JP2001318640A - Reflection type image display device using hologram color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type image display device using a hologram color filter in which the display light diffracted in the direction perpendicular to the plane of the reflection type image display element and again diffracted by the hologram color filter to the illumination light source side is separated from the illumination light and an image with small distortion of the image can be displayed by a coaxially disposed projection optical system. SOLUTION: The reflection image display device 1 consists of the combination of a hologram color filter 2 consisting of repetition of element holograms which disperse colors of the illumination light 6 entering at an oblique incident angle and condense the light, and a reflection type spatial modulating element 5. In the device, the display light 9 reflected by the reflection type spatial modulating device 5 and again diffracted by the hologram color filter 2 exit to the direction almost opposite to the illumination light 6. A polarization separation means 10 is disposed in the optical path of the illumination light 6 to separate the display light 9 from the illumination light 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type image display device using a hologram color filter.
The present invention relates to a reflection type image display device using a hologram color filter capable of projecting a bright and undistorted image.

[0002]

2. Description of the Related Art The applicant of the present invention has filed many patent applications concerning a hologram color filter and a transmission type color liquid crystal display device using the same. A holographic color filter applied to a reflective liquid crystal display device or a DMD (digital micromirror device) to form a reflective image display device is also disclosed in Japanese Patent Application Laid-Open No. 9-281917 (Japanese Patent Application No. 8-95289). In the proposal.

[0003]

However, in Japanese Patent Application Laid-Open No. 9-281917, reflected light from a reflective display device (reflective liquid crystal display device, DMD) is directed in a direction perpendicular to the surface of the display device. The light is not reflected on the surface, but is reflected on the oblique direction. When projecting this reflected light with a projection lens, the arrangement relationship between the display element and the projection lens is a tilted arrangement, and the optical arrangement is limited.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to diffract light in a direction perpendicular to the surface of a reflection type image display device, and use a hologram color filter to provide an illumination light source side. Another object of the present invention is to provide a reflection type image display device using a hologram color filter capable of displaying an image with small image distortion by using a coaxially arranged projection optical system by separating display light diffracted again from illumination light.

[0005]

A reflection type image display apparatus using a hologram color filter according to the present invention, which achieves the above object, comprises an element hologram which disperses and condenses illumination light incident at an oblique incident angle. A reflection type image display device comprising a combination of a hologram color filter composed of repetitions and a reflection type spatial modulation element, wherein display light reflected by the reflection type spatial modulation element and re-diffracted by the hologram color filter is illuminated. In a reflection type image display device which emits light in a direction substantially opposite to the light, a polarization separating means is arranged in an optical path of the illumination light to separate the display light from the illumination light.

In this case, it is desirable that the polarization splitting angle by the polarization splitting means is substantially equal to the incident angle of the illumination light, and the display light is emitted substantially perpendicularly to the surface of the reflective spatial light modulator.

It is desirable that the reflection type spatial modulation element rotates the plane of polarization of incident light in accordance with the degree of modulation of the pixel.

The polarized light separating means may be constituted by a polarized light separating prism or an array thereof, or may be constituted by a holographic polarizing beam splitter or a polarizing beam splitter formed of a transmission type diffraction grating.

Further, the display light may be projected by a projection optical system.

In the present invention, since the polarization splitting means is arranged in the optical path of the illumination light to separate the display light from the illumination light, a bright and undistorted color image can be observed and displayed. When configured as an image display device, the projection optical system does not need to be tilted, and the degree of freedom of the optical system is dramatically improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a reflection type image display apparatus using a hologram color filter according to the present invention will be described with reference to embodiments.

The basic principle of the present invention is disclosed in JP-A-9-2819.
In a reflection-type image display device using a hologram color filter as described in No. 17, diffracted light that is separated by the hologram color filter and incident on the reflection-type image display element is substantially perpendicular to the surface of the image display element. The light reflected by the reflection type image display device is diffracted again to the illumination light source side by the hologram color filter, and polarization separation means such as a Wollaston prism which changes the emission direction according to the direction of the polarization plane is set. The display light is separated from the direction of the illumination light so that an image with small image distortion can be displayed. This display light can be projected by a projection optical system having a coaxial arrangement instead of an eccentric arrangement.

The illumination light incident angle of the hologram color filter and the polarization separation angle of the polarization separation means are set so that the direction of separation of the display light by the polarization separation means is substantially perpendicular to the display surface of the reflection type image display device. Is desirably set. In this case, when the projection optical system is configured as a projection image display device, the projection optical system does not need to be tilted. Such a setting dramatically improves the degree of freedom of the optical system.

Next, an embodiment of the present invention will be described. First,
Referring to FIG. 3, the diffracted light, which is split by hologram color filter 2 and enters reflection type image display element 5, in particular, its central ray (principal ray of green component 7 G) is reflected by image display element 5.
The reflective image display device 1 set so as to be substantially perpendicular to the surface will be described.

In FIG. 3, the reflection type image display element 5 is
For example, the spatial light modulator 3 is composed of a transmissive spatial light modulator 3 formed of a liquid crystal display element and a reflective layer 4 such as an aluminum film disposed on the back surface of the transmissive spatial light modulator 3. The transmissive spatial light modulator 3 is regularly partitioned into pixels 3 '. The hologram color filter 2 is spaced apart from the front side (observation side) of the transmission type spatial light modulator 3. A black matrix (not shown) is arranged between the pixels 3 ′ of the transmissive spatial light modulator 3. The distance between the hologram color filter 2 and the reflection layer 4 is selected to be substantially equal to the converging distance (focal length) of each array-shaped minute hologram 2 ′ constituting the hologram color filter 2.

Here, the hologram color filter 2
Are the three primary color pixels R, G, B of the transmissive spatial light modulator 3.
Corresponding to each set of three pixels 3 ′ adjacent to each other in the direction of the plane of the transmissive spatial light modulator 3 in the array, at the same pitch as the repetition period. , And one micro hologram 2 ′ is arranged corresponding to each set of three pixels 3 ′ adjacent in the direction of the plane of the transmissive spatial light modulator 3, and each micro hologram 2 ′ The light 7G of the green component in the illumination light 6 incident at an angle θ with respect to the normal line of the hologram color filter 2 is converted into three primary color pixels R, G, and B corresponding to the minute hologram 2 ′. It is formed in a Fresnel zone plate shape so as to converge light nearly vertically near the center pixel G. The minute hologram 2 'is composed of a transmission hologram such as a relief type, a phase type, and an amplitude type, which has little or no wavelength dependence of the diffraction efficiency, and diffracts at different diffraction angles depending on the wavelength.

With this arrangement, the white illuminating light 6 is incident from the surface of the hologram color filter 2 at an incident angle θ.
Is incident, the wavelength is dispersed by the hologram color filter 2, and the light condensing position for each wavelength is dispersed in a direction parallel to the surface of the hologram color filter 2. Among them, the red wavelength component 7R is near the surface of the reflective layer 4 at the position of the pixel R displaying red, the green component 7G is near the surface of the reflective layer 4 at the position of the pixel G displaying green, and blue. The hologram color filter 2 is arranged and arranged such that the component 7B of the color component 7B is diffracted and condensed in the vicinity of the surface of the reflection layer 4 of the pixel B that displays blue. Passes through each pixel 3 ',
The light is reflected by the reflective layer 4 and transmits the corresponding pixels R, G, and B again from the back surface side to become light 8R, 8G, and 8B, respectively, and the reflected light 8 further enters the hologram color filter 2 substantially perpendicularly. The light is re-diffracted by the hologram color filter 2 to become a diffracted light 9, and exits in a direction substantially opposite to the illumination light 6.

The reason why the reflected light 8 is re-diffracted by the hologram color filter 2 and emitted in a direction substantially opposite to the illumination light 6 is that the hologram color filter 2 has no wavelength dependence of the diffraction efficiency as described above. FIG. 4 shows an example of the wavelength dependence of the diffraction efficiency. FIG. 4 shows the diffraction efficiency when the illumination light 6 incident on the hologram color filter 2 is S-polarized light and P-polarized light. The difference in the diffraction efficiency between the S-polarized light and the P-polarized light is small. .

Here, in the present invention, the diffractive components 7R, 7G, 7B of the respective colors enter the pixels R, G, B of the transmission type spatial light modulator 3 which display red, green, blue, respectively. The transmissive spatial light modulator 3 is configured to receive the modulation of the rotation of the polarization plane according to the display state of the pixel, and when the light is reflected by the reflective layer 4 and reciprocates through the pixel 3 ′, the maximum modulation or the minimum modulation is performed. Then, the polarization plane is rotated by 90 °. Such a transmissive spatial light modulator 3 includes, for example, a TN liquid crystal display element. In addition, the transmissive spatial light modulator 3 includes a transmissive spatial light modulator of an amplitude modulation type and a quarter-wave plate disposed on the incident side thereof. And so on.

As described above, the diffracted light 7 that is split by the hologram color filter 2 and enters the reflection type image display element 5 (the diffracted components 7R, 7G, and 7B are collectively referred to as a diffracted light 7), particularly the central ray thereof. In the reflection type image display device 1 in which the (main ray of the green component 7G) is set to be substantially perpendicular to the surface of the image display element 5, display light (diffraction light) is displayed.
9 emits in a direction substantially opposite to the illumination light 6, and the display light 9 cannot be separated from the illumination light 6 as it is, and is not suitable for a display device.

Therefore, in the present invention, a polarization separating means for separating the display light 9 from the illumination light 6 is used. As such polarized light separating means, a polarized light separating prism such as a Wollaston prism, a Nicol prism, a Gran Thompson prism, a Gran Foucault prism, and a Lochon prism can be used. -2
A holographic polarization beam splitter comprising a volume hologram proposed in JP-A-48417 and JP-A-7-234316 and a polarization beam splitter comprising a transmission-type diffraction grating proposed in JP-A-61-240204 can be used. . Furthermore, a polarization separation prism array in which polarization separation prisms are arranged in a plane in an array can be used. However, FIG. 1 and FIG.
As can be seen from the arrangement of FIG.
In the case of a polarizing beam splitter that separates at an angle of 0 °, it is not desirable because the display surface of the reflective image display device 1 is viewed obliquely.

FIG. 1 is an optical path diagram showing one embodiment of a reflection type image display apparatus using a hologram color filter according to the present invention. 3 is used as the reflection type image display device 1, a white light source 11 such as a metal halide lamp is used as a light source of the illumination light 6, and a Wollaston prism is used as a polarization separation unit in the optical path of the illumination light 6. 10 is arranged. This Wollaston prism 10
Are set so that the separation angle between the S-polarized light and the P-polarized light is substantially equal to the incident angle θ of the illumination light 6 to the hologram color filter 2. The polarizing plate 12 is placed in the optical path of the illumination light 6 incident on the Wollaston prism 10 from the light source 11.
Is arranged.

With such an arrangement, the illumination light 6 emitted from the light source 11 becomes, for example, P-polarized light by the polarizer 12, and the illumination light 6 emitted from the Wollaston prism 10 remains hologram at the incident angle θ with P polarization. The diffracted light 7 incident on the color filter 2, where it is split into red, green, and blue components, is incident on the reflective image display element 5 almost perpendicularly, and changes from the P-polarized state according to the state of each pixel 3 '. The polarization plane undergoes rotation modulation and reflected light 8
Then, the light enters the hologram color filter 2 substantially perpendicularly from the back surface side and is diffracted again to become a diffracted light 9. This diffracted light 9 enters the Wollaston prism 10 from the opposite side,
The modulated S-polarized light component in the diffracted light 9 is
Is separated from the illumination light 6 so as to form a separation angle θ with the illumination light 6 from the display device 9, and exits from the reflective image display device 1 as display light 9 ′, and the display light 9 ′ is reflected from the reflective image display device. 1
Is equivalent to exiting from the front. Therefore, a bright and undistorted color image can be observed by observing the display light 9 '. Further, by disposing the projection lens 13 in the optical path of the display light 9 ′ without decentering, a bright and undistorted color image can be projected on the screen 14. In the above arrangement, the polarizing plate 12 is not always necessary.

FIG. 2 is an optical path diagram showing another embodiment of the reflection type image display device using the hologram color filter according to the present invention. 3 is used as the reflection-type image display device 1, a white light source 11 such as a metal halide lamp is used as a light source of the illumination light 6, and this embodiment is used as polarization separation means in the optical path of the illumination light 6. In the example, a holographic polarizing beam splitter 10 'of Japanese Patent Application Laid-Open No. 7-248417 is arranged. The separation angle between the S-polarized light and the P-polarized light of the holographic polarization beam splitter 10 ′ is set to be substantially equal to the incident angle θ of the illumination light 6 to the hologram color filter 2. Then, a polarizing plate 12 is disposed in the optical path of the illumination light 6 incident on the holographic polarizing beam splitter 10 'from the light source 11.

With such an arrangement, also in this case,
Illumination light 6 emitted from a light source 11 is converted into, for example, P-polarized light by a polarizing plate 12, and the holographic polarization beam splitter 1
The illuminating light 6 that has exited 0 ′ enters the hologram color filter 2 at an incident angle θ with P polarization, where the diffracted light 7 split into red, green, and blue components is substantially perpendicular to the reflective image display element 5. , And the polarization plane undergoes rotation modulation from the state of P-polarized light according to the state of each pixel 3 ′ to become reflected light 8. It becomes light 9. The diffracted light 9 enters the holographic polarization beam splitter 10 ′ from the opposite side, and is illuminated so that the modulated S-polarized light component in the diffracted light 9 forms a separation angle θ with the illumination light 6 from the light source 11. The light 6 is separated from the light 6 to become the display light 9 ′ and exits from the reflective image display device 1, and the display light 9 ′ is equivalent to exiting from the reflective image display device 1 in the front direction. Therefore, a bright and undistorted color image can be observed by observing the display light 9 '. Further, by disposing the projection lens 13 in the optical path of the display light 9 ′ without decentering, a bright and undistorted color image can be projected on the screen 14. Also in this case, the polarizing plate 12
Is not necessary.

As described above, in the reflection type image display device of the present invention, the illumination light 6 and the display light 9 are emitted in substantially opposite directions. Since the display is made to appear almost in front of the reflection type image display device 1, a bright and undistorted color image can be observed and displayed. In the case of a projection image display device, the projection optical system does not need to be tilted. The degree of freedom of the optical system is dramatically improved.

Although the reflection type image display apparatus using the hologram color filter of the present invention has been described based on several embodiments, the present invention is not limited to these embodiments, and various modifications are possible. . The transmissive spatial light modulator is not limited to the transmissive liquid crystal display element, and various spatial light modulators can be used. Further, the reflection layer is not limited to a reflection layer such as an aluminum film, and a reflection layer using a hologram may be used.

[0028]

As is apparent from the above description, according to the reflection type image display apparatus using the hologram color filter of the present invention, the display light is separated from the illumination light by disposing the polarization separation means in the optical path of the illumination light. Because it separates, you can observe and display a bright and undistorted color image,
When configured as a projection image display device, the projection optical system does not need to be tilted, and the degree of freedom of the optical system is dramatically improved.

[Brief description of the drawings]

FIG. 1 is an optical path diagram showing one embodiment of a reflection type image display device using a hologram color filter according to the present invention.

FIG. 2 is an optical path diagram showing another embodiment of the reflection type image display device using the hologram color filter according to the present invention.

FIG. 3 is an optical path diagram of the reflection type image display device used in FIGS. 1 and 2;

FIG. 4 is a diagram illustrating an example of the wavelength dependence of the diffraction efficiency of a hologram color filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reflection type image display apparatus 2 ... Hologram color filter 2 '... Micro hologram 3 ... Transmission type spatial light modulator 3' ... Pixel 4 ... Reflection layer 5 ... Reflection type image display element 6 ... Illumination light 7 ... Diffraction light 7R 7G, 7B: Diffraction spectral component 8: Reflected light 8R, 8G, 8B: Reflected light component 9: Diffracted light (display light) 9 ': Display light 10: Wollaston prism 10': Holographic polarization beam splitter 11: Light source 12 ... Polarizing plate 13 ... Projection lens 14 ... Screen

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03B 21/00 G03B 21/00 D G09F 9/00 360 G09F 9/00 360Z H04N 9/31 H04N 9/31 Z F term (Ref.) GG46

Claims (6)

[Claims] 1. A reflection type image display device comprising a combination of a hologram color filter formed by repeating element holograms for dispersing and converging illumination light incident at an oblique incident angle and a reflection type spatial modulation element. In a reflective image display device in which display light reflected by the reflection type spatial modulation element and re-diffracted by the hologram color filter emerges in a direction substantially opposite to the illumination light, a polarization separation unit is provided in an optical path of the illumination light. A reflection type image display device using a hologram color filter, wherein the reflection type image display device is disposed to separate the display light from the illumination light. 2. A display device according to claim 1, wherein a polarization separation angle of said polarization separation means is substantially equal to an incident angle of said illumination light, and said display light is emitted substantially perpendicular to a surface of said reflection type spatial modulation element. Item 2. A reflection type image display device using the hologram color filter according to Item 1. 3. The reflection type using a hologram color filter according to claim 1, wherein the reflection type spatial modulation element rotates a plane of polarization of incident light in accordance with a degree of modulation of a pixel. Image display device. 4. The apparatus according to claim 1, wherein said polarization separation means comprises a polarization separation prism or an array thereof.
A reflection type image display device using the hologram color filter according to any one of the above. 5. The apparatus according to claim 1, wherein said polarization separating means comprises a holographic polarizing beam splitter or a polarizing beam splitter comprising a transmission type diffraction grating.
4. A reflection type image display device using the hologram color filter according to any one of items 1 to 3. 6. The reflection type image display device using a hologram color filter according to claim 1, wherein the display light is projected by a projection optical system.