JPH04241341A - Rear projection type screen - Google Patents

Abstract

PURPOSE:To reduce ghost, to reduce the generation of moire and to obtain a high-quality image by forming a lens-like curved surface on the rise surface of a Fresnel lens. CONSTITUTION:The screen is constituted of the Fresnel lens and a lenticular lens. Then, the rise surface 5 of the Fresnel lens is formed to be the projecting and/or recessed lens-like curved surface. Therefore, light emitted from the respective rise surfaces 5 does not become the collimated beams of light and it is scattered to proper angular width. As the result, the ghost is hardly viewed in the case that the screen is observed from the emitting direction of the light.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to screens for use in rear projection television receivers.

0002

[Prior Art] Rear projection screens (hereinafter referred to as "screens") used in rear projection televisions can be roughly divided into single-screen and dual-screen types, but both types use Fresnel lenses and lenticular lenses. is necessary. In that case, Fresnel lenses usually do not have anti-reflection coatings, so there is reflection on the Fresnel lens surface, resulting in some defects on the image.

When viewing the screen of a rear-projection television that incorporates a normal screen from a close distance, especially from the top to the bottom, when the entire screen is white, the bottom of the screen is colored in red, green, and blue bands, and horizontal lines appear. When the image is displayed, a double image can be seen at the same position. Such an image phenomenon is generally called a ghost.

0004

[Problems to be Solved by the Invention] This phenomenon will be explained with reference to the drawings. FIG. 6 shows how light incident on a Fresnel lens is reflected within the lens and exits. Light incident from the flat surface 2 of the Fresnel lens 1 passes through the Fresnel surface 3.
The light is emitted from the light beam and goes toward the viewer (upward in the drawing), but on the other hand, reflected light 4 is generated. The reflected light 4 is totally reflected by the flat surface 2 and again heads toward the side where the Fresnel surface is formed, but this time it is emitted from the rise surface 5. This emitted light ray 6 is directed toward the center of the Fresnel lens and is emitted at a relatively large angle. FIG. 7 is a side view of a rear projection television equipped with a filter consisting of a Fresnel lens and a lenticular lens, and shows the ray trajectory of the outgoing light ray 6 that causes the above-mentioned ghost at each Fresnel position. . As a result, when observing from above at a close distance, a ghost is seen at the bottom of the screen.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a filter with almost no ghosts caused by Fresnel lenses.

[0006]

[Means for Solving the Problems] The above object is to provide a screen of the present invention, that is, a screen composed of a Fresnel lens and a lenticular lens, in which a part or all of the rising surface of the Fresnel lens has a convex and/or concave shape. In a screen composed of a Fresnel lens and a lenticular lens, the shape of the adjacent rise surfaces of some or all of the rise surfaces of the Fresnel lenses is This is achieved by a screen characterized by an angle of 0.1° or more.

The screen of the present invention will be explained with reference to the drawings. First, FIG. 8 shows how ghost light is generated by a conventional screen. In other words, FIG. 8 shows a situation in which ghost light emitted by a Fresnel lens in a conventional screen is emitted from the Fresnel lens, and the light emitted from each rise surface 5 becomes a parallel ray 6, so that the light rays are directed toward the emission direction (in the drawing). (from top to bottom), you will see a bright ghost light.

On the other hand, FIGS. 1 and 2 show how light passes through the Fresnel lens used in the screen of the present invention. 2) Since the lens-like curved surface is formed, the light emitted from each rise surface 5 does not become a parallel ray in any case, but is diffused over an appropriate angular width. f) When observed, ghosts are almost invisible.

FIGS. 3 and 4 show another aspect of the present invention, that is, a single rise surface has a plurality of convex (FIG. 3) or concave (FIG. 4) lens-like curved surfaces. These convex and concave lens-like curved surfaces may be mixed on a single rise surface, and may be formed on the entire surface or a part of the rise surface. When formed on a part of a single rise surface, it is preferable to form it so that it occupies 10% or more of the area of the rise surface so that the light emitted from the rise surface can be sufficiently diffused.

FIG. 5 also shows another embodiment of the invention. In other words, each rise surface has a linear cross-sectional shape like the conventional one, but by changing the angle of adjacent rise surfaces, the exit angle of the light emitted from each rise surface can be changed. It is something that The light emitted from each rise surface has a single exit angle, but
Since the emission angles of the light emitted from adjacent rise surfaces are different, the effect is similar to that of emitting convex or concave lens-shaped curves from multiple rise surfaces, and such rise surfaces are formed. Even if you observe the Fresnel lens from the exit direction (from top to bottom in the drawing), you will hardly see any ghosts. In that case, it is desirable that the angle between adjacent rise surfaces is 0.1° or more.

As described above, it is preferable that the rise surfaces that form lens-like curved surfaces or have different angles between adjacent surfaces account for 3% or more of the total rise surfaces constituting the Fresnel lens.

Furthermore, in the present invention, the contrast of dark lines produced by the Fresnel lens is reduced by increasing the number of light reflection paths inside the Fresnel lens.
This has the effect of making it difficult to see moire caused by the combination of the black stripe in the lenticular lens and the dark line of the Fresnel lens.

[0013]

[Examples] The present invention will be explained in more detail with reference to Examples below. Example 1 The rise surface of the Fresnel lens was made into a convex lens shape as shown in FIG. 1 only at the radial position where ghost light was noticeable. The radius of curvature of this lens was set to 0.05 mm, and it was brought into close contact with a lenticular lens having a screen gain of 5.0 to form a screen, and ghosts were observed. Example 2 The rise surface of the Fresnel lens was made into a concave lens shape as shown in FIG. 2 only at the radial position where ghost light was noticeable. The radius of curvature of this lens was set to 0.05 mm, and it was brought into close contact with a lenticular lens having a screen gain of 5.0 to form a screen, and ghosts were observed. Example 3 Only at the radial position where ghost light is noticeable, the rise surface of the Fresnel lens was formed into a plurality of convex lens shapes as shown in FIG. 3. The number of lenses in a single rise surface was 4, the radius of curvature of the lens was 0.03 mm, and ghosts were observed by closely contacting a lenticular lens with a screen gain of 5.0 to form a screen. Example 4 The rise surface of the Fresnel lens was formed into a plurality of concave lens shapes as shown in FIG. 4 only at radial positions where ghost light was noticeable. The number of lenses in a single rise surface was 4, the radius of curvature of the lens was 0.03 mm, and ghosts were observed by closely contacting a lenticular lens with a screen gain of 5.0 to form a screen. Example 5 As shown in FIG. 5, the angles of a plurality of adjacent rise surfaces of the Fresnel lens were set at different angles only at radial positions where ghost light was noticeable. 10 adjacent rise surfaces
The angle was changed by 0.5°. Therefore 1st and 1
The angular difference of the 0th rise surface is 4.5°. A lenticular lens with a screen gain of 5.0 was placed in close contact with the lens to form a screen, and ghosts were observed.

In each of the examples, ghosts were less visible than in screens using conventional Fresnel lenses.

As described above, the entire rise surface of the Fresnel lens may be curved into a lenticular shape or shaped at a different angle, but since it is rare for the light rays that cause ghosts to enter the entire rise surface. As described above, the same effect can be obtained even if only the position where the light beam that causes the ghost is incident is curved or the angle is changed.

[0016]

Effects of the Invention When the screen of the present invention is used, ghosts can be reduced, moiré can be reduced, and images of higher quality can be obtained.

[Brief explanation of the drawing]

FIG. 1 A partial cross-sectional view of a Fresnel lens in the screen of the present invention.

[Fig. 2] Partial cross-sectional view of a Fresnel lens in the screen of the present invention.

FIG. 3 is a partial cross-sectional view of a Fresnel lens in the screen of the present invention.

FIG. 4 A partial cross-sectional view of a Fresnel lens in the screen of the present invention.

FIG. 5 is a partial cross-sectional view of a Fresnel lens in the screen of the present invention.

[Figure 6] Diagram showing the trajectory of ghost light generated by a Fresnel lens

[Figure 7] Diagram showing a situation where ghosts occur

[Figure 8] Partial cross-sectional view of a Fresnel lens in a conventional screen

[Explanation of symbols]

3 Fresnel surface 5 Rise surface 6 Output light

Claims (4)

[Claims] Claim 1: In a rear projection screen composed of a Fresnel lens and a lenticular lens, a convex and/or concave lenticular curved surface is formed on part or all of the rising surface of the Fresnel lens. Features a rear projection screen. 2. A rear projection screen composed of a Fresnel lens and a lenticular lens, characterized in that the angle formed by some or all of the adjacent rise surfaces of the Fresnel lens is 0.1° or more. Rear projection screen. 3. The rear projection screen according to claim 1, wherein one or more lenticular curved surfaces are formed on a single rising surface of the Fresnel lens. 4. The rear projection screen according to claim 1, wherein a portion of the raised surface of the Fresnel lens accounts for 3% or more of the entire surface.