JP2889153B2 - Projection screen - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection screen,
Particularly, the present invention relates to a projection screen capable of obtaining a clear image even in a bright environment. 2. Description of the Related Art Projection screens are widely used to obtain images projected by slide projectors, video projectors, moving image film projectors and the like. This projection screen is roughly classified into a transmission type screen which irradiates projection light from the back side and sees it from the front side, and a reflection type screen which irradiates projection light from the front side and looks at the reflected light. Regardless of the type, in order to realize an easy-to-view screen, it is necessary to devise an image that satisfies the following three requirements. (1) Bright image. (2) High contrast images. (3) An image with a wide viewing angle. [0003] The conventional technology for improving a projection screen mainly includes "(1) bright image" among these three requirements.
Has been made to gain. In particular, a screen used for a video projector uses a cathode ray tube as a projection device, and therefore has a problem that the absolute light quantity is insufficient, and various devices for obtaining a bright image have been made. However,
Since the fluorescent screen of a cathode ray tube has a saturation characteristic that it does not become brighter than a certain level even if the electron beam is intensified, it must be devised to make it look bright using a limited light flux. At present, measures are taken to narrow the viewing angle and obtain a bright image only when viewed from a predetermined angle range with respect to the screen. In other words, in order to satisfy the requirement of (1) obtaining a bright image among the above three requirements, the requirement of obtaining (3) an image with a wide viewing angle must be sacrificed. become. On the other hand, "(2) High contrast image"
Some attempts have been made with respect to the requirement to obtain Here, the contrast is nothing less than the ratio between the white level and the black level of an image. The larger the ratio, the clearer and more easily an image can be seen. First, considering what determines the white level, the white level is determined by the projection light of the projector. That is, the highest illuminance of light incident on the unit area of the screen corresponds to the white level. On the other hand, the black level is determined by the brightness of the room where the screen is placed, regardless of the projection light of the projector. For example, in a slide projector, the black level portion is a portion through which light in the original image of the slide film does not pass, and the corresponding portion of the screen is not irradiated with light from the projector. However, if there is a so-called room light in the surroundings, the light is illuminated by the light and has a predetermined illuminance. Therefore, as shown in FIG. 5, the white level is substantially determined by the performance of the projector, while the black level varies depending on the brightness of the room. In order to obtain a high-contrast image, it is necessary to increase the difference between the white level and the black level, that is, to darken the room. This is one of the major drawbacks of the conventional screen, which causes the whole image to be whitish and unclear in a bright room. [0005] A screen called a "black screen" in which a parallel layer made of a scale of a sword fish is provided on the screen surface has also been developed. However, this screen lowers the black level and the white level at the same time. The contrast cannot be increased. In addition, there is a disadvantage that the viewing angle is narrowed in order to brighten the image. Although a certain amount of image can be obtained even in a bright room, the color reproducibility is poor, and the image becomes dark and unclear.
Therefore, adopting this black screen is not a fundamental solution. In order to be able to obtain a clear image even in a bright room, keeping the black level low even in a bright room is the only fundamental solution. As one method of keeping the black level low, there is a method of forming a screen using a substance that is whitened only with respect to light from a specific direction. That is, a substance that is normally a black substance, but changes to white only when light is irradiated from the direction of the projector is applied on the screen. However, it is very difficult to develop a material that has a degree of whitening that is linear with respect to the intensity of light from the projector, that has good color reproducibility, and that can freely set the light distribution characteristics. Difficult to implement and very unlikely. Another way to keep the black level low is to block room light from the screen. For example, a light control film developed by 3M USA
It has the property of blocking room light from the screen. However, this light control film is originally designed to improve contrast by being attached to a screen such as an LED or a CRT display, and is extremely inappropriate for application to a screen. That is, this light control film requires a manufacturing process of alternately stacking and bonding a transparent plate and a black film to form a multilayer body, and cutting and polishing the multilayer body, which is very costly. It is. [0007] Generally, a projection screen has a much larger area than an LED display, a CRT display, or the like. Therefore, when a light control film is stuck on the entire surface of the screen having a large area. The result is a very expensive screen. Further, since this light control film causes surface reflection, it is very difficult to see when applied to a screen, and it is extremely difficult to put it to practical use. As described above, the conventional projection screen has a problem that a clear image cannot be obtained in a bright environment because no fundamental measures have been taken to enhance the contrast of the image. The present invention has been made in view of the above circumstances, and it is possible to increase a black level by effectively blocking external light other than projection light, and to obtain high contrast even in a bright place. It is intended to provide a projection screen. According to the present invention, as a means for solving the above problems, there is provided a diffusing surface for receiving projection light from a projection device and diffusing the light to at least a projection image observation side. A transparent plate disposed in parallel with the diffusion surface and on the projection image observation side of the diffusion surface, and passing the diffused light from the diffusion surface toward the projection image observation side. On the projection image observation side, a large number of parallel small projections having one flat transparent micro surface parallel or inclined with respect to the diffusion surface at the top are integrally formed with the projection image. It is formed so as to be exposed on the observation side, and each of the minute ridges has
Substantially perpendicular to the diffusing surface and transparent in the plane
Two side portions are formed so as to sandwich the minute surface and come into contact with this via a ridge, and further, a light-shielding opaque layer having a non-reflective surface is applied to this side portion, and each opaque layer is It is characterized by being supported by the minute ridges on which it is applied. In the above configuration, the projection light emitted from the projection device is diffused by the diffusion surface to become diffused light, and the diffused light passes through the flat transparent fine surface of the transparent plate toward the projected image observation position. Become. At this time, since the opaque layer is formed on the side surface of the minute protrusion and has a small width in the optical path direction, and is further provided so as to be substantially perpendicular to the diffusion surface, The opaque layer hardly prevents diffused light toward the projection image observation position. On the other hand, most of the light from the outside is shielded by the opaque layer having the light shielding property, and does not reach the diffusion surface. Part of the light from the outside impinges on the flat transparent micro surface and is reflected on the surface, but is almost perpendicular to the diffusion surface.
The fact that the two side portions are formed so as to be in contact with the flat transparent micro surface via the ridge means that the surface of the transparent plate is flat.
It means that every other planar transparent micro surface is formed. Therefore, the surface reflected light reaching the observer is halved. Since the transparent plate having such a function is disposed on the projected image observation side so as to cover the diffusion surface, the transparent plate functions as a louver. That is, the transparent plate on which the opaque layer is formed has a function of transmitting only the projection light from the projection device and the diffusion light from the diffusion surface based on the projection light. By shielding the light from the outside in this manner, an effect of keeping the black level low even in a bright environment is obtained, and a clear image with high contrast can be obtained even in a bright room. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1A is a perspective view showing an embodiment of a transparent plate used for a projection screen according to the present invention.
In this figure, only a part of the transparent plate is shown. The transparent plate 1 is three-dimensionally formed of, for example, an acrylic resin or the like, and a plurality of parallel small ridges (hereinafter simply referred to as small ridges) are formed on the surface. An opaque layer 2 having a non-reflective surface is formed on a part of the plurality of minute protrusions. In order to form the opaque layer 2, for example, a minute surface to be formed is roughened into a so-called satin finish by a method such as chemical treatment or sand spraying, and a matte black paint is applied from above. Can be implemented. Since the surface of the transparent plate 1 side is also roughened by the rough surface treatment, the formed opaque layer 2 becomes a non-reflective surface on both sides, and has a light shielding property. The transparent plate 1 is provided so as to cover a diffusion surface for diffusing the projection light from the projection device, and the opaque layer 2 does not cross the optical path of the diffusion light from the diffusion surface to the projected image observation position. It is formed on a side surface formed substantially perpendicular to the diffusion surface. Then, not opaque layer 2 is formed
A flat surface at the top, that is, a flat transparent micro surface (hereinafter, simply referred to as a micro surface) 3 is formed so as to be parallel to the diffusion surface. The two side portions are formed so as to be in contact with the one minute surface 3 via a ridge. FIG. 1A shows an example in which minute protrusions are formed only on one side of the transparent plate 1. However, as shown in FIG. 1B, minute protrusions are formed on both sides. Is also good. FIG.
FIG. 1 (b) shows the same position in the height direction of the minute ridges on one side and the other side of the transparent plate, which are alternately shifted as shown in FIG. 1 (c). You may. 1 (a), 1 (b) and 1 (c), the micro surface 3 is parallel to the diffusion surface.
As shown in (d), the minute surface 3 may be inclined with respect to the diffusion surface. FIGS. 2A and 2B are side views of an embodiment in which a screen is actually formed using the transparent plate shown in FIG. 1A. FIG. 2A shows the diffusion surface 4 on the other side of the transparent plate 1, that is, on the side opposite to the side on which the fine ridges are formed.
Is formed. FIG. 2B shows a diffusion plate 4 formed on a diffusion plate 5 which is a transparent plate separate from the transparent plate 1. Although FIG. 2B shows two transparent plates arranged in layers, a configuration in which three or more transparent plates are arranged in layers is also possible. In FIG. 2A, the projection light from the projection device passes through the minute surface 3 and diffuses on the diffusion surface 4, and the diffused light passes through the minute surface 3 again and exits from the screen, and the projected image is projected. Head to the position where you observe. On the other hand, most of the external light from the surrounding environment is blocked by the opaque layer 2,
It does not reach the diffusion surface 4. That is, most of the light passing through the transparent plate 1 is occupied by the projection light from the projection device and its diffused light. Therefore, the black level of the projected image formed on the diffusion surface 4 is kept low even when used in a bright environment, and a clear image with high contrast can be obtained. Another feature of this screen is that two upper and lower opaque layers 2 are formed so as to be in contact with one fine surface 3 via a ridge. That is, on the surface of the transparent plate 1, every other minute ridge is formed. As described above, since the transparent plate 1 is formed by three-dimensionally molding an acrylic resin or the like, light is considerably reflected on the surface. However, if every other minute ridge is formed, the reflection of external light on the minute surface 3 can be reduced by half. The opaque layers 2 are provided at a minute pitch of, for example, about 0.2 mm. When the screen is observed with the naked eye, the stripes formed by the opaque layers 2 do not adversely affect the projected image. The embodiment shown in FIG. 2 is a reflection type screen, that is, a type in which a projection device is placed in front of a diffusion surface and the diffused light reflected from the diffusion surface is observed from the front. The present invention is similarly applied to a transmission type screen as shown, that is, a screen in which the projection device 6 is placed behind the diffusion surface 4 and the transmitted diffused light from the diffusion surface 4 is observed from an observation point 7 in front. it can. Such a transmission type screen is usually provided with a box for blocking external light behind,
In many cases, the projection device is housed and used in this box, but in the case of a so-called open type transmission screen as shown in FIG. 3, it is necessary to prevent external light from entering the diffusion surface from behind. By the way, as a problem peculiar to the projection screen, there is a so-called "vignetting" in which the projected image on the diffusing surface 4 is partially missing, but by disposing an optical system at a position adjacent to the transparent plate 1, this problem can be solved. The occurrence of "vignetting" can be prevented. FIG. 4A is an explanatory diagram showing the phenomenon of this so-called "vignetting". For example, FIG. 4A shows a case where the projection device 6 is arranged on the right side of the transmission screen shown in FIG. 2A. . 4 (a), 4 (b) and 4 (c) are diagrams for explaining the principle of the "vignetting" phenomenon. Therefore, the opaque layer 2 is illustrated as projecting extremely from the diffusion surface 4, and the minute surface 3 inclined with respect to the diffusion surface 4 and the thickness of the transparent plate are not illustrated. The projection light from the projection device 6 is irradiated onto the diffusion surface 4, and the transmitted diffusion light from the projection surface 6 is observed at the observation point 7. However, since the opaque layer 2 is formed in front of the diffusion surface 4, the luminous flux actually observed at the observation point 7 is only the hatched portion in the figure which is not shielded by the opaque layer 2. In other words, only the projected image of the portion indicated by the thick line on the diffusion surface 4 can be observed. That is, the image appears dark and dark on the upper and lower sides of the screen, and so-called "vignetting" of the image occurs. FIG. 4 (b)
When the opaque layer 2 is formed at a predetermined angle in advance as shown in FIG.
Can be prevented, but the number of observation points is limited to only one point, which is not practical. Therefore, as shown in FIG. 4C, an optical system 8 is provided behind the diffusing surface 4 so that the projected light is focused only on the portion indicated by the thick line on the diffusing surface 4. If the diffusion surface 4 is formed such that the diffusion characteristic of the transmitted diffused light has a characteristic that spreads at an angle α as shown in the figure, for example, the hatched area in the figure does not become the optical path of the diffused light. Even if the opaque layer 2 is provided in the area, "vignetting" of the image
Does not occur. As such an optical system 8, for example, a lenticular lens, a micro lens, or the like may be used. Although the opaque layer and the diffusing surface may be arranged in various directions, the external light from the top has the greatest effect on the screen. Therefore, the external light from the top can be effectively blocked as much as possible. It is desirable to adopt such an arrangement. Although several embodiments have been described above, these unique effects are finally listed as follows. (1) Since external light can be shielded from the diffusion surface, the black level of the projected image can be kept low regardless of the brightness of the surrounding environment, and a clear image with high contrast can be obtained. (2) Since the transparent plate can be manufactured by three-dimensional molding of an acrylic resin or the like, it can be realized at a very low cost. (3) By forming every other minute protrusion of the transparent plate, the influence of surface reflection can be reduced by half. (4) By combining with an optical system, so-called "vignetting" of an image can be prevented. As described above, according to the present invention, the black level can be increased by effectively blocking external light other than the projection light, and a high contrast can be obtained even in a bright place. It becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial perspective view showing a shape of a transparent plate used for a screen according to an embodiment of the present invention. FIG. 2 is a partial side view showing a configuration of a screen according to the embodiment of the present invention. FIG. 3 is an explanatory diagram of a general transmission screen. FIG. 4 is an explanatory view of so-called “vignetting” development of an image. FIG. 5 is an explanatory diagram showing a relationship between contrast and surrounding brightness. [Description of Signs] 1 Transparent plate 2 Opaque layer 3 Micro surface 4 Diffusion surface 5 Diffusion plate

Claims (1)

(57) [Claims] A diffusion surface for receiving projection light from the projection device and diffusing it to at least the projection image observation side, disposed on the projection image observation side of the diffusion surface in parallel with the diffusion surface, and from the diffusion surface And a transparent plate that allows the diffused light to pass toward the projection image observation side. The transparent plate has, on the projection image observation side, one planar transparent parallel or inclined to the diffusion surface. Small surface on top
A large number of parallel small ridges are formed integrally and exposed to the projected image observation side, and each of the small ridges is substantially perpendicular to the diffusion surface and has a planar shape. Two side portions are formed so as to sandwich the transparent micro surface and contact with this via a ridge, and further, a light-shielding opaque layer having a non-reflective surface is applied to this side portion, and each opaque layer is A projection screen, which is supported by minute projections provided with the projection. 2. 2. The projection screen according to claim 1, wherein the plurality of parallel small protrusions are formed only on one side of the transparent plate, and the diffusion surface is formed on the other side. 3. 2. The projection screen according to claim 1, wherein the plurality of parallel minute protrusions are formed on both sides of the transparent plate, and the transparent minute surfaces on both sides are parallel to each other. 4. The said diffusion surface and the said many parallel minute protrusion are each formed in the separate transparent plate, and these several transparent plates are mutually arrange | positioned in layered form, The 1st characterized by the above-mentioned.
4. The projection screen according to any one of claims 1 to 3. 5. 5. The optical system according to claim 1, wherein an optical system is arranged on an optical path of the projection light incident on the diffusion surface and / or the diffusion light emitted from the diffusion surface and at a position where occurrence of vignetting can be prevented. The projection screen described in Crab. 6. The projection screen according to claim 1, wherein the diffusion surface is a diffusion surface that reflects and diffuses projection light. 7. 6. The projection screen according to claim 1, wherein the diffusion surface is a diffusion surface that transmits and diffuses projection light. 8. 8. The projection screen according to claim 1, wherein the transparent plate is made of an acrylic resin. 9. 9. The projection screen according to claim 1, wherein the opaque layer is made of a matte black paint. 10. The projection screen according to any one of claims 1 to 9, wherein the surface of the opaque layer is formed of a satin-like rough surface.