JPH09101468A - Color type deformable mirror device and projection type image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color type deformable mirror device which can displays a color image with a single plate by making individual mirrors of a deformable mirror device (DMD) separate one of the primary colors of light. SOLUTION: This device has a plurality of deformable mirrors 7 which perform deflecting operation for reflecting incident light selectively in response to an applied electronic signal and diffraction gratings formed on the deformable mirrors 7. As compared with a conventional color DMD which uses colored resist, since the color separation can be performed by the diffraction gratings which are about 0.2μm deep, there is no such problem that the flatness of the mirrors 7 can not be obtained because of residual stress and the mirror mass is reduced, so fast response can be made. Further, the diffraction gratings corresponding to the primary colors R, G, and B can be formed at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to the field of electronic devices, and more particularly to a color type deformable mirror device and a projection type image display device using the same.

[0002]

2. Description of the Related Art Color type deformable mirror device (DM
D) is a semiconductor device having a plurality of deflectable mirrors, and the reflection path of incident light can be determined by electronically controlling the angle of each mirror. For example, it is possible to form reflected light as a visible image by appropriately forming a high-density array of the mirrors.

The structure and operating principle of one DMD pixel will be briefly described with reference to FIG. In FIG. 15, 222 is a silicon substrate. A spacer layer 224 is made of resist, for example. 226 and 228 are metal layers, for example, A
An alloy of l, Ti, and Si is deposited. 230 is a mirror unit. The mirror portion 230 is supported by hinge portions 234 and 236 having one end in the spacer layer and floats in the hollow. An insulating layer 244 is made of, for example, a silicon oxide film. Two address electrodes 2 are formed on the insulating layer 244.
42, 246 and two landing electrodes 240, 241
Although the landing electrode 241 is disposed at the back of the address electrode 246, it is not shown in the figure because it is in a position that cannot be seen.

FIG. 16 is a diagram showing the operating principle of a DMD pixel.
It has shown typically the BB 'cross section of FIG. In the figure, the same parts as those in FIG. 15 are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 16, the mirror section 230 and the landing electrodes 240 and 241 are set to the same potential VB, and the mirror section 230 is moved to the address electrodes 242 and 246 by applying a voltage φa as an address signal. To deflect. For example, when the differential bias VB <0, when an address signal voltage having a polarity as shown in the figure is applied, a potential difference is generated between the address electrode 246 and the mirror section 230, and these form a capacitor that sandwiches an air layer, and an electric charge is generated. By being charged, an electrostatic attraction force is generated between the mirror part 230 and the address electrode 246, and the mirror part is deflected to the + a side in the figure. A single part of the mirror part comes into contact with the landing electrode 241 to stop the rotation. At this time, since the mirror part 230 and the landing electrode 241 have the same potential, an electric shock (short circuit, residual charge, etc.) may occur. It is a mechanism that does not occur. Next, when an address signal having a polarity opposite to that shown in the figure is applied, the mirror section is deflected to the −a side in the figure.

By the above operation, the reflection direction of the light incident on the DMD can be changed, and the light is incident on the projection lens only in one of the states of + a and -a. The light can be turned on and off. Furthermore, a monochrome image can be obtained by arranging and controlling such DMD pixels in a matrix.

Several attempts have been made to date for color image formation of such DMDs. First,
The first method uses three DMDs, each DMD having a different primary color source or color filter, and combines the three monochromatic DMD images into a single image. This is a so-called “three-plate type” method for obtaining a color image (color image). However, in such a method, the chip alignment is complicated, the output is converged, the cost of the optical element is excessive, and the size tends to be large, which is difficult for consumer use.

As a second method for solving this problem, a color image can be obtained with a single device chip by directly forming a color filter on the mirror and appropriately disposing these color mirrors. There is something like this. As such an example, for example, JP-A-5-19
The color type deformable mirror device described in Japanese Patent No. 6881 can be used.

Hereinafter, such a conventional color type deformable mirror device will be described. FIG. 17 shows a perspective view of a conventional color deformable mirror device. In FIG. 17, reference numeral 260 denotes a color type deformable mirror device, for example, a mirror element 214 on an SRAM.
Are arranged in an array, and the incident light can be modulated by inputting an electronic control signal from the pin 262 and deflecting the mirror element 214.

FIG. 18 shows an example of the arrangement of the mirror elements 264 and the colors of the filters. By arranging the three primary colors of RGB (red, green and blue) in a checkered pattern as shown in FIG.
A color image can be emitted by injecting white light and modulating it. In addition, in the following sentences,
Red, green, and blue are abbreviated as R, G, and B, respectively.

FIG. 19 is a diagram showing a color filter forming process of a conventional color type deformable mirror device. Hereinafter, the color filter forming step will be described with reference to FIG.

In FIG. 19, reference numeral 322 denotes a substrate, which includes circuits necessary for controlling the mirror elements 314a to 314c according to an input signal, but this is not shown. Reference numeral 324 denotes a sacrificial layer, which is removed in the final step of the color-type deformable mirror device, thereby forming the hollow-held mirror elements 314a to 314c, but not yet removed at this stage. A colored resist 326 is a mixture of a dye and a resist so that any one of the three primary colors is displayed. At this time, the colored resist 326 usually has a thickness of 1 to 3 μm. 328 is ultraviolet light,
The colored resist 326 is exposed by ultraviolet light 328, leaving a necessary portion, and a color filter is formed only on a predetermined mirror element 314a by the subsequent development processing. 33
Reference numeral 0 denotes a protective layer, which has a function of protecting the colored resist 326 from dry etching (hereinafter abbreviated as D / E) at the subsequent exposure / development step and removal of the sacrificial layer. Protective layer 3
28 is patterned to leave a portion to be protected, and FIG.
It becomes the state of d of 9. The protective layer 330 needs to be at least transparent to visible light and is made of, for example, silicon dioxide.

A similar process is performed by using colored resists 332 and 334.
By also performing the above, the color filter capable of displaying the three primary colors is arranged on the mirror element together with the colored resist 326.

[0014]

However, in the above-described conventional structure, for example, the thickness of the conventional DMD mirror element is about 0.4 μm, whereas the thickness of the color filter is extremely large, 1 to 3 μm. Furthermore, the structure with a protective layer on top of it causes residual stress between the color filter and the mirror, which makes it difficult to obtain a flat mirror surface and is extremely disadvantageous for high-speed operation of the mirror. There was a problem that there is.

Further, it is necessary to dispose filters for the three primary colors and to form a layer for protecting the filters for each color, which increases the number of steps and complicates the process.

The color-type deformable mirror device of the present invention solves the above-mentioned conventional problems. The mirror surface is flat because there is no residual stress, it is advantageous for high-speed operation, and it can be manufactured in a small number of steps. An object of the present invention is to provide a color type deformable mirror device.

[0017]

In order to achieve this object, the color deformable mirror device of the first invention performs a deflection operation of selectively reflecting incident light in response to an applied electronic signal. A device having a plurality of deformable mirrors obtained has a structure in which a diffraction grating is formed on the deformable mirrors.

The color deformable mirror device of the second invention is the color deformable mirror device of the first invention such that the deformable mirror has a longitudinal direction in a direction perpendicular to the rotation axis when deflecting. The diffraction grating is formed on the deformable mirror, and the light is made incident on a surface perpendicular to the deformable mirror surface and parallel to the longitudinal direction of the diffraction grating.

A color deformable mirror device according to a third aspect of the present invention is the color deformable mirror device according to the first aspect of the present invention, which has a longitudinal direction in a direction perpendicular to the rotation axis when the color deformable mirror is deflected. Is formed, the wavelength of the incident light is λ, and the pitch of the diffraction grating is Λ.
Is 0.9 sin ⁻¹ [λ / (2Λ)] ≦ α ≦ ± 1.1 sin ⁻¹ [λ / from the plane parallel to the longitudinal direction of the diffraction grating and perpendicular to the color-type deformable mirror.
(2Λ)] on a surface inclined by an angle α and perpendicular to the longitudinal direction of the diffraction grating and not incident on a surface perpendicular to the color deformable mirror. There is.

The color type deformable mirror device of the fourth invention has a structure in which a Fourier diffraction grating is formed as the diffraction grating in the first invention.

The projection type image display apparatus of the fifth invention is a device provided with a plurality of deformable mirrors capable of performing a deflecting operation of selectively reflecting incident light in response to an applied electronic signal. As a configuration including a color-type deformable mirror device array in which color-type deformable mirror devices in which a diffraction grating is formed on a mirror are arranged in an array, and a light source for making light incident on the color-type deformable mirror device array There is.

A method for producing a color deformable mirror device according to a sixth aspect of the present invention is a method for manufacturing the color deformable mirror device according to the fourth aspect of the present invention, in which the first layer is formed on the mirror, and It is characterized in that it includes a step of forming a Fourier diffraction grating by forming two layers and then heating and melting them.

With this configuration, the color-type deformable mirror device of the first invention performs color separation by the diffraction grating formed with a step of about 0.2 μm, which is different from the conventional resist filter method. Since there is no residual stress, the flatness of the mirror can be maintained, and since the mass is small, it is possible to follow high-speed operation. In addition, RGB
Since it is possible to form the diffraction gratings corresponding to the three colors at once, the manufacturing process thereof is also simplified.

In the color type deformable mirror device of the second invention, since the plane on which the incident light is color-separated is parallel to the rotation axis of the deformable mirror, the light having a predetermined wavelength is rotated by the rotation of the deformable mirror. It is possible to prevent light of a different wavelength from being mixed in when turning on and off.

In the color deformable mirror device of the third invention, since the color separation is performed by the Littrow diffraction phenomenon by the diffraction grating formed on the deformable mirror, the color purity is high (the wavelength band width is narrow), Further, it is possible to provide a color type deformable mirror device having a relatively good light utilization efficiency.

In the color type deformable mirror device of the fourth invention, since the diffraction grating on the mirror is in the shape of a Fourier diffraction grating, the color purity remains as good as in the third invention, and the high diffraction efficiency is obtained. It is possible to realize a color type deformable mirror device in which

In the projection type image display apparatus of the fifth aspect of the invention, color type deformable mirror devices are arranged in an array form, light is made incident, and the mirrors corresponding to the three primary colors of light are individually driven, whereby a single plate is used. It becomes possible to project a full-color image.

A method of manufacturing a color deformable mirror device according to a sixth aspect of the present invention is the color deformable mirror device according to the fourth aspect of the present invention, in which two layers having different softening temperatures are used when forming a Fourier diffraction grating on the mirror. By patterning the material into a predetermined shape and heating it to melt it,
For example, it is possible to form a diffraction grating corresponding to the three primary colors of light at the same time as compared with the case of forming this by hologram exposure, and it is possible to easily form a Fourier diffraction grating.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a color type deformable mirror device according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a substrate, which is made of, for example, silicon. An insulating layer 2 is formed by thermally oxidizing the substrate 1 to form a thermal oxide film of 0.1 μm. 3
Is a spacer, which is formed by applying a resist by spin coating and baking, for example, and has a thickness of, for example, 4 μm. Reference numerals 4a and 4b are landing electrodes, and 5a and 5b are address electrodes. For example, Al is vapor-deposited by 0.1 μm, for example, and wet-etched with phosphoric acid (hereinafter abbreviated as W / E) to form a pattern. It is formed. Reference numeral 6 denotes a hinge, which is formed by depositing an alloy of Al, Ti, and Si, and has a thickness of 0.08 μm, for example. The composition ratio of the alloy is determined so that the coefficient of thermal expansion of the alloy 3 is almost the same as that of the spacer 3.
i: Si = 500: 1: 5.

Reference numeral 7 denotes a diffractive mirror, which is formed by depositing a layer made of the same material as that of the hinge 6 by 0.5 μm, for example, and then forming a diffraction grating on the surface by a predetermined depth D / E. In this embodiment, the diffraction grating is a two-level diffraction grating having a rectangular cross section, for example. The diffractive mirror 7 is supported by a hinge 6 having the other end on the spacer 3 and has a hollow structure.

In this embodiment, the diffractive mirror 7 is electrically connected to the landing electrodes 4a and 4b by a wiring (not shown). On the other hand, the address electrode 5
Similarly, an arbitrary voltage can be applied to a and 5b by wiring (not shown).

With respect to the color type deformable mirror device configured as described above, the step of forming the diffraction grating on the mirror will be described with reference to FIG. FIG. 2 shows a process of forming a diffraction grating in the AA ′ cross section of FIG. 1. In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 2, reference numeral 21 is a metal layer. 22
Is a mask. Hereinafter, the diffraction grating forming process will be sequentially described with reference to FIG. (A) 0.5 μm of Al-Ti-Si alloy is deposited, and D / E is performed to form a mirror shape. At this stage, the spacer 3 has not been removed yet. (B) A resist is spin-coated and exposed / developed to form a mask 22. (C) The metal layer 21 is dug vertically by D / E using, for example, BCl ₃ . (D) The resist is removed.

By forming a diffraction grating on the metal layer 21 as described above, a diffractive mirror can be formed. In addition,
Λ shown in (d) is a pitch which is one period of the diffraction grating, and d is a line width. In this embodiment, for example, d = Λ / 2 (that is, Duty ratio =) in order to maximize the diffraction efficiency. 1:
1). Further, t is the depth of the diffraction grating.

Next, the principle of functioning as a color mirror by providing a diffraction grating on the mirror will be described.

FIG. 3 (a) is a plan view of the diffractive mirror, and FIG. 3 (b) is a sectional view taken along the line AA 'of FIG. 3 (a).
In the figure, the same parts as those in FIG. Hereinafter, the coordinate axes will be described as shown in the figure. In FIG. 3, reference numeral 31 denotes incident light, which is parallel light having a wavelength λ, for example. Reference numeral 32 is the first-order diffracted light. Although other high-order diffracted lights are actually generated, they are omitted and not shown. In addition, in the following description of this embodiment,
Next-order diffracted light will be simply referred to as diffracted light. Also, θ
Is the diffraction angle and α is the angle of incidence. The diffraction angle θ is given by the following equation.

Θ = sin ⁻¹ (λ / Λ) As is apparent from this equation, the diffraction angle θ can be arbitrarily set by the wavelength λ of the incident light and the pitch Λ of the diffraction grating. Further, when Λ is a constant value, the diffraction angle θ changes depending on the value of the wavelength λ of the incident light. Therefore, by utilizing this phenomenon,
For example, even if the incident light has a wide wavelength distribution such as white light, the colors can be separated.

Further, as shown in FIG. 3, in the color deformable mirror device of this embodiment, the longitudinal direction is in the direction (x direction) perpendicular to the rotation axis (y axis) when the deformable mirror deflects. The diffraction grating is formed so that light is incident from a plane (zx plane) parallel to the longitudinal direction of the diffraction grating and perpendicular to the mirror surface. With this configuration, the incident light is sequentially dispersed according to the wavelength in the θ direction on the plane inclined by + α from the yz plane in the figure to the x axis direction. At this time, since the deflection axis of the mirror is the y-axis, for example, light having a wavelength other than the predetermined wavelength indicated by G in FIG. 3 does not enter the projection lens regardless of the deflection state of the mirror, and the color The effect is that the vividness of does not change.

On the other hand, the diffraction grating depth t at which the maximum diffraction efficiency is obtained is given by the following equation. t = λ / (4cosα) In the following texts, the wavelengths of R, G, and B are set to 0.6, 0.5, and 0.4 μm, respectively, but these values can be changed as appropriate. Is. For example, when R, G, and B lights are incident at an incident angle α = 30 °, the optimum depths are 0.17, 0.14, and 0.12 μm, respectively.
When the depth of the diffraction grating is this optimum depth, the intensity of the emitted light 32 is about 40% of the intensity of the light of the predetermined wavelength contained in the incident light 31. In this way, in the conventional color filter system, a color mirror is obtained by forming a filter having a thickness of several μm, but according to the method of the present embodiment, 0.1 to 10 Color separation is possible with a step difference of about 0.2 μm, which does not affect residual stress, which has been a problem in the past, and reduces the mass of the mirror.

On the other hand, from the equation expressing the optimum depth, it is understood that the depth t needs to be changed according to the wavelength λ of the diffraction target. For these, the above manufacturing process is sequentially repeated for each color mirror. It can be obtained. However, the present inventors have discovered that sufficient diffraction efficiency can be obtained even if all mirrors have the same depth t.

Next, FIG. 4 shows the diffraction efficiency with respect to the wavelength when all the mirrors are formed at the depth optimized with the light having the wavelength of 0.5 μm. As shown in FIG. The diffraction efficiencies of light having wavelengths of 0.4, 0.5, and 0.6 μm are 35, 41, and 38%, respectively, and it can be seen that there is no significant difference. Although this error is relatively small, it is possible to preset and adjust the wavelength intensity distribution of the incident light, so that the process of forming the diffraction grating on the mirror can be completed only once. , The manufacturing process becomes extremely easy. The optimum groove depth at each wavelength is as described above. On the contrary, in this embodiment, the groove depth error is suppressed to 500 angstroms or less between all the mirrors. The diffraction efficiency is at least 35% or more.

Next, FIG. 5 is a view for explaining the principle of obtaining a color image in an actual color type deformable mirror device. In FIG. 5, the same parts as those in FIG. Omit it. In FIG. 5, 4
Reference numeral 1 denotes a projection lens, the diameter of which is φ and the distance from the color type deformable mirror device is L. Also, 2
θ _c represents the angle at which the emitted light enters the projection lens 41 and is projected on a screen (not shown), and as is clear from the figure, there is a relationship of tan θ _c = φ / (2L).

Further, generally, there is an F value (= L / φ) as a numerical value representing the brightness of the entire projection system by the ratio of these L and φ, but this parameter is used in the following sentences without notice. 42 is incident white light.

In FIG. 5, (a) shows a green light, (b) shows a red light, and (c) shows a mirror for projecting a blue light. A color image can be obtained by combining the three primary colors formed by these mirrors. As described above, in each of the mirrors (a) to (c), the pitch of the diffraction grating is changed according to the color to be emitted. Further, as can be seen in, for example, FIG. 5A, in order to make only the green light (G) enter the projection lens 41 and the red light (R) and the blue light (B) leave the projection lens 41, Δθ Both _RG and Δθ _GB must be greater than θ _c .

In Table 1, for each of the cases of FIGS. 5 (a)-(c), as an example, when color separation is achieved in a standard F = 3 projection system, in each of the RGB mirrors. The values of the diffraction angles θ _R , θ _G , and θ _B of the light of each wavelength, the diffraction angle of each mirror (the part surrounded by the thick line in the table) and the pitch when the remaining two types of mirrors have the same diffraction angle Shows.

[0046]

[Table 1]

For example, (a) is as shown in FIG.
The diffraction angles of R and B when color separation is performed in the G mirror and the pitch at which the R mirror and the B mirror generate 41.42 °, which is the same diffraction angle as the G mirror, are shown. R
By setting the pitches so that the diffraction angles of the mirrors corresponding to the respective GB wavelengths are equal, the color-type deformable mirror device of the present embodiment was set by simply allowing white light to enter the device. A color image is projected in the diffraction angle direction.

Incidentally, as is clear from (Table 1), the finest pitch is the B mirror when the color separation of the R mirror is achieved, and the pitch is 0.546 μm. In this embodiment, for example, a two-level diffraction grating is used, and the line width is 0.27 μm.

FIG. 6 shows a partially enlarged plan view of a color type deformable mirror device manufactured under the above design conditions. In FIG. 6, 51 is white light. 52 is R
Mirrors, 53 is a G mirror, and 54 is a B mirror. 55 is red light, 56 is green light, and 57 is blue light.

As shown in FIG. 6, the incident white light 51 is color-separated by the diffraction grating on each mirror and diffracted in the direction determined by the pitch of the diffraction grating. A color image can be obtained by arranging these separated lights to be turned on / off by rotating the mirror part and to enter the projection lens (not shown) to be projected on the screen.

As described above, according to the present embodiment, by providing the diffraction grating on the mirror, color separation is performed with a step difference of about 0.2 μm, which is superior to the conventional resist filter method. Since there is no residual stress, the flatness of the mirror can be maintained, and since the mass is small, it is possible to follow high-speed operation. Further, by adopting a configuration in which white light is made incident on a plane perpendicular to the grating vector of the diffraction grating, color shift due to rotation of the mirror does not occur, and a highly pure color image can be obtained.

In this embodiment, the diffraction grating of the two-level type has been described. However, the diffraction efficiency is set as a four-level or eight-level diffraction grating having a cross section of four steps and eight steps, respectively. However, in the present embodiment, the value is small, for example, Λ / λ˜1.4, and even if a 4-level or 8-level diffraction grating is manufactured in such a region, the scalar diffraction theory is used. Efficiency does not improve as much as the well-known values (81% and 95%, respectively). The line width of the diffraction grating is 1/4 and 1/8 of the pitch.
Therefore, manufacturing becomes extremely difficult. On the contrary, since there is a constraint that the pitch of the diffraction grating is determined by the F value of the projection system, it becomes necessary to select a manufacturable F value.

FIG. 7 shows how the minimum pitch of the diffraction grating on the mirror changes depending on the F value of the projection system. If the minimum line width that can be manufactured is, for example, 0.3 μm, the minimum pitches of the diffraction gratings of 2, 4, and 8 levels are 0.6, 1.2, and 2.4 μm, respectively. The F values are 4, 9, and 18, respectively, and although the diffraction efficiency can be increased, the brightness of the entire projection system is reduced. Therefore, in practice, it is better to use a two-level diffraction grating as in this embodiment. You can get a bright image.

On the other hand, in order to further improve the color purity of the light diffracted by the diffraction grating, an optical path limiting means such as a slit may be provided between the color type deformable mirror device and the projection lens.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. The color deformable mirror device of the present embodiment is different from the first embodiment only in the method of incident light on the diffraction grating provided on the mirror and the method of color separation. Only the operation method will be described.

The color-type deformable mirror device of this embodiment is extremely suitable when extremely high color purity is required.

The diffraction grating generally has a Littrow angle θ _L. Figure 8 illustrates this Littrow angle,
It is sectional drawing of a deformable mirror. In the figure, the same parts as those in FIG. In FIG. 8, 74 is the incident light, and 75 is 1 under the Littrow condition.
It is the next diffracted light. When light of wavelength λ is incident at this Littrow angle, the light is highly efficiently diffracted in the same direction as the incident direction.
Note that, as shown in FIG. 8, the Littrow angle θ _L is expressed by the following equation.

Θ _L = sin ⁻¹ [λ / (2Λ)] FIG. 9 shows how the diffraction efficiency changes when the pitch Λ is changed with respect to the wavelength λ in the diffraction grating with the duty ratio of 1: 1. FIG. 6 is a diagram showing whether or not there is a change, with the ratio of the depth t of the diffraction grating and the wavelength λ as a parameter. From this FIG.
It can be seen that high diffraction efficiency is obtained near λ / Λ = 0.7 and 0.9 to 1.1. On the other hand, in manufacturing the diffraction grating, the larger Λ is, the easier the manufacturing is. Therefore, in the present embodiment, λ /
We are designing around Λ = 0.7. Specifically, at least the center wavelength of the diffracted light emitted by the pitch of the diffraction grating
The diffraction efficiency is at least 40% or more by setting the range within 1.3 to 1.7 times. Further, comparing the difference due to the parameter t / Λ, it is understood that the diffraction efficiency does not change significantly even if the depth t changes a little. From this, similarly to the diffraction grating of the first embodiment, the depth can be made constant for the three primary color mirrors, and the diffraction grating portion corresponding to each color can be formed at one time.

Next, consider the influence when the actual incident angle deviates from the Littrow diffraction angle. For example, λ / Λ = 0.7
Then, the Littrow diffraction angle is calculated to be 20.5 °. When the incident angle θL shifts by + 5 ° to 25.5 °, the center wavelength of the emitted light is 0.5 μm in the case of a G mirror, for example.
The green light changes from 0.62 μm to red light, and an appropriate color image cannot be obtained. The present inventors have made this color transition at least at a center wavelength of 0.05
It was discovered that the accuracy of the incident angle needs to be controlled within a range of ± 10% (corresponding to ± 2 ° for a G mirror) in order to suppress the variation within a range of μm or less. By making the light incident at ± 0.5 °, an image with extremely high color purity could be obtained.

Next, FIG. 10 is an enlarged view of the mirror portion of the color-type deformable mirror device of this embodiment manufactured in consideration of the above characteristics. FIG. 10 (a) is a top view and FIG. 10B is a cross-sectional view taken along the line AA ′ of FIG. 93 is incident light. 94 is emitted light.

As shown in FIG. 10, white incident light is incident at an angle β with respect to a plane perpendicular to the longitudinal direction of the diffraction grating. When light is incident as in this embodiment, that is, when the incident angle β is not 0, it becomes equivalent by replacing λ with λcosβ in the description of FIG. 8 above. In this embodiment, for example, λcos β / Λ = 0.7 and the value of β is set to 30 °, for example. In this embodiment, for example, the depth t is 0.16 μm with the wavelength of the incident light being 0.5 μm as a reference.
By doing so, it is possible to obtain a diffraction efficiency of 50% or more even for light having wavelengths of 0.6 μm and 0.4 μm.
The pitches Λ of the diffraction gratings of the RGB mirrors at this time are, for example, 0.74 μm, 0.62 μm,
0.50 μm. Also, the Littrow angle at this time is sin-
1 (0.7) = 44.4 °, which is determined by the mask pattern initially manufactured, and can be made equal for each wavelength of the three primary colors. Therefore, the color type deformable mirror device and the projection optical system are Assembling is easy because it is only necessary to adjust the incident angle θL of the color-type deformable mirror device with respect to the optical path so that the position will be at the Littrow angle. By entering the light as described above, the light of the accurately set wavelength is diffracted in the incident white light, and a filter having an extremely high color purity can be formed. Further, by forming such a diffraction grating on the mirror and rotating the mirror, the direction of the reflected light is changed in the same manner as in the conventional color-type deformable mirror device, so that the three primary colors projected on the display are displayed. A color image can be obtained by turning the light on and off.

The manufacturing process of the diffraction grating is the same as that of the first embodiment, and it can be manufactured by D / E of the mirror portion by a predetermined thickness using a resist mask, for example.

As described above, the diffractive mirror of the color deformable mirror device of this embodiment can be easily manufactured in the same manner as in the first embodiment, and the light separated and projected by the diffraction grating on each mirror. Since the wavelength of is uniquely determined by the pitch of each diffraction grating, a color image of extremely high purity can be obtained.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. The color deformable mirror device of this embodiment is different from the second embodiment only in the diffraction grating provided on the mirror, and therefore only the diffraction grating on this mirror will be described below.

The color deformable mirror device of this embodiment has a high color purity because light is incident on the diffraction grating at the Littrow angle θL as in the case of the second embodiment, and the color deformable mirror device of the second embodiment is used. It has the advantage of higher light utilization efficiency than the device.

FIG. 11 is a sectional view of the mirror portion of the color type deformable mirror device of this embodiment. In FIG. 11, the same parts as those in FIG. 8 are designated by the same reference numerals and the description thereof is omitted. In FIG. 11, 101 is a diffraction grating portion. 102
Is the incident light. Reference numeral 103 is emitted light.

The diffraction grating of this embodiment shown in FIG. 11 has a so-called Fourier diffraction grating shape.
The Fourier diffraction grating is generally a diffraction grating having a sectional shape represented by the following formula.

Y = (t / 2) [sin (2πx / Λ) + γs
in (4πx / Λ + δ)] where t is the groove depth of the diffraction grating, Λ is the pitch of the diffraction grating, γ is the second harmonic amplitude coefficient, and δ is the phase shift amount.
On the other hand, the Littrow angle θ _L shown in FIG. 11 is expressed by the following equation.

Θ _L = sin ⁻¹ [λ / (2Λ)] In the Littrow diffraction phenomenon of the Fourier diffraction grating as in this embodiment, when only 0th and 1st order diffracted light is generated, the 1st order diffracted light intensity Is generally known to be the maximum, and the condition is that the wavelength λ and the pitch Λ must satisfy the following conditions.

2/3 <λ / Λ <2 Therefore, the Littrow angle at which the maximum diffraction efficiency is obtained is 19.5 ° <θL <90 ° On the other hand, if the Littrow angle θL is, for example, 30 °,
The values of the pitch Λ are 0.4, 0.5 and 0.6 μm for the wavelengths of 0.4, 0.5 and 0.6 μm, respectively, and the minimum line width (= Λ / 2) at this time is obtained. ) Is 0.2 μm corresponding to a wavelength of 0.4 μm.

Next, FIG. 12 shows the relationship between the Littrow angle θL and the minimum line width. From FIG. 12, for example, if the minimum line width is 0.2 μm or more, the Littrow angle is 3
It can be seen that it is necessary to set it to 0 ° or less. From the above, in the manufacture of the diffraction grating, it is easier to manufacture if the line width is as large as possible. Therefore, in this embodiment, for example, by setting the Littrow angle to 20 °, high diffraction efficiency is obtained. , A line width of 0.3 μm forms a diffraction grating that is easy to manufacture. At this time, the value of λ / Λ is 0.68. At this time, for example, by forming a diffraction grating having a profile in which the value of γ is 0.1 and the value of δ is -90 °, a high value of 90% or more is obtained. The diffraction efficiency could be obtained.

Next, FIG. 13 is a diagram for explaining a method of manufacturing the diffraction grating of the mirror portion of the color type deformable mirror device of this embodiment. In FIG. 13, 121 is a spacer layer made of, for example, a resist. 122a-c are mirror parts. 123 is a resist layer. Reference numeral 124 is exposure light. Reference numerals 125, 126, 127 and 128 denote light shielding means, for example, stencil masks. Reference numeral 129 is a reflective film.

A method of manufacturing a Fourier diffraction grating will be described below with reference to FIG. (A) A positive resist is applied by, for example, spin coating to form a resist layer 123 having a thickness of 1.5 μm. (B) The exposure light 124 is split into two by, for example, a beam splitter (not shown), and these are irradiated onto the resist from the opening of the light shielding means 128 at an incident angle φ _R. The incident angle φ is expressed by the following equation, where λe is the wavelength of the exposure light and Λ is the pitch of the diffraction grating to be manufactured.

Φ = 2 sin ⁻¹ (λe / 2Λ) The inventors used a He—Cd laser with a wavelength of 0.4416 μm as the exposure light. Therefore, if the Littrow angle θL is, for example, 20 ° for the reason described above, the pitches of the diffraction gratings of the R mirrors are, for example, 0.88 μm, and in order to form the diffraction gratings of this pitch, φ _R = 29.1 ° There is. The exposure time is, for example, 15 seconds. In the same manner as in (c) and (b), exposure is performed with φ _G = 35.2 ° in order to form a diffraction grating for a G mirror having a pitch of 0.73 μm. In the same manner as in (d) and (b), exposure is performed with φ _B = 44.8 ° to form a diffraction grating for a B mirror having a pitch of 0.58 μm. (E) The resist between the RGB mirrors is exposed. (F) Development is performed to obtain a Fourier diffraction grating shape, and then baking is performed at 120 ° C., for example. (G) Reflective film 1 with Au deposited to a thickness of 0.15 μm, for example, by vapor deposition
29 are formed.

The Fourier diffraction grating can be formed on the mirror portion by the above steps. As described above, in the color-type deformable mirror device of the present embodiment, the Fourier diffraction grating is formed in the mirror portion, so that the light utilization efficiency can be made extremely high to 90% or more while the color purity remains high. It is possible.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings. The color type deformable mirror device of this embodiment is different from that of the third embodiment in that
Since only the manufacturing method of the diffraction grating formed on the mirror is different, only the manufacturing process of the diffraction grating will be described below.

FIG. 14 is a diagram for explaining a method of manufacturing the Fourier diffraction grating of the mirror section in the color type deformable mirror device of this embodiment. In the figure, reference numeral 130 is a mirror portion substrate. 131 is a first resist layer. 132 is a second resist layer.

The method of manufacturing the Fourier diffraction grating of this embodiment will be described below with reference to FIG. (A) A resist is applied by spin coating to form a first resist layer 131. After that, exposure and development are performed and baking is performed at, for example, 120 ° C. to remove the photosensitivity of the first resist layer 131. (B) A resist is applied by spin coating to form the second resist layer 132. After that, exposure and development are performed. Note that the first resist layer 131 and the second resist layer 132 use resists having different softening temperatures, and the first resist layer 131 softens at a lower temperature and a so-called resist flow occurs. In this embodiment, for example, the first resist layer 1
The resist flow starts at 140 ° C. for 31 and 160 ° C. for the second resist layer 132. (C) For example, baking is performed at 160 ° C. for 20 minutes to generate a resist flow. At this time, the second resist layer 1
Since 32 is not softened more than the first resist layer 131, it is possible to manufacture a diffraction grating having a shape close to a so-called sine waveform as shown in the figure.

The diffraction grating manufacturing method of this embodiment can manufacture only a simple sine wave-shaped diffraction grating as compared with the manufacturing method of the third embodiment. Therefore, the diffraction efficiency is about 70%, but since the pitch of the diffraction grating can be determined at the time of patterning the second resist layer, the diffraction gratings of the mirrors corresponding to the three RGB colors can be formed at the same time, and the manufacturing process Extremely simplified. Further, the method of Example 3 required a laser that emits ultraviolet rays, but in this Example, since the production can be performed by a normal exposure and development process, it is extremely advantageous in terms of cost when the apparatus is included. is there.

[0080]

As described above, in the color deformable mirror device of the first invention, color separation is possible by the diffraction grating formed with a step of about 0.2 μm, and there is no residual stress. The flatness can be maintained, and since the mass is small, it can follow high-speed operations. In addition, RGB
Even if the diffraction gratings corresponding to the three colors are formed at one time, the utilization efficiency of the light separated by the respective mirrors is acceptable, so that the manufacturing process thereof is also simplified.

Further, in the color type deformable mirror device of the second invention, since the plane for separating the incident light is parallel to the mirror rotation axis, the mirror is rotated so that the light of a predetermined wavelength is projected onto the projection lens. When switching between incident light and non-incident light, since there is no color separation in the rotation direction, a vivid image can be obtained.

In the color type deformable mirror device of the third invention, since the diffraction grating formed on the deformable mirror performs color separation by the Littrow diffraction phenomenon, the color purity is high (the wavelength bandwidth is narrow). ), And a color-type deformable mirror device having relatively good light utilization efficiency can be provided.

In the color deformable mirror device of the fourth invention, the diffraction grating on the mirror is in the shape of a Fourier diffraction grating, so that the color purity is high and extremely high as in the third invention. It is possible to realize a color-type deformable mirror device that can obtain diffraction efficiency.

Further, in the projection type image display apparatus of the fifth invention, color type deformable mirror devices are arranged in an array, and light is incident on the mirror type deformable mirror devices to individually drive the mirrors corresponding to the three primary colors of light. This makes it possible to project a full-color image with a single plate.

The method of manufacturing the color deformable mirror device of the sixth invention is the same as the method of manufacturing the color deformable mirror device of the fourth invention, wherein the softening temperature is different when the Fourier diffraction grating is formed on the mirror. By patterning the material of the layer into a predetermined shape and heating and melting it, it is possible to simultaneously form a diffraction grating corresponding to the three primary colors of light, as compared with the case of forming this by hologram exposure. This makes it possible to easily form a Fourier diffraction grating.

[Brief description of the drawings]

FIG. 1 is a perspective view of a color type deformable mirror device according to a first embodiment of the present invention.

2A to 2D are process diagrams of forming a diffraction grating in the embodiment.

3A is a plan view of the diffractive mirror of the embodiment, and FIG. 3B is a sectional view taken along the line A-A ′ of FIG.

FIG. 4 is a characteristic diagram showing a change in diffraction efficiency with respect to a wavelength of a diffraction mirror designed at a wavelength of 0.5 μm in the example.

5 (a) to (c) are color image projection principle diagrams of the color deformable mirror array device of the same embodiment.

FIG. 6 is a plan view of a color deformable mirror device of the same embodiment.

FIG. 7 is a diagram showing the relationship between the F value and the minimum pitch of the diffraction grating of the projection type image display device of the same embodiment.

FIG. 8 is a sectional view of a mirror portion of a color type deformable mirror device according to a second embodiment.

FIG. 9 is a characteristic diagram showing the relationship between λ / Λ and the diffraction efficiency with t / Λ as a parameter in the diffraction grating of the same example.

10A is a top view of a mirror portion of the color deformable mirror device of the same embodiment, and FIG. 10B is a sectional view taken along line AA ′ of FIG.

FIG. 11 is a sectional view of a color type deformable mirror device mirror portion of a third embodiment.

FIG. 12 is a characteristic diagram showing the relationship between the Littrow angle θL and the minimum line width of a diffraction grating having a design wavelength of 0.4 μm in the same example.

13 (a) to (g) are process diagrams showing a method for manufacturing a Fourier diffraction grating on a mirror in the same example.

FIGS. 14A to 14C are process diagrams showing a method of manufacturing a color type deformable mirror device Fourier diffraction grating according to a fourth embodiment.

FIG. 15 is a perspective view of a conventional color deformable mirror device.

FIG. 16 is a diagram showing an operation of a conventional color deformable mirror device.

FIG. 17 is a perspective view of a conventional color type deformable mirror array device.

FIG. 18 is a typical color arrangement diagram of a conventional example.

19A to 19F are process diagrams of forming a color filter of a conventional example.

[Explanation of symbols]

 1 substrate 2 insulating layer 3 spacers 4a, 4b landing electrodes 5a, 5b address electrodes 6 hinges 7 diffractive mirror

Claims (17)

[Claims] 1. A device having a plurality of deformable mirrors capable of performing a deflection operation of selectively reflecting incident light in response to an applied electronic signal, the device including a diffraction grating on the deformable mirror. A color-type deformable mirror device characterized in that 2. The color deformable mirror device according to claim 1, wherein the diffraction grating has a stepwise cross section. 3. The diffraction grating is formed on the deformable mirror so as to have a longitudinal direction in a direction perpendicular to a rotation axis when the deformable mirror deflects, the diffraction grating being perpendicular to the deformable mirror surface and the diffraction grating. The color deformable mirror device according to claim 1, wherein light is incident on a surface parallel to the longitudinal direction of the. 4. The diffraction grating is formed so as to have a longitudinal direction in a direction perpendicular to a rotation axis when a deformable mirror deflects. When a wavelength of incident light is λ and a pitch of the diffraction grating is Λ, From the plane parallel to the longitudinal direction of the diffraction grating and perpendicular to the color deformable mirror, 0.9 sin ^-1 [λ / (2
Λ)] ≦ α ≦ ± 1.1 sin ⁻¹ [λ / (2Λ)] on a plane inclined by an angle α, and perpendicular to the longitudinal direction of the diffraction grating and to the color-type deformable mirror. The color deformable mirror device according to claim 1, wherein light is incident from a direction that is not on a vertical surface. 5. The color deformable mirror device according to claim 4, wherein the diffraction grating has a pitch of 1.3 to 1.7 times the center wavelength of the diffracted light to be emitted. 6. The color deformable mirror device according to claim 1, wherein the diffraction grating is a Fourier diffraction grating. 7. The diffraction grating is formed so as to have a longitudinal direction in a direction perpendicular to a rotation axis when a deformable mirror is deflected. When a wavelength of incident light is λ and a pitch of the diffraction grating is Λ, From the plane parallel to the longitudinal direction of the diffraction grating and perpendicular to the color deformable mirror, 0.9 sin ^-1 [λ / (2
Λ)] ≦ α ≦ ± 1.1 sin ⁻¹ [λ / (2Λ)] on a plane inclined by an angle α, and perpendicular to the longitudinal direction of the diffraction grating and to the color-type deformable mirror. 7. The color deformable mirror device according to claim 6, wherein light is incident from a direction that is not on a vertical surface. 8. A plane parallel to the longitudinal direction of the diffraction grating and inclined by 20 to 30 ° from a plane perpendicular to the color deformable mirror and not parallel to a normal vector of the color deformable mirror surface. 7. The color deformable mirror device according to claim 6, wherein light is incident from a direction. 9. A color deformable mirror device having a plurality of deformable mirrors capable of performing a deflecting operation for selectively reflecting incident light in response to an applied electronic signal, and a diffraction grating formed on the deformable mirrors. A projection-type image display device, comprising: a color deformable mirror device array in which the elements are arranged in an array; and a light source that makes light incident on the color deformable mirror device array. 10. A color deformable mirror device array comprises a mirror group having at least three kinds of diffraction gratings having different pitches, which diffracts diffracted light of at least one of the three primary colors of light at equal angles. The projection type image display device according to claim 9. 11. A diffraction grating formed on a mirror group having diffraction gratings of at least three kinds of pitches, wherein the difference in depth of the diffraction grating is 500 angstroms or less in all of the three kinds of mirrors. The projection type image display device according to claim 10. 12. A lens is arranged at a position where the emitted light can be switched between incident and non-incident depending on the deflection state of the color deformable mirror device among the emitted lights emitted from the color deformable mirror device. Item 10. The projection-type image display device according to Item 9. 13. The projection type image display apparatus according to claim 12, wherein the distance from the color deformable mirror device to the lens is three times or more the lens diameter. 14. A method of manufacturing a color deformable mirror device according to claim 6, wherein a first layer is formed on the mirror, a second layer is further formed, and then these are heated and melted. A method of manufacturing a color-type deformable mirror device, characterized in that the method includes a step of forming a Fourier diffraction grating. 15. The method for manufacturing a color deformable mirror device according to claim 14, wherein the material of the first layer has a lower softening temperature than the material of the second layer. 16. The method of manufacturing a color-type deformable mirror device according to claim 14, wherein the material of the first layer and the second layer is an organic material. 17. The method for manufacturing a color deformable mirror device according to claim 16, wherein the organic material is resist or polyimide.