JPS63223613A - Oscillation mirror device - Google Patents

Abstract

PURPOSE:To permit tracking control with high accuracy by decreasing the mutually inducted electromotive force of a 1st coil and 2nd coil to suppress the resonance of a basic frequency F0 and forming a moving body part to have the prescribed stable Bode diagram of a quadratic system. CONSTITUTION:The 2nd coil 8 is provided on the outside of a closed 1st magnetic circuit where the 1st coil 6 is positioned. The induced electromotive force is generated in the 2nd coil 8 by the magnetic field in the 2nd magnetic circuit, when the 2nd coil 8 is subjected to turning motion. However, the mutual induction effect with the 1st coil is hardly generated as the 1st magnetic circuit is closed. The induced electromotive force generated in the 2nd coil is mostly dependent of the magnetic field generated by a magnet 7 on the 2nd coil side. The frequency characteristic of the moving body part is suppressed only in the resonance of the basic frequency without applying an undesirable fluctuation to the high-frequency range of the Bode diagram as such induced electromotive force is negative-fed back to the 1st coil. The moving body part having the stable transmission function of the prescribed quadratic system is thereby obtd. and the tracking control with the high accuracy is permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a vibrating mirror device that can be used as an optical deflector for an optical disk device that optically records information on a recording medium or optically reproduces information from the recording medium. It is something.

BACKGROUND OF THE INVENTION In recent years, in optical disk devices that record information on or reproduce information from a recording medium at extremely high density, vibrating mirror devices have been used to provide high-precision control for tracks formed on a recording medium when recording or reproducing information. Tracking 'f
I am using i1m.

An example of the conventional vibrating mirror device described above will be described below with reference to the drawings.

FIG. 5 shows a schematic diagram of a conventional vibrating mirror device. Reference numeral 1 denotes a rectangular plate-shaped reflecting means with a flat reflecting surface. Reference numeral 2 denotes an elastic member formed of a thin flat metal plate that extends in a direction perpendicular to the reflecting surface of the reflecting means 1, and has a rotation axis in a direction parallel to the reflecting surface of the reflecting means 1, and rotates around the rotation axis. The reflecting means 1 is movably supported. A base 3 fixes both ends of the elastic member 2. 40
is a magnet, and both magnetic poles are provided at substantially symmetrical positions with respect to the rotation axis. Reference numeral 6 denotes a first coil fixed to the elastic member 2 at a position facing both magnetic poles of the magnet 40, and when a current is applied, the elastic member 2 is deformed and the coil is rotated to the reflecting means l. Make it move.

A second coil 8 is fixed to the first coil 6 at a position facing both magnetic poles of the magnet 40. Reference numeral 9 denotes a yoke member that has a magnetic gap in which the first coil and the second coil are located and forms a closed loop magnetic circuit.

The operation of the vibrating mirror device configured as described above will be described below. By applying a current to the first coil 6, the reflecting means 1 is caused to rotate, and the second coil 8 is also caused to rotate. At this time, the second coil 8 interlinks with the magnetic flux of the magnetic gap, and an induced electromotive force proportional to the interlinking speed is generated at both ends of the second coil 8. Here, the induced electromotive force is E, the linkage speed is V, the magnetic flux density on the 8 points of the second coil in the magnetic gap is B, and the second coil 8 moving in a magnetic field having the above magnetic flux density When the length of is L, the induced electromotive force E is expressed by equation (1).

EmBLv(v)...(l) In addition, the second coil 8 has the same voltage as the current applied to the first coil 6 in order to rotate the reflecting means l. A mutually induced electromotive force is generated by mutual induction with the coil 6 of the first coil.

As described above, when the reflecting means l is rotating, two types of induced electromotive force are mainly generated, and the frequency characteristics of the induced electromotive force in the second coil 8 at this time are as shown in FIG. , the fundamental frequency F of the movable body portion equipped with the reflecting means 1
It depends on the induced electromotive force that has a maximum value at O and the mutually induced electromotive force that tends to increase as the wave number becomes larger.

The frequency characteristics of the displacement of the movable body portion when a current is applied to the first coil 6 are as shown in FIG. The broken line A is the frequency characteristic when the induced electromotive force near the fundamental frequency FO generated in the second coil 8 is not fed back to the applied current of the first coil 6, and the solid line B is the frequency characteristic when the induced electromotive force near the fundamental frequency FO generated in the second coil 8 is not fed back to the applied current of the first coil 6. In order to suppress the resonance of the fundamental frequency FO that causes the operation, the induced electromotive force near the fundamental frequency FO generated in the second coil 8 is negatively fed back to the current applied to the first coil 6. That is, by providing the second coil in the first coil, undesired resonance at a specific frequency is suppressed, and the reflecting means l is rotated to perform tracking am.

Problems to be Solved by the Invention However, the above configuration has the following problems. That is, as shown in FIG. 6, by applying a current to the first coil 5 to rotate the reflecting means 1, a mutually induced electromotive force is generated in the second coil 8 due to mutual induction. occurs, and becomes dominant in the high range of the frequency characteristics of the second coil 8. When the induced electromotive force of the second coil 8 having the frequency characteristic is negatively fed back to the current applied to the first coil 6, the resonance of the fundamental frequency FO is suppressed.

However, as shown in FIG. 7, due to the negative feedback of the mutually induced electromotive force, the high frequency range of the Bode diagram of the movable body changes as shown by the solid line B, and a predetermined feedback gain and control band are obtained. If you try to do so, it becomes a very difficult control target.

In addition, if it is desired to reduce the influence of the mutually induced electromotive force, a circuit such as a low frequency pass filter may be added to the frequency characteristics of the second coil 8 to reduce the mutually induced electromotive force in the high frequency range. As a result, negative feedback must be provided to the first coil, resulting in a problem that the circuit becomes complicated.

In view of the above problems, the present invention reduces the mutually induced electromotive force of the second coil caused by the mutual induction between the first coil and the second secondary coil, and suppresses the resonance of the fundamental frequency FO. In addition, the present invention provides a vibrating mirror device which makes the Bode diagram of the movable body part a predetermined stable quadratic system and performs highly accurate tracking control.

Means for Solving the Problems In order to solve the above problems, the vibrating mirror device of the present invention includes a plate-shaped reflecting means whose reflecting surface is flat and rotating in a direction parallel to the reflecting plane of the reflecting means. an elastic member having a moving axis and supporting the reflecting means so as to be movable around the rotating axis; a base for fixing the elastic member; a yoke member having a gap between both magnetic poles of the first coil-side magnet and covering the first coil-side magnet; the first coil-side magnet and the yoke; a first coil member fixed to the elastic member so as to be located in the gap portion of the closed first magnetic circuit configured with the member and facing the first coil-side magnet;
a coil, at least one second coil-side magnet provided outside the closed first magnetic circuit, and a second coil-side magnet fixed to the elastic member so as to face the second coil-side magnet. This configuration includes a second coil forming a magnetic circuit.

Effect The present invention has the above-described configuration, and by providing the second coil outside the closed first magnetic circuit in which the first coil is located, the interaction between the first coil and the second coil is improved. The induction effect is reduced, and the induced electromotive force generated in the second coil is made almost dependent on the magnetic field generated by the second coil side magnet. This induced electromotive force is
By providing negative feedback to the coil, the frequency characteristics of the movable body part are suppressed only to the resonance of the fundamental frequency without causing undesired fluctuations in the high frequency range of the Bode diagram.

EXAMPLE Hereinafter, a vibrating mirror device according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a vibrating mirror device according to an embodiment of the present invention, and FIG. 2 is a sectional view.

Reference numeral 1 denotes a rectangular plate-shaped reflecting means with a flat reflecting surface. Reference numeral 2 denotes an elastic member made of a thin metal flat plate that extends in a direction perpendicular to the reflecting surface of the reflecting means 1, and has a rotation axis in a direction parallel to the reflecting surface of the reflecting means 1. The reflecting means 1 is movably supported. A base 3 fixes both ends of the elastic member 2. Reference numeral 4 denotes a first coil-side magnet, and both magnetic poles are provided at substantially bilaterally symmetrical positions about the rotation axis on the side of the surface of the reflecting means that faces the reflecting surface. Reference numeral 5 denotes a yoke member having a gap between both magnetic poles of the primary coil side magnet and provided to cover the first coil side magnet, and the first yoke member 5 is closed due to the configuration with the first coil side magnet. form a magnetic circuit. A first coil 6 is located in the gap of the closed first magnetic circuit and is fixed to the elastic member 2 so as to face the first coil-side magnet. Reference numeral 7 denotes a second coil-side magnet forming a second magnetic circuit, and is located at a symmetrical position around the rotation axis on the outer peripheral surface of the yoke member 5, which is outside the closed first magnetic circuit. There are two fixed. 8 is the second
The coil is fixed to the elastic member 2 so as to face the second coil-side magnet.

The operation of the vibrating mirror device configured as described above will be described below. By applying a current to the first coil 6, the reflecting means l is rotated and the second coil 8 is also rotated. At this time, the second coil 8 generates an induced electromotive force due to the magnetic field in the second magnetic circuit, but the mutual induction effect with the first coil is almost non-existent because the first magnetic circuit is closed. The frequency characteristics of the induced electromotive force in the second coil are as shown in FIG.

As described above, according to this embodiment, by providing the second coil outside the closed first magnetic circuit, the induced electromotive force is negatively fed back to the current applied to the first coil. As shown in Fig. 4, the frequency characteristics of the displacement of the movable body part can suppress undesired resonance at the fundamental frequency while maintaining stability in the high frequency range of the Bode diagram, resulting in stable tracking control. can be done.

Furthermore, by arranging the first magnetic circuit and the second magnetic circuit symmetrically about the rotation axis on the reflective back side of the reflecting means 1 without adding a special compensation circuit, A small-sized vibrating mirror device can be provided.

Effects of the Invention As described above, the present invention includes a plate-shaped reflecting means having a flat reflecting surface, a rotating shaft in a direction parallel to the reflecting plane of the reflecting means, and movable around the rotating axis. an elastic member that supports the reflecting means, a base for fixing the elastic member, a first coil-side magnet provided on the side of the reflecting means that faces the reflecting surface, and the first coil-side magnet. a yoke member having a gap between both magnetic poles of a magnet and provided to cover the first coil-side magnet; a closed first magnetic circuit comprising the first coil-side magnet and the yoke member; a first coil fixed to the reflecting means so as to be located in the gap and facing the first coil-side magnet; and at least one second coil provided outside the closed first magnetic circuit. a second coil that is fixed to the reflecting means so as to face the second coil-side magnet and forms a second magnetic circuit; By arranging the two magnetic circuits at symmetrical positions with respect to the rotation axis, mutual induction of the second coil occurs due to mutual induction between the first coil and the second coil. By reducing the electromotive force, it is possible to obtain a stable transfer function of a predetermined quadratic system for the movable body portion consisting of the reflecting means and the elastic member, and highly accurate tracking control can be performed.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a vibrating mirror device according to an embodiment of the present invention, FIG. 2 is a sectional view of FIG. 1, FIGS.
FIG. 5 is a partially cutaway perspective view of a conventional vibrating mirror device, and FIGS. 6 and 7 are frequency characteristic diagrams of a conventional example. 1... Reflection means, 2... Elastic member, 3
... Base, 4 ... First coil side magnet, 5 ... Yoke member, 6 ... First coil, 7 ... ...Second coil side magnet, 8...
...Second coil, 9... Yoke member, 40.
·····magnet. Name of agent: Patent attorney Toshio Nakao and 1 other person
1st stage 2-jla'J$t 3-1 unit 4- 1st coil side magnet #I1 figure 5- Yoke member 6- 1st coil 7° - 12 (7) Coil side magnet 8- name 2nd coil No. Figure 2

Claims (1)

[Claims] a plate-shaped reflecting means with a flat reflecting surface; an elastic member having a rotation axis in a direction parallel to the reflection plane of the reflecting means and supporting the reflecting means so as to be movable around the rotation axis; A first coil-side magnet provided on a surface side of the reflecting means that faces the base for fixing the elastic member and the reflecting surface, and a gap portion between both magnetic poles of the first coil-side magnet, a yoke member provided so as to cover the first coil-side magnet;
a first coil fixed to the elastic member so as to be located in the air gap of the closed first magnetic circuit composed of the coil-side magnet and the yoke member, and to face the first coil-side magnet; , at least one second coil-side magnet forming a second magnetic circuit provided outside the closed first magnetic circuit, and the elastic member facing the second coil-side magnet. A vibrating mirror device, comprising a fixed second coil, and wherein the first magnetic circuit and the second magnetic circuit are arranged at symmetrical positions with respect to the rotation axis.