JPH03189633A - Reflection type projection screen - Google Patents

Abstract

PURPOSE:To prevent the lowering of contrast regardless of the projecting direction of external light by arraying and disposing many fine reflection mirrors provided with recessed part whose central part is depressed at large ratio with respect to the width of a peripheral part. CONSTITUTION:A projected light beam 4 is projected from a direction perpendicular to a screen and a projected light beam 41 is projected from an oblique direction. The projected light beams 4 and 41 are reflected by the fine concave mirror 3 or 31. Since a main light beam returns toward a projector, the distribution of luminous intensity is intense in the direction toward the projector and diffused light is properly obtained in a direction other than the direction toward the projector. The concave surfaces of the mirrors 3 and 31 are formed by depressing the central part at the comparatively large ratio with respect to the width of the peripheral part. Then, the reflected light of the projected light beam is allowed to have directivity, so that the effect to the above distribution of the luminous intensity is enhanced and the reflected light can be returned to a viewer side. Thus, a bright and high-contrast video is viewed in a bright room.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reflective projection screen that can provide a bright, high-contrast projected image even in a bright environment.

[Prior Art] Conventional reflective projection screens are often made of white cloth or a material made of a large number of irregularly attached glass or transparent resin microspheres, and the images projected and formed on the screen are The light was diffusely reflected and was viewed as an image by viewers scattered in various directions. Such screens provide almost perfect diffused reflection, which allows for a wide viewing angle, but the contrast of the image, which is the object of viewing, is significantly impaired due to unnecessary external light irradiation that is difficult to avoid in normal environments. In many cases, it became necessary to darken the entire room in which viewing was performed.

As a countermeasure to the above problem, JP-A-56-1611
No. 8 and Japanese Unexamined Patent Publication No. 16119/1987 disclose a screen in which directivity is improved by regularly arranging a large number of minute curved surfaces that are concave or convex in the horizontal and vertical directions. There is.

In addition, this publication mentions that a highly directional screen has already been developed in which fine concave surfaces formed by stamping metal foil are assembled, and a bright image can be seen within a narrow area in front of the screen. It is said that such screens are difficult to manufacture, and their surface shape collapses during use, making them unsustainable for long-term use.

On the other hand, in Japanese Patent Application Laid-open No. 55-64228, a large number of microlens groups are arranged, and the light portion thereof is made to be a mirror surface.

A screen has been disclosed that blocks unnecessary external light and efficiently reflects image light by having the other portions as light absorbers.

[Problems to be solved by the invention] However, among the above-mentioned conventional countermeasure techniques, the former spreads the reflected light, does not provide sufficient directivity, and does not provide enough contrast to withstand viewing in a bright room. I can't get the image,
Furthermore, the latter has a problem in that it does not take into account the fact that the image on the outer periphery of the screen becomes dark.

The present invention does not have the problems of the above-mentioned conventional technology, can obtain a sufficiently bright image within a predetermined viewing angle range, and even when irradiated with external light from a direction different from the projection direction from the video projector. It is an object of the present invention to provide a reflective projection screen in which almost no decrease in contrast is observed.

[Means for Solving the Problem] In order to achieve the above object, in the present invention, a large number of micro-reflecting mirrors each having a concave surface with a concave central portion at a relatively large ratio to the width of the peripheral portion are arranged. I decided to arrange it to form a screen surface.

In order to increase the directivity to some extent, the aperture width of the microreflector is b, the depth of the concave surface is d, and d≧b/3.

The cross-sectional shape of the concave surface of the micro-reflector is made into a circle, an ellipse, a knife line, or a polygon similar to the above six shapes formed by a group of short straight lines to facilitate manufacturing. Also, the surface of the microreflector itself.

There is no need to apply a high-class and expensive finish such as a so-called mirror finish to the mold and the like; rather, a rough surface finish that causes scattering and reflection is better, as will be described later.

[Operation] The image rays from the projector reach the screen surface and are reflected by a group of minute reflecting mirrors, but since the concave surface is quite deeply concave, each reflected ray is strongly reflected toward the projector, and the main axis Rays that deviate from the rays are moderately scattered. In the present invention, the aperture ll1gb of the microreflector and the depth d of the concave surface are
The ratio can be adjusted as appropriate to obtain the desired directivity and viewing angle.

[Example] Fig. 1 is a diagram of a first embodiment of the invention in which a large number of micro concave mirrors are arranged, and Fig. 2 is a diagram of a second embodiment in which a large number of micro concave grooves are arranged. Mirror (1 side), 2 is a screen base on which a large number of micro concave mirrors are arranged, 3 is a terminal child of the micro concave mirror, 21 is a screen base on which a large number of concave mirror grooves are arranged, 31 is a micro concave groove mirror-JAF. The screen base 2 can be formed by press molding or injection molding of plastic.

In the case of the screen base 21, it can be formed by extrusion molding in addition to the above-mentioned molding method. The reflecting mirror 1 can be formed by vapor deposition of a metal such as AQ or Ag, a thin film forming method such as plating, or a coating method such as spraying.

3 and 4 are model diagrams of a concave mirror, and the present invention will be explained in detail using these. 4 indicates projection light from a direction perpendicular to the screen, and 41 indicates projection light from an oblique direction. The projected light from the oblique direction is intended for the outer periphery of the screen.

As shown in FIG. 3, the projected lights 4, 41 are reflected by the minute concave mirror element 3 or the minute concave groove mirror element 31 (hereinafter referred to as reflective elements), but the principal ray of the reflected light is directed toward the projector. Therefore, looking at the reflected light intensity distribution, it can be seen that the reflected light intensity distribution is strong in the projector direction, and moderately diffused light can be obtained in other directions.

FIG. 4(a) shows that the concave surface of the concave mirror according to the present invention is deep (
FIG. 4(b) shows a case where the ratio of the depth d to the aperture width is large, and FIG. Concave mirror element 3
The reflected and scattered light from the central portion a, which accounts for 70 to 80% of the total amount of light, is mainly reflected within the range shown in these figures. Ranges 51 and 52 indicated by cross-hunting can be regarded as bright ranges in which one reflection region overlaps. With the current state of technology, rear projection (
When using a rear projection (rear projection) or a transmissive screen, images are bright and with good contrast, whereas when using a front projection (front projection) or reflective screen, good contrast cannot be obtained and the interior of the projection room is darkened. One of the major reasons for this is that the projected light is not reflected efficiently to the viewer, but is also reflected in useless places, resulting in a large loss of light quantity. That is, in a white screen, a portion of the image light is transmitted, resulting in a loss, and in a situation where the image light is diffusely reflected in all directions within a 180° range, the image light is reflected in unnecessary directions. On the other hand,
Even a front projection reflective screen is similar to using a rear projection transmissive screen if the reflection is effectively diffused only within the area where the viewer is present.

This results in bright, high-contrast images.

Fig. 4(b) shows the case where the concave surface of the microreflector is shallow, and in addition to not having a mirror surface that reflects the projection light coming from an oblique direction toward the projector, the area 5 shown by cross hunting is shown in Fig. 4(b).
2 expands and becomes darker than the range 51 shown in FIG. 4(a). As mentioned earlier, the reflected light scattering range only needs to be the range where the viewer is as expected in advance, and the case shown in Figure 4(b) is too wide, whereas the range shown in Figure 4(a) It can be seen that the results are effectively narrowed down in the case shown in . In this way, the directivity changes depending on the concave shape, mainly as shown in Figure 4(a).
In the present invention, d is determined by the aperture III (aperture diameter) b and the concave depth d shown in Figure 1.
It was decided that ≧b/3.

The above explanation has been about the lateral (horizontal) viewing angle. The viewing angle in the vertical (vertical) direction may be narrower than that in the horizontal direction, but it is of course necessary to have a certain degree of widening. In the case of the second embodiment in which a large number of minute concave grooves are arranged as shown in FIG. 2, it is necessary to ensure a certain viewing angle in the vertical direction as well, so the reflective surface of the minute concave groove mirror element 31 prevents reflected light. It is necessary to have a rough surface finish to scatter it to some extent. In order to create such diffuse reflection in the vertical direction,
It is effective to roughen the reflecting surface of the ig in a hairline shape in the lateral direction.

Although FIGS. 1 and 2 show cases where the cross-sectional shape of the concave surface is circular, the purpose of the present invention can almost be achieved with the concave shape not only circular but also elliptical, elliptical, parabolic, etc. . Furthermore, it is not limited to a continuous curved surface, but may be a polygonal or polyhedral shape similar to each of the above-mentioned curves, or a partition that protrudes relatively high from the surrounding area of the reflective elements at the boundary where minute reflective elements are adjacent to each other. A structure with walls is also effective.

FIG. 5 is a diagram showing a third embodiment of the present invention in which a microlens element 61 integrated with a micro concave mirror element 3 is provided, and FIG.
The figure shows a fourth embodiment in which a lenticular element 62 integrated with a minute concave groove mirror element 31 is provided. In addition, in the opening, 6 is a lens base, and 7 is a protective film of a back coat.

A microlens (or lenticular) serves to improve directivity, and its effect can be further enhanced by combining it with the minute concave reflector according to the present invention. In this case, it is necessary to align the principal axes of the lens and the concave mirror. Good directivity can be obtained if the concave mirror has a continuous surface that is the focal point of the lens. However, even if the concave mirror is not on the continuous plane of the lens focal position, it is still effective if it is located near it. However, if the continuous surface of the focal position is compared to a spherical surface (or cylindrical surface), a spherical surface (or cylindrical surface) having the same center has a large directivity effect of the present invention.

FIGS. 7(a) and 7(b) are cross-sectional views showing the fifth and sixth embodiments of the present invention, where 8 is a light absorber (black body) and the back of the joint of the microlens (or lenticular). and is provided between the reflective elements. The microlens 61 (or lenticular 62) condenses the projected light 4 onto the reflective element surface or its vicinity by its condensing action. This reflected light is reflected by the reflective element surface and returns toward the projector. Unnecessary external light that enters at an oblique angle of incidence irradiates the light absorber 8 and is absorbed, so it does not return to the viewer and does not affect the image.

Even in the case of the lens-integrated reflective elements shown in Figures 5, 6, and 7 (a) and (b), the reflective mirror surface has a rough surface to scatter the reflected light due to the vertical viewing angle. It is effective to finish the

Microlens group (or lenticular group) of the present invention
The screen base 1 may be made of a transparent elastomer (e.g., acrylic rubber, silicone rubber, etc.), or the screen base 1 may be made of an elastomer (e.g., chloroprene rubber, butyl rubber, etc.).
By configuring this, it can be made into a roll-up screen. This makes it possible to create a reflective projection screen that is easy to carry.

[Effects of the Invention] As explained above, according to the present invention, since the projection light beam can be returned to the viewer side with directivity given to the reflected light by the micro concave reflector group, even with a reflective projection screen, The effect is that you can enjoy bright, high-contrast images even in a bright room.

[Brief explanation of drawings]

FIG. 1 is a diagram of a first embodiment of the present invention in which a large number of micro concave mirrors are arranged, FIG. 2 is a diagram of a second embodiment in which a large number of micro concave grooves are arranged, and FIGS. 3 and 4 are diagrams of the operation of the present invention. A schematic diagram for explaining the principle, FIG. 5 is a diagram of the third embodiment of the present invention, and FIG. 6 is a diagram of the fourth embodiment of the present invention.
Example diagram, Figure 7 (,) is the fifth example diagram, Figure 7 (b)
is a diagram of a sixth embodiment. 1... Reflection mirror, 2, 21... Screen base. 3.31...Reflection element, 4,41...Projection light, 6.
... Lens base, 8... Light absorber.

Claims (1)

[Claims] 1. A reflective projection characterized in that a large number of minute reflecting mirrors each having a concave surface whose central portion is concave at a relatively large ratio to the width of the peripheral portion are arranged and arranged. screen. 2. The reflective projection screen according to claim 1, wherein d≧b/3, where b is the aperture width of the micro-reflector and d is the depth of the concave surface. 3. The cross-sectional shape of the concave surface of the micro-reflector is circular, elliptical, projectile-shaped, or a polygon formed by a group of short straight lines similar to each of the above shapes. A reflective projection screen according to claim 1 or 2. 4. Claims 1 to 4, wherein the reflective surface of the micro-reflector has a rough finish that scatters and reflects incident light.
3. The reflective projection screen according to any one of 3. 5. Claims 1 to 4, characterized in that the minute reflecting mirror is formed integrally with a microlens or a lenticule.
The reflective projection screen according to any one of the above. 6. The reflective projection screen according to claim 5, wherein a light absorber having a minute width is interposed between adjacent minute reflecting mirrors arranged in alignment.