JPH05181078A - Biaxial actuator - Google Patents

Abstract

PURPOSE:To provide a biaxial actuator whose controlling accuracy is improved and where stable control is executed. CONSTITUTION:The biaxial actuator always regularly corrects an emitting optical axis with respect to the deviation of an incident optical axis by using a corner cube 1. As for this biaxial actuator, bobbins 7, 27 arround which driving coils 9, 29 are wound are arranged in gaps between inner yokes 11, 31 and outer yokes 13, 33 which constitute a magnetic circuit, and magnetic fluids 43, 53 are provided at least between the inner yokes 11, 31 and the bobbins 7, 27, thereby forming air chambers 45, 55. Since pressure in the air chambers 45, 55 is changed at the time of moving X axis and Y axis driving units 17, 37, fluid resistance by the flowing in the driving direction of the magnetic fluids 43, 53 is used to constitute a fluid resistance damper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-axis actuator used for an optical axis control device, and more particularly to a precision XY stage,
The present invention relates to a biaxial actuator that can be used for optical heads and the like.

[0002]

2. Description of the Related Art This kind of optical axis control device is provided as a device for controlling a constant optical axis, for example, by driving a mirror, a corner cube or the like about two axes of XY. This optical axis control device employs a biaxial actuator as a control mechanism for driving and positioning a mirror or the like. This biaxial actuator is roughly classified into two types according to the optical axis control system.
When using a corner cube, for example, Japanese Patent Laid-Open No. 3-4
A voice coil type actuator as disclosed in Japanese Patent No. 1629 is used as a control mechanism for optical axis correction, and has the same configuration as an optical pickup or the like. When a piezoelectric element or the like is used, an XY stage or the like as described in "Precision Engineering Spring Conference Papers" (SHO 62-F31) is used as an optical axis correction control mechanism.

By the way, a two-axis actuator adopting a voice coil system similar to the above optical pickup uses a damper in order to improve controllability. The structure of this damper is such that the movable part is supported by a leaf spring or the like, and the leaf spring is applied with an elastic body or the like, or the elastic body or the like is sandwiched, and the damping is caused by the deformation of the elastic body. The force is used as a damper. Further, as another configuration of the damper, there is also a configuration in which the support body itself that supports the movable portion is made of an elastic body such as a rubber material, and serves as both a support and a damper.

[0004]

In the biaxial actuator having the voice coil mechanism as described above, since the damping force of the elastic body provided in the support mechanism is used as the damper, the movable part with respect to the coil current is applied. Hysteresis has occurred in the straight-ahead characteristics indicated by the amount of displacement. Therefore, when a servo system is configured with the above actuator, its hysteresis becomes a non-linear element,
Oscillation and hunting occur in the servo system, and the control accuracy is reduced, which is not preferable for control. Further, in the biaxial actuator having the voice coil mechanism as described above, when an elastic body is adopted for the damper mechanism, there is a change in the temperature characteristic in the viscous characteristic of the elastic body.
The inclination of the straight traveling characteristic may change depending on the temperature. Therefore, when the servo system is configured as described above, there is a problem that the loop gain of the entire servo system changes to cause oscillation and the like, and stable control cannot be performed. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, improve control accuracy, and provide a two-axis actuator that enables stable control.

[0005]

In order to achieve the above object, the biaxial actuator of the present invention is a biaxial actuator used in an optical axis control device for correcting an outgoing optical axis with respect to a deviation of an incoming optical axis. A bobbin around which a drive coil is wound is disposed in a gap between an inner yoke and an outer yoke that form a magnetic circuit, and an air chamber is formed by providing a magnetic fluid at least between the inner yoke and the bobbin. It is a feature. The air chamber is sealed by a magnetic fluid provided in the magnetic gap of the magnetic circuit. In the air chamber, either end surface of the inner yoke may be sealed with a transparent body. Further, it is preferable that the air chamber also serves as an inner yoke that is a part of the magnetic circuit. Further, a cross-sectional shape of a portion of the bobbin disposed in the gap of the magnetic circuit is wedge-shaped in a direction of an end surface of the inner yoke. In addition, the air chamber of the biaxial actuator according to claim 1 is characterized in that either end surface of the inner yoke is sealed with a transparent body. Further, the magnetic fluid provided in the magnetic gap of the magnetic circuit reduces magnetic resistance and is also used as a fluid seal.

[0006]

In the above biaxial actuator, a bobbin around which a drive coil is wound is arranged in the gap between the inner yoke and the outer yoke, and an air chamber is formed by providing a magnetic fluid at least between the inner yoke and the bobbin. Since the pressure in the air chamber changes when the X-axis / Y-axis drive unit moves, the fluid resistance damper is configured using the fluid resistance due to the flow in the driving direction of the magnetic fluid. As a result, the damper has good linearity. The air chamber is reliably sealed by the magnetic fluid provided in the magnetic gap of the magnetic circuit. Further, since the cross-sectional shape of the portion of the bobbin disposed in the gap of the magnetic circuit is wedge-shaped in the direction of the end surface of the inner yoke, it is possible to prevent the magnetic fluid from coming off the magnetic gap and to reduce the viscosity of the magnetic fluid. Can be used. Further, in the air chamber, either end surface of the inner yoke is sealed with a transparent body to facilitate measurement and the like. Further, the air chamber also serves as an inner yoke that is a part of the magnetic circuit to achieve the phenomenon of the number of parts. The magnetic fluid provided in the magnetic gap of the magnetic circuit reduces the magnetic resistance and also serves as a fluid seal.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the biaxial actuator of the present invention will be described below with reference to FIGS. FIG. 6 is an explanatory diagram showing the principle configuration when the optical axis is controlled using a corner cube. In FIG. 6, the corner cube 101 is fixed to the holder 103. The holder 103 is supported by a leaf spring 105. A bobbin 107 is fixed to the holder 103. Further, the bobbin 107 has a drive coil 1 on its outer cylinder surface.
09 is wound. The drive coil 109 is arranged in the gap between the inner yoke 111 and the outer yoke 113. The inner yoke 111 and the outer yoke 113 are the permanent magnets 1.
It is magnetized by 15. Drive unit 1 having the above configuration
17, the corner cube 101 can be moved in the left-right direction in the drawing. A damper mechanism (not shown) of the present invention is added to the bobbin 107. Further, the laser incident light Li is guided to the corner cube 101 by a relay lens 121, a collimator lens 123, and a mirror 125. Further, the reflected light Lr reflected by the corner cube 101 passes through the λ / 4 wavelength plate 127 and the polarization beam splitter (PBS) 129, and most of it is output as laser emission light Lo, and the rest is incident on the four-division photodiode 131. To be done.

The laser light Ld input to the four-divided photodiode 131 is converted by the photodiode 131 into an electric signal having an intensity corresponding to the position in the diode 131 and input to the control circuit 133. The control circuit 133 forms a control signal for equalizing the four signals of the photodiode 131, and the drive coil 10
Supply to 9. The operation of the device having such a configuration will be briefly described. When the laser incident light Li shown by the solid line becomes the laser incident light Li ′ which is deviated as shown by the alternate long and short dash line, the reflected light Lr ′ that has passed through the corner cube 101. And enters the four-divided photodiode 131. Then, the reflected light Lr ′ from the four-division photodiode 131.
Four detection signals are output according to the deviation of These detection signals are input to the control circuit 133, and the control circuit 133
Is used as a driving signal for correction. This control circuit 13
By supplying the drive signal from the drive coil 109 to the drive coil 109, the corner cube 101 operates as shown by the dotted line on the left side of the drawing, and makes the position of the laser emission light Lo constant.

The relay lens 121 and the collimator lens 123 are for making the laser light Li parallel to the solid line. Further, although the above-mentioned configuration shows one axis, in actuality, the direction perpendicular to the plane of the drawing is also configured in the same manner as the above-mentioned drive unit and position control is performed. next,
The biaxial actuator for controlling the optical axis of the corner cube as described above will be described in detail. FIG. 1 is a sectional view showing an embodiment of the biaxial actuator of the present invention. In FIG. 1, the corner cube 1 is fixed to a holder 3. An X-axis bobbin 7 is fixed to the holder 3 so as to sandwich the inner circumferential portion of the circular X-direction leaf spring 5. The X-axis bobbin 7 has an X-axis drive coil 9 on its outer cylinder surface.
Is wound. The X-axis drive coil 9 is arranged in the gap between the X-axis inner yoke 11 and the X-axis outer yoke 13. The X-axis inner yoke 11 and the X-axis outer yoke 13 are magnetized by the permanent magnet 15 to form a magnetic circuit.
The X-axis inner yoke 11 and the X-axis outer yoke 13 including the permanent magnet 15 are fixed to the inner case 19. Similarly, X
The outer peripheral portion of the direction leaf spring 5 is fixed to the inner case 19. The X-axis drive unit 17 is formed of these. With the above configuration, the X-axis drive unit 17 is elastically supported by the inner case 19. When the coil terminal (not shown) of the X-axis drive coil 9 is energized, the X-axis drive unit 17 becomes movable in the XX 'direction by the electromagnetic force in the XX' direction.

Similarly, a Y-axis bobbin 27 is fixed to a protrusion provided at a position perpendicular to the XX 'direction of the inner case 19 so as to sandwich the inner circumferential portion of the circular Y-direction leaf spring 25. There is. A Y-axis drive coil 29 is wound around the outer cylinder surface of the Y-axis bobbin 27. This Y-axis drive coil 29
Are arranged between the Y-axis inner yoke 31 and the Y-axis outer yoke 33. The Y-axis inner yoke 31 and the Y-axis outer yoke 33 are magnetized by the permanent magnet 35 to form a magnetic circuit. Y-axis inner yoke 3 including this permanent magnet 35
1. The Y-axis outer yoke 33 is fixed to the base 39. Similarly, the outer peripheral portion of the Y-direction leaf spring 35 is
Is stuck to. With these, the Y-axis drive unit 3
Make up 7. The structure of the damper added to the above basic structure will be described below. An X transparent body 41 is fixed to the end surface of the X-axis inner yoke 11. An X magnetic fluid 43 is provided between the magnetic gap of the magnetic circuit including the X-axis inner yoke 11 and the X-axis outer yoke 13 and the X-axis bobbin 7. As a result, the X-axis bobbin 7, the X-axis inner yoke 11, and the X magnetic fluid 43 form the X air chamber 45. In the above-mentioned embodiment, the X transparent body 41 is set to X
Although it is provided on the inner end surface of the in-axis yoke 11,
It may be provided on the outer end face of No. 1.

On the other hand, a Y transparent body 51 is fixed to the end surface of the Y-axis inner yoke 31. In addition, the Y-axis inner yoke 31, Y
A Y magnetic fluid 53 is provided between the magnetic gap of the magnetic circuit including the off-axis yoke 33 and the Y-axis bobbin 27. As a result, the Y-axis bobbin 27, the Y-axis inner yoke 31,
The Y magnetic fluid 53 forms the Y air chamber 55. Although the Y transparent body 51 is provided on the inner end surface of the Y-axis inner yoke 31 in the above embodiment, it may be provided on the outer end surface of the Y-axis inner yoke 31.

The operation of such a configuration will be described based on FIG. 1 and with reference to FIGS. FIG. 2 is a characteristic diagram showing the operating frequency characteristic of the X-axis drive unit, in which the horizontal axis represents the energization frequency [Hz] to the X-axis drive coil and the vertical axis represents the gain [dB].
And the phase [degree]. FIG. 3 is a characteristic diagram showing the operating frequency characteristics of the Y-axis drive unit, in which the horizontal axis represents the energization frequency [Hz] to the Y-axis drive coil, and the vertical axis represents the gain [dB] and phase [degree]. ing. When the holder 3 moves in the XX ′ direction by energizing the X-axis drive coil 9 of the X-axis drive unit 17, the air pressure in the X air chamber 45 rises and falls, and the pressure difference causes the X magnetic fluid 4 to flow.
3 flows. The fluid resistance at that time is generated in a form proportional to the moving speed, and this acts as a damping force. Similarly, when the Y-axis drive coil 29 of the Y-axis drive unit 37 is energized, the inner case 19 including the X-axis drive unit 17 operates in the YY 'direction. As a result, the air pressure in the Y air chamber 55 rises and falls, and the Y magnetic fluid 53 flows due to the pressure difference. The fluid resistance at that time is generated in a form proportional to the moving speed, and this acts as a damping force.

FIG. 2 shows the operating frequency characteristic of the X-axis drive unit and FIG. 3 shows the operating frequency characteristic of the Y-axis drive unit 37. The X magnetic fluid 43 and the Y magnetic fluid 53 are shown.
It is possible to easily change PGX and PGY representing the damping effect in the figure by appropriately selecting the viscosity coefficient of, and the optimum value may be selected. In the above-described embodiment, since a rubber material such as an elastic body is not used in the portion that generates the damping force, the straight traveling characteristics of the X-axis drive unit 17 and the Y-axis drive unit 37 of the present invention are as shown in FIG. The characteristic La has linearity, and the hysteresis unlike the conventional characteristics Lb and Lc disappears. If a magnetic fluid having a low viscosity such as kerosene is selected for the X magnetic fluid 43 and the Y magnetic fluid 53, the temperature dependence is reduced, and a damping mechanism that is not easily affected by temperature changes can be configured. When a magnetic fluid having a low viscosity is used as the X magnetic fluid 43, the X-axis bobbin 7 of the X-axis drive coil 9 is provided with respect to the X-axis inner yoke 11 and the X-axis outer yoke 13 as shown in FIG. However, it is necessary to make the cross section into a wedge shape and take measures to prevent separation from the magnetic gap. Magnetic fluid with low viscosity is
When used for the magnetic fluid 43, as a by-product effect,
The reluctance of the magnetic gap is reduced and the efficiency of the magnetic circuit is increased.

Even when a magnetic fluid such as kerosene having a low viscosity is selected for the Y magnetic fluid 53, the shape of the Y-axis bobbin 27 is the same as that of the X-axis, as shown in FIG. To As a result, the magnetic resistance of the magnetic gap also decreases on the Y-axis side, and the efficiency of the magnetic circuit can be increased.

[0015]

As described above, in the biaxial actuator according to claim 1, since the air chamber is formed by the inner yoke, the bobbin and the magnetic fluid, and the fluid resistance damper is formed by the flow of the magnetic fluid. There is an effect that the hysteresis is not generated, the temperature change is small, and the control accuracy can be improved. In the air chamber according to the second aspect, since the air chamber is sealed by the magnetic fluid arranged in the magnetic gap, the machining accuracy of the inner yoke outer cylinder and the bobbin inner cylinder may be low, and there is an effect of being inexpensive. .. In the bobbin according to the third aspect, the portion disposed in the magnetic gap has a shape for preventing the magnetic fluid from coming off, so that there is an effect that the long-term reliability is improved. In the air chamber of the fourth aspect, since the inner yoke end face is sealed with the transparent body, it is easy to apply to an external characteristic measuring instrument using a laser or the like, and there is an effect that assemblability can be improved. In the air chamber of the fifth aspect, since the inner yoke is also used as a part of the formation of the air chamber, there is an effect that the number of parts is reduced and the cost is reduced. In the magnetic fluid according to claim 6, since the magnetic fluid also serves as a magnetic resistance reducing agent for the magnetic gap and as a seal, the number of parts is reduced and the cost is reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a biaxial actuator of the present invention.

FIG. 2 is a characteristic diagram showing X-axis direction operation characteristics of the embodiment of the present invention.

FIG. 3 is a characteristic diagram showing Y-axis direction operation characteristics of the embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a straight traveling characteristic of the embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a part of another embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a principle configuration of optical axis control to which an embodiment of the present invention is applied.

[Explanation of symbols]

 1 Corner Cube 3 Holder 7 X Axis Bobbin 9 X Axis Drive Coil 11 X Axis Inner Yoke 13 X Axis Outer Yoke 15 Permanent Magnet 17 X Axis Drive Unit 19 Inner Case 31 Y Axis Inner Yoke 33 Y Axis Outer Yoke 35 Permanent Magnet 37 Y Axis drive unit 39 Base 41 X transparent body 43 X magnetic fluid 45 X air chamber 51 Y transparent body 53 Y magnetic fluid 55 Y air chamber

Claims (6)

[Claims] 1. A biaxial actuator used in an optical axis control device for correcting an outgoing optical axis with respect to a deviation of an incoming optical axis, wherein a drive coil is wound around a gap between an inner yoke and an outer yoke which form a magnetic circuit. And a bobbin, and a magnetic fluid is provided at least between the inner yoke and the bobbin to form an air chamber. 2. The biaxial actuator according to claim 1, wherein the air chamber is sealed by a magnetic fluid provided in a magnetic gap of a magnetic circuit. 3. The biaxial actuator according to claim 1, wherein a cross-sectional shape of the portion of the bobbin disposed in the gap of the magnetic circuit is wedge-shaped in a direction of an end surface of the inner yoke. 4. The biaxial actuator according to claim 1, wherein either end face of the inner yoke of the air chamber is sealed with a transparent body. 5. The biaxial actuator according to claim 1, wherein the air chamber also serves as an inner yoke which is a part of a magnetic circuit. 6. The biaxial actuator according to claim 1, wherein the magnetic fluid provided in the magnetic gap of the magnetic circuit serves to reduce magnetic resistance and also serves as a fluid seal.