JPH09281917A - Image display device using hologram color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a bright reflection type color display device by constituting the image display device with a hologram color filter, a transmission type space light modulator and a reflection layer and lighting from the holo-gram color filter side. SOLUTION: A polymer-distributed liquid crystal(PDLC) display element 31 is used as the space light modulator, and the hologram color filter 5 is arranged separately on the surface side (observation side) of the PDLC display element 31 regularly divided to pixels 3l'. Further, the reflection layer 32 such as an aluminum film is arranged on the rear surface of the PDLC display element 31. Then, white lighting light 33 is made incident from the surface side of the hologram color filter 5 at an incident angle θ. Since then, respective color components 34R, 34G, 34B are made incident on the pixels R, G, B respectively displaying red, green, blue, and are intensity modulated according to the display states of respective pixels to arrive at eyes of an observer, a color image display becomes possible by combining the modulation states of the pixels R, G, B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device using a hologram color filter, and more particularly to a spatial light modulator such as a polymer dispersed liquid crystal display device and a digital micromirror device type display device and a hologram color filter. The present invention relates to a combined reflection type image display device.

[0002]

2. Description of the Related Art Conventionally, in a color liquid crystal display device using an absorption color filter using a pigment, a dye or the like,
The backlight is indispensable for display.
However, if white light is simply irradiated from behind the color liquid crystal display device, its utilization efficiency is very low. The main reasons are as follows.

[0003] The area occupied by the black matrix other than the cells of each color is large, and the light hitting it is wasted. Among white light incident on each pixel, R (red), G (green),
Since the color components passing through the B (blue) color filter are limited, other complementary color components are wasted. There is a loss due to absorption in the color filter.

In order to solve such a problem, for example, a microlens array is installed in front of a color filter,
2. Description of the Related Art There has been conventionally known a method of increasing the utilization efficiency of a backlight by concentrating a backlight of white light on color filter cells R, G, and B, respectively.

[0005] However, even with this method, it is not possible to irradiate the white light 3 to each of the color filter cells R, G, B in a spectral manner, so that the above-mentioned problem cannot be solved.

Further, a liquid crystal projector in which the use efficiency of light is improved by using three dichroic mirrors and a microlens array without using such a color filter has been proposed in Japanese Patent Application Laid-Open No. Hei 4-60538. In this case, the above-mentioned absorption color filters using pigments, dyes and the like become unnecessary, and the above-mentioned problems (1) to (5) are solved, and the luminance of a color image is improved. However, since three dichroic mirrors are required, optical The system and equipment become large and bulky. In addition, there is a problem that the cost becomes high.

In view of such a situation, the present applicant has proposed in Japanese Patent Application No. 5-12170, etc. a color filter using a hologram and a color filter using the hologram in order to significantly improve the utilization efficiency of a liquid crystal display backlight or the like. We have proposed a liquid crystal display device using.

Further, a liquid crystal projection display device which changes the liquid crystal display device using such a hologram color filter to a projection type and displays a bright color image on a screen is proposed in Japanese Patent Application No. 5-242292. did.

A liquid crystal display device and a liquid crystal projection display device using such a hologram color filter will be briefly described below. First, a liquid crystal display device using a hologram color filter will be described with reference to the sectional view of FIG. In the figure, a hologram array 5 constituting a color filter is arranged at a distance from the backlight 3 incident side of a liquid crystal display element 6 which is regularly divided into liquid crystal cells 6 '(pixels). On the back surface of the liquid crystal display element 6, a black matrix 4 provided between the liquid crystal cells 6 'is arranged. In addition to the above, polarizing plates (not shown) are arranged on the incident side of the hologram array 5 and on the exit side of the liquid crystal display element 6. An absorption type color filter that transmits light of colors corresponding to the R, G and B color separation pixels is additionally arranged between the black matrixes 4 as in the conventional color liquid crystal display device. You may do it.

The hologram array 5 corresponds to a repeating period of R, G, and B color-separating pixels, that is, each set of three liquid crystal cells 6'adjacent to each other in the in-plane direction of the liquid crystal display element 6. It is composed of minute holograms 5'arranged in an array at the same pitch as the repeating pitch, and the minute holograms 5'are aligned in groups of three liquid crystal cells 6'adjacent to each other in the direction of the paper surface of the liquid crystal display element 6 to form one group. The micro holograms 5'are arranged one by one, and each micro hologram 5'corresponds to the micro hologram 5'the light of the green component in the backlight 3 which is incident at an angle θ with respect to the normal line of the hologram array 5. It is formed in a Fresnel zone plate shape so as to collect light on the liquid crystal cell G at the center of the three color-dividing pixels R, G, and B. The micro hologram 5 ′ has a relief type, which has no or little wavelength dependence of the diffraction efficiency.
It consists of transmission holograms such as phase type and amplitude type. Here, the term "diffraction efficiency has no or little wavelength dependency" does not mean that it is a type that diffracts only a specific wavelength and hardly diffracts other wavelengths like a Lippmann hologram. Is also diffracted, and the diffraction grating whose diffraction efficiency has little wavelength dependence diffracts at different diffraction angles depending on the wavelength.

With such a structure, when the white backlight 3 which is incident at an angle θ with respect to the normal line from the surface of the hologram array 5 on the side opposite to the liquid crystal display element 6 is incident, the wavelength is changed. The diffraction angles of the minute holograms 5'are different depending on the wavelengths, and the focusing positions for each wavelength are dispersed in the direction parallel to the surface of the hologram array 5. Among them, the red wavelength component is located at the position of the liquid crystal cell R displaying red, the green component is located at the position of the liquid crystal cell G displaying green, and the blue component is located at the position of the liquid crystal cell B displaying blue. By arranging the hologram array 5 so as to diffract and collect light, each color component passes through each liquid crystal cell 6 ′ with almost no attenuation in the black matrix 4 and the liquid crystal cell 6 ′ at the corresponding position. Color display can be performed according to the state. The angle of incidence θ of the backlight 3 on the hologram array 5 depends on the hologram recording conditions, hologram array 5
Of the hologram array 5, the distance between the hologram array 5 and the liquid crystal display element 6, and the like.

As described above, by using the hologram array 5 as a color filter, each wavelength component of the conventional color filter backlight can be made incident to each liquid crystal cell 6'without being absorbed, and its utilization efficiency is improved. Can be significantly improved.

Further, the liquid crystal display device using the hologram color filter having the structure as shown in FIG. 6 is used as it is as a direct-viewing type liquid crystal display device or as a spatial light modulator for projection display. It can be used as a projection display device. FIG. 7 is a cross-sectional view in that case, in which the first polarizing plate 12 is arranged close to or integrally with the entrance side of the hologram array 5, and the second polarizing plate 13 is arranged close to or integrally with the exit side of the liquid crystal display element 6. Has been done. The color liquid crystal display device 11 is illuminated by a white parallel backlight 3 from an illumination device 14 composed of a combination of a metal halide lamp 15 and a parabolic mirror 16, for example, and is modulated by the color liquid crystal display device 11. The image is enlarged by a projection lens 18 via a field lens 17 disposed near the liquid crystal display device 11 and is enlarged and formed on a screen 19, so that a bright projected image can be obtained.

In the liquid crystal display device using the hologram color filter as described above, the liquid crystal display element 6 including the black matrix 4 is actually shown in FIG.
As shown in the cross section in FIG. 1, the liquid crystal display element 6 is composed of, for example, a liquid crystal layer 25 such as twisted nematic sandwiched between two glass substrates 21 and 22, and is formed on the inner surface of the glass substrate 21 on the backlight side. Is provided with a black matrix 4 and a uniform transparent counter electrode 23, and on the inner surface of the glass substrate 22 on the display surface side, a transparent pixel electrode 24 and a TFT (not shown) are provided independently for each liquid crystal cell R, G, B. Is provided. An alignment layer (not shown) is also provided on the liquid crystal layer 25 side of the electrodes 23 and 24. The hologram color filter 5 or 10 provided on the surface of the substrate 26 on the side of the liquid crystal display element 6 that is close to or bonded to the glass substrate 21 on the backlight side is arranged, and the polarizing plate 12 is provided on the backlight side of the substrate 26. Polarizing plates 13 are attached to the outer surface of the observation-side glass substrate 22 of the liquid crystal display element 6, for example, and their transmission axes are arranged so as to be orthogonal to each other. The polarizing plate 12 on the backlight side
Instead of sticking to the backlight side of the substrate 26,
As shown by the dotted line in FIG. 8, it may be placed in the optical path of the backlight 3 away from the hologram color filter 5.

Color display is possible by controlling the voltage applied between the transparent pixel electrode 24 and the transparent counter electrode 23 for each pixel of the liquid crystal display element 6 to change the transmission state thereof. .

On the other hand, a polymer dispersed liquid crystal (PDCL) display element has been proposed as a liquid crystal display element. this is,
Display is performed by controlling the white turbid state and the transparent state by turning the voltage on and off. A bright display is possible because a polarizing plate is not used unlike conventional liquid crystal display elements such as twisted nematic (TN) liquid crystal. (“Flat Panel Display” '91, pp. 214-2)
24). Such a liquid crystal is composed of a polymer / liquid crystal composite film, and there are a liquid crystal phase separated into droplets in the polymer and a liquid crystal continuous phase. .

A digital micromirror device (DMD) has also been proposed as a display element capable of two-dimensional display by minute deformation of a mirror. This is shown in FIG.
As shown in the perspective view in (a), the minute mirrors M corresponding to the respective pixels are two-dimensionally arranged, and the mirror M ′ at a predetermined address is tilted about a diagonal line to make the mirror M ′
The light incident from a certain direction is reflected in a direction different from that of the mirror that is not tilted, and a two-dimensional pattern is displayed ("IEEE Spectrum Vol.30,
No. 11, pp. 27-31). FIG. 9B shows a support driving structure of each mirror M. Each mirror M has a pair of support posts P which are erected on the silicon substrate S at one diagonal corner.
Is supported via a torsion hinge T by a voltage applied to one of a pair of electrodes E provided on the substrate S on the back side of the mirror M, and the diagonal line between the hinges T is axially moved by electrostatic force. Then, the surface of the mirror M is rotated.

[0018]

As described above, the image display device using the hologram color filter proposed by the present applicant is based on the premise that a normal liquid crystal display element such as a TN liquid crystal is used, and , The backlight was made to enter from the back side. However, no image display device has been proposed in which a hologram color filter is combined with a reflective type such as a polymer dispersion type liquid crystal display device, a DMD type display device, or the like in which the illumination light is incident from the surface side of the spatial light modulator.

The present invention has been made in view of such a situation, and an object thereof is to use a hologram color filter proposed by the present applicant to make illumination light incident from the surface side and to provide a spatial light modulator. Polymer dispersed liquid crystal display device,
It is an object of the present invention to provide a bright reflection type color image display device which can also use a DMD type display element.

[0020]

An image display device using a hologram color filter of the present invention that achieves the above object comprises an illumination light source and an array of element condensing holograms. , A hologram color filter for wavelength-dispersing white light incident at a predetermined angle with respect to the normal line of the hologram recording surface in a direction substantially along the hologram recording surface, and a reflection arranged near the light condensing surface And a transmissive spatial light modulator arranged between the hologram color filter and the reflective layer.

Application of voltage as a transmissive spatial light modulator,
It is also possible to use a polymer-dispersed liquid crystal display element that controls the cloudy state and the transparent state by releasing the liquid crystal display element. Further, as the reflective layer, it is also possible to use a reflection hologram in which interference fringes are distributed and recorded so as to reflect the separated color components.

An image display device using another hologram color filter of the present invention comprises an illumination light source and an array of element condensing holograms, each element condensing hologram being a normal to the hologram recording surface. On the other hand, the hologram color filter that disperses the white light incident at a predetermined angle in the direction substantially along the hologram recording surface and disperses it, and tilts independently by an external signal placed near the light collecting surface. And a digital micromirror device type display element comprising a two-dimensional array of micromirrors whose angles can be controlled.

In these image display devices, the reflected light may be enlarged and projected by the projection optical system. In that case, the projection optical system is provided with means for blocking the light traveling in directions other than the vicinity of the predetermined direction. It is desirable to have it.

In the present invention, since the image display device is composed of the hologram color filter, the transmissive spatial light modulator, and the reflection layer, and the illumination is performed from the hologram color filter side, a bright reflection type color image display is provided. The device can be realized. As the transmissive spatial light modulator, a polymer dispersion type liquid crystal display element, a DMD type display element, etc. can be used in addition to a normal liquid crystal display element. By using these, a brighter color image display can be performed.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image display device using the hologram color filter of the present invention will be described below. FIG. 1 shows a schematic sectional view of one embodiment of a reflection type image display device using a hologram color filter as shown in FIG. In this embodiment, a polymer dispersed liquid crystal (PDLC) display element 31 is used as a spatial light modulator. In the figure, the hologram color filter 5 is arranged separately on the front side (observation side) of the PDLC display element 31 which is regularly divided into pixels 31 '. A reflective layer 32 such as an aluminum film is arranged on the back surface of the PDLC display element 31. A black matrix (not shown) (see FIG. 6) is arranged between the pixels 31 of the PDLC display element 31. The distance between the hologram color filter 5 and the reflective layer 32 is selected to be substantially equal to the light collecting distance (focal length) of the minute hologram 5 '.

Also in this case, the hologram color filter 5 has the repeating period of the R, G, and B color-separating pixels of the PDLC display element 31, that is, three pixels 31 'adjacent to each other in the in-plane direction of the PDLC display element 31. Corresponding to each of the groups, the minute holograms 5 ′ are arranged in an array at the same pitch as the repeating pitch, and the minute holograms 5 ′ are three pixels 31 ′ adjacent to each other in the in-plane direction of the PDLC display element 31. One micro hologram 5 ′ is arranged corresponding to each group, and each minute hologram 5 ′ is a light of the green component of the illumination light 33 that enters at an angle θ with respect to the normal line of the hologram color filter 5. 34G is also formed in a Fresnel zone plate shape so as to condense 34G in the vicinity of the pixel G at the center of the three color separation pixels R, G, B corresponding to the minute hologram 5 '. It is. The minute hologram 5'is formed of a transmission hologram such as a relief hologram, a phase hologram, or an amplitude hologram, which has little or no wavelength dependency of diffraction efficiency. Here, the term "diffraction efficiency has no or little wavelength dependency" does not mean that it is a type that diffracts only a specific wavelength and hardly diffracts other wavelengths like a Lippmann hologram. Is also diffracted, and the diffraction grating whose diffraction efficiency has little wavelength dependence diffracts at different diffraction angles depending on the wavelength.

With such an arrangement, the white illumination light 3 from the surface side of the hologram color filter 5 at an incident angle θ.
When 3 is incident, the wavelength is dispersed by the hologram color filter 5, and the condensing position for each wavelength is dispersed in the direction parallel to the surface of the hologram color filter 5. Among them, the red wavelength component 34R is near the surface of the reflective layer 32 at the position of the pixel R that displays red, and the green component 34G is near the surface of the reflective layer 32 at the position of the pixel G that displays green. By arranging the hologram color filter 5 so that the component 34B of the above is diffracted and condensed near the surface of the reflective layer 32 of the pixel B displaying blue, each color component is hardly attenuated by the black matrix. Through each pixel 31 ′, is reflected by the reflective layer 32, passes through the corresponding pixels R, G, B again from the rear surface side, is further incident on the hologram color filter 5, and is then almost lit by the hologram color filter 5. Transmitted light 35 without being diffracted
It becomes R, 35G, 35B, and enters the observer's eye. Therefore, the components 34R, 34G, and 34B of the respective colors enter the pixels R, G, and B displaying red, green, and blue, respectively, and undergo intensity modulation according to the display states of those pixels and reach the eyes of the observer. Therefore, it is possible to display a color image by combining the modulation states of the pixels R, G, and B.

Here, the PDLC display element 31 performs display by controlling the white turbid state and the transparent state by turning on and off the voltage as described above, and since a polarizing plate is not necessary, the TN liquid crystal display element is provided. It is possible to display brighter than a normal liquid crystal display device such as. Moreover, since the hologram color filter 5 having a high utilization efficiency of the illumination light 33 is used for displaying a color image, a brighter color image can be displayed.

An image display device using the hologram color filter 5 having the structure shown in FIG. 1 can be used as a projection image display device. FIG. 2 is a sectional view in that case. For example, a metal halide lamp 15 and a parabola similar to those in FIG. 7 are provided at a predetermined incident angle θ on the surface side (hologram color filter 5 side) of the image display device 30 in FIG. When the white parallel illumination light 33 from the illumination device 14 including the combination of the surface mirrors 16 is made incident, the display light 35 which is dispersed by the hologram color filter 5 and modulated by the PDLC display element 31 is made incident on the opening of the projection lens 18. Since the image is projected, the color image displayed on the image display device 30 is enlarged and formed on the screen 19, and a bright color projection image can be obtained. At this time, when the emission angle of the display light 35 is large, the lens and the screen may be eccentrically arranged.

In the case of FIG. 1, since the simple reflective layer 32 is arranged on the back surface of the PDLC display element 31, the directions of the respective color components 35R, 35G and 35B reaching the observer are mutually opposite as is apparent from FIG. It will be different. Therefore, when looking directly at the image displayed on the image display device 30, there is a possibility that a pseudo color may appear depending on the viewing direction. Further, when this is used as the projection image display device as shown in FIG. 2, in order to make all the color components 35R, 35G, 35B enter the projection lens 18, a projection lens 18 having a large aperture is used. Must be used.

Therefore, in the embodiment shown in FIG. 3, a reflection hologram 36 is used instead of the reflection layer 32. A volume phase hologram (Lippmann hologram) is used as the reflection hologram 36, and reflections in the vicinity of the positions where the red diffraction component 34R, the green diffraction component 34G, and the blue diffraction component 34B dispersed by the hologram color filter 5 are condensed respectively. Fringes 36R and 3 in the hologram 36
The interference fringes 36R and 6G so that the 6G and 36B respectively reflect only the red wavelength light, the green wavelength light, and the blue wavelength light.
36G and 36B are selectively triple-recorded, and the inclinations of the interference fringes 36R, 36G, and 36B respectively cause the red diffraction component 34R, the green diffraction component 34G, and the blue diffraction component 34B to travel in substantially the same direction. Reflected light 35R, 3
5G and 35B are configured so as to be reflected and diffracted.

Therefore, in the case of this embodiment, the directions of the respective color components 35R, 35G, 35B in the display light reaching the observer are substantially the same, and the direction viewed when the image displayed on the image display device 30 is directly viewed. As a result, the possibility that a pseudo color will be attached decreases, and when this is used as a projection image display device as shown in FIG. 2, the directions of the color components 35R, 35G, and 35B are substantially the same, so the projection lens 18 As a result, a small caliber will do.

In the embodiment shown in FIG. 4, the digital micromirror device (DM) described with reference to FIG. 9 is used as a spatial light modulator arranged on the back side of the hologram color filter 5.
D) 37 is an example in which the red color diffraction component 34R and the green color diffraction component 3 are separated by the hologram color filter 5.
4G, so that the minute mirror 38 of the DMD 37 is positioned near the position where the blue diffraction component 34B is condensed respectively,
MD37 is arranged. With such an arrangement, in the case of FIG. 4, since the positions of the pixels R and B are modulated, the reflected lights 35R and 35B are reflected in a predetermined direction, while the pixel G is modulated. Therefore, the reflected light 35G is reflected in a different direction from the reflected lights 35R and 35B. Therefore,
For example, by observing from the direction of the reflected lights 35R and 35B, a color image can be observed and a bright color image display can be performed.

This embodiment can also be used as a projection image display device. FIG. 5 shows a sectional view in that case. The image display device 30 receives white parallel illumination light 33 from the illumination device 14.
The configuration until the incident light is similar to that in the case of FIG. In the configuration using the DMD 37 of FIG. 5, the emission angle of the display light 35 that forms the projection image is large, so the projection lens 18 and the screen 19 may be eccentrically arranged with respect to the image display device 30. When the DMD 37 is used, there is reflected light 40 (reflected light 35G in the case of FIG. 4) which is emitted in a direction different from that of the display light 35 even when the minute mirror 38 constituting the pixel is not modulated. In order to remove the slit 39, a slit 39 is arranged near the rear focal point of the projection lens 18, and even if the unnecessary reflected light 40 enters the projection lens 18, the direction is different from that of the display light 35. You cannot pass through to reach screen 19. Therefore, only the display light 35 whose reflection direction is changed by being modulated by the micro mirror 38 reaches the screen 19 to form a bright color display image. On the contrary, the display light 35 is blocked by the slit 39, and the reflected light 4
It is also possible to display an image by passing only 0.

The image display device using the hologram color filter of the present invention has been described above based on some embodiments, but the present invention is not limited to these embodiments and various modifications can be made. For example, instead of a PDLC display element, a TN type or a super twist nematic (S
It is also possible to use a normal liquid crystal display device of the TN) type.

[0036]

As is apparent from the above description, according to the image display device using the hologram color filter of the present invention, the image display device is composed of the hologram color filter, the transmissive spatial light modulator and the reflective layer. , Because it was lit from the hologram color filter side,
It is possible to realize a bright reflective color image display device. As the transmissive spatial light modulator, a polymer dispersion type liquid crystal display element, a DMD type display element, etc. can be used in addition to a normal liquid crystal display element. By using these, a brighter color image display can be performed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of a reflection type image display device using a hologram color filter of the present invention.

FIG. 2 is a cross-sectional view of a projection image display device using the image display device shown in FIG.

FIG. 3 is a schematic cross-sectional view similar to FIG. 1 of an image display device of another embodiment.

FIG. 4 is a schematic cross-sectional view similar to FIG. 1 of an image display device of yet another embodiment.

5 is a cross-sectional view of a projection image display device using the image display device shown in FIG.

FIG. 6 is a schematic sectional view of a liquid crystal display device using a hologram color filter.

7 is a sectional view of a liquid crystal projection display device using the liquid crystal display device of FIG.

FIG. 8 is a cross-sectional view of a liquid crystal display element.

FIG. 9 is a diagram for explaining the configuration and operation of the digital micromirror device.

[Explanation of symbols]

 5 ... Hologram array (hologram color filter) 5 '... Micro hologram 14 ... Illumination device 15 ... Metal halide lamp 16 ... Parabolic mirror 18 ... Projection lens 19 ... Screen 30 ... Image display device 31 ... Polymer dispersed liquid crystal (PDLC) Display element 31 '... Pixel 32 ... Reflective layer 33 ... Illumination light 34R, 34G, 34B ... Diffractive spectral component 35 ... Display light 35R, 35G, 35B ... Transmitted light (reflected light) 36 ... Reflective hologram 36R, 36G, 36B ... Interference fringe 37 ... Digital micromirror device (DMD) 38 ... Micromirror 39 ... Slit 40 ... Unwanted reflected light R, G, B ... Color separation pixels

Claims (6)

[Claims] 1. An illuminating light source and an array of element converging holograms, each element condensing hologram recording white light entering at a predetermined angle with respect to a normal line of a hologram recording surface. A hologram color filter that disperses wavelengths in a direction substantially along the surface and disperses the light, a reflective layer disposed near the light condensing surface, and a transmissive spatial light modulator disposed between the hologram color filter and the reflective layer. An image display device using a hologram color filter characterized by comprising: 2. The hologram color according to claim 1, wherein the transmissive spatial light modulator is a polymer-dispersed liquid crystal display device that controls a cloudy state and a transparent state by applying and releasing a voltage. Image display device using a filter. 3. The hologram color filter according to claim 1 or 2, wherein a reflective hologram in which interference fringes are distributed and recorded so as to reflect spectral components is used as the reflective layer. Image display device. 4. An illuminating light source and an array of element condensing holograms, each element condensing hologram recording white light incident at a predetermined angle with respect to a normal line of a hologram recording surface. A digital consisting of a hologram color filter that disperses wavelengths in a direction substantially along the surface and disperses the light, and a two-dimensional array of micromirrors whose tilt angles can be independently controlled by signals from the outside arranged near the condensing surface. An image display device using a hologram color filter, which comprises a micromirror device type display element. 5. The image display device using the hologram color filter according to claim 1, wherein the reflected light is enlarged and projected by a projection optical system. 6. The image display device using a hologram color filter according to claim 5, wherein the projection optical system includes means for blocking light traveling in a direction other than the vicinity of the predetermined direction.