JPH0784196A - Optical deflector and display device using the same - Google Patents

Abstract

PURPOSE:To provide a mechanical optical deflector and a display device using the deflector miniaturizing the area of a mirror, having a large effective voltage and capable of controlling a deflection angle by means of the drive of an optical write system. CONSTITUTION:This optical deflector is formed on the upper surface of a light transmissive substrate and provided with photodetector parts 11-13 making the resistance value to be changed according to light quantity being projected, mechanically movable parts 16-18 arranged so as to be opposed to the photodetector parts on the substrate with a air gap and supporting one end of optical deflector plate 16 electrically connected to the photodetector parts in series as a free end, and a voltage applying means applying the voltage to the photodetector parts and the optical deflector plate in series. When the lower surface of the substrate is irradiated with a control light beam, the resistance value of the photodetector part is decreased and the ratio of voltage applied on the optical deflector plate among the voltage applied by the voltage applying means is increased, thereby the free end of the optical deflector plate is attracted to the side of photodetector part, the optical deflector plate is inclined with the supporting end as center and the proejcted light beam made incident from the first surface side of the substrate is made to be deflected/reflected in accordance with the tilt of the optical deflector plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflector, and more particularly to an optical writing type optical deflector which is manufactured by using a micromechanics technique and whose displacement is controlled by using electrostatic attraction, and a display device using the optical deflector.

[0002]

2. Description of the Related Art At present, a main optical deflector applies the amount of light emitted from the back surface to a minute area by using an electro-optical effect used for adjusting the amount of light of a ferroelectric material such as a liquid crystal cell or PLZT. Solid-state optical shutter controlled by voltage (Journal of the Electrophotographic Society, Vol. 30, No. 4, 1991, p447
494), there is a mechanical optical deflector using light reflection such as a galvanometer. The optical shutter is applied to an optical printer head of an electrophotographic printer as a display device by forming a one-dimensional array, a liquid crystal display in which liquid crystal cells are two-dimensionally arranged, and the like.

A mechanical optical deflector uses a multi-wavelength light source because it can be deflected or shielded regardless of the wavelength of light by using reflection on a mirror surface as an optical element for optical communication such as an optical switch. However, it is useful when the wavelength of the light source fluctuates, but it is inferior to the solid-state optical shutter in terms of high-speed response, miniaturization, arraying, etc., and its application fields are limited.

In recent years, a micromachine having an extremely small movable mechanism using a semiconductor photolithography process has been studied by a micromechanics technique. A typical micromachine is a wobble micromotor (M. Mehregan
y et al. , "Operation of mi
crofabricated harmonic an
d ordinary side-drive mot
ors ”, Proceedings IEEE Mic
ro Electro Mechanical System
ems Workshop 1990, p1-8), and linear microactuator (P. Cheung e)
t al. , "Modeling and position
ion-detection of a polysi
licon linear microactuato
r ”, Micromechanical Sensor
s, Actuators and Systems A
SME 1991, DS C-Vol. 32, p269
-278), a piezoelectric bimorph cantilever (USP4,
906, 840) and the like have been proposed.

These micromachines are manufactured by a semiconductor photolithography process, and can be easily arrayed and reduced in cost. High-speed response can be expected by miniaturization. As an optical deflector which is a mechanical optical element, K. E. Peter
Torsion by silicon proposed by sen
al Scanning Mirror (IBM J.
RES. DEVELOP. , Vol. 24, No. 5,
9.1980, pp. 631-637) and the deformation of the cantilever, scanning with a laser beam by Micromechan.
ical light modulator arra
y ("Dynamic Micromechanics
on Silicon Technologies an
d Devices "IEEE Trans.on E
electron Devices, Vol. ED-2
5, No. 10, Oct. 1978, p1241-12
49).

In the application of a light deflector to a display device, M.M.A., in which a plurality of pixels are arranged on a plane by using reflection of a metal thin film having a flexible beam, A. Mi proposed by Cadman et al.
chrome mechanical display ("Ne
w Micromechanical Display
Using Thin Metallic Film
s "IEEE Electron Device Le
tters, Vol. EDL-4, 1983, pp3-
4), L.S. J. Spatial light modulator by Hornbeck (Japanese Patent Laid-Open No. 2-8812), R.K. N. MirrorMatrix Tube (IEEE T by Thomas et al.
rans. on Electron Devices,
Vol. ED-22, No. 9, Sep. 1975, p
765-775).

[0007]

The reflection type mechanical optical deflector shown by Cadman and Hornbeck, etc., is of the electrical writing type, and its operation is mainly a binary display using deflection in two directions. Is proposed to be applied to the display. When this optical deflector is formed into an array and used as a display device, particularly when used as a television device, gradation display (8 bits, 256 gradations) is a problem. As a method of stably performing multi-gradation display in binary display, an area modulation method in which a spatial light modulator is combined and gradation is expressed by the area ratio, or a time width in which the spatial light modulator is modulated is used. A pulse width modulation method for expressing gradation can be considered.

Regarding the area modulation method, for example, in the case of displaying 8 bits and 256 gradations, 2 unit pixels for binary display are used.
Since it is necessary to combine 56 pixels into one pixel, the spatial force of the display image is significantly reduced. That is, if one spatial light modulator is one unit element, one pixel will be represented by four 16-element elements, and therefore one pixel will be 160 μm square when the size of one unit element is 10 μm square. Even if a 1 × batch exposure apparatus is used, the resolution is about 500 pixels at 3 inches, and the display apparatus becomes larger when aiming for higher resolution, and the display apparatus is manufactured on a Si wafer by using a semiconductor photolithography process. 1 substrate (Si wafer)
Since the number of cut-out display devices per unit is reduced, the yield rate and the production number are reduced, which leads to an increase in the price of the display device.

On the other hand, in the pulse width modulation method, when displaying 8 bits and 256 gradations, 130 μs (1 = 1/30) is required to scan a frame frequency of 30 Hz.
/ 256), it is necessary to scan one screen. For example,
In a display device having 1000 scanning lines, the scanning time for one scanning line is within 0.1 μs. Also, the transfer of the shift register necessary to transfer the data for one scanning line is
When the number of pixels for one scanning line is 2000 (in consideration of HDTV compatibility), the shift time per cycle is 0.0
Within 6 ns. Therefore, the drive frequency of the shift register is about 16 GHz, a drive means for dividing the screen of the display device is required, and the load of the drive system becomes very large. As a result, the cost of the peripheral circuit for driving the display device is increased, and the price of the display device is increased as described above.

Therefore, when the light deflector is applied to a display device, in order to obtain a display device with a small load on the drive system, the deflection angle is controlled for each light deflector to give a gradation expression for each pixel. Is desirable.

Further, in a display device using a mechanical optical deflector, the image is projected on the screen by the reflection type. At this time, it is important for the projection type display to improve the screen brightness. A metal halide lamp (MH lamp) or a xenon short arc lamp (Xe-sa lamp) is used as a high-intensity lamp for projection to obtain high brightness. Usually, the light source has a finite emission diameter, and the appropriate device size and lens diameter are determined by the lamp used.

When a transistor for address control is provided for each pixel in binary display, a stepper is used as an exposure device when forming a pattern of a transistor capable of high speed response in an optical deflector by electric writing. The device size is determined by the exposure field of the stepper. Based on the current reticle mask size and the reduction ratio of the optical system, the exposure field is diagonally 22 to 25 mm (1.2 to 1.4 mm).
The maximum device size is 1.4 inches or less. A 1.4-inch diagonal device has a suitable emission diameter of about 1 to 2 mm, which is a currently usable lamp as a Xe-sa lamp.

However, the life of the Xe-sa lamp is 1000
It is short and not suitable for television equipment. In order to manufacture a high-brightness display, it is preferable to use a long-life MH lamp (having a life of up to 6000 hours) having a light source diameter of several mm. This requires a device size of 2 inches or more. In other words, it is desirable to use a driving system that can operate independently for each pixel without using a high-speed response transistor for address control.

As a method of driving the optical deflector without using the address control transistor, an optical writing type liquid crystal light valve (CdS-LCL) utilizing the photocapacitance effect of a photodiode composed of CdS and CdTe is used.
V, L. M. Fraas et al., “Novell charg”
e-storage-diode structure
for use with light-activ
aged displays ”, Journal of
Applied Physics, Vol. 47, N
o. 2, 1976, p576-583). LCL
V has a device size of about 2 inches and a light source diameter of 5
An MH lamp of about mm can be used.

However, the response speed of the LCLV depends on the response speed of the liquid crystal ("Projection Television Design No. 107", p151, published by Trikeps Co., Ltd.), and it is desired to have a high response speed in a low temperature range. The LCLV using a mechanical micromirror, which can be expected to have a high-speed response for light modulation, is a D.I. Proposed by Armitage ("MIC
ROMIROR SPATIAL LIGHT MO
DULATOR "United States Pat"
ent Number: 4, 698, 602). However, in 4,698,602, since the photocapacitance effect is used, the effective voltage to the micromirror is equal to that of the liquid crystal for the writing light (to 100 μW / cm ² ) to the optical writing type light valve. It is a low voltage of about V. The fast response is determined by the spring constant of the beam supporting the micromirror and the shape of the mirror, and the response improves as the spring constant increases.

However, in order to displace the micromirrors by electrostatic attraction under a low voltage, the mirror area must be increased, and if high-speed response is to be achieved at the same time, the mirror area is about 100 μm square. In order to display a television device, particularly a high-definition image, it is necessary to reduce the area of the mirror and increase the number of pixels. That is, it is necessary to increase the effective voltage in order to reduce the mirror area and increase the electrostatic attractive force. A light valve that drives a micromirror by the photocapacitance effect cannot obtain a sufficient resolution as a display device, particularly a television device.

Further, in 4, 698, 602, the Si substrate used to reduce the capacitance of the diode is int.
Since the substrate is made of resin and has a substrate thickness of about 100 μm, a bonding process of Si and glass is required (D. Armitage, “High-Speed S”).
"patial Light Modulator", IE
EE Journal of Quantum Ele
ctronics, Vol. QE-21, No. 8, 1
985, p1241-1248). If there is a bonding defect or the like, the writing light is scattered and interferes at the interface between Si and glass, resulting in a decrease in photosensitivity. This is not preferable in terms of process because the yield is lower than that of the LCLV described above.

In view of the above problems, it is an object of the present invention to provide an optical deflector capable of realizing the following and a display device using the same. (1) A mechanical optical deflector capable of controlling a deflection angle by an optical writing type drive. (2) An optical deflector that can reduce the mirror area and obtain a large effective voltage. (3) An optical deflector that can secure a high yield without a bonding process. (4) A projection-type display device capable of displaying a high-definition image, which includes an optical deflector that realizes these contents.

[0019]

That is, the optical deflector of the present invention, which has been made to achieve the above object, is formed on the first surface of a light transmissive substrate and has a resistance value depending on the amount of light irradiated. And a photo-deflecting plate made of an electric conductor thin film which is arranged so as to face the photo-detecting part on the first surface of the substrate with a gap and is electrically connected in series with the photo-detecting part. In addition, a mechanical movable portion that supports one end of the light deflection plate as a free end and the other end opposite to the free end as a support end, and a voltage application unit that applies a voltage in series to the light detection unit and the light deflection plate. When the control light is radiated from the second surface side that faces the first surface of the substrate, the resistance value of the light detection unit decreases,
By increasing the ratio of the voltage applied by the voltage applying means to the light deflection plate, the free end of the light deflection plate is attracted to the photodetection section side, and the light deflection plate tilts toward the support end center, and The projection light incident from the first surface side is deflected and reflected according to the inclination of the light deflection plate.

The photodetection section includes a first fixed electrode formed in layers on the first surface of the substrate, a photoconductor layer formed on the first fixed electrode, and a photoconductive layer. A second fixed electrode formed in layers on the body layer, the photoconductive layer made of an amorphous silicon thin film, the first fixed electrode made of a light transmissive conductive thin film, The voltage applying means preferably applies an AC sine wave voltage.

Further, the mechanically movable portion includes the light deflection plate, a beam that supports the light deflection plate and is elastically deformed, and a support portion that supports the beam. It is preferable that one end of the light deflection plate is connected to a free end of a bending spring and is arranged above the bending spring, or that the beam is formed of a twisting pin that rotatably supports the light deflection plate.

Further, it is preferable that the mechanical movable portion is formed on the photodetection means via an insulating layer and has a supporting electrode for applying a voltage.

The display of the present invention comprises a plurality of optical deflectors having a common substrate, a projection lens and a diaphragm for projecting incident light on a screen, and a plurality of the optical deflectors. A projection light source for irradiating light on the light deflection plate,
From the second surface side of the substrate of the plurality of light deflectors, each light deflector is irradiated with control light, reflected by the light deflector plate of the plurality of light deflectors, and reflected through the projection lens and the diaphragm. Optical writing means for projecting an image by light on a screen.

Further, it is preferable that the optical writing means is an image information display means arranged so as to face the second surfaces of the substrates of the plurality of optical deflectors.

[0025]

In the optical deflector of the present invention configured as described above, the resistance changes due to the amount of the control light incident on the photodetection section provided on the substrate due to the photoconductive effect, and the resistance changes. Along with this, the voltage applied to the mechanically movable parts connected in series changes, and the tilt angle of the light deflection plate changes due to electrostatic attraction as the applied voltage changes. That is, the projection light incident on the light deflection plate is deflected according to the amount of control light incident on the light detection unit. As the area of the light deflecting plate, that is, the mirror, is reduced, the applied voltage is increased to increase the effective voltage to the movable portion of the machine to obtain a desired deflection angle. Since the mirror area can be reduced, the light deflector is arrayed to form the light valve, thereby realizing a high-definition display device.

[0026]

Embodiments of the optical deflector of the present invention and a display device using the same will be described below with reference to the drawings. FIG. 1 is a perspective view showing the configuration of an embodiment of the optical deflector of the present invention. FIG. 2 is a sectional view taken along line AA of the embodiment shown in FIG. Figure 3
FIG. 2 is a diagram showing an equivalent circuit of the embodiment of FIG. 1 when driving the embodiment of FIG.

The substrate 10 is made of glass so that the writing light WL for writing the light incident from the lower surface is transmitted. A first fixed electrode 11, a photoconductor layer 12, and a second fixed electrode 13 are sequentially formed on the upper surface of the substrate 10 to form a photodetection section. An insulating layer 14 is formed on the second fixed electrode 13 of the photodetecting section, and a supporting electrode 15 having an opening 19 at the center is formed on the insulating layer 14.

On the support electrode 15, two support portions 18 fixed to the support electrode 15 support the support electrode 15.
And two flexible springs 17 extending along the opening 19 in parallel with the support electrode with a space therebetween, and connected to the free ends of the flexible springs 17 and folded back from the free ends of the flexible springs 17 onto the flexible springs 17. As described above, the mechanical movable portion is configured by the bending spring 17 and the one movable electrode 16 that extends in parallel with the bending spring 17 while keeping a distance. In this case, the bending spring 17 serves as a beam that elastically deforms and supports the movable electrode, and the movable electrode 16 has a role of a mirror for deflecting the projection light IL incident from above (the projection light IL is movable). Due to the inclination of the electrode 16, the light is reflected like the projection light RL1 or RL2).

The function of the embodiment shown in FIG. 1 will be described with reference to FIG. The photoconductor layer 12 includes the first and second fixed electrodes 1
It works as an optical sensor by making ohmic contact with 1 and 13. The supporting electrode 15 is the second fixed electrode 13
And an additional capacitance Cox is formed via the insulating layer 14, and the movable electrode 16 forms a mirror capacitance Cm between the movable electrode 16 and the second fixed electrode 13 through the opening 19 of the support electrode 15. Support electrode 1
Reference numeral 5 supports the movable electrode 16 and is electrically connected to the movable electrode 16.

In this embodiment, the voltage Va is applied between the first fixed electrode 11 and the support electrode 15. The applied voltage Va is a sine wave alternating current. If the angular frequency of the sine wave is ω, the overall impedance Z (Z = R + jX) of the circuit is the real part R
Is Rs and the imaginary part X is − (1 / Cox + 1 / Cm) / ω. That is, the resistance Rs of the photoconductor layer decreases as the amount of writing light increases, and the voltage Vm applied to the mirror capacitance Cm increases, so that the electrostatic attraction to the movable electrode 16 increases, and accordingly the movable electrode 16 increases. The inclination angle θ becomes larger. By taking Cox larger than Cm, the imaginary number X can be changed with respect to the change in Cm when the tilt angle of the movable electrode increases.
The change of can be suppressed. Since Vm changes with the angular frequency ω, the angular frequency of displacement of the movable electrode also becomes ω. Further, by disposing the bending spring 17 on the supporting electrode, the spring itself that is deformed is configured so that no voltage is applied to it, and the leakage light to the light detecting portion of the projection light to the movable electrode provided with the supporting electrode in the portion other than the opening is prevented. Has the role of blocking.

In the optical deflector of the present invention, a mirror formed by laminating dielectric thin films, which is essential in LCLV, is unnecessary. In the conventional optical deflector using the electrostatic actuator, the fixed point of the mirror, that is, the position of the connecting portion between the bending spring 17 and the movable electrode 16 is displaced toward the substrate side or is not displaced. In the container, the connecting portion is displaced upward, and the tilt angle is substantially increased.

Next, the optical polarization of the first embodiment shown in FIG.
FIG. 4 shows an example of the manufacturing process of the actuator (electrostatic actuator).
5 and the manufacturing process chart of FIG. As substrate 10
As the glass, a glass 20 having a good light transmittance was used. Glass base
On the plate, indium / titanium / oxide thin film 21
(Hereinafter referred to as ITO thin film 21) is In₂O₃/ SnO
₂Sputtering, which is one of the vacuum deposition methods using a target
A film having a film thickness of 0.2 μm was formed by using the ring method. Next
And SiH by plasma CVD method_FourPhotoconductive with gas
Amorphous silicon film (a-Si) 22 to be a body layer
5 μm formed, and further SiH_FourTo Phoshin (PH₃)
0.1 μm n-type a-S mixed and used as the second fixed electrode
The i layer 23 is formed. The photodetector is formed by the above process
To do. On top of the n-type a-Si layer 23 of the photodetector, a layer of Al
Target, reactive sputter phosphorus with oxygen gas
Al to be an insulating layer₂O₃Forming 24 (Fig.
4 (a)).

Next, the manufacturing process of the mechanical movable portion will be described. First, an Al thin film 25 having a thickness of 300 nm is deposited by a sputtering method, a photoresist is applied and patterned by a photolithography process, and reactive ion etching is performed on the Al thin film 25 using a mixed etching gas of BCl ₃ and Cl _2. Patterning is performed by a method (RIE) to form openings 19 to form support electrodes (not shown),
The photoresist used for patterning is removed (FIG. 4).
(B)).

Next, the photoresist 101 was applied by a spin coater to a thickness of 1.5 μm, and a sacrifice layer which was removed in the final step to form voids was formed. The photoresist is Hoechst (H
Oechst) positive photoresist, trade name AZ1350J was used. The photoresist 101 is partially removed by photolithography to form a support for the mechanically movable portion (FIG. 4C). Next, an Al thin film 26 to be the bending spring 17 and the supporting portion 18 was formed by a 75 nm sputtering method (FIG. 4D).

The temperature of the substrate holder during sputtering was set to 5 ° C. to suppress the thermal stress during film formation. Al thin film 26
On the other hand, the bending spring 17 and the supporting portion 18 were patterned by photolithography (FIG. 4E). An underlying layer 27 is formed on the thus-formed flexible spring 17 so as not to damage the photoresist 101 when the photoresist 102, which serves as a second sacrificial layer for forming a gap between the movable electrode and the flexible spring 17, is applied. (Fig. 4 (f)).
The underlaying layer is made of SiO ₂ of 50n by the sputtering method.
m, a film was formed.

Next, a photoresist 102 was applied in the same manner as the photoresist 101 to form a second sacrificial layer to be removed in the final step (FIG. 5 (g)). The film thickness of the photoresist 102 is 1.5 μm, and the gap between the insulating layer and the movable electrode is 3 μm. The photoresist 102 was the same as the photoresist 101. Photoresist 10
2 is partially removed by photolithography for the purpose of mechanical and electrical connection between the bending spring 17 and the movable electrode (FIG. 5 (h)). The SiO ₂ in the part of the photoresist 102 that has been partially removed is removed by RIE using CF ₄ gas. The movable electrode is an Al thin film 2 under the condition of forming the bending spring 17.
8 was deposited. The film thickness was 300 nm (Fig. 5)
(I)). The Al thin film 28 is patterned by photolithography with the photoresist 103, and the support electrode 15 is formed.
Similarly, the Al thin film 28 was patterned to form the movable electrode 16 (FIG. 5 (j)).

Finally, the photoresists 101 and 102 and the underlayer 27 are RIEed with a mixed gas of oxygen and CF _4.
It was removed by etching (FIG. 5 (k)). At this time, the insulating layer Al ₂ O ₃ is not etched to prevent etching of the photodetection portion below the opening. Through the above manufacturing steps, FIG.
It was possible to obtain the optical deflector shown in. The method of removing the organic polymer film under the Al thin film by dry etching is described in M. A. Proposed by Cadman et al. (Cited above).

The shape of the optical deflector formed by the above method will be described. The movable electrode 16 is 23 μm square and C
The support electrode 15 and the opening 19 were arranged so that ox was 5 fF and Cm was 0.8 fF. The mechanical resonance frequency of the light deflector, that is, the response frequency of light deflection was 75 kHz. Further, a-Si has a photoconductivity of 5 × 10 ⁻⁸ (Ω · c) with respect to a writing light amount (WL) of 100 μW / cm ^2.
m) It is ^-1 . The wavelength of the writing light is 600 nm. Vm / V when changing the amount of writing light when the applied voltage Va is 100 V and the frequency of the sine wave is 1 kHz
FIG. 6 shows the measurement results of the ratio a and the maximum value Θ of the tilt angle θ of the movable electrode operating in a sine wave (in FIG. 6, the arrow indicates the vertical axis of the pointing direction).

As shown in FIG. 6, the applied voltage Vm to the movable electrode is 3 with respect to the writing light amount of 100 μW / cm ^2.
Since a voltage of about 0 V was applied, the maximum tilt angle at that time was 6 °. In the conventional photocapacitance effect, an applied voltage of about several V can be obtained. Therefore, in the case where the optical deflector of the present invention has the same response frequency and mirror area, the tilt angle is 0.5 ° or less. Let's understand better.

In the optical deflector using the photocapacitance effect, in order to increase the tilt angle, it is necessary to lower the response frequency and widen the mirror area, which reduces the frequency of the AC voltage. The optical deflector of the present invention is capable of controlling the deflection angle by the writing light quantity as shown in FIG. 6 by the optical writing drive, and is an optical deflector capable of obtaining a large effective voltage even if the mirror area is reduced. Has become.
Further, as shown in the manufacturing process, an optical write-driven optical deflector can be manufactured by using the thin film forming process and the photolithography process, and the high yield without the bonding process used in the conventional manufacturing process can be achieved. It is an optical deflector that can be secured.

Next, a second embodiment of the optical deflector of the present invention will be described with reference to the configuration diagram of FIG. In the optical deflector of the embodiment of FIG. 1, the bending spring 17 is flexibly deformed, whereas in the present embodiment, the movable electrode 36 is rotationally displaced about the rotation axis of the torsion spring 37. For this reason, the movable electrode 36 is provided with a contact hole 40 for forming the movable electrode supporting portion 381 so as to be coupled with the torsion spring 37. First fixed electrode 3 formed on the substrate 10
1, photoconductor layer 32, second fixed electrode 33, insulating layer 34
Is formed similarly to the embodiment of FIG. 1, but the opening 39 of the support electrode 35 is formed so as to face the half surface of the movable electrode 36.

Further, a third embodiment of the optical deflector of the present invention will be described with reference to the configuration diagram of FIG. In the optical deflector of the embodiment shown in FIGS. 1 and 7, the mechanical movable portion is formed as a thin film on the light detecting portion, but in the embodiment shown in FIG. 8, the light detecting portion and the mechanical movable portion are independent. Is formed. First fixed electrode 41, photoconductor layer 42, second fixed electrode 4
The photodetector and the insulating layer 44 composed of 3 are formed into a thin film on the second fixed electrode 43 of the first substrate 111, and the second substrate 11
A support electrode 45, a support portion 48, a bending spring 47, and a movable electrode 46 serving as a mirror are formed on the second electrode 2. Then the first
In addition, the first substrate 111 and the second substrate 1 in the state where the second substrate is provided with a gap between the movable electrode 46 and the insulating layer 44.
Fix 12 The support electrode 45 is arranged so that the projection light to the mirror does not enter the bending spring 47, and the reflected light when the bending spring is deformed is the noise light (leakage light) of the reflected light of the mirror.
To prevent

When the first substrate 111 and the second substrate 112 are fixed, a substrate bonding process is required. Armit
It is not necessary to bond Si, which will be the photodiode, to the entire surface of the substrate, as long as the void can be formed. As a result, the yield of the photodetector due to the bonding does not decrease. Further, the structure of the optical deflector in FIG. 8 makes it possible to secure a large area for receiving the electrostatic attraction to the movable electrode. The insulating layer 44 has a role of preventing the movable electrode from coming into contact with the second fixed electrode due to an excessive voltage applied due to an abnormality in the AC voltage power supply. The insulating layer 44 may not be provided by stabilizing the AC voltage power supply.

The configuration, operation, and manufacturing process of the optical deflector of the present invention have been described above with reference to the embodiments. Any photoconductor layer may be used as long as its conductivity changes with respect to the wavelength of writing light. For visible light, CdS, CdSe,
CdS / Se or the like may be used, and a material having excellent transient response of photocurrent is preferable. a-Si is plasma CV
D is one of the materials that can be manufactured inexpensively in a large area and has excellent transient response. If infrared light is used as the writing light, HgCdTe or the like may be used for the photoconductor layer. Any substrate can be used as long as it is transparent to the wavelength of the writing light to the photodetection section, and in the present invention, inexpensive and easily available glass is used. As the first fixed electrode material, a metal, a semiconductor or the like can be used unless the amount of light to the photoconductor layer is significantly reduced. IT
A material having a high light transmittance and a high conductivity, such as O or SnO ₂ , is more preferable for the first fixed electrode.

In the manufacturing process, the same material was used as the sacrificial layer, but any material can be used as long as it can be removed without corroding the insulating layer, the fixed electrode and the mechanical movable portion when removing to form the void portion. Different materials may be used as the material for each void. Although a photoresist is used as the sacrificial layer material in the examples, it is not particularly limited.
As another sacrificial layer material, a metal alloy thin film made of Ti or Ti / W is formed by a vacuum evaporation method such as a resistance heating evaporation method or an electron beam evaporation method, and hydrogen peroxide solution is used to remove the void forming material. A similar optical deflector of the present invention can also be formed by removing it by etching. Also,
Although an Al thin film was used as the mechanical movable part and the fixed electrode,
Au, Ni, Pt, Ti, Co, Ag, Cu, G if the material is not etched when removing the sacrificial layer material
It is possible to use any metal, alloy, semimetal, or semiconductor having a low resistance and electrical conductivity capable of forming a thin film, such as e, In, or Si.

Next, an embodiment of a display device using the optical deflector of the present invention will be described with reference to the drawings. FIG. 9 shows a light valve 200 used in an embodiment of the display device of the present invention.
2 is a diagram showing an example of arrangement of optical deflectors (for example, individual optical deflectors have substantially the same configuration as the optical deflector shown in FIG. 1) in FIG. FIG. 9A shows a pattern diagram of the first fixed electrode. The first fixed electrode 51 is formed in a line on the substrate. Although not shown in the drawing, all the first fixed electrodes 51 are electrically connected at the line ends. The photoconductor layer was uniformly formed on the substrate surface. Second fixed electrode 5
3 is independently patterned as shown in FIG. 9B. At this time, the photoconductor layer may be patterned in the same manner as the second fixed electrode 53. The insulating layer is uniformly formed on the second fixed electrode.

Next, a supporting electrode 55 is formed into a film, and the first fixed electrode 5 is formed in a line having an opening 59 as shown in FIG. 9C.
Patterned to intersect 1 (spring not shown in the drawing). Finally, the movable electrode 56 is shown in FIG.
As shown in (d), the first fixed electrode 51 and the second fixed electrode 53 are arranged at positions intersecting with each other. By arranging the plurality of optical deflectors described above, each optical deflector can be independently driven by one AC voltage power supply with respect to the writing light.

FIG. 10 is a view for explaining the operation principle in one embodiment of the display device of the present invention. In this embodiment, the light valve 200 shown in FIG. 9 is used. Figure 10
In order to simplify the operation description, the light valve 2
Only one optical deflector at 00 is shown. Figure 10
10A is a diagram when there is no writing light WL, and FIG.
(B) is a diagram when the movable electrode is inclined by θ with respect to the writing light WL. In FIG. 10, the display of the applied voltage power supply of the AC sine wave voltage and the light source for optical writing shown in FIG. 3 are omitted.

Projection light is emitted from the parallel light source 201 to the light valve 200, and the projection light is reflected by each light deflector. When there is no writing light (FIG. 10A), the incident projection light does not enter the projection lens diaphragm surface limited by the projection lens 202 and the diaphragm 203, and the reflected light of the optical deflector is reflected on the screen 204. As not being frustrated. However, as shown in FIG. 10B, one light deflector is tilted by θ by the writing light, and the reflected light is deflected by 2θ, and the projection lens diaphragm surface and the reflected light overlap 21.
3 appears. Only the overlap 213 is projected on the screen through the projection lens 202 and focused. As the amount of writing light increases, the overlap 213 increases and the brightness at the focus on the screen increases.

The mirror vibrates at the same frequency as the AC voltage power supply, and the brightness at the focus changes periodically. The cumulative amount of light per unit time (television frame frequency 30 Hz) that passes through the plane of the projection lens diaphragm corresponds to the brightness of one pixel. By setting the frequency of the AC voltage to be sufficiently higher than the frame frequency, the uneven brightness is eliminated. Since the optical deflector of the present invention has a sufficient response speed as described in the embodiments, there is no particular problem as long as it is a sine wave of about 1 kHz or more, and it is possible to further increase the frequency. Needless to say. That is, the display device of the present invention has a response speed that is sufficiently compatible with HDTV and the like.

In the optical deflector of the present invention, the deflection angle can be changed by the light quantity of the writing light, and in the display device using this, the brightness on the screen can be adjusted according to the writing light quantity in each optical deflector. Different displays can be displayed. The display device of the present invention does not require a polarization beam splitter essential for LCLV, and the large deflection angle enables the display device to be configured without using the Fourier plane mask in Armitage.
It goes without saying that the display device can be formed by using the Schlieren optical system.

Therefore, by optically writing desired image data as an image in the light valve by using an image information display means such as a small CRT or a transmissive liquid crystal display, the reflected light from each mirror and the projection lens diaphragm surface can be changed. The solid angle of the overlapping part changes and the amount of light on the screen changes,
It is possible to display an image having a gradation according to the light and shade of the light amount of the image that has been optically written. Since the deflection angle can be changed in an analog manner, gradation display is performed on the screen when viewed as an image. In other words, the display device using the optical deflector of the present invention can be used to manufacture a projection-type display that can be applied to a television device capable of gradation display for each pixel in which one pixel is one mirror.

In order to colorize an image formed by this display device, three light valves and optical systems, image information display means and three parallel light sources shown in FIG. , Or RED consisting of different dyes between the light valve and the projection lens,
Place each color filter of GREEN and BLUE,
Coloring can be achieved by projecting on the same screen. As another method, it is also possible to separate the projection light of one parallel light source into three primary colors by using a dichroic mirror and make each projection light enter three light valves. In this case, the image information display means writes the image information corresponding to the three primary colors in each light valve.

[0054]

As described above, according to the optical deflector of the present invention, the resistance of the photodetector changes depending on the amount of incident light due to the photoconductive effect, and the mechanical movable part connected in series with the change of the resistance. The applied voltage to the light deflector changes, and the tilt angle of the light deflector can be controlled by electrostatic attraction according to the change in the applied voltage. The projection light incident on the light deflector depends on the amount of light incident on the photodetector. It became possible to deflect. Further, as the area of the light deflecting plate, that is, the mirror is made smaller, the applied voltage of the AC voltage power source is increased to increase the effective voltage to the movable part of the machine and obtain the desired deflection angle. As a result, it is possible to provide a high-definition display device that can be applied to a television device capable of gradation display by reducing the mirror area and forming an array of light deflectors to form a light valve.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a first embodiment of an optical deflector of the present invention.

2 is a sectional view taken along line AA of the embodiment shown in FIG.

FIG. 3 is a diagram showing an equivalent circuit of the embodiment of FIG. 1 when driving the embodiment of FIG.

4 (a), (b), (c), (d), (e),
(F) is a manufacturing process diagram showing an example of a manufacturing process of the optical deflector (electrostatic actuator) of the first embodiment shown in FIG. 1.

5 (g), (h), (i), (j), (k) are
FIG. 5 is a manufacturing process chart showing manufacturing processes after the manufacturing process shown in the manufacturing process chart of FIG. 4.

FIG. 6 is a diagram showing the relationship among the writing light quantity, the effective voltage, and the tilt angle of the optical deflector of the embodiment of FIG.

FIG. 7 is a perspective view showing the configuration of a second embodiment of the optical deflector of the present invention.

FIG. 8 is a perspective view showing the configuration of a third embodiment of the optical deflector of the present invention.

9 (a), (b), (c) and (d) are diagrams showing an example of a plurality of arrays of optical deflectors used in an embodiment of the display device of the present invention.

FIG. 10A is a diagram for explaining the operation of one embodiment of the display device of the present invention when there is no writing light.
FIG. 6B is a diagram illustrating an operation when the movable electrode is inclined by θ with respect to the writing light in the presence of the writing light.

[Description of Reference Signs] 10 substrate 11, 31, 41, 51 first fixed electrode 12, 32, 42 photoconductor layer 13, 33, 43, 53 second fixed electrode 14, 34, 44 insulating layer 15, 35 , 45, 55 support electrode 16, 36, 46, 56 movable electrode 17, 47 bending spring 18, 38, 48 support portion 19, 39 opening 20 glass 21 ITO layer 22 a-Si layer 23 n-type a-Si layer 24 Al ₂ O ₃ 25, 26, 28 Al thin film 27 Underlayer 37 Torsion spring 40 Contact hole 41 Movable electrode support 101, 102, 103 Photoresist 111 First substrate 112 Second substrate 200 Light valve 201 Parallel light source 202 Projection lens 203 diaphragm 204 screen 211 reflected light 212 projection lens diaphragm surface 213 overlapping

Claims (13)

[Claims] 1. A light-transmissive substrate formed on a first surface of the substrate,
An electrical detector, which is arranged so as to face the photodetector on the first surface of the substrate with a gap, and which is electrically connected in series with the photodetector, which changes the resistance value depending on the amount of light emitted. A mechanical movable part that includes a light deflection plate made of a conductive thin film, supports one end of the light deflection plate as a free end, and the other end opposite to the free end as a support end, and connects the light detection part and the light deflection plate in series. When the control light is applied from the second surface side facing the first surface of the substrate, the resistance value of the photodetector is lowered, and the voltage applying means applies the voltage. As the ratio of the voltage applied to the light deflector increases, the free end of the light deflector is attracted to the photodetector side, and the light deflector tilts to the center of the support end, and the first surface side of the substrate. An optical deflector that deflects and reflects projection light that is incident from an optical deflector according to the inclination of the optical deflector. 2. The photodetection section includes a first fixed electrode formed in layers on the first surface of the substrate, and a photoconductor layer formed on the first fixed electrode. The optical deflector according to claim 1, comprising a second fixed electrode formed in layers on the photoconductor layer. 3. The optical deflector according to claim 2, wherein the photoconductor layer is made of an amorphous silicon thin film. 4. The optical deflector according to claim 2, wherein the first fixed electrode is made of a light-transmissive conductive thin film. 5. The optical deflector according to claim 1, wherein the voltage applying means applies an AC sine wave voltage. 6. The optical deflector according to claim 1, wherein the mechanical movable portion includes the light deflector plate, a beam that supports the light deflector plate and is elastically deformed, and a support portion that supports the beam. 7. The optical deflector according to claim 6, wherein the beam is a flexible spring that is flexible. 8. The light deflector according to claim 7, wherein one end of the light deflection plate is connected to a free end of the bending spring, and the light deflection plate is arranged above the bending spring. 9. The optical deflector according to claim 6, wherein the beam comprises a twisting pin that rotatably supports the optical deflecting plate. 10. The optical deflector according to claim 1, wherein the mechanical movable portion is formed on the light detection means via an insulating layer. 11. The optical deflector according to claim 10, wherein the mechanical movable portion has a support electrode for applying a voltage. 12. An optical deflector according to claim 1, wherein a plurality of substrates are arranged in common, a projection lens and a diaphragm for projecting incident light on a screen, and an optical deflector plate of the plurality of optical deflectors. From a projection light source that irradiates light and from the second surface side of the substrate of the plurality of light deflectors, control light is emitted to each of the light deflectors, and the control light is reflected by the light deflection plates of the plurality of light deflectors. A display device comprising an optical writing means for projecting an image of reflected light on a screen through a projection lens and a diaphragm. 13. The display device according to claim 12, wherein the optical writing unit is an image information display unit arranged so as to face the second surfaces of the substrates of the plurality of optical deflectors.