JP4270412B2 - Light diffusing element composite and image display system using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light diffusing element composite and an image display system using the same, and in particular, has a light scattering function represented by a viewing angle widening film of a direct-view display such as a transmission screen of a projector or a liquid crystal display device. The present invention relates to a light diffusing element complex and an image display system using the light diffusing element complex.
[0002]
[Prior art]
Conventionally, the following elements have been known as elements having a light scattering function.
a. An element having a surface with fine irregularities b. Element in which fine particles having different refractive indexes are dispersed in a transparent material c. Hologram element recorded by interfering scattered light and reference light.
[0003]
[Problems to be solved by the invention]
However, the principle of light scattering of the elements a and b is that the light beam is randomly bent by the fine irregularities and fine particles on the surface. Therefore, although the amount of scattering can be controlled to some extent, the scattered light cannot be controlled with high precision, such as concentrating the scattered light at a specific angle, and is scattered in an originally unnecessary direction, There was the fault that the utilization efficiency of light was bad. Moreover, since light from any direction is scattered, the transparency is poor. In particular, it is not suitable for applications such as “I want to scatter light in a certain direction but want to look transparent from the other directions”, for example, a window glass of a building.
[0004]
In the case of the hologram element that records the scattered light of c described above, the scattering angle can be controlled, and only light in a specific direction can be scattered by the angle selectivity specific to the hologram. However, the hologram has the characteristics of wavelength selectivity and light dispersibility, and this works as a defect. Wavelength selectivity is the property that only light of a specific wavelength is diffracted. For this reason, when dealing with a color image, there is a problem that light of a specific wavelength is emphasized and a specific color appears. . In addition, the light dispersibility is a property in which the angle at which the light is diffracted for each wavelength is different, so that there is a problem that the color changes depending on the viewing position.
[0005]
The present invention has been made in view of such problems of the prior art, and its purpose is to scatter for a predetermined incident angle range but to transmit without scattering at other angles, It is an object to provide a light diffusing element composite with very little light dispersion and wavelength selectivity and an image display system using the same.
[0006]
[Means for Solving the Problems]
The light diffusing element composite of the present invention that achieves the above object projects diffused light having a predetermined incident angle range onto a photosensitive material having a thickness, and causes mutual interference fringes in the diffused light flux to enter the photosensitive material. Volume-type transmission type that has the function of converting the incident light at a predetermined incident angle to diffuse on the incident side of the recorded light diffusing element and diffusing incident light at other incident angles without diffusing it An optical deflection element made of a hologram is arranged.
[0010]
The image display system using the light diffusing element composite according to the present invention is such that the above light diffusing element composite is in close contact with or close to the observation side of the image display apparatus.
[0011]
In that case, the image display device may be a transmissive liquid crystal display device, a reflective liquid crystal display device, or the like.
[0012]
Moreover, the image display system which forms an image on the above light-diffusion element composite_body | complex may be sufficient.
[0013]
Furthermore, an image display system in which the above light diffusing element complex is provided on a window glass of a building, an image is formed thereon by a projector from one side, and observed from the other side may be used.
[0014]
In the present invention, a light diffusing element formed by projecting diffused light having a predetermined incident angle range onto a thick photosensitive material and recording mutual interference fringes in the diffused light beam in the photosensitive material is used. However, the other side of the incident angle range is not scattered, but the light diffuser and the wavelength selectivity are extremely low. The present invention can be applied to a line-of-sight control film, a projection screen, etc. that cannot be seen, and when applied to an image display system, there is no problem that a specific color is tinted or the color changes depending on the viewing position.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the principle of the light diffusing element composite according to the present invention, examples thereof, and application examples will be described with reference to the drawings.
A method for manufacturing a light diffusing element used in the present invention will be described with reference to FIGS.
In FIG. 1, reference numeral 1 denotes a photosensitive material having a thickness (volume) such as a photopolymer, which can record a volume interference fringe (Bragg grating). Reference numeral 2 denotes a transmission diffusion plate such as ground glass or an opal plate. Such a transmission diffusion plate 2 is in close contact with the photosensitive material 1 (FIG. 1A) or arranged so as to be opposed to the photosensitive material 1 with a predetermined distance (FIG. 1B) to transmit and diffuse. When the laser beam 3 is incident from the side of the plate 2 opposite to the photosensitive material 1, diffused light (scattered light) 4 is emitted to the photosensitive material 1 side of the transmission diffusion plate 2. The diffused light 4 is incident on the photosensitive material 1, and the light in the diffused light beam interferes to record a large number of interference fringes in the photosensitive material 1.
[0016]
FIG. 3A is a cross-sectional view schematically showing the interference fringes 5. In the arrangement of FIG. 1, the central ray (principal ray) of the diffused light 4 is incident on the photosensitive material 1 substantially perpendicularly. The fringes 5 are formed by multiple recording of a large number of interference fringes having various inclinations within an angle range of about ± Δ centering on the interference fringes perpendicular to the surface of the photosensitive material 1. Of course, the angle range of about ± Δ is the same not only for the cross section of FIG. 3A but also for all cross sections forming an angle with the cross section.
[0017]
Therefore, as shown in FIG. 3 (b), the light diffusing element 10 of the present invention recorded and produced in this way has a solid angle Ω centered on a normal line perpendicular to the surface (this angular range is recorded). The angle 11 of the diffused light 4 is approximately the same as the angle range of the diffused light 4 in this case.) The incident light 11 is diffracted by the multiple interference fringes 5 and has a solid angle centered on a normal normal to the surface of the light diffusing element 10. The diffused light 12 is distributed in Φ. On the other hand, the light 13 incident outside the solid angle Ω is not diffracted by the multiple interference fringes 5 but becomes the directly transmitted light 14. That is, in the light diffusing element 10 of the present invention, when the light 11 is incident within the solid angle Ω determined by the angle range of the diffused light 4 at the time of recording, the light 13 is diffracted and diffused, but the light 13 is incident from other angles. Then, since it is transmitted without being scattered, it becomes transparent.
[0018]
Moreover, since the direction of the average interference fringe in the interference fringe 5 coincides with the normal direction perpendicular to the surface of the light diffusing element 10, when the light 11 is incident within the solid angle Ω centered on this direction, the light Almost no dispersion occurs and very little occurs. For the same reason, the wavelength selectivity is very small.
[0019]
Therefore, in the light diffusing element 10 of the present invention, (1) incident light at a specific angle is scattered and light from other angles is transmitted and appears transparent. (2) The color reproducibility of the scattered image is good from anywhere and can be used as a light diffusing screen having the characteristics that the color is not visible and visible.
[0020]
FIG. 2 is a diagram for explaining a method of manufacturing the light diffusing element 10 of the present invention using the microlens array 6 instead of the transmissive diffusing plate 2. In this case, the microlens array 6 is exposed to light. The microlens array 6 is placed in close contact with the material 1 or opposed to the photosensitive material 1 so as to face the material 1 at a predetermined distance, and the laser light 3 is incident from the opposite side of the microlens array 6 to the photosensitive material 1. A group of divergent light beams 7 exiting from each microlens to the photosensitive material 1 side is made incident on the photosensitive material 1, and light in the divergent light beam group is caused to interfere with each other so that a large number of interference fringes are formed as in the case of FIG. By recording within 1, the light diffusing element 10 of the present invention is produced.
[0021]
By the way, the above light diffusing element 10 scatters light 11 incident within a solid angle Ω centered on the normal of the surface of the light diffusing element 10 as diffused light 12 on the opposite surface side of the light diffusing element 10. However, in order to scatter the light incident from the oblique direction of the light diffusing element 10 within the solid angle Φ centered on the normal line on the opposite surface side, the light is deflected toward the incident side of the light diffusing element 10. What is necessary is just to arrange | position an element. An example is shown in FIG. FIG. 4A shows an optical deflection element composed of the transmission hologram 17. This angle-converts the light 15 incident from an obliquely upward direction of the light deflection element into light directed in the front direction on the transmission side. The transmission hologram 17 is produced by allowing two parallel lights to enter each other at an angle from the same side. In particular, the recording material has a thickness as in the case of the light diffusing element 10. In the case of using a photosensitive material capable of recording volume interference fringes, it is desirable that only light incident from a specific oblique direction is angle-converted as described above, and light incident from other directions passes directly.
[0022]
When such a light deflection element 17 is placed in close contact with the incident side of the light diffusing element 10 or at a distance (FIG. 4B), the light 15 incident from an obliquely upward direction of the light diffusing element 10 is transmitted on the transmission side. It can be set as the diffused light 12 which goes to a front direction. Hereinafter, such an element composed of the light deflecting element 17 and the light diffusing element 10 is referred to as a light diffusing element complex 10 ′ in the present invention. In such a configuration, when the volume type transmission hologram 17 is used, the light 15 incident from an oblique direction within a predetermined angle range is diffracted and diffused, but the light incident from other angles is diffused. It has the property of transmitting without being scattered. In the following description, the light diffusing element 10 includes the light diffusing element complex 10 ′.
[0023]
Now, the light diffusing element 10 according to the present invention can expand the observable angle range by being closely or closely arranged on the observation side of an image display device such as a liquid crystal display device. This is shown in FIG. In the example of this figure, a transmissive color liquid crystal display device is used as the image display device. In the transmissive color liquid crystal display device 20, a liquid crystal layer 26 such as twisted nematic liquid crystal is sandwiched between transparent glass plates 21 and 22, and the surface in contact with the liquid crystal layer 26 of the transparent glass plate 21 on the observation side is striped. A color filter 23 composed of RGB arranged in a shape and a transparent pixel electrode 24 including TFTs laminated on the surface side thereof are provided, and a surface of the transparent glass plate 22 on the backlight 27 side in contact with the liquid crystal layer 26 is provided. A common counter electrode 25 is provided, and an alignment film, a black matrix, etc. (not shown) are provided on the surfaces of the electrodes 24 and 25. The pixel electrode 24 can be controlled independently for each of R (red), G (green), and B (blue) pixels. Instead of the transparent pixel electrode 24 and the transparent common counter electrode 25, a matrix electrode structure in which one is a transparent signal electrode and the other is a transparent scanning electrode may be used. Further, polarizing plates (not shown) are arranged on the incident side and the emission side of the liquid crystal display device 20 in accordance with the operation principle of the liquid crystal display element.
[0024]
In such a transmissive color liquid crystal display device 20, as shown in FIG. 5A, the angle range in which the display image can be observed when viewed from the front side is limited to the narrow angle range indicated by θ in the figure, When viewed from a position outside the angular range θ, the display image cannot be seen.
[0025]
However, as shown in FIG. 5B, when the light diffusing element 10 according to the present invention is disposed in close contact with or close to the observation side of the transmissive color liquid crystal display device 20, the backlight 27 can transmit the transmissive color liquid crystal display device 20. Since the light passing through the transparent pixels is diffused according to the above principle, the observable angle range is expanded from θ to α (α> θ), and the angle range where the display image can be viewed from the front side is expanded.
[0026]
Next, an example of expanding the observable angle range when a reflective color liquid crystal display device is used as the image display device will be described. 6A, the reflective color liquid crystal display device 30 includes a liquid crystal layer 36 such as twisted nematic liquid crystal sandwiched between a transparent glass plate 31 and a glass plate 32, and the liquid crystal of the transparent glass plate 31 on the observation side. On the surface in contact with the layer 36, there are provided a color filter 33 made of RGB arranged in a stripe shape and the like, and a transparent pixel electrode 34 including TFTs laminated on the surface side thereof, and a glass plate 32 on the opposite side to the observation side. A metal reflective layer 35 also serving as a common counter electrode is provided on the surface in contact with the liquid crystal layer 36, and an alignment film, a black matrix, etc. (not shown) are provided on the surfaces of the electrodes 34 and 35. The pixel electrode 34 can be controlled independently for each of R (red), G (green), and B (blue) pixels. A polarizing plate (not shown) is arranged on the incident side of the liquid crystal display device 30 according to the operation principle of the liquid crystal display element.
[0027]
The light diffusing element 10 according to the present invention is placed in close contact or close to the observation side of the reflective color liquid crystal display device 30. However, in the case of this example, the central ray of the diffused light when producing the light diffusing element 10 is arranged obliquely with respect to the photosensitive material (see FIG. 8 to be described later), and in the vicinity of the a direction in FIG. Only incident light is diffused. In this case, the a direction is preferably within an angle range of 10 to 60 ° with respect to the normal line of the light diffusing element 10.
[0028]
Due to such an arrangement, the external light 38 incident from an oblique front opposite to the direction a of the reflective color liquid crystal display device 30 is transmitted without being scattered by the light diffusing element 10 and passes through the transparent pixel region. Since the light is regularly reflected by the metal reflection layer 35, passes again through the transparent pixel region in the direction a, enters the light diffusing element 10, and is diffused according to the above principle, the observable angular range is expanded to α.
[0029]
FIG. 6B is a modification of FIG. 6A, and this reflective color liquid crystal display device 30 ′ includes a transparent common counter electrode 35 ′ instead of the metal reflective layer 35 serving also as a common counter electrode, The reflection layer 37 having a sawtooth cross section disposed on the glass plate 32 side is used, and the light diffusing element 10 diffuses only light incident from the vicinity of the direction perpendicular to the surface. In this configuration, external light 38 incident from obliquely forward of the reflective color liquid crystal display device 30 ′ is transmitted without being scattered by the light diffusing element 10, passes through the transparent pixel region, and is reflected in the front direction by the reflective layer 37. Since the light passes through the transparent pixel region and enters the diffusing element 10 and is diffused by the above principle, the observable angle range is expanded to α. In this case, the incident range of the external light 38 is preferably between 10 and 60 ° with respect to the normal line of the light diffusing element 10, and the observable angle range α is preferably about ± 30 °.
[0030]
Further, the light diffusing element 10 of the present invention can be used for a transmissive screen of a projector. FIG. 7 shows a display in which the light diffusing element 10 is attached to the window glass 40, an image is projected on the light diffusing element 10 from a projector 41 installed in the room, and is visible from the outside of the window glass 40. As described above, since the light diffusing element 10 can be seen from the other side except from a predetermined direction, the outside of the window glass 40 can be seen from the room, but the outside person can see the projection image of the projector 41 and prevent peeping. Can do.
[0031]
FIG. 8 shows an example of a light diffusing element specifically manufactured.
As shown in FIG. 8A, an argon laser having a wavelength of 514 nm and an output of 5 W is used as the laser light source 42, a ground glass having a roughness of 1000 and a size of 30 × 50 cm is used as the transmission diffusion plate 2, and the photosensitive material 1 is large. Using a photopolymer HRF600X for holograms manufactured by DuPont having a size of 30 × 50 cm, the photosensitive material 1 was disposed at an angle of 15 ° with respect to the transmission diffusion plate 2 by 35 cm. The laser light 3 from the laser light source 42 is diverged by the optical system 43, irradiated to the entire surface of the transmissive diffusion plate 2, and the diffused light 4 that has been transmitted is irradiated to the photosensitive material 1, and then light diffusion is performed by a predetermined method. Element 10 was fabricated.
[0032]
As shown in FIG. 8B, a projector 41 is installed with respect to the light diffusing element 10 so that the optical axis is inclined by 15 °, and an image is projected onto the light diffusing element 10. An image with good color reproducibility was obtained. Further, the light diffusing element 10 was transparent, and the other side could be seen when viewed from the side.
[0033]
Although the light diffusing element of the present invention has been described based on the principle, examples, and application examples, the present invention is not limited to these examples and can be variously modified and applied. For example, the present invention can also be applied to a line-of-sight control film suitable for applications such as peep prevention in which the other side can be seen through or not visible depending on the viewing direction.
[0034]
【The invention's effect】
As is clear from the above description, according to the present invention, diffused light having a predetermined incident angle range is projected onto a photosensitive material having a thickness, and interference fringes of light in the diffused light beam are recorded in the photosensitive material. Because it uses a light diffusing element that scatters within a predetermined incident angle range but transmits without scattering at other angles, and uses light diffusing elements that have very little light dispersion and wavelength selectivity. It can be applied to line-of-sight control films, projection screens, etc., where the other side can be seen or not seen through depending on the viewing direction, and when applied to an image display system, the specific color may be tinted or the color may vary depending on the viewing position. The problem of changing does not occur.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining one method of manufacturing a light diffusing element according to the present invention.
FIG. 2 is a diagram for explaining another method of manufacturing a light diffusing element according to the present invention.
FIG. 3 is a diagram for explaining the principle and operation of a light diffusing element according to the present invention.
FIG. 4 is a diagram for explaining a light diffusing element combined with a light deflecting element;
FIG. 5 is a diagram for explaining the configuration and operation when the light diffusing element of the present invention is applied to a transmissive color liquid crystal display device.
FIG. 6 is a diagram for explaining the configuration and operation when the light diffusing element of the present invention is applied to a reflective color liquid crystal display device.
FIG. 7 is a diagram for explaining the operation when the light diffusing element of the present invention is applied to a window glass.
FIG. 8 is a diagram for explaining one specific example of the light diffusing element of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photosensitive material 2 ... Transmission diffuser plate 3 ... Laser light 4 ... Diffused light 5 ... Interference fringe 6 ... Micro lens array 7 ... Diverging light beam 10 ... Light diffusing element 11 ... Incident light 12 ... Diffused light 13 ... Incident light 14 ... Direct transmission Transmitted light 15 ... incident light 16 ... microprism array (light deflection element)
17. Transmission hologram (light deflection element)
DESCRIPTION OF SYMBOLS 20 ... Transmission type color liquid crystal display device 21,22 ... Transparent glass plate 23 ... Color filter 24 ... Transparent pixel electrode 26 ... Liquid crystal layer 25 ... Common counter electrode 27 ... Backlight 30, 30 '... Reflection type color liquid crystal display device 31 ... Transparent glass plate 32 ... Glass plate 33 ... Color filter 34 ... Transparent pixel electrode 35 ... Metal reflective layer 35 'also serving as a common counter electrode ... Transparent common counter electrode 36 ... Liquid crystal layer 38 ... External light 37 ... Reflective layer 40 having a sawtooth cross section ... Window glass 41 ... Projector 42 ... Laser light source 43 ... Optical system

Claims (6)

A diffused light having a predetermined incident angle range is projected onto a photosensitive material having a thickness, and a mutual incident fringe in the diffused light beam is recorded on the incident side of the light diffusing element. An optical deflecting element comprising a volume type transmission hologram having a function of transmitting the incident light with a different incident angle without diffusing the incident light is disposed. Light diffusion element composite . An image display system, wherein the light diffusing element complex according to claim 1 is disposed in close contact with or close to the observation side of the image display device.   3. The image display system according to claim 2, wherein the image display device is a transmissive liquid crystal display device.   3. The image display system according to claim 2, wherein the image display device is a reflective liquid crystal display device. An image display system, wherein an image is formed on the light diffusing element complex according to claim 1. An image display system comprising: a light diffusing element composite according to claim 1 provided on a window glass of a building; an image is formed on the image by a projector from one side; and the image is observed from the other side.

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