function. In this figure, numerals 1 and 2 are magnets and yokes that constitute a magnetic circuit for focusing, and numerals 3 and 4 are magnets and yokes that constitute a magnetic circuit for tracking. Reference numeral 5 denotes an optical system holder on which an objective lens 6 is attached as an optical system, and coils 7 and 8 fixed to both opposing sides of the optical system holder 5 are arranged in the magnetic circuits for focusing and tracking, respectively. has been done. 9.10 is a support spring that holds the optical system holder 5 movably in the focusing direction; 11.12 is a support spring that holds the optical system holder 5 movably in the tracking direction;
are connected via. 14 is the magnet 1.3, yoke 2.4, optical system holder 5, support springs 9, 10, 11.
This is the base on which the 12th grade is placed.

In the device configured as described above, by applying a current to the coil 7.8, each magnet 1.3 yoke 2.4
Focusing and tracking of the objective lens 6 mounted on the optical system holder 5 can be performed via the respective support springs 9, 10° 11, 12 by the interaction of electromagnetic forces generated by the magnetic circuit consisting of the .

(Problems to be Solved by the Invention) However, in the above-mentioned device, since the movable part is supported by a temporary spring, the optical axis may be tilted due to twisting of the temporary spring.

Furthermore, there is a drawback that resonance occurs with high-frequency drive signals and operation tends to become unstable.

The present invention was made in order to solve the problems of the above-mentioned conventional example, and it is an object of the present invention to provide an optical system driving device that can drive an optical system with high precision and stability.

(Means for Solving the Problems) In order to solve the above problems, an optical system driving device according to the present invention includes an optical system and a guide member provided substantially parallel to a direction perpendicular to the optical axis of the optical system. a movable element movable along the guide member; a driving means for moving the movable element in a direction perpendicular to the optical axis; The gist of this is that the optical system is composed of a bimorph element that moves in the optical axis direction.

(Example) Hereinafter, the present invention will be explained in detail with reference to an illustrated example.

FIG. 1 is a perspective view showing an optical system driving device according to the present invention. In this figure, 101 is a movable element, and bearing parts 102 and 103 are formed at both ends of the movable element 101, respectively, substantially parallel to each other. 104 is the bearing part 102
This is a tracking coil wound concentrically around the outer circumferential surface of the Reference numeral 105 denotes a shaft made of a magnetic material that is inserted into the bearing portion 102 as a guide member, 106 is a shaft that is inserted into the bearing portion 103 as a guide member, and the movable element 101 is moved in the axial direction of the shafts 105 and 106 (A-A' 107 and 107a are bimorph elements, and the bimorph element 107 and 107a are movable in the force direction.
The axial direction of the shaft 105 (A-A
'They are mounted opposite each other parallel to the direction of force. The bimorph element 107.107a consists of two piezoelectric plates bonded together that expand and contract in the longitudinal direction.When one of the plates expands, the other contracts, causing a bending displacement as a whole. Objective lens 1 as a system
08 is mounted so that its optical axis B is perpendicular to the axial direction of the shaft 105 (A-A' force direction). It is a neutral holding part provided perpendicularly to the (A-A' direction), and shafts 10 are provided on both sides of the neutral holding part 109, respectively.
A pin 110 is attached parallel to the axial direction (A-A' direction) of 6. 111 is an elastic member such as rubber formed in a U-shape, and is arranged so that the inner surface of the elastic member 111 comes into contact with the pin 110 of the neutral holding part 109 (
(See FIG. 3) e 112 is a base on which each of the above-mentioned constituent members is arranged.

The optical system driving device according to the present invention is configured as described above, and first, a case in which the objective lens 108 is driven in the focus direction will be described. FIG. 2(A) shows the state before applying voltage to the bimorph elements 10'7 and 107a. In this state, the bimorph elements 107 and 107a attached to the mover 101 are maintained parallel to each other, so the objective Lens 108 is not displaced. And Figure 2 (
As shown in b), a voltage is applied to the bimorph elements 107 and 107a, and the bimorph element 10 is turned off.

By bending and displacing 107a in the same direction (optical axis B direction) by a displacement iH, bimorph elements 107.107
The objective lens 108 attached to the tip of a also has its optical axis B.
direction by a displacement i1H. At this time, since the bimorph elements 107 and 107a are mounted parallel to each other and facing each other, the objective lens 108 is displaced in the direction of the optical axis B, and the tilting of the optical axis B of the objective lens 108 does not occur when driving in the focus direction. do not have.

Next, when driving the objective lens 108 in the tracking direction, the bearing portion 102. The mover 101 moves in the axial direction ( The objective lens 108 attached to the movable element 101 via the bimorph elements 107 and 107a is displaced in the tracking direction.At this time, as shown in FIG. The movement of the child 101 is transmitted to an elastic member 111 made of rubber or the like via a pin 11O provided in the neutral holding part 109, and a damping effect of the objective lens 108 is obtained by the elastic displacement of the elastic member 111. It acts as a holding function.

Further, although this embodiment is an example in which the present invention is applied to an optical system drive device of an optical disk device, it is obvious that the present invention can also be applied to other optical devices such as a shape detection device and a laser processing machine.

Incidentally, in the above-mentioned embodiment, the case where only the objective lens is driven as an optical system has been explained, but it is also applicable to the case where the entire optical system including a light source etc. is driven.

(Effects of the Invention) As explained above, the optical system drive device according to the present invention has the following features:
By driving the optical system using a movable movable element and a bimorph element, it is possible to drive the optical system with high precision and stability without tilting the optical axis.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an optical system drive device according to the present invention, Fig. 2 (a) is a side view showing the main parts of the device, and Fig. 2 (b)
3 is a plan view showing a neutral holding section of the device, and FIG. 4 is a perspective view showing a conventional optical system driving device. 101... Mover, 102, 103... Bearing part, 1
04... Coil, 105, 106... Axis, 107° 107a... Bimorph element, 108... Objective lens, 109... Neutral holding part, 111... Elastic member. Agent Patent Attorney Jo Taira Yamashita Figure 2 (A) Portion C Figure 3 Figure 4vA

Claims (1)

[Claims] an optical system, a guide member provided substantially parallel to the direction perpendicular to the optical axis of the optical system, a movable element movable along the guide member, and a movable member disposed substantially parallel to the optical axis of the optical system; An optical system driving device comprising a driving means that moves in the optical axis direction, and a bimorph element that connects the movable element and the optical system and moves the optical system in the optical axis direction with respect to the movable element.