JP2001033727A - Light deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rock a reflection mirror part at high speed and to rock it at a wide deflecting angle even in the case of low driving electric power by making the reflection mirror part light in weight while maintaining the rigidity of the reflection mirror part. SOLUTION: This light deflector 1A is provided with the reflection mirror part 7 having a light reflection surface 7a on its front surface, a pair of supporting parts 8 and 8 supporting the mirror part 7 so as to freely rock with respect to a base 2, and a pair of fixed electrodes 10 and 11 arranged on the mirror part 7 side of the base 2. In the deflector 1A, voltage is applied between the pair of electrodes 10 and 11 and the mirror part 7, so that the mirror part 7 is rocked by electrostatic force with the pair of supporting parts 8 and 8 as a rocking center axis CL. As for the thickness of the mirror part 7, it is formed so that a rear surface side of the surface 7a is successively thinned toward free ends on both sides from the supporting parts 8 while the front surface side where the surface 7a is provided holds flatness. Namely, the rear surface of the mirror part 7 is made a linear inclined surface 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflector that reflects light such as a laser beam to deflect light.

[0002]

2. Description of the Related Art Scanning devices for optical equipment such as electrophotographic copying machines, laser beam printers, bar code readers, etc., optical deflecting devices for optical disk tracking control devices, and display devices for scanning laser beams and projecting images. For example, an optical polarizer is used.

Generally, there are a rotating polygon mirror (polygon mirror) and a turbulent reflecting mirror (galvano mirror) as an optical deflector for mechanically deflecting light. The galvano mirror type is a polygon mirror type. The mechanism can be downsized compared to, and in recent semiconductor process technology, a prototype example of a micro mirror using a silicon substrate has been reported.
Furthermore, miniaturization, weight reduction, and cost reduction can be expected.

FIGS. 8 and 9 show a conventional example of such a galvanomirror type optical deflector. FIG. 8 is an exploded perspective view of the optical deflector, and FIG. 9 is a schematic sectional view of the optical deflector. 8 and 9, the base 2 of the optical deflector 1C has a flat rectangular shape, and a pair of upright portions 3 and 4 are integrally formed on both left and right sides of the base 2 to protrude. The vibrating body 5 is arranged on the setting parts 3 and 4.

The vibrating body 5 has a rectangular outer frame portion 6 and a reflecting mirror portion 7 arranged in an opening 6a of the outer frame portion 6.
A pair of support portions 8, which connect the reflection mirror portion 7 and the outer frame portion 6 at an axial position passing substantially through the center of gravity of the reflection mirror portion 7,
8 is provided. The outer frame portion 6 is fixed on the upright portion 3, and the pair of support portions 8, 8 are connected to the base 2 via the outer frame portion 6.
It is fixed to. The reflection mirror unit 7 includes a pair of support units 8,
8 is swingable as a swing center axis CL (shown in FIG. 9). Further, a light reflecting film is formed on the surface of the reflecting mirror section 7 to form a light reflecting surface 7a.

Further, a pair of left and right fixed electrodes 10 and 11 are arranged on the base 2.
Are disposed at positions opposing the left and right rear surfaces of the reflection mirror unit 7. The outer frame 6 is used as an electrode on the other side of the pair of fixed electrodes 10 and 11, and the pair of fixed electrodes
Between the switch 11 and the outer frame 6
2, a voltage can be selectively applied. The outer frame 6 and the reflection mirror 7 are electrically at the same potential.

In the above configuration, when a voltage is applied between one of the fixed electrodes 10 and the reflection mirror section 7 via the outer frame section 6, the reflection mirror section 7 is attracted by electrostatic force and the reflection mirror section 7 is moved. A pair of support portions 8, 8 are pivoted about a central axis CL.
When a voltage is applied between the other fixed electrode 11 and the reflection mirror section 7 via the outer frame section 6, the reflection mirror section 7 is attracted by electrostatic force and the reflection mirror is rotated. The part 7 pivots the pair of support parts 8, 8 about the swing center axis CL.
And rotate clockwise. Therefore, the changeover switch SW
1 and SW2 are alternately turned on and off, and a voltage is alternately applied to the pair of fixed electrodes 10 and 11, whereby the reflection mirror section 7 swings. The reflection angle of the light applied to the reflection mirror unit 7 is changed by the swing of the reflection mirror unit 7, and the light is deflected.

[0008]

By the way, in the conventional example, in order to swing the reflecting mirror portion 7 at high speed, it is desirable that the weight of the reflecting mirror portion 7 is lighter. Here, as shown in FIG. 10, when the thickness t of the reflecting mirror portion 7 is reduced for weight reduction, inconveniences such as bending of the light reflecting surface 7a occur, which causes a problem in rigidity.

To increase the deflection angle (deflection angle) of the reflection mirror section 7, as shown in FIG.
It is necessary to set the gap between the pair of fixed electrodes 10 and 11 to be large. However, the electrostatic force is
Since it is inversely proportional to the power, a very large voltage is required to obtain the required driving force.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is possible to swing at a high speed by reducing the weight of the reflection mirror while maintaining the rigidity of the reflection mirror, and to reduce the driving force. It is an object of the present invention to provide an optical deflector that can swing with a wide deflection angle even under electric power.

[0011]

According to a first aspect of the present invention, there is provided a reflecting mirror having a light reflecting surface on a surface thereof, a pair of supporting portions for swingably supporting the reflecting mirror with respect to a base,
The base has a pair of fixed electrodes disposed on the side of the reflection mirror, and applies a voltage between the pair of fixed electrodes and the reflection mirror so that the reflection mirror is electrostatically applied to the pair of fixed electrodes. In the optical deflector that swings with the support portion as the swing center axis, the thickness of the reflection mirror portion is set such that the front surface side having the light reflection surface keeps a flat surface, and the back surface side of the light reflection surface is separated from each of the support portions. It is characterized in that it is formed so as to become gradually thinner toward at least one free end.

According to a second aspect of the present invention, in the optical deflector according to the first aspect, the thickness change of the reflection mirror portion is continuous.

According to a third aspect of the present invention, in the optical deflector according to the first aspect, the thickness change of the reflection mirror portion is stepwise.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 show a first embodiment of the present invention. FIG. 1 is a schematic sectional view taken along line AA of FIG. 2, FIG. 2 is a schematic plan view of an optical deflector 1A, FIGS. 4 is a schematic sectional view of the optical deflector 1A for explaining the operation of the reflection mirror unit 7.

In FIGS. 1 to 4, the first embodiment is compared with the conventional example, and the same components are denoted by the same reference numerals in the drawings to avoid redundant description, and the description thereof will be omitted. Only the configuration will be described.

That is, in the first embodiment, the thickness of the reflection mirror portion 7 is such that the front surface side having the light reflection surface 7a keeps a flat surface and the back surface side of the light reflection surface 7a has a pair of support portions 8,8.
From the top to the free ends on both sides. The back surface is formed as a linear inclined surface 20 so that the thickness change of the reflection mirror unit 7 is left-right symmetric and continuously thin. Other configurations are the same.

In the above configuration, as shown in FIG. 1, when no voltage is applied to the pair of fixed electrodes 10, 11, the reflection mirror section 7 is located at the neutral position. In this state, when the changeover switch SW1 is turned on, a voltage is applied between one fixed electrode 10 and the reflection mirror section 7 via the outer frame section 6, and the left side of the reflection mirror section 7 is subjected to electrostatic force. The reflecting mirror portion 7 is attracted and rotates counterclockwise about the pair of support portions 8, 8 as the swing center axis CL due to the torsion of the pair of support portions 8, 8. Then, as shown in FIG.
Is tilted to an angle α at which the free end on the left side contacts the fixed electrode 10.

Next, when the changeover switch SW1 is turned off and the changeover switch SW2 is turned on, the suction force of one fixed electrode 10 is released, and the pair of twisted support portions 8, 8 is elastically restored. A force is applied to return the reflection mirror unit 7 to the original position, and a voltage is applied between the other fixed electrode 11 and the reflection mirror unit 7 via the outer frame unit 6. The reflection mirror portion 7 is attracted by electrostatic force and rotates clockwise about the pair of support portions 8 and 8 as the swing center axis CL due to the torsion of the pair of support portions 8 and 8. Then, as shown in FIG. 4, the free end on the right side of the reflection mirror unit 7 is inclined to an angle β at which the free end contacts the fixed electrode 11.

Next, the changeover switch SW1 is turned on and the changeover switch SW2 is turned off. The on / off control of the changeover switches SW1 and SW2 is repeated, whereby the reflection mirror section 7 swings. The light illuminating the light reflecting surface 7a of the oscillating reflecting mirror 7 has its reflection angle changed by the oscillating movement of the reflecting mirror 7, and is thereby deflected.

In the above operation, the reflecting mirror 7 is gradually thinned from the pair of supporting portions 8 toward the free ends on both sides.
And the thickness of the pair of support portions 8, 8 is large, so that the reflection mirror portion 7 is strong against the torsional stress of the pair of support portions 8, 8. Has become. Therefore, the weight of the reflection mirror unit 7 is reduced while maintaining the rigidity of the reflection mirror unit 7, whereby the reflection mirror unit 7 can swing at high speed.

The swing angles α and β of the light reflecting surface 7 a of the reflecting mirror section 7 are determined by the dimensions L 1 and L 2 from the pair of supporting portions 8 and 8 to the free end of the reflecting mirror section 7 and the reflecting mirror section. 7 is uniquely determined by the gap distances D1, D2 between the back surface of the free end 7 and the pair of fixed electrodes 10, 11. When the same condition is set in the present invention and the conventional example, the gap interval between the back surface of the reflection mirror unit 7 and the pair of fixed electrodes 10 and 11 is the same in all positions in the conventional example. According to the present invention, the width becomes gradually narrower toward the center from the free end of the reflection mirror portion 7, thereby providing the following advantages.

That is, as shown in FIG.
In the neutral position, the gap between the back surface of the reflection mirror unit 7 and the pair of fixed electrodes 10 and 11 is narrower as the position is closer to the center of the pair of supporters 8 and 8, that is, When the mirror section 7 starts to incline from the neutral position, the electrostatic force in the narrow gap portion works effectively. As the reflection mirror section 7 is inclined, the gap interval is narrowed not only in the vicinity of the center section but also in the section away from the center section, so that the electrostatic force works more effectively, and as a result, the area of the reflection mirror section 7 is fully utilized. Electrostatic force is obtained. That is, in the present invention and the conventional example, when the same deflection angle is obtained by setting the gap interval between the free end of the reflection mirror unit 7 and the pair of fixed electrodes 10 and 11 to be the same, the present invention is better. Deflection is possible with a much smaller voltage. Therefore, it is possible to swing with a wide deflection angle even under a low driving power.

The swing angles α and β of the light reflecting surface 7a of the reflecting mirror section 7 are the same from the viewpoint of the stability of the light deflection speed, that is,
Left and right thickness distributions of the reflection mirror section 7 and a pair of fixed electrodes 1
In many cases, the positions of 0 and 11 are set symmetrically.

In the first embodiment, the outer frame 6, the reflection mirror 7, and the pair of supports 8, 8 are integrally formed as the vibrator 5, so that they are formed integrally with the reflection mirror 7. The pair of support portions 8, 8 themselves are also configured to be thick. That is, the outer frame portion 6, the reflection mirror portion 7, and the pair of support portions 8, 8 are integrally formed as the vibrator 5, and in the conventional example, the thickness of the reflection mirror portion 7 is reduced to reduce the weight. The thickness of the pair of support portions 8 is also reduced when
Although a problem also occurs in the durability and long-term reliability of the support portion 8, in the present invention, the thickness of the pair of support portions 8, 8 can be increased, so that the durability due to twisting can be maintained, and a problem in long-term reliability occurs. Never do.

In the first embodiment, since the thickness change of the reflection mirror 7 is set to be continuously reduced, when the reflection mirror 7 swings, the back surface of the reflection mirror 7 and a pair of Since the gap interval between the fixed electrodes 10 and 11 can be continuously approached, the electrostatic force can be applied efficiently.

FIG. 5 is a schematic sectional view of an optical deflector 1B showing a second embodiment of the present invention. In FIG. 5, the difference between the second embodiment and the first embodiment is that the rear surface has a stepped surface so that the thickness change of the reflection mirror unit 7 is symmetrical and thin in a stepwise manner. 21 is the only point formed. Since other configurations are the same, the same reference numerals are given to the drawings to avoid redundant description, and the description is omitted.

In the second embodiment, substantially the same operations and effects as those in the first embodiment can be obtained. In addition, the first
It is not easy to make the back surface of the reflection mirror section 7 linearly inclined as in the embodiment by the dry etching technique or the like, and the angle or the like is limited by the Si anisotropic etching technique or the like. In this regard, the step-like shape as in the second embodiment can be easily formed by repeating lithography and etching techniques divided stepwise, which is easy in manufacturing.

The optical deflector 1 according to the present invention thus configured
B is effective for high-speed driving because the effect of air resistance can be eliminated by vacuum sealing using a method such as anodic bonding.

FIG. 6 is a schematic configuration diagram of a display device using the optical deflectors 1A and 1B. In FIG. 6, laser light emitted from a laser light source 30 is applied to a horizontal scanning optical deflector 3.
1 is irradiated. The reflection mirror portion of the horizontal scanning light deflector 31 is swung in synchronization with the horizontal frequency, and the reflected light is scanned in the horizontal direction by the swing. The laser light reflected here is applied to the vertical scanning optical deflector 32. In the vertical scanning optical deflector 32, the reflection mirror portion is swung in synchronization with the vertical frequency, and the reflected light is scanned in the vertical direction by the swing. The laser beam reflected here is the screen 33
Is irradiated.

The optical deflectors 1A and 1B are used as the horizontal scanning optical deflector 31. As described above, since the optical deflector 1 can swing at a high speed and a wide deflection angle, it is synchronized with a scanning frequency of several tens kHz. Can be swung. Of course, the optical deflectors 1A and 1
B may be used.

FIG. 7 is a schematic configuration diagram of another display device using the optical deflectors 1A and 1B. In FIG. 7, a laser beam emitted from a laser light source 30 is applied to a horizontal scanning optical deflector 31. The reflection mirror portion of the horizontal scanning light deflector 31 is swung in synchronization with the horizontal frequency, and the reflected light is scanned in the horizontal direction by the swing. The laser light reflected here is applied to the vertical scanning optical deflector 32. In the vertical scanning optical deflector 32, the reflection mirror portion is swung in synchronization with the vertical frequency, and the reflected light is scanned in the vertical direction by the swing. The reflected laser beam passes through the focusing lens 34 and irradiates the optically addressed spatial modulation element 35. The optical address type spatial modulation element 35 writes this optical information, amplifies the lightness and luminance on the surface side, and displays the amplified light information on the liquid crystal.

On the other hand, the light from the lamp 36 passes through an infrared cut filter 37, a lens 38, and a wavelength filter 39, and is incident on a polarization beam splitter 40.
This reflected light is applied to the optically addressed spatial modulation element 35. The light reflected by the light addressing type spatial modulation element 35 is again incident on the polarization beam splitter 40, and the light transmitted therethrough is irradiated on the screen 33 via the lens 41.

The optical deflectors 1A and 1B are used as the horizontal scanning optical deflector 31, and can oscillate at a high speed and a wide deflection angle as described above. Can be swung. Of course, the optical deflectors 1A and 1
B may be used.

According to the application example, the optical deflector 1A,
Although the display device is shown as an application example of 1B, it is of course applicable to a scanning device of an optical device such as an electrophotographic copying machine, a laser beam printer, a bar code reader, and an optical deflection device of a tracking control device of an optical disk. It is.

In the first embodiment, the thickness is reduced continuously from the pair of support portions 8, 8 of the reflection mirror portion 7 toward the free end. In the second embodiment, the thickness of the reflection mirror portion 7 is reduced. Although the thickness is reduced stepwise from the pair of support portions 8 toward the free end, the thickness may be reduced by combining continuous and stepwise.

In the first and second embodiments, the reflecting mirror portion 7 is formed so that the thickness is reduced from the pair of support portions 8 toward both free ends. It may be formed so that the thickness is reduced only from 8, 8 toward any one free end.

[0038]

As described above, according to the first aspect of the present invention, a reflecting mirror portion having a light reflecting surface on its surface, and a pair of supporting members for swingably supporting the reflecting mirror portion with respect to the base. And a pair of fixed electrodes disposed on the reflection mirror side of the base, and a voltage is applied between the pair of fixed electrodes and the reflection mirror to apply the electrostatic force to the reflection mirror. In the optical deflector that oscillates with the pair of support portions as the oscillating central axes, the thickness of the reflection mirror portion is such that the front surface side having the light reflection surface keeps a flat surface, and the back surface side of the light reflection surface is each of the above. Since it is formed so as to gradually become thinner from the support portion toward at least one free end, it is possible to swing at high speed by reducing the weight of the reflection mirror while maintaining the rigidity of the reflection mirror, and low driving power. Wide deflection angle even under It is possible to swing.

According to the second aspect of the present invention, in the optical deflector according to the first aspect, since the thickness change of the reflection mirror portion is continuous, when the reflection mirror portion swings,
Since the gap between the back surface of the reflection mirror portion and the fixed electrode can be continuously approached, the electrostatic force can be applied efficiently.

According to the third aspect of the present invention, in the optical deflector according to the first aspect, the thickness change of the reflection mirror portion is stepwise, so that the reflection mirror portion is divided stepwise. It can be easily made by repeating the etching technique, and is easy to manufacture.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention and is a schematic sectional view taken along line AA of FIG.

FIG. 2 is a schematic plan view of the optical deflector, showing the first embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of the optical deflector for illustrating the operation of the reflection mirror unit according to the first embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of the optical deflector for illustrating the operation of the reflection mirror unit according to the first embodiment of the present invention.

FIG. 5 is a schematic sectional view of an optical deflector according to a second embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a display device using an optical deflector.

FIG. 7 is a schematic configuration diagram of another display device using an optical deflector.

FIG. 8 is an exploded perspective view of a conventional optical deflector.

FIG. 9 is a schematic sectional view of a conventional optical deflector.

FIG. 10 is a cross-sectional view of a conventional optical deflector when the thickness of a reflection mirror portion is reduced.

FIG. 11 is a schematic cross-sectional view of a conventional optical deflector in which a gap between a reflection mirror and a base is widened.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1A, 1B Optical polarizer 2 Base 7 Reflecting mirror part 7a Optical anti-slope surface 8 Support part 10, 11 Fixed electrode 20 Linear inclined surface 21 Step surface

Claims (3)

[Claims] A reflecting mirror having a light reflecting surface on a surface thereof; a pair of supporting portions for swingably supporting the reflecting mirror with respect to a base; and a pair of supporting members disposed on the reflecting mirror side of the base. A voltage that is applied between the pair of fixed electrodes and the reflection mirror portion, and the reflection mirror portion swings about the pair of support portions with the electrostatic force by the electrostatic force. In the deflector, the thickness of the reflection mirror portion is gradually reduced as the front surface side having the light reflection surface keeps a flat surface, and the back surface side of the light reflection surface moves toward at least one free end from each of the support portions. An optical deflector characterized by being formed as described above. 2. The optical deflector according to claim 1, wherein the thickness change of the reflection mirror portion is continuous. 3. The optical deflector according to claim 1, wherein the thickness change of the reflection mirror portion is stepwise.