JP2004029163A - Screen for picture display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a large-area screen for picture display at once and to allow the screen to have a high reflection factor. <P>SOLUTION: A diffusing plate 1, a reflective hologram layer 2, and a light absorbing layer 3 are laminated in order from the front side being an incidence surface of picture display light. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image display screen that projects image display light from a front side by a so-called front projector (image projection device) and displays an image toward the front side.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an image display screen has been proposed in which image display light is projected from a front side by a so-called front projector (image projection device) and an image is displayed toward the front side. As a front projector, a so-called film projector, CRT projector, liquid crystal projector, DLP projector, and the like have been proposed.
[0003]
When displaying image information by projecting image display light on a conventional image display screen using such a front projector, the image display screen does not absorb light in the visible light wavelength region. Therefore, in order to express black on the image display screen, the surrounding illumination of the image display screen is darkened, or the image display light from the front projector is brightened, and the image display of the ambient illumination light is used. It is necessary to feel that the scattered light from the screen is relatively sufficiently darker than the image display light.
[0004]
However, it is inconvenient to darken the surrounding illumination because the area other than the image display surface of the image display screen on which the image display light is projected becomes dark. Also, making the image display light sufficiently bright causes an increase in power consumption and an increase in temperature in the front projector, and is limited and difficult.
[0005]
In order to solve such a problem, it is conceivable to provide the image display screen with a wavelength selective reflection structure that reflects only light having a specific wavelength (light having the wavelength of the image display light). As such a wavelength selective reflection structure, a structure using Bragg reflection by a photonic crystal, a structure using multiple reflection by a dielectric multilayer film, and the like can be considered.
[0006]
[Problems to be solved by the invention]
By the way, in the image display screen as described above, when a structure that reflects only light having the wavelength of the image display light using Bragg reflection by the photonic crystal is provided, it is suitable for manufacturing a relatively large area. However, the reflectance is less than about 60%, which is not very high.
[0007]
On the other hand, when a structure that reflects only light having the wavelength of image display light using multiple reflection by a dielectric multilayer film is provided, a high reflectance of 90% or more can be obtained. Since a so-called vacuum process is required, a large-area image display screen cannot be created at a time. In such a case, it is necessary to create a plurality of small-area image display screens and to connect these image display screens to form a large-area image display screen.
[0008]
Therefore, the present invention is proposed in view of the above-mentioned situation, and provides an image display screen that can produce a large area at a time and obtain a high reflectance. It is assumed that.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, an image display screen according to the present invention is an image display screen in which image display light is projected from a front side and a display image is observed from the front side. The diffusion plate, the reflection type hologram layer, and the light absorption layer are laminated in this order from the front side which is the surface.
[0010]
In this image display screen, the image display light incident from the front side is diffused by a diffusion plate, wavelength-selectively reflected by a reflection type hologram layer, and components not reflected by the reflection type hologram layer are absorbed by light. Absorbed by the layer.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
The image display screen according to the present invention is an image display screen in which image display light is projected from the front side and a display image is observed from the front side, and as shown in FIG. The diffusion plate 1, the reflection hologram layer 2, and the light absorption layer 3 are laminated in this order from the front side. A refractive index matching liquid layer 4 is provided between the diffusion plate 1 and the reflection type hologram layer 2. Then, a transparent substrate 5 is provided between the reflection type hologram layer 2 and the light absorption layer 3. The refractive index matching liquid layer 4 is a transparent layer having a refractive index close to that of the diffusion plate 1 and the reflection type hologram layer 2.
[0013]
In this image display screen, image display light projected from a projection type image display device (projector) enters the diffusion plate 1, is diffused in the diffusion plate 1, and passes through the refractive index matching liquid layer 4. Incident on the reflection type hologram layer 2. In the reflection type hologram layer 2, the image display light is reflected after its wavelength is selected. The reflection hologram layer 2 is configured to have a wavelength selection characteristic of selecting and reflecting only light in the wavelength band of image display light and transmitting light in other wavelength bands.
[0014]
Therefore, in this image display screen, the image display light is reflected to the front side, and the component of the wavelength band different from the image display light among the external light such as the peripheral illumination light is transmitted through the transparent substrate 5. The light reaches the absorption layer 3 and is absorbed by the light absorption layer 3. Therefore, it is desirable that the light absorbing layer 3 absorbs light substantially over the entire visible wavelength range of humans.
[0015]
Further, in this image display screen, the diffusion plate 1 has such a characteristic that, for image display light incident from the front side, the image display light is transmitted more than the front side, and more light is diffused to the rear side. It is desirable to have. This is because if there is a large amount of diffused light toward the front side in the diffusion plate 1, the diffusion plate 1 itself appears cloudy, which causes a reduction in the contrast of the displayed image.
[0016]
The reflection type hologram layer 2 of the image display screen is composed of a hologram created by exposing with one or more (one wavelength) or two or more (two wavelengths) light sources. Alternatively, it may be formed by laminating two or more holograms. Further, by configuring the reflection type hologram layer 2 so as to regularly reflect the image display light incident from the front side and emit the light at the same exit angle as the incident angle, the image display light from the projection type image display device (projector) can be obtained. The image display light projected toward the display screen can be reflected toward the image observer without being reflected toward the image display device, and a bright image can be observed.
[0017]
【Example】
Hereinafter, a specific configuration of the image display screen according to the present invention will be described.
[0018]
[Example 1]
As shown in FIG. 2, the reflection type hologram layer 2 of the image display screen has a single frequency of 457 nm (blue), 532 nm (green) and 647 nm (red), and the first to the fourth modes of the transverse mode TEM00. 3 is formed by exposure using laser beams emitted from the laser light sources 6, 7, and 8.
[0019]
The laser beams emitted from the laser light sources 6, 7, and 8 are condensed by first to third objective lenses 9 having a numerical aperture of 0.40, respectively, and are formed by first to third optical elements each having a pinhole having an aperture diameter of 10 μm. After passing through the three spatial filters 10, the first to third collimator lenses 11 of f400 form a parallel light beam.
[0020]
A light beam from the first laser light source is reflected and deflected by the mirror 12, passes through the first dichroic mirror 13, is reflected by the second dichroic mirror 14, and enters the photosensitive film 15.
[0021]
The light beam from the second laser light source is reflected and deflected by the first dichroic mirror 13, is reflected by the second dichroic mirror 14, and enters the photosensitive film 15.
[0022]
The light beam from the third laser light source passes through the second dichroic mirror 14 and enters the photosensitive film 15.
[0023]
In this way, the light beams from the first to third laser light sources are multiplexed by the first and second dichroic mirrors 13 and 14 and are incident on the photosensitive film 15.
[0024]
The light incident on the photosensitive film 15 passes through the photosensitive film 15, is reflected by a metal deposition mirror 16 disposed behind the photosensitive film 15, and enters the photosensitive film 15 from the back side. At this time, the luminous flux incident on the photosensitive film 15 from the laser light sources 6, 7, 8 side and the luminous flux reflected by the metal deposition mirror 16 and returned to the photosensitive film 15 interfere within the photosensitive film 15 and cause interference fringes. To form The photosensitive film 15 is exposed to light corresponding to the interference fringes.
[0025]
After the completion of the exposure, the photopolymer of the photosensitive film 15 is polymerized by using ultraviolet light, and further subjected to a heat treatment, whereby the reflection hologram layer 2 can be formed. This reflection type hologram layer 2 is attached to the front surface of a transparent substrate 5 as shown in FIG.
[0026]
As shown in FIG. 3, such a hologram created by the so-called “Lipman method” has a reflectance peak in a wavelength band near 457 nm (blue), 532 nm (green) and 647 nm (red). ing. The reflectance of light in other wavelength bands of the blue, green and red wavelength bands is substantially zero.
[0027]
Then, on the back surface of the transparent substrate 5, a light absorbing layer 3 is formed as shown in FIG. The light absorbing layer 3 is formed by applying an absorbent that absorbs light in the entire visible light band to the rear surface of the transparent substrate 5.
[0028]
The diffusion plate 1 is disposed on the front surface of the reflection hologram layer 2 via the refractive index matching liquid layer 4. This diffusion plate 1 is made of a transmission type diffusion film. As the refractive index matching liquid forming the refractive index matching liquid layer 4, a fat or oil having an appropriate refractive index, for example, a "standard liquid" (n = 1.49, k = 0) manufactured by Cargill Co. can be used. it can. The refractive index matching liquid layer 4 has a refractive index close to that of the diffusion plate 1 and the reflection hologram layer 2, and matches the refractive indexes of the diffusion plate 1 and the reflection hologram layer 2.
[0029]
The diffusion plate 1 is formed of a transparent material such as glass or a transparent plastic material, and has a structure for causing light scattering on the front surface or inside, or has a structure in which diffusion particles are dispersed. As shown in FIG. 4, the diffuser 1 diffuses almost all components of the light beam incident from the front side to the rear side. The ratio of the front-side diffused light to the back-side diffused light measured by the total light amount is about 1: 1700. As described above, since the diffusion plate 1 has almost no component that scatters incident light from the front side to the front side, the diffuser plate 1 does not appear cloudy even if it is disposed on the front side in the image display screen.
[0030]
In addition, when the scattering profile of the diffused light toward the back side with respect to the incident light from the front side of the diffuser 1 is measured, the scattering angle with respect to the optical axis (the axis perpendicular to the front surface of the diffuser 1) is θ. , The light intensity I in that direction is in a state proportional to cos θ raised to the 66th power.
[0031]
I = kcos ⁶⁶ θ (∵k: proportionality constant)
In the image display screen created as described above, the reflected light to the front side with respect to the incident light from the front side has wavelengths of 457 nm (blue), 532 nm (green), and 647 nm (green) as shown in FIG. Only light near (red) is light that is reflected and scattered.
[0032]
Therefore, most of the wavelength components not reflected by the image display screen out of the white external light such as room illumination light are absorbed by the light absorbing layer 3, and the wavelength at which the image display light has a peak in the reflection characteristics of the image display screen. , A high-contrast image display in which the influence of external light is significantly reduced can be performed.
[0033]
[Example 2]
As shown in FIG. 6, the reflection hologram layer 2 of the image display screen may be configured by stacking a plurality of holograms 2a, 2b, 2c. As shown in FIG. 7, the first hologram 2a constituting the reflection type hologram layer 2 is emitted from the first laser light source 6 of the single mode, transverse mode TEM00 having the oscillation wavelength of 457 nm (blue), as shown in FIG. It is created by exposure using a laser beam. The laser beam emitted from the first laser light source 6 is condensed by an objective lens 9 having a numerical aperture of 0.40, passes through a spatial filter 10 formed of a pinhole having an aperture diameter of 10 μm, and is collimated by a collimator lens 11 of f400. The light flux is formed and enters the photosensitive film 15.
[0034]
The light incident on the photosensitive film 15 passes through the photosensitive film 15, is reflected by a metal deposition mirror 16 disposed behind the photosensitive film 15, and enters the photosensitive film 15 from the back side. At this time, the light beam incident on the photosensitive film 15 from the first laser light source 6 side and the light beam reflected by the metal deposition mirror 16 and returned to the photosensitive film 15 interfere within the photosensitive film 15 and cause interference fringes. Form. The photosensitive film 15 is exposed to light corresponding to the interference fringes.
[0035]
After the completion of the exposure, the first hologram 2a can be formed by polymerizing the photopolymer of the photosensitive film 15 using ultraviolet light and performing heat treatment.
[0036]
In such a hologram exposed by the so-called “Lipman method”, a favorable diffraction efficiency of about 90% can be obtained as shown in FIG.
[0037]
As shown in FIG. 7, the second hologram 2b constituting the reflection type hologram layer 2 is emitted from the second laser light source 7 of the single mode, transverse mode TEM00 having an oscillation wavelength of 532 nm (green). It is created by exposure using a laser beam. The laser beam emitted from the second laser light source 7 is condensed by an objective lens 9 having a numerical aperture of 0.40, passes through a spatial filter 10 composed of a pinhole having an aperture diameter of 10 μm, and is collimated by a collimator lens 11 of f400. The light flux is formed and enters the photosensitive film 15.
[0038]
The light incident on the photosensitive film 15 passes through the photosensitive film 15, is reflected by a metal deposition mirror 16 disposed behind the photosensitive film 15, and enters the photosensitive film 15 from the back side. At this time, the luminous flux incident on the photosensitive film 15 from the second laser light source 7 side and the luminous flux reflected by the metal deposition mirror 16 and returned to the photosensitive film 15 interfere within the photosensitive film 15 and cause interference fringes. Form. The photosensitive film 15 is exposed to light corresponding to the interference fringes.
[0039]
After the completion of the exposure, the second hologram 2b can be formed by polymerizing the photopolymer of the photosensitive film 15 using ultraviolet light and performing heat treatment.
[0040]
Further, as shown in FIG. 7, the third hologram 2c constituting the reflection type hologram layer 2 is emitted from the third laser light source 8 of the single mode, transverse mode TEM00 having an oscillation wavelength of 647 nm (red). It is created by exposure using a laser beam. The laser beam emitted from the third laser light source 8 is condensed by an objective lens 9 having a numerical aperture of 0.40, passes through a spatial filter 10 composed of a pinhole having an aperture diameter of 10 μm, and is collimated by a collimator lens 11 of f400. The light flux is formed and enters the photosensitive film 15.
[0041]
The light incident on the photosensitive film 15 passes through the photosensitive film 15, is reflected by a metal deposition mirror 16 disposed behind the photosensitive film 15, and enters the photosensitive film 15 from the back side. At this time, the luminous flux incident on the photosensitive film 15 from the third laser light source 8 side and the luminous flux reflected by the metal deposition mirror 16 and returned to the photosensitive film 15 interfere within the photosensitive film 15 and cause interference fringes. Form. The photosensitive film 15 is exposed to light corresponding to the interference fringes.
[0042]
After the completion of the exposure, the third hologram 2c can be formed by polymerizing the photopolymer of the photosensitive film 15 using ultraviolet light and further performing a heat treatment.
[0043]
The first to third holograms 2a, 2b, 2c constitute a reflection type hologram layer 2 by being laminated with refractive index matching liquid layers 4a, 4b therebetween. That is, as shown in FIG. 6, the third hologram 2c is attached to the front surface of the transparent substrate 5. The second hologram 2b is arranged on the front side of the third hologram 2c via the refractive index matching liquid layer 4b. The first hologram 2a is disposed on the front side of the second hologram 2b via the refractive index matching liquid layer 4a.
[0044]
As the refractive index matching liquid forming the refractive index matching liquid layers 4a and 4b, an oil or fat having an appropriate refractive index, for example, a "standard liquid" (n = 1.49, k = 0) manufactured by Cargill Co. is used. be able to. These refractive index matching liquid layers 4a and 4b have refractive indexes close to those of the holograms 2a, 2b and 2c forming the reflection hologram layer 2, and match the refractive indexes of the holograms 2a, 2b and 2c.
[0045]
Then, a light absorbing layer 3 is formed on the rear surface of the transparent substrate 5 as shown in FIG. The light absorbing layer 3 is formed by applying an absorbent that absorbs light in the entire visible light band to the rear surface of the transparent substrate 5.
[0046]
In addition, the diffusion plate 1 is disposed on the front surface of the first hologram 2 a of the reflection hologram layer 2 via the refractive index matching liquid layer 4. This diffusion plate 1 is made of a transmission type diffusion film. As the refractive index matching liquid forming the refractive index matching liquid layer 4, a fat or oil having an appropriate refractive index, for example, a "standard liquid" (n = 1.49, k = 0) manufactured by Cargill Co. can be used. it can. The refractive index matching liquid layer 4 has a refractive index close to each of the holograms 2a, 2b, 2c forming the diffusion plate 1 and the reflection type hologram layer 2, and the refractive index of the diffusion plate 1 and the reflection type hologram layer 2 To match.
[0047]
The holograms 2a, 2b, 2c may be superposed in any order. However, since the amount of diffraction from the hologram on the side closer to the observer (front side) of the display image increases, the hue of the display image changes depending on the order of superposition of the holograms 2a, 2b, and 2c. Therefore, an appropriate order can be set according to the spectral characteristics of the image display light in the projection-type image display device (projector) to be used, the preference of the observer regarding the hue, and the like.
[0048]
The diffusion plate 1 used in this embodiment is the same as the diffusion plate 1 used in the first embodiment.
[0049]
In the image display screen created as described above, the reflected light to the front side with respect to the incident light from the front side has wavelengths of 457 nm (blue), 532 nm (green), and 647 nm (green) as shown in FIG. Only light near (red) is light that is reflected and scattered.
[0050]
Therefore, most of the wavelength components not reflected by the image display screen out of the white external light such as room illumination light are absorbed by the light absorbing layer 3, and the wavelength at which the image display light has a peak in the reflection characteristics of the image display screen. , A high-contrast image display in which the influence of external light is significantly reduced can be performed.
[0051]
The holograms 2a, 2b, and 2c that form the reflection hologram layer 2 may be transmission holograms, and a reflection plate may be provided in place of the light absorption layer 3 to reflect only the image display light and reduce the outside light. By absorbing light in other wavelength bands of the wavelength band of the image display light, it is possible to configure an image display screen capable of performing high-contrast image display in which the influence of external light is significantly reduced.
[0052]
【The invention's effect】
As described above, in the image display screen according to the present invention, in this image display screen, the image display light incident from the front side is diffused by the diffusion plate, and the wavelength is selected in the reflection hologram layer. The component reflected and not reflected by the reflection hologram layer is absorbed by the light absorbing layer.
[0053]
Therefore, in this image display screen, only light in the wavelength band corresponding to the wavelength of the image display light projected from the projection type image display device (projector) is reflected, and light in other wavelength bands is not reflected. In addition, an image with high contrast can be displayed even in an environment where the surrounding illumination light is strong.
[0054]
Further, the reflection type hologram layer can be easily formed to have a large area, and a high reflectance can be obtained in a specific wavelength band.
[0055]
That is, the present invention can provide an image display screen that can produce a large area at a time and can obtain a high reflectance.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of an image display screen according to the present invention.
FIG. 2 is a side view showing a configuration of an apparatus for creating a reflection hologram of the image display screen.
FIG. 3 is a graph showing a spectral reflection characteristic of a reflection hologram of the image display screen.
FIG. 4 is a graph showing optical characteristics of a diffusion plate of the image display screen.
FIG. 5 is a graph showing a spectral reflection characteristic of the image display screen.
FIG. 6 is a cross-sectional view showing another example of the configuration of the image display screen according to the present invention.
FIG. 7 is a side view showing the configuration of an apparatus for creating a reflection hologram of the image display screen shown in FIG. 6;
8 is a graph showing a spectral reflection characteristic of a hologram constituting a reflection hologram of the image display screen shown in FIG.
FIG. 9 is a graph showing optical characteristics of a diffusion plate of the image display screen shown in FIG.
[Explanation of symbols]
1 Diffusion plate, 2 reflection hologram, 3 light absorption layer, 4 refractive index matching liquid layer, 5 transparent substrate

Claims (6)

An image display screen in which image display light is projected from the front side and a display image is observed from the front side,
A diffusion plate, a reflection hologram layer, and a light absorption layer; and the diffusion plate, the reflection hologram layer, and the light absorption layer are arranged from the front side, which is an incident surface of image display light, from the front side. An image display screen characterized by being laminated in the order of an absorption layer. 2. The image display device according to claim 1, wherein the diffusion plate transmits the image display light transmitted from the front side and diffuses more light to the rear side than the front side. screen. 2. The image display screen according to claim 1, wherein the reflection hologram layer is formed of a hologram formed by exposing with at least one or more light sources. 2. The image display screen according to claim 1, wherein the reflection hologram layer is formed by laminating at least one or more holograms. 2. The image display screen according to claim 1, wherein the reflection hologram layer regularly reflects the image display light incident from the front side and emits the image display light at the same exit angle as the incident angle. The image display screen according to claim 1, wherein the light absorbing layer absorbs light over substantially the entire visible light wavelength region of humans.

Images