JPS63119029A - Optical system driving device - Google Patents

Abstract

PURPOSE:To obtain the titled device low in resonance sharpness, capable of suppressing the rolling phenomenon of a driven part and excellent in frequency response by forming an elastic member by plural line materials. CONSTITUTION:The line pencil 30, which is an elastic member, is formed by twisting plural phosphor bronze lines 32 of about 0.05mmphi together and a liquid 34 of a viscoelastic body is impregnated to a twisting line spring 30. By fixing tightly one edge of the twisting line spring 30 to the moving member, is the driven member and fixing tightly other edge to the base which is a fixed subject, the driven body is supported. Thus, the optical type driving device can be obtained which is small in the resonance sharpness of the primary resonance value, can suppress the rolling phenomenon of a moving member and is satisfactory in the frequency response.

Description

[Detailed description of the invention] [Industrial use! ′? ] The present invention relates to an optical system drive device a that is suitably used, for example, to drive an objective lens of an optical head in an optical information recording/reproducing device.

[Prior Art] Conventionally, there has been an optical type in which information is recorded on the recording medium and/or information recorded on the recording medium is reproduced by irradiating a spot of laser light onto the surface of the information recording medium. Information recording and reproducing devices have been put into practical use.

An example of such a device is an optical disk device. The optical disc, which is a recording medium on which information is reproduced by this optical disc device, has a length of about 1 to 2 m and a length of 1 to 2 m.
An information track consisting of information pits of about 3 m in length is formed in a spiral shape or concentric circle shape. When reproducing the information recorded as the information pit string, without rotating the optical disk, a laser beam is irradiated from an optical head in the form of a minute spot onto the information track of the optical disk, and the information pit string is scanned by the beam spot. let When the reflected or transmitted light of the light irradiated onto the optical disk surface is detected by a photodetector, the optical value of the light incident on the photodetector depends on whether or not there is an information bit at the beam spot position. Change in nature. In this way, a reproduced signal corresponding to the information pit string can be obtained.

In addition, in such an optical disk device, it is extremely important to accurately scan the information bit string between the recording medium and the minute spot at all times. For this purpose, autofocusing that corrects a focus shift caused by warping of the recording medium and autotracking that corrects an irradiation position shift due to eccentricity of the recording medium, etc. are required. As a method of realizing this autofocusing function and o + -) racking function, there is a method of driving the objective lens as shown in Fig. 7. tl is considered. Incidentally, FIG. 7 is a perspective view showing a conventional objective lens driving device.

In the conventional objective lens driving device 2 shown in FIG. 7, the number 4 is a base made of a rigid body.

As shown in the figure, the base 4 is installed with, for example, an optical information recording/reproducing device M (not shown) or the like in the y-z plane. In the vicinity of the four corners of the base 4, one ends of elastic members 68 to 6d, which are isotropic viscoelastic bodies made of fine metal rods or the like, are each fixed as shown in the figure.

The other ends of the elastic members 63 to 6d are as shown in the figure.

They are fixed to four ends of a movable member 10, which is a holder that holds the objective lens 8.

As shown in the figure, the elastic members 6a to 6d are arranged in a line with each other.

A focusing coil 12 for driving the objective lens 8 in the focusing direction (two directions) is wound around the outer periphery of the side surface of the movable member 10.

Furthermore, at both ends of the movable member 10 in the y direction,
Tracking coils 14a and 14b are provided for driving the objective lens 8 in the tracking direction (y direction).

The objective lens driving device 2 also has a magnetic circuit 20 in which a magnet 18 is fixed to the U-shaped yoke 16. The yoke part of the magnetic circuit 20 on the side to which the magnet 18 is fixed is arranged to be located in the gap between the base 4 and the focusing coil 12, and the yoke part on the side without the magnet 18 is arranged as a movable member lO. It is arranged so as to be inserted into an opening 22a provided in the. Furthermore, although not shown, an magnetic circuit similar to the magnetic circuit 20 is also arranged in the opening 22b so as to face the magnetic circuit 20.

In the objective lens driving wave z2 described above, the method of driving the objective lens 8 is to use a magnetic field created by the magnet 18 and the yoke 16, and a current flowing in a direction perpendicular to the magnetic field, which is the focusing coil 12 and the tracking coil 14a.

This is done by the electromagnetic force generated by the current flowing through 14b. This allows the objective lens 8 to be driven in the focusing direction (two directions) and the tracking direction (y direction).

The objective lens HA moving device 2iz as described above has the following problems.

That is, when the elastic members 6a to 6d supporting the movable member 10 are made of metal rods, for example, the resonance sharpness (q) at the lowest resonance frequency (f,') of the elastic member 6 is
o) becomes high, deteriorating the responsiveness of the servo system. This is because the internal loss of the metal rod is small, making it difficult to damp resonance.

On the other hand, when a viscoelastic member made of a material such as rubber is used as the elastic member 6, it is possible to lower the resonance sharpness compared to the method using the metal rod. but,
This method also has the following drawbacks.

[Problem to be solved by the invention] That is, when a rubber material is used as a viscoelastic body, the resonance sharpness is determined by the viscosity of the rubber material, so if the rubber material hardens due to temperature changes etc. or higher (q
o) will also be higher. As a result, the performance of the servo system deteriorates. Also, materials whose viscosity changes little with respect to temperature changes generally have poor damping properties and are unsuitable for use as support members. Furthermore, rubber materials tend to age over time, and as a support means that needs to be used for a long period of time, reliability remains a problem.

In addition, because the movable end of conventional support members made of metal rods or rubber materials is designed to move freely in all directions, slight unbalance of the driving force and the center of gravity of the driven object may be caused by the driving force. Due to a slight deviation from the center of the driven object, unnecessary coupled resonance occurs in the operating band when the driven object vibrates, so-called rolling phenomenon occurs, and the optical axis of the objective lens moves while being tilted, which often impairs servo performance. .

FIG. 8 is a graph showing the frequency characteristics of the objective lens when a rolling phenomenon actually occurs.

[・4 As shown in FIG. 4, sub-resonance occurred near f, making the servo system unstable and often resulting in failure to read good signals.

[Purpose] The present invention has been made in view of the problems of the prior art described above, and its purpose is to reduce the resonance sharpness of the primary resonance value, suppress the rolling phenomenon of the driven part, and provide a good frequency response. The object of the present invention is to provide an optical system driving device.

[Means for Solving the Problems] According to the present invention, the objective in item E includes: a movable member holding an optical system; an elastic member having one end fixed to the movable member and the other end fixed to a fixed member; The present invention is achieved by an optical system driving device having a means for driving the movable member, wherein the elastic member is formed by overlapping a plurality of wire rods.

[Example] Hereinafter, an example according to the present invention will be described specifically and in detail based on the drawings.

Figure 1 shows the optical system drive according to the present invention. FIG. 2 is a partial front view showing an example of an elastic member used in the IJ device.

As shown in the figure, a stranded wire bundle spring 3 which is an elastic member of the present invention
0 is approximately 0.05■■φ multiple phosphor blue gi4 wires 32,
(Four pieces in this embodiment) are formed by twisting them together. Furthermore, the stranded wire spring 30 is impregnated with an armpit body 34 of viscoelastic material.

In the optical system driving device according to the present invention, one end of the stranded wire spring 30, which is an elastic member configured as described above, is fixed to a movable member which is a driven body, and the other end is fixed to a base which is a fixed object. By doing so, the driven body is supported.

Hereinafter, the effect of the elastic member configured as described above as a spring will be explained.

FIG. 2 is a diagram for explaining the operating principle of the elastic member as a spring in this embodiment and the conventional example.

As shown in the figure, one end of the spring material 36 is fixed to the fixed wall 38, and the other end is fixed to a mass point 40 having a mass m. In this figure, as an example of a conventional example, when a spring material made of, for example, a single wire of phosphor bronze is used as the spring material 36, and assuming that the force applied to the mass point 40 is F, the Mm equation is as follows.

Here, k is the elastic constant of the spring material, and C is the viscosity coefficient of the spring material.Normally, the viscosity coefficient C of metal is c(1), so the peak value of the primary resonance value is a very high value. (~30d
Take B).

On the other hand, when the stranded wire spring 30 shown in FIG. 1 is used as the spring member 36 as an example of this embodiment, the N dynamic equation is as follows.

mx=-kx-(c+c'+c'')x+F□(2) where C' is the viscosity coefficient of the viscoelastic body, and c'' is the viscosity coefficient due to the effect of shear friction between the phosphor bronze wires 32.0 Normally Since c<(c+c'+c")<1, the peak value of the -order resonance value can be lowered. (~
15 dB) Next, the effect of the elastic member of the present invention on the rolling phenomenon of a movable member that is a driven body will be explained.

3(a) and 3(b) are views showing the rolling phenomenon of the movable member according to the embodiment of the present invention, and FIG. 3(a) is a plan view of the movable member 10, and FIG. 3(b) is a plan view of the movable member 10. is the same figure (a)
It is a figure seen from the A direction.

As shown in FIG. 3(b), four stranded wire springs 46a to 4
6d, the winding directions of the springs located diagonally with each other are made to match, for example, in a right-handed thread direction, and the winding directions of the other spring located on the other diagonal line are made to match in the left-hand thread direction.

By doing this, the rotational force 50 in the clockwise rotation direction generated with the center 48 of the movable member IO as the rotation center is suppressed by the left-handed twisted wire springs 46b, 46d, and conversely, the rotational force 52 in the left-handed rotation direction is suppressed by the rotational force 52 in the left-handed rotation direction. Screw-wound stranded wire spring 46
a, 46c, thereby suppressing the occurrence of a rolling phenomenon of the movable member IO.

As a result, ideal frequency characteristics as shown in the solid line graph in FIG. 4 are obtained in FIG. 0, and the broken line indicates the frequency characteristics obtained when a single metal wire is used as the elastic member.

Further, the four stranded wire springs 46a to 46d are connected to the focusing coil and the tracking coil, respectively, and also serve as conducting wires.

Furthermore, the four-wood stranded wire spring 46 may be made of a non-conductive material such as a polymer material. In this case, the frequency characteristics of the movable member lO have a more effective damping effect than a metallic stranded wire spring. Shows good properties.

5 and 6 are partial front views showing other embodiments of the stranded wire spring.

As shown in FIG. 5, the stranded wire spring 5 of this embodiment has a core material 52, which is a single metallic wire, at the center in the longitudinal direction. Furthermore, the stranded wire spring 5o has one or more non-conductive single wires 54 made of polymeric material or the like wound around the outer periphery of the core material 52 in a stranded manner. The viscoelastic liquid may or may not be impregnated into the stranded wire spring.

With this configuration, the core material 52 can be used as a conductive wire for tracking and focusing coils. Further, it can have a greater damping effect than a stranded wire spring simply made of metal wire.

As shown in FIG. 6, the wire spring 60 of this embodiment is made by twisting a plurality of non-conductive single wires 62 made of polymeric material or the like. Further, as shown in the figure, a conducting wire 64 for focusing and tracking coils is wound around the stranded wire spring 60. The conductive wires 64 are VI adhesives 66a, 66k)
It is bonded to the twisted wire spring 60 by. The viscoelastic liquid may or may not be impregnated into the wire bundle spring 60.

In this way, by using the stranded wire spring 60 as a guide for the conductor wire 64 of the coil, breakage of the conductor wire 64 can be prevented.

In addition, the stranded wire spring of the present invention is not only composed of one type of single wire, but may also be a combination of a metal wire and a single wire made of a polymer material, or a combination of a single wire made of a different material such as a gold wire. It may be a conductive member made by combining metal whiskers or carbon fibers in a molecular material, or a non-conductive member made by combining ceramic whiskers into a polymer material.

By constructing the wire rod from a suitable material in this manner, a stranded wire spring having desired elastic constants and viscous constants can be constructed.

[Effects of the Invention] As described above in detail and specifically, the present invention is an optical system drive device that uses a twisted wire spring formed by twisting a plurality of wire rods around an elastic member that supports a flexible fh member. Therefore, it is possible to provide an optical wIA moving device in which the resonance sharpness of the primary resonance value is small, the rolling phenomenon of the movable member can be suppressed, and the frequency response is good.

[Brief explanation of the drawing]

FIG. 1 is a partial front view showing an embodiment of a stranded wire spring used in an optical system driving device according to the present invention, FIG. 2 is a diagram for explaining the operating principle of the elastic member, and FIG. ) and (b
) is a diagram showing the rolling phenomenon of an ar dynamic member, FIG. 4 is a graph showing frequency characteristics, FIGS. 5 and 6 are partial front views showing other embodiments of the stranded wire spring, and FIG. 7 is a conventional FIG. 8, a perspective view of the objective lens driving device, is a graph showing frequency characteristics. 4... Base 8... Objective lens 10... Movable member 30... Stranded wire spring agent Patent attorney Seki Yamashita Figure 1 Figure 2 Figure 3 Figure 4 fI''XM (Hz ) Fig. 7 Fig. 8 Layer Nitanka ()-1zJ

Claims (2)

[Claims] (1) In an optical system drive device having a movable member holding an optical system, an elastic member having one end fixed to the movable member and the other end fixed to a fixed member, and means for driving the movable member; An optical system driving device, wherein the elastic member is formed by twisting a plurality of wires. (2) The optical system driving device according to claim (1), wherein four elastic members are provided, and each elastic member is arranged parallel to each other.