JP2002277963A - Back projection screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back projection screen which has wide horizontal and vertical field angles while maintaining resolution. SOLUTION: The lenticular lens 162 of the back projection screen 16 diffuses transmitted light more widely in the horizontal direction than in the vertical direction. On the projection surface A of the lenticular lens 162, a vertical diffusion sheet 18 which diffuses the transmitted light more widely in the vertical direction than in the horizontal direction is provided to obtain the back projection screen which has wide field angles not only horizontally, but also vertically. Further, the horizontal diffusion of the transmitted light by the vertical diffusion sheet is small, so a decrease in the resolution can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear projection screen used for a projection display device.

[0002]

2. Description of the Related Art FIG. 7 is a schematic configuration diagram of a conventional projection display apparatus using a rear projection screen. In this figure, 13 is a light valve for displaying an image, 15 is a projection lens for enlarging and projecting the image formed on the light valve 13, 16 is a rear projection screen, and 17 is an observer.

[0003] The image formed on the light valve 13 is
The image is optically enlarged and projected on the rear projection screen 16 via the projection lens 15. Then, the enlarged and projected light is imaged by the rear projection screen 16 and the observer 1
7 can observe the enlarged image.

FIG. 8 is a perspective view for explaining the structure of a conventional rear projection screen. In this figure, reference numeral 16 denotes a rear projection screen indicated by the same reference numerals in FIG. 161 is a Fresnel lens, and 162 is a lenticular lens. The surface A is an emission surface of the lenticular lens 162. The surface B is an incident surface of the lenticular lens 162 on which the projection light from the Fresnel lens 161 is incident, and is constituted by a series of cylindrical lenses periodically arranged in the horizontal direction in parallel with the emission surface A. Reference numeral 162a denotes a diffusion layer of the lenticular lens 162 sandwiched between the exit surface A and the entrance surface B of the lenticular lens 162, and 162b denotes a colored layer formed along the entrance surface B of the diffusion layer 162a. As shown in FIG. 8, the lenticular lens 162 includes a diffusion layer 162a and a coloring layer 162b. As shown in the figure, the surface B of the lenticular lens 162
Face the Fresnel lens 161.

A projection lens is arranged on the rear projection screen 16 on the Fresnel lens 161 side, and an observer who views an image is located on the lenticular lens 162 side.

That is, in the configuration shown in FIGS. 7 and 8, the image formed on the light valve 13 is incident on the Fresnel lens 161 of the rear projection screen 16 by the projection lens 15. At this time, the light beam incident on the peripheral portion of the rear projection screen 16 from the projection lens 15 is
The traveling direction can be changed by 61 and the Fresnel lens 161
, Is converted into a light flux that is parallel to or slightly converges with the normal to the rear projection screen 16. Then, the transmitted light of the Fresnel lens 161 is formed and diffused by the lenticular lens 162, and is viewed as an image from the observer side of the rear projection screen 16.

By the way, as described above, the projection lens 1
5 is transmitted through the Fresnel lens 161,
Lenticular lens 162 as a parallel or convergent light beam
Incident on the incident surface B. As shown in FIG. 8, on the incident surface B side of the lenticular lens 162, a cylindrical lens array periodically arranged in the horizontal direction is formed.

FIG. 9 is an enlarged sectional view in the horizontal direction for explaining the operation of the lenticular lens 162 in the conventional rear projection screen. The projection light transmitted through the Fresnel lens 161 (the light emitted from the Fresnel lens) is condensed in the diffusion layer 162a by the cylindrical lens array of the lenticular lens 162 as shown in FIG. as a result,
The light is diffused in the horizontal direction, and the horizontal viewing angle of the rear projection screen is increased.

The diffusion layer 162a of the lenticular lens 162 is made of a transparent thermoplastic resin mixed with a diffusing material, for example, acrylic resin, vinyl chloride resin, styrene resin, acryl-styrene copolymer resin, polyolefin resin, polyester. It is manufactured by molding resin, polycarbonate resin and the like. As the diffusing material, inorganic particles (silica, calcium carbonate, aluminum hydroxide, talc, muscovite, etc.) and crosslinked styrene or acrylic particles or silicon resin particles are used.

The diffusion layer 1 of the lenticular lens 162
When light passes through a medium mixed with a diffusing agent such as 62a, a light diffusion phenomenon occurs. In other words, the diffusion layer 162a enlarges the horizontal and vertical viewing angles of the rear projection screen by the light diffusing action.

By the way, the cylindrical lens array periodically arranged in the horizontal direction as shown in FIG. 8 has no function of diffusing light in the vertical direction. Therefore, only the diffusion layer 162a plays a role of diffusing light in the vertical direction of the lenticular lens 162, that is, a function of expanding the vertical viewing angle of the rear projection screen.

The coloring layer 162b is manufactured by molding a transparent thermoplastic resin mixed with a coloring agent. The coloring layer 162b attenuates light.

As can be seen from FIG. 9, the light emitted from the Fresnel lens passes through the inside of the colored layer 162b in the thickness direction of the colored layer 162b, that is, in a direction substantially perpendicular to the surface of the cylindrical lens. On the other hand, external light from the emission surface A of the lenticular lens travels in the coloring layer 162b in the length direction of the surface of the cylindrical lens array, that is, along the surface of the cylindrical lens array. Obviously, the distance that external light passes through the colored layer 162b is longer than the distance that emitted light from the Fresnel lens passes through the colored layer 162b. Therefore, there is an effect of greatly attenuating only external light. In other words, the colored layer 162b has a function of improving the contrast of an image by reducing the reflectance of the lenticular lens 162 with respect to external light incident from the observer when viewing a display image.

The details of the lenticular lens having the colored layer 162b are described in, for example, Sekig
uchi, M .; Honda, K .; Oda, "Ultra
High Contrast Screen ”ID
W'99, pp. 323-326, (1999).

The light valve has a liquid crystal panel (LC).
D) and Digital Micromirror D
device (DMD), Thin-Film Micr
omirror Array (TMA), Image
light Amplifier (ILA), Grat
ing Light Valve (GLV) or the like is applied.

For details of a projection display device using a DMD, see, for example, L. A. Yoder, "Digital
Light Processing: Spannin
gthe Display Industry wit
h Digital Solutions ”, LCD /
PDP International'98 (199
8), and details of a projection type display device using a GLV element are described in, for example, D.S. M. Bloo
m, "The Grating LightValve
e: revolutionizing display
technology ", SPIE Vol.301
3, pp. 165-171, (1997).

[0017]

As described above, the horizontal viewing angle of the conventional rear projection screen is determined by the refraction effect of the lenticular lens 162 by the cylindrical lens array and the light diffusion phenomenon by the diffusion material of the diffusion layer 162a. It is enlarged. On the other hand, the vertical viewing angle is diffused only by the light diffusion phenomenon by the diffusion material of the diffusion layer 162a. Therefore, the vertical viewing angle of the conventional rear projection screen is narrower than the horizontal viewing angle.

FIG. 10 is a characteristic diagram showing a visual field characteristic of a conventional rear projection screen. The horizontal axis is the angle with respect to the normal of the rear projection screen (0 degree), and the vertical axis is the screen gain. This figure also shows that the vertical viewing angle is narrower than the horizontal viewing angle.

Incidentally, the lenticular lens needs to have a thickness of 0.5 to 3 mm in consideration of moldability. Therefore, the thickness of the diffusion layer of the lenticular lens for forming an image necessarily becomes 0.5 to 3 mm. In order to increase the viewing angle of the rear projection screen, it is conceivable to increase the thickness of the diffusion layer and increase the amount of diffusion material mixed in.However, when the amount of diffusion material mixed increases, the details of the displayed image can be clearly displayed. And the resolution is consequently reduced. That is, even if a fine image is formed by the projection lens, the image is blurred due to light scattering by the light diffusion effect in the diffusion layer of the lenticular lens.

Therefore, in the structure of the conventional rear projection screen, there is a limit in diffusing the projection light by the diffusion layer and expanding the vertical viewing angle while maintaining the resolution.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a rear projection screen having a wide horizontal and vertical viewing angle while maintaining resolution. I do.

[0022]

According to a first aspect of the present invention, there is provided a rear projection screen, comprising: a lenticular lens; a diffusion sheet disposed on an exit surface of the lenticular lens, for diffusing a light beam from the exit surface in a predetermined direction. It is characterized by having.

The rear projection screen according to claim 2 is
2. The rear projection screen according to claim 1, wherein the lenticular lens diffuses a light beam more widely in a second direction perpendicular to the first direction than in a first direction, and the diffusion sheet is more diffused than the second direction. Is also characterized in that the light beam is diffused widely in the first direction.

[0024] The rear projection screen according to claim 3 is:
3. The rear projection screen according to claim 2, wherein the diffusion sheet is formed by a periodic layer structure in the first direction including a plurality of layers having different refractive indexes.

The rear projection screen according to claim 4 is
3. The rear projection screen according to claim 2, wherein the diffusion sheet is formed by a periodic layer structure in the first direction including a layer having a reflective property and a transparent layer. 4.

The rear projection screen according to claim 5 is
The rear projection screen according to claim 3, wherein the layer has a structure waving in a normal direction of the diffusion sheet.

[0027]

<First Embodiment> FIG. 1 is a perspective view showing a configuration of a rear projection screen according to a first embodiment. In this figure, the same elements as those shown in FIG. 8 are denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 1, a vertical diffusion sheet 18 is further adhered to an emission surface A of the lenticular lens 162 of the rear projection screen according to the present embodiment by an adhesive 19. Vertical diffusion sheet 18
Have the property of diffusing transmitted light in the vertical direction compared to the horizontal direction. As the adhesive 19, it is desirable to use an adhesive having a high transmittance (for example, a transmittance of 90% or more) in order to avoid a decrease in contrast. As the lenticular lens, the conventional lenticular lens shown in FIG. 8 can be used as it is. In this case, as shown in FIG.
2 is used. That is, also in this case, the lenticular lens 162 has an action of diffusing the transmitted light more widely in the horizontal direction than in the vertical direction.

FIG. 2 is a vertical sectional view for explaining the structure and operation of the vertical diffusion sheet 18 of the rear projection screen according to the first embodiment. As shown in this figure, the vertical diffusion sheet 18 is composed of a high-refractive-index material 18a and a low-refractive-index material 18 arranged in the vertical direction (vertical direction) of the display surface of the rear projection screen, that is, the exit surface A of the lenticular lens.
b has a periodic layer structure.

The interface between the layers is wavy in the normal direction of the sheet. Here, it is desirable that both the high refractive index material 18a and the low refractive index material 18b be made of a resin material transparent to visible light in order to avoid a decrease in contrast.

As shown in FIG. 2, when the light emitted from the lenticular lens is incident on a vertical diffusion sheet having a periodic layer structure composed of layers having different refractive indexes, a boundary surface waving in the normal direction of the sheet. Is diffused in the vertical direction by reflection and refraction at Therefore, the vertical viewing angle of the rear projection screen is enlarged.

FIG. 3 is a characteristic diagram obtained by actually measuring the angle distribution (scattering intensity angle distribution) of the scattering intensity of the transmitted light of the vertical diffusion sheet 18 of the rear projection screen according to the first embodiment.
The horizontal axis represents the angle with respect to the normal line of the vertical diffusion sheet (0 degree), and the vertical axis represents the screen gain. It can be seen that the diffusion intensity angle distribution in the horizontal direction is narrow, while the diffusion intensity angle distribution in the vertical direction is wide. In other words, the vertical diffusion sheet has a function of diffusing the transmitted light widely only in the vertical direction.

FIG. 4 is a characteristic diagram obtained by actually measuring the visual field characteristics of the rear projection screen according to the first embodiment. It can be seen that, due to the action of the vertical diffusion sheet 18, the viewing angle in the vertical direction is particularly enlarged as compared with the viewing characteristics of the conventional rear projection screen shown in FIG.

FIG. 5 is a diagram for comparing the field-of-view characteristic value of the rear projection screen according to the first embodiment with the field-of-view characteristic value of the conventional rear projection screen, which is read from FIGS. . In this figure, PG is the screen gain peak value, αH is 水平 horizontal half-value angle, αV
Represents a half vertical half angle. From this figure, it can be seen that the vertical half-value angle of the rear projection type screen according to the present embodiment is significantly larger than that of the conventional rear projection screen, but the horizontal half-value angle is hardly changed.

As described above, in the rear projection screen of the present embodiment, the vertical viewing angle can be greatly increased by bonding and fixing the vertical diffusion sheet to the surface of the conventional lenticular lens. Unlike the case where the amount of the diffusion material mixed in the diffusion layer 162a is increased, the vertical diffusion sheet has little effect on the horizontal diffusion, so that the resolution can be maintained. It is also possible to control the angles almost independently.

Therefore, it is possible to provide a rear projection screen having a wide viewing angle in the horizontal and vertical directions while maintaining the resolution.

In the above description, the structure in which the interface between layers of the diffusion sheet having different refractive indices is wavy in the normal direction of the sheet is shown. Due to this waving, not only a wide scattering intensity angle distribution of the transmitted light in the vertical direction is obtained, but also a gentle diffusion characteristic of the transmitted light is obtained, and a good viewing angle characteristic is obtained in the rear projection screen.

Further, when the waving is not provided, that is, when the respective layers are substantially parallel, the amount of transmitted light which is not diffused becomes dominant and the light diffusing effect is weakened, but the effect of diffusing the transmitted light by a certain reflection phenomenon is obtained. It is clear that

Furthermore, in the present embodiment, two different layers are used as layers constituting the periodic multilayer structure of the diffusion sheet.
Although the layers having different kinds of refractive indices are shown, the number of kinds of the refractive indices of the layers is not limited thereto. Obviously, the effect of (1) can be obtained.

Although the lenticular lens has a function of diffusing transmitted light in the horizontal direction as an example here, the lenticular lens to which the present invention is applied has an effect of diffusing transmitted light widely in the horizontal direction. However, the present invention is not limited to this. In addition, as an example of a diffusion sheet, a vertical diffusion sheet having a wide scattering intensity angle distribution of transmitted light in the vertical direction has been described as an example.However, the direction in which the diffusion sheet diffuses transmitted light widely is limited to the vertical direction. Absent. In other words, if a diffusion sheet having a wide diffusion effect in the direction in which the diffusion of transmitted light from the lenticular lens is narrow is used,
Similar effects can be obtained.

It is also apparent that a combination of a lenticular lens and a diffusion sheet for diffusing transmitted light widely in a predetermined direction can also provide the effect corresponding to the combination.

The diffusion sheet having a periodic layer structure of layers having different refractive indexes as described above includes:
Lumisty and others. For details of Lumisty, see Taisuke Okita, Kazumitsu Kawamura, Tetsuro Ohno, Masahiro Ueda, Shinichiro Kitayama, Jiro Hozumi: "Polymer Film with Light Control Function-Lumisty-", Sumitomo Chemical, pp. 37-48 (199
See 1).

<Second Embodiment> FIG. 6 is a vertical sectional view for explaining the structure and operation of a vertical diffusion sheet according to a second embodiment. As shown in this figure, the vertical diffusion sheet 18 has a transparent resin material 18c arranged in the vertical direction (vertical direction) of the display surface of the rear projection screen, that is, the emission surface A of the lenticular lens, and has reflection characteristics such as metal. It is formed by a periodic layer structure of the material 18d.

The interface between the layers is wavy in the normal direction of the sheet. Here, in FIG. 6, for convenience of explanation, a layer of a transparent resin material 18c and a material 18d having a reflection characteristic
The thickness of each layer is shown to be approximately the same. However, when the thickness of the layer of the material 18d having the reflection characteristic increases, the amount of light transmitted through the vertical diffusion sheet decreases.
The thickness of the layer 8d is preferably thinner than the layer of the transparent resin material 18c.

The schematic structure of the rear projection screen using the vertical diffusion sheet 18 shown in FIG.
As described with reference to FIG. 1, the description is omitted here.

As shown in FIG. 6, the transparent resin material 18
When the light emitted from the lenticular lens is incident on a vertical diffusion sheet composed of a periodic layer structure made of a material 18d having a reflection characteristic c and the material 18d, the transmitted light is transmitted in the vertical direction due to reflection at the interface waving in the normal direction of the sheet. It is spread to. Therefore, the vertical viewing angle of the rear projection screen is enlarged.

From the description of the first embodiment, it is clear that, similarly to the vertical diffusion sheet of the first embodiment, the vertical diffusion sheet hardly has a function of diffusing transmitted light in the horizontal direction.

Therefore, the vertical diffusion sheet 18 shown in FIG.
Also in the rear projection screen according to the second embodiment using the method described above, the viewing angle in the vertical direction can be greatly expanded, similarly to the rear projection screen according to the first embodiment.
Unlike the case where the amount of the diffusion material mixed in the diffusion layer 162a is increased, the vertical diffusion sheet has little effect on the horizontal diffusion, so that the resolution can be maintained. It is also possible to control the angles almost independently.

Therefore, it is possible to provide a rear projection screen having a wide viewing angle in the horizontal and vertical directions while maintaining the resolution.

The reflection at the interface between the different refractive index layers described with reference to FIG. 2 is based on Fresnel's law. Therefore, the incident angle dependence on the sheet is large,
When the angle of incidence on the sheet is large (when the angle of incidence on the interface is small), the reflectance decreases, and the light diffusion effect decreases. However, the reflection by the material 182d having the reflection characteristics shown in FIG. 6 has a small incident angle dependency, and therefore, the effect of facilitating the design adjustment of the vertical diffusion sheet can be obtained.

Here, in the above description, the structure in which the interface between the layer of the transparent resin material of the diffusion sheet and the layer of the material having the reflection characteristic is wavy in the normal direction of the sheet is shown. Due to this waving, not only a wide scattering intensity angle distribution of the transmitted light in the vertical direction is obtained, but also a gentle diffusion characteristic of the transmitted light is obtained, and a good viewing angle characteristic is obtained in the rear projection screen.

When this waving is not provided, that is, when the layers are substantially parallel, the amount of transmitted light that is not diffused becomes dominant and the light diffusion effect is weakened, but the effect of diffusing the transmitted light by a certain reflection phenomenon is obtained. It is clear that

[0052]

As described above, according to the rear projection screen of the first aspect, the lenticular lens,
Since there is provided a diffusion sheet that is disposed on the exit surface of the lenticular lens and diffuses a light beam from the exit surface in a predetermined direction, the viewing angle of the rear projection screen can be enlarged in a predetermined direction. Further, since the diffusion of the light beam in a direction other than the predetermined direction in the diffusion sheet is small, the resolution does not decrease as compared with the conventional rear projection screen having no diffusion sheet. Therefore, it is possible to provide a rear projection screen having a wide viewing angle in a predetermined direction while maintaining the resolution.

By selecting a diffusion sheet,
Only the viewing angle of the rear projection screen in a predetermined direction can be independently controlled.

The rear projection screen according to claim 2 is
2. The rear projection screen according to claim 1, wherein the lenticular lens has a second direction perpendicular to the first direction rather than the first direction. 3.
In the rear projection screen, a wide viewing angle can be obtained not only in the second direction but also in the first direction because the diffusion sheet diffuses the light beam widely in the first direction and the diffusion sheet diffuses the light beam more widely in the first direction than the second direction. Can be. In addition, since the diffusion of the light flux in the diffusion sheet in a direction other than the first direction is small, the resolution does not decrease as compared with the conventional rear projection screen having no diffusion sheet. Therefore, while maintaining the resolution,
A rear projection screen having a wide viewing angle in a first direction (for example, a horizontal direction) and a second direction (for example, a vertical direction) can be provided.

By selecting a diffusion sheet,
Only the viewing angle of the rear projection screen in the first direction can be independently controlled.

The rear projection screen according to claim 3 is
3. The rear projection screen according to claim 2, wherein the diffusion sheet is formed by a periodic layer structure having a plurality of layers having different refractive indexes in the first direction, so that the light from the lenticular lens exit surface incident on the diffusion sheet. The light beam is diffused in the first direction by reflection and refraction at the boundary surface between the layers. Therefore, the diffusion sheet can increase the viewing angle of the rear projection screen in the first direction. Further, since the diffusion of the light flux in the diffusion sheet in directions other than the first direction is small,
The resolution does not decrease as compared with the conventional rear projection screen having no diffusion sheet. Therefore, it is possible to provide a rear projection screen having a wide viewing angle in the first direction and the second direction while maintaining the resolution.

The rear projection screen according to claim 4 is
3. The rear projection screen according to claim 2, wherein the diffusion sheet is formed by a periodic layer structure in a first direction of a layer having a reflection characteristic and a transparent layer, so that the lenticular lens exit surface incident on the diffusion sheet. Is diffused in the first direction by reflection at the boundary surface of each layer. Therefore, the diffusion sheet can increase the viewing angle of the rear projection screen in the first direction. In addition, the first in the diffusion sheet
Since the diffusion of the luminous flux in directions other than the direction is small, there is no reduction in resolution as compared with a conventional rear projection screen having no diffusion sheet. Therefore, it is possible to provide a rear projection screen having a wide viewing angle in the first direction and the second direction while maintaining the resolution.

Further, the reflection by the layer having the reflection characteristic has a small incident angle dependency, and a sufficient light diffusing effect can be obtained even for a light beam having a large incident angle to the diffusion sheet. Further, therefore, the effect that the design adjustment of the diffusion sheet is facilitated can be obtained.

The rear projection screen according to claim 5 is
In the rear projection screen according to claim 3 or 4, since the layer forming the diffusion sheet has a structure waving in the normal direction of the diffusion sheet, the scattering intensity of a wide light beam in the first direction in the diffusion sheet. An angular distribution is obtained.

Further, the diffusion of the luminous flux is increased, a gentle diffusion characteristic of transmitted light is obtained, and a good viewing angle characteristic is obtained on the rear projection screen.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a rear projection screen according to Embodiment 1.

FIG. 2 is a vertical sectional view for describing the structure and operation of a vertical diffusion sheet of the rear projection screen according to the first embodiment.

FIG. 3 is a characteristic diagram obtained by actually measuring a scattering intensity angle distribution of transmitted light of the vertical diffusion sheet 18 of the rear projection screen according to the first embodiment.

FIG. 4 is a characteristic diagram obtained by actually measuring a visual field characteristic of the rear projection screen according to the first embodiment.

FIG. 5 is a diagram for comparing the visual field characteristic value of the rear projection screen according to the first embodiment with the visual field characteristic value of the conventional rear projection screen.

FIG. 6 is a vertical sectional view for explaining the structure and operation of a vertical diffusion sheet according to a second embodiment.

FIG. 7 is a schematic configuration diagram of a projection display device using a conventional rear projection screen.

FIG. 8 is a perspective view illustrating a configuration of a conventional rear projection screen.

FIG. 9 is an enlarged horizontal cross-sectional view for explaining the operation of a lenticular lens in a conventional rear projection screen.

FIG. 10 is a characteristic diagram showing a visual field characteristic of a conventional rear projection screen.

[Explanation of symbols]

13 light valve, 15 projection lens, 16 rear projection screen, 161 Fresnel lens, 162 lenticular lens, 162a diffusion layer, 162b coloring layer, 162c cylindrical lens row, 18 vertical diffusion sheet, 18a high refractive index material, 18b low refractive index Material with a ratio of 18c, transparent resin material, material with 18d reflection characteristics.

Claims (5)

[Claims] 1. A rear projection screen comprising: a lenticular lens; and a diffusion sheet disposed on an emission surface of the lenticular lens and diffusing a light beam from the emission surface in a predetermined direction. 2. The rear projection screen according to claim 1, wherein the lenticular lens diffuses a light beam more widely in a second direction perpendicular to the first direction than in a first direction. A rear projection screen, wherein a light beam is diffused more widely in the first direction than in the second direction. 3. The rear projection screen according to claim 2, wherein the diffusion sheet is formed by a periodic layer structure in the first direction by a plurality of layers having different refractive indexes from each other. Rear projection screen. 4. The rear projection screen according to claim 2, wherein the diffusion sheet is formed by a periodic layer structure in the first direction of a layer having a reflection characteristic and a transparent layer. Features a rear projection screen. 5. The rear projection screen according to claim 3, wherein the layer has a wavy structure in a direction normal to the diffusion sheet.