JPH0612687A - Biaxial actuator - Google Patents

Abstract

PURPOSE:To enhance mechanical rigidity and to execute driving control always stably up to a high band by combining a cube holder, supporting mechanism and driving mechanism. CONSTITUTION:A corner cube 10 is fixed and held to the cube holder 11 and a moving body 15 is fixed onto a base 17 by means of 4 pieces of supporting wires 16 and is constituted as to be freely movable in X-X' and Y-Y' directions. The wires 16 consisting of viscoelastic members 19, 20 constitute the supporting mechanism. Magnetic fluid 25 is provided between the surfaces of yokes 24a, 24b on the side facing driving coils 12, 13 and the surface of the holder 11 fixed with the coils 12, 13. The magnetic flux from the yoke 24b passes one side of the coil 12, then passes a plate 14 consisting of a magnetic material having a high magnetic permeability and enters the inside of the plane of the yoke 24a through the other one side of the coil 12. Electromagnetic force is acted in the X-X' and Y-Y' directions by energizing the coils 12, 13 from their terminals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an optical head, precision XY
In fields such as stages and semiconductor mask analyzers,
The present invention relates to an actuator that biaxially drives a mirror or a corner cube.

[0002]

2. Description of the Related Art Conventionally, an actuator used in an optical axis control device or the like has a different control mechanism depending on whether a lens or a corner cube is used as a member for adjusting an optical axis. -1502
There are some disclosed in Japanese Patent No. 37 and Japanese Utility Model Laid-Open No. 1-133222. The general structure is composed of a holding member for holding the lens or the corner cube, a support mechanism for supporting the holding member with a leaf spring, a coil spring, or the like, and a coil and a magnetic circuit for driving and controlling the support mechanism. It consists of a drive mechanism. In this case, the electromagnetic force generated by energizing the coil from the outside
It is configured by a so-called voice coil mechanism that displaces the holding member to a desired position. The magnetic circuit used in such a drive mechanism generally has a coil wound around a holding member disposed in the magnetic gap, and the magnetic pole surface of the permanent magnet and a yoke surface or a different magnetic pole surface are opposed to each other. There is.

FIG. 8 shows a concrete example of a mechanism for controlling an optical axis by using a corner cube. The laser emission light passes through the relay lens 1 and the collimator lens 2, is reflected by the mirror 3, is reflected by the corner cube 4, is transmitted through the λ / 4 plate 5, and is transmitted or reflected by the polarization beam splitter 6. The transmitted light is detected by the four-division light receiving element 7 and used as a beam for controlling the optical axis, and the reflected light is used as a beam for emission after controlling the optical axis.

In this case, when the laser emission light shown by the solid line is displaced along the optical axis as shown by the alternate long and short dash line, the optical axis shift is detected by the four-division light receiving element 7, and the optical axis shift is matched accordingly. The corner cube 4 is moved by the amount in the direction indicated by the arrow (here, the position indicated by the dotted line in the left direction). Accordingly, the light reflected by the polarization beam splitter 6 can be used as laser light whose optical axis is controlled.

[0005]

The width g of the magnetic gap of the conventional magnetic circuit is set to be very narrow in order to improve the driving efficiency. Along with this, the member thickness of the coil portion wound around the holding member of the lens or the corner cube is very thin, about 0.5 mm or less, which lowers the mechanical rigidity. Therefore, as shown in the vibration characteristics of FIG. 9, member resonance occurs, and the phase curve 8 (9 is a gain curve) begins to cause a phase delay (after point P) near 10 KHz. If this phase lag is incorporated into the control system, the phase will be delayed in the high frequency range, and stable control up to the high frequency band will not be possible.This will result in a decrease in control accuracy and, in the worst case, an oscillation phenomenon. It may be out of control.

When a coil spring or a leaf spring is used as the support mechanism, a surging phenomenon occurs in which the coil portion starts free vibration at several KHz, and in the case of a leaf spring, higher-order mode vibration occurs. , The phase curve 8 is disturbed as shown by the point Q in FIG. When a continuous operation signal is applied to this disturbed portion, the control system oscillates and becomes uncontrollable as in the case described above.

[0007]

According to a first aspect of the present invention, there is provided a support comprising a cube holder for holding a corner cube for maintaining a laser beam on a constant optical axis and four support wires for supporting the cube holder. A mechanism, a drive coil fixed to each side surface of the cube holder and having two sides facing in parallel to the optical axis and having a flat plate shape and a rectangular cross section, and magnetic fluxes opposite to each other are given to the two sides facing each other In order to do so, a biaxial actuator is constituted by a drive mechanism having a magnetic circuit arranged to face the drive coil.

According to a second aspect of the present invention, in the first aspect of the present invention, the magnetic circuit of each pair of shafts has a substantially hexagonal cross section and two faces facing the two sides of the drive coil are equal sides. The permanent magnet is magnetized in two directions and a pair of yokes each having a triangular cross section and having an inclined surface fixed to an equal side of the permanent magnet.

According to the invention of claim 3, claim 1 or 2
In the invention described above, a magnetic material plate in which a magnetic material is mixed and solidified is provided in the concave portion of the cube holder facing the top of the permanent magnet.

According to a fourth aspect of the invention, in the first, second or third aspect of the invention, a magnetic fluid is arranged between the cube holder and the surface of the yoke of the magnetic circuit on the side facing the drive coil.

According to the invention of claim 5, claims 1, 2,
In the invention described in 3 or 4, the support wire is made of a viscoelastic member having viscoelasticity and having a different thickness, and an elastic rod.

According to the invention of claim 6, in the invention of claim 5, the viscoelastic member is provided on the abdomen of the elastic rod in the third vibration mode.

[0013]

According to the first aspect of the present invention, since the drive mechanism is constituted by the plane coil fixed to the cube holder and the magnetic circuit having no magnetic gap facing each other, the thin portion of the cube holder is eliminated, and the mechanical structure is eliminated. It is possible to increase the rigidity and eliminate the occurrence of member resonance up to a high band.

According to the second aspect of the present invention, the magnetic circuit has a composite structure of a permanent magnet and a yoke, so that the magnetic flux density at the coil portion can be increased.

According to the third aspect of the invention, since the magnetic plate is provided, the magnetic flux density in the magnetic flux path can be increased.

According to the fourth aspect of the invention, since the magnetic fluid is disposed between the yoke and the cube holder, the magnetic permeability μ becomes higher than that in the air, the magnetic resistance decreases, and the magnetic flux at the coil portion is reduced. It is possible to increase the density.

According to the fifth aspect of the present invention, since the support wire has a composite structure of the elastic rod and a viscoelastic body having a different thickness, unnecessary resonance of the elastic rod can be efficiently suppressed.

According to the sixth aspect of the present invention, since the viscoelastic body is provided on the abdomen of the elastic rod in the third mode, it is possible to eliminate the occurrence of hysteresis or the like in the movement characteristics.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. The corner cube 10 is fixed and held by a cube holder 11 having a through hole in the center. The cube holder 11 has drive coils 12 and 13 each having a rectangular cross section fixed to four side surfaces in the X and Y axis directions, which are opposed surfaces parallel to the optical axis A. A recess is formed in the central portion of the side surface to which the drive coils 12 and 13 are attached, and a magnetic plate 14 which is hardened by mixing a magnetic material such as barium ferrite is fixed to the recess. The movable body 15 is configured. The movable body 15 is fixed on the base 17 via four support wires 16 and is movable in the XX 'and YY' directions. As shown in FIG. 2, the support wire 16 has a strip-shaped elastic rod 18 provided at the center thereof and a viscoelastic member 19 thinly applied around the elastic rod 18.
And a viscoelastic member 20 thickly formed on the outside of the viscoelastic member 19 has a multilayer structure. FIG. 3 shows a state of the vibration mode of the elastic rod 18. (A) ~
(D) shows the vibration modes from the 1st to the 4th order, and the higher the higher-order vibration mode (third order or higher), the higher the energy for damping the vibration becomes, so that a strong viscoelastic member is required. Become. Therefore, in this configuration, the outer viscoelastic member 20
Is provided on the abdomen in the third vibration mode as shown in (c).
The support wire 16 including the elastic rod 18 and the viscoelastic members 19 and 20 constitutes a support mechanism (not shown).

The optical axes A of the drive coils 12 and 13
A pair of magnetic circuits 21 and 22 are arranged in the X- and Y-axis directions on the sides opposite to the two sides a and b parallel to. As shown in FIG. 4, the magnetic circuits 21 and 22 have a substantially hexagonal cross section and face two sides a and b of the drive coils 12 and 13.
Permanent magnet 2 magnetized in the directions of two sides a and b with the surface being an equal side
3 and a pair of yokes 24a, 24b each having a triangular cross section and having slopes fixed to the equal sides of the permanent magnet 23. In addition, as shown in FIG.
The magnetic fluid 25 is provided between the surface of the cube holder 11 facing the drive coils 12 and 13 and the surface of the cube holder 11 to which the drive coils 12 and 13 are fixed. The magnetic circuit 21 and the magnetic circuit 22 are arranged such that the adjacent surfaces of the yokes 24a and 24b that are adjacent to each other at a right angle have the same polarity. Incidentally, the drive coils 12, 1
3 and the magnetic circuits 21 and 22 constitute a drive mechanism (not shown).

In such a configuration, first, the flow of magnetic flux generated in the magnetic circuits 21 and 22 will be described with reference to FIG. The magnetic flux φ emitted from the surface of the yoke 24b passes through one side b of the drive coil 12, passes through the magnetic plate 14 having a high magnetic permeability μ, passes through the other side a of the drive coil 12, and enters the plane of the yoke 24a. . At this time, since the magnetic flux φ passes through the magnetic fluid 25, it advances in the direction of low magnetic resistance. However, the leakage magnetic flux passing through the surface 23a side of the permanent magnet 23 is very small because the distance between the magnetic poles is longer than the magnetic flux φ emitted from the yokes 24a and 24b.

By energizing from the terminals of the drive coils 12 and 13, an electromagnetic force acts in the XX 'and YY' directions to allow movement. At this time, the forces acting on the opposite sides of the drive coil 12 in the direction perpendicular to the optical axis cancel each other. Here, the cube holder 11 has magnetic circuits 21 and 2.
2 does not have a magnetic gap or the like and does not need to be thin, sufficient mechanical rigidity is obtained, and a phase delay on the high frequency side (point R) caused in the actuator vibration characteristic of FIG.
Disappears, and the phase curve 8 shown in FIG. 6 is obtained. In addition, the support wire 16 that supports the movable body 15 including the cube holder 11 driven by electromagnetic force uses a thin viscoelastic member 19 for the primary and secondary vibration modes and a thick viscoelastic member for the tertiary and higher vibration modes. Attenuate with member 20. As shown in FIG. 7, the displacement characteristic of the movable body 15 causes hysteresis as shown by a dotted line curve 26 when only thick viscoelasticity is performed, but in this configuration, almost no hysteresis occurs as shown by a curve 27. Does not occur. Therefore, as described above, as shown by the phase curve 8 in FIG. 6, it becomes possible to obtain a vibration characteristic without a phase delay up to a high range, and thereby a high range of drive control can be achieved.

Further, by providing the magnetic circuits 21 and 22, the magnetic plate 14, and the magnetic fluid 25, the magnetic flux density in the coil portion and the magnetic flux path can be increased, so that the displacement force for drive control can be increased. Can be obtained efficiently.

Further, since the supporting wire 16 is composed of viscoelastic members 19 and 20 having different thicknesses, unnecessary resonance of the elastic rod 18 can be efficiently suppressed, and the precision of drive control can be improved. it can. Moreover, since the viscoelastic members 19 and 20 are provided on the abdomen of the elastic rod 18 in the third mode, hysteresis does not occur in the movement characteristics, and thus drive control can be improved.

[0025]

According to the first aspect of the present invention, there is provided a cube holder for holding a corner cube for maintaining a laser beam on a constant optical axis, a support mechanism including four support wires for supporting the cube holder, and A drive coil which is fixed to each side surface of the cube holder and has two sides facing in parallel with the optical axis and has a flat plate shape and a rectangular cross section, and the drive for applying opposite magnetic fluxes to the two opposite sides of the drive coil. Since the biaxial actuator is constituted by the driving mechanism having the magnetic circuit arranged opposite to the coil, the driving mechanism is constituted by the flat coil fixed to the cube holder and the magnetic circuit having no magnetic gap facing the planar coil. Since the thin part of the cube holder is eliminated, the mechanical rigidity can be increased, and the member resonance up to a high frequency band. Since it is possible to eliminate that as occurs, it is capable of performing always stable drive control to high bandwidth.

According to a second aspect of the present invention, in the first aspect of the present invention, the magnetic circuit of each pair of axes has a substantially hexagonal cross section and two faces facing the two sides of the drive coil are equal sides. Since the permanent magnet is magnetized in two sides and the pair of yokes has a triangular cross section and the slope is fixed to the equal side of the permanent magnet, the magnetic flux density in the coil portion can be increased. Therefore, the displacement force for drive control can be efficiently obtained.

According to a third aspect of the present invention, in the first or second aspect of the invention, the concave portion of the cube holder facing the apex of the permanent magnet is provided with a magnetic plate mixed with a magnetic substance and solidified. It is possible to increase the magnetic flux density in the magnetic flux path, so that the displacement force for drive control can be efficiently obtained.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, the magnetic fluid is disposed between the cube holder and the surface of the yoke of the magnetic circuit that faces the drive coil. The magnetic permeability μ is higher than that in the air, the magnetic resistance is reduced, and the magnetic flux density at the coil portion can be increased, whereby the displacement force for drive control can be efficiently obtained.

The invention according to claim 5 is the invention as defined in claims 1, 2, and 3.
Alternatively, in the invention described in 4, the support wire is composed of a viscoelastic member having viscoelasticity and having a different thickness, and an elastic rod. Therefore, it is possible to efficiently suppress unnecessary resonance of the elastic rod. It is possible to increase the bandwidth of drive control.

According to the invention of claim 6, in the invention of claim 5, since the viscoelastic member is provided on the abdomen of the elastic rod in the third vibration mode, it is possible to eliminate the occurrence of hysteresis or the like in the movement characteristics. This makes it possible to improve the accuracy of drive control.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing the configuration of a biaxial actuator that is an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a support wire.

FIG. 3 is a state diagram showing a vibration mode of a support wire.

FIG. 4 is an exploded perspective view of a magnetic circuit.

FIG. 5 is an explanatory diagram showing the flow of magnetic flux generated between a magnetic circuit and a coil unit.

FIG. 6 is a characteristic diagram showing vibration characteristics of the actuator of this embodiment.

FIG. 7 is a characteristic diagram showing a state of a displacement amount of a movable part with respect to a coil current.

FIG. 8 is an optical path diagram showing the principle of conventional optical axis control.

FIG. 9 is a characteristic diagram showing vibration characteristics of a conventional actuator.

[Explanation of symbols]

 10 Corner Cube 11 Cube Holder 12 and 13 Drive Coil 14 Magnetic Plate 16 Support Wire 18 Elastic Rod 19 and 20 Viscoelastic Member 21 and 22 Magnetic Circuit 23 Permanent Magnets 24a and 24b Yoke 25 Magnetic Fluid

Claims (6)

[Claims] 1. A cube holder that holds a corner cube that keeps a laser beam on a constant optical axis, a support mechanism that includes four support wires that support the cube holder, and a cube holder that is fixed to each side surface of the cube holder. A drive coil having a flat plate shape and a rectangular cross section having two sides facing each other in parallel to the optical axis, and a magnetic circuit arranged so as to face the drive coil so as to apply mutually opposite magnetic fluxes to the two sides facing each other. A biaxial actuator comprising: a drive mechanism having: 2. The pair of magnetic circuits of each shaft has a substantially hexagonal cross section and two sides facing the two sides of the drive coil are equilateral sides, and a permanent magnet magnetized in the two side directions has a triangular cross section. 2. The biaxial actuator according to claim 1, wherein the biaxial actuator has a pair of yokes each having an inclined surface fixed to an equal side portion of the permanent magnet. 3. The biaxial actuator according to claim 1, wherein a magnetic plate mixed with a magnetic substance and solidified is provided in a concave portion of the cube holder facing the top of the permanent magnet. 4. The biaxial actuator according to claim 1, wherein a magnetic fluid is disposed between the cube holder and the surface of the yoke of the magnetic circuit that faces the drive coil. 5. The biaxial actuator according to claim 1, 2, 3, or 4, wherein the support wire comprises a viscoelastic member having viscoelasticity and having a different thickness, and an elastic rod. 6. The biaxial actuator according to claim 5, wherein the viscoelastic member is provided on the abdomen of the elastic rod in the third vibration mode.