JPH0478840A - Backprojection transmission type screen - Google Patents

Abstract

PURPOSE:To effectively prevent the occurrence of a cone or a rainbow and to obtain a high-quality image without changing the shape of a Fresnel lens by disposing a polarizing film on the exiting side of light from a light source with respect to the lens surface of the Fresnel lens. CONSTITUTION:The polarizing film 34 is disposed at least on the exiting side between the incident side and the exiting side of the light from the light source with respect to the lens surface of the Fresnel lens. Therefore, in the case that the light from the light source which is made incident on the Fresnel lens is polarized light projected from a liquid crystal projector, for example, the polarizing film 34 is made to function as an analyzer. Therefore, main light from the light source is made to be transmitted through the Fresnel lens but stray light reflected inside, which is transmitted through the polarizing film 34 and emitted from the lens surface, is remarkably reduced because the plane of polarization of most stray light is changed. As a result, the cone or the rainbow caused by the stray light is prevented from occurring and the image quality of a screen is improved.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a rear projection transmission type screen, and particularly to a rear projection transmission type screen suitable for application to a projection device such as a projection television such as a liquid crystal display, a CRT projector, etc.

BACKGROUND ART 1 For example, as a transmissive screen for displaying an image projected from a liquid crystal 10 dioctor or a CRT glodictor, one having a Fresnel lens is known. The above-mentioned transmission screen has the disadvantage that image quality is degraded due to stray light generated inside the Fresnel lens. That is, as shown in an enlarged partial cross-sectional view in FIG.
At the same time, the outgoing light L2 is emitted from A in the target direction as a parallel light beam, and at the same time, a part of the light reflected by the inner wall of the lens is reflected back M within the 7-Renel lens lo and becomes stray light. When this stray light is emitted from the lens surface (ray L3 emitted in the lower right direction in the figure), it causes a cone to be generated.
If the light is emitted from a non-lens surface (light ray L4 emitted in the lower left direction in the figure), it will cause a rainbow to occur. Here, as shown in FIG.
This is a phenomenon in which a fan-shaped white light (cone) C is visually recognized above the center of the Fresnel lens. This cone C is visible below the center of the Fresnel lens when the screen 12 is viewed from a position lower than the center of the Fresnel lens. The rainbow is a phenomenon in which, as shown in FIG. 4, when an observer views the screen 12 from a slightly higher position, rainbow-shaped light (rainbow) R is visible near both ends of the lower part of the screen 12. It is. As described above, when stray light occurs inside the Fresnel lens 10 and is emitted in a direction other than the direction in which it should originally travel, a cone C or a rainbow R occurs, and the quality of the image projected onto the screen 12 deteriorates. I will do it. Therefore, conventionally, in order to prevent the above-mentioned cone C and rainbow R from occurring, methods such as roughening the shape of the non-light emitting part of the Fresnel lens have been taken. [Problems to be Solved by the Invention] However, as described above, it is technically difficult to roughen only the shape of the non-light emitting part of the Fresnel lens by mechanical cutting, etc. There was a problem in that even if it was roughened, the occurrence of cones and rainbows could not be sufficiently reduced. The present invention was made to solve the above problems, and
The purpose of the present invention is to provide a rear projection transmission screen that can effectively prevent the occurrence of cones and rainbows and obtain high-quality images without changing the shape of a Fresnel lens.

[Means to solve the problem]

The present invention is a rear projection transmissive screen that projects light source light from the back, transmits the light source light from a Fresnel lens to a lenticular lens, and observes the projected image, the light source being directed to the lens surface of the Fresnel lens. The above object is achieved by disposing a polarizing film on at least the negative side of the light incident side and the light output side. The present invention also provides a rear projection transmissive screen applied to a transmissive liquid crystal projector, which projects light source light from the back, transmits the light source light from a Fresnel lens to a lenticular lens, and observes the projected image. , the above object is similarly achieved by disposing a polarizing film on the light source light output side of the lens surface of the Fresnel lens.

[Action and effect]

In the present invention, since a polarizing film is provided on the exit side of the lens surface of the Fresnel lens, when the light source light incident on the Fresnel lens is polarized light projected from a liquid crystal projector, for example, the polarizing film is It becomes possible to function as an analyzer. Therefore, the main light source light can pass through the Fresnel lens, but most of the stray light reflected inside has a changed plane of polarization, so it passes through the polarizing film and exits from the lens surface. The amount of stray light generated will be significantly reduced. As a result, it is possible to prevent cones and rainbows from occurring due to stray light, and it is possible to improve the image quality of the screen. Furthermore, since the first polarizing film is provided on the incident side of the lens surface of the Fresnel lens, and the 21st polarizing film is provided on the exit side thereof, the light source light that enters the Fresnel lens is different from normal light projected from, for example, a CRT projector. In the case of light, stray light can be similarly reduced by arranging the second polarizing film at a position that serves as an analyzer with respect to the first polarizing film,
It is possible to prevent the formation of cones and rainbows. As described above, according to the present invention, it is possible to reduce unnecessary light for an image, such as stray light, without changing the shape of the Fresnel lens, and it is possible to obtain a high-quality screen image.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic partial sectional view showing an enlarged rear projection transmission type screen according to an embodiment of the present invention. The rear projection transmission screen 20 of this embodiment includes a Fresnel lens 30 disposed on the side where the light source light L1 projected from the projector is incident, and a Fresnel lens 30 arranged parallel to the side from which the light transmitted through the Fresnel lens 30 is emitted. It is composed of a lenticular lens 4o arranged. The Fresnel lens 30 includes, in order from the incident side of the light source light L1, a triacetate film 32 with a thickness of 75 μm, a triacetate film 32 with a thickness of 25 μm.
It is formed with a four-layer structure consisting of a first polarizing film 34 with a thickness of m, an acrylic resin film 36 with a thickness of 200 μm, and a Fresnel lens layer 38 with a thickness of 100 μl. Fresnel lens surfaces 30A are formed on the Fresnel lens layer 38 at a pitch of 0.112'nn. The lenticular lens 40 also includes, in order from the incident side, a lenticular lens layer 42 with a thickness of 100 μm, a triacetate film 44 with a thickness of 75 μl, and a second layer with a thickness of 25 μl.
It has a 4-layer structure made of Nobumitsu [46] and triacetate M4B with a thickness of 75 μm. In the lenticular lens layer 42, lenticular lens surfaces 40A are formed at a pitch of 0.25++n, and in the non-light condensing portion of the lenticular lens surface 40A on the surface of the triacetate WA 48 on the opposite side, A black stripe 49 is formed. Further, the first @ optical film 34 constituting the Fresnel lens 30 is
The second polarizing film 46 constituting the lenticular lens 40 is formed by stretching polyvinyl alcohol (PVA) lli colored with iodine, and the second polarizing film IIg! 46 is arranged to function as an analyzer for the first @optical film 34. In the rear projection transmission screen 20 of this embodiment described above, the first @ light 834 is arranged on the incident side of the lens surface 30A of the Fresnel lens 30, and the second @ light M46 as an analyzer is arranged on the exit side. has been done. Therefore, when the screen 20 is projected with a projector (not shown), the light source light L1 consisting of normal light is incident on the Fresnel lens 30, the incident light source light L1 is polarized by the first @ light M34, and the main The light source light is transmitted as parallel light from the lens surface 30A of the Fresnel lens layer 38 to the lenticular lens 40.
It is emitted to the side. At that time, stray light that causes cones and rainbows is also emitted. When the parallel light rays and stray light transmitted through the Fresnel lens 30 are incident on the lenticular lens 40, the parallel light rays, which are the main light source light with the same polarization plane, pass through the second polarizing film 46 and are emitted to the outside. Ru. However, the stray light that has been repeatedly reflected within the Fresnel lens 30 is blocked by the second polarizing film 46 because the plane of polarization has changed. As a result, when the screen 20 is observed from the lenticular lens 40 side, the occurrence of cones and rainbows caused by the stray light is effectively prevented, and an image with excellent image quality can be observed. Furthermore, in this embodiment, since the second polarizing film 46 is formed inside the lenticular lens 40, the contrast of the screen can be improved at the same time. Although the present invention has been specifically described above, it goes without saying that the present invention is not limited to what has been shown in the above embodiments, and can be modified in various ways without departing from the gist thereof. For example, in the embodiment described above, the case where the light source light L1 is normal light is explained, but the light source light may be polarized light, as in the case of projecting with a liquid crystal projector or the like. In this case, the polarizing film is a Fresnel light. It is only necessary to arrange it on the exit side with respect to the lens surface 30A of the lens 30, and the first polarizing film 36 in the embodiment described above can be omitted. Furthermore, the first polarizing film disposed on the incident side with respect to the lens surface of the Fresnel lens is not limited to the case where it is formed inside the Fresnel lens 30 as shown in the above embodiment; It may be arranged on the side (front) - on the line or as a separate body. Similarly, the 211i optical film disposed on the exit side with respect to the lens surface of the Fresnel lens is similar to the lenticular lens 40.
It is not limited to the case where it is formed inside the lenticular lens, but it may be provided integrally or separately at either the entrance (front) or exit 1pJ (rear) of the lenticular lens. It goes without saying that the S structure and its forming material are not limited to those shown in the above embodiments, but can be arbitrarily changed as long as they have similar functions.

[Brief explanation of drawings]

FIG. 1 is a schematic partial cross-sectional view showing an enlarged rear projection transmission screen according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the conventional problem, and FIG. FIG. 4 is a diagram for explaining the generated cone. FIG. 4 is a diagram for explaining the rainbow generated on the screen. 46...Second polarizing film, C...Cone, Ll...Light source light, R...Rainbow

Claims (2)

[Claims] (1) A rear projection transmission screen that projects light source light from the back, transmits the light source light from a Fresnel lens to a lenticular lens, and observes the projected image, wherein the light source light is projected onto the lens surface of the Fresnel lens. 1. A rear projection transmissive screen, characterized in that a polarizing film is disposed on at least an incident side and an output side of the screen. (2) A rear projection transmissive screen applied to a transmissive liquid crystal projector that projects light source light from the back, transmits the light source light from a Fresnel lens to a lenticular lens, and observes the projected image, the Fresnel A rear projection transmission screen characterized in that a polarizing film is provided on the light source light output side of the lens surface of the lens.