JPH04249236A - Projection screen - Google Patents

Abstract

PURPOSE:To reduce the moire caused by the modulating operation of a Fresnel lens without defocusing by providing a gap between a Fresnel lens sheet and a lenticular sheet. CONSTITUTION:The moire due to the combination of the LCD grating, Fresnel lens sheet 1, the lenticular lens 2, etc., of an LCD panel 5 is caused by modulating the LCD grating with the Fresnel lens pattern. Therefore, the modulation by the Fresnel lens 1 is only made not to reach the lenticular lens sheet 2. For the purpose, the gap S is so constituted that S>=PXL/R, where R is the effective radius of a projection lens, L is the projection distance from the projection lens 6 to the incidence-side lenticular lens surface of the lenticular lens sheet 2, and P is the pitch of the Fresnel lens 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection screen onto which an image from an LCD projector or the like is projected, and more particularly to a projection screen that reduces the occurrence of moiré.

0002

2. Description of the Related Art Conventionally, this type of projection screen has been known to be a combination of a Fresnel lens sheet and a lenticular lens sheet, on which an image from a light source is projected.

When using an LCD projector as a light source, in addition to moiré caused by a lenticular lens and a Fresnel lens, moire caused by a lenticular lens and an LCD grating, and moire caused by a Fresnel lens and an LCD grating,
There was a possibility that moire, etc. would occur between the lenticular lens, Fresnel lens, and LCD grid.

[0004] In order to reduce the occurrence of moiré, the combination of pitches of lenticular lenses and Fresnel lenses has been optimized, or defocusing has been used to intentionally blur the images.

[0005]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, the lens sheet is made to have a finer pitch as the pitch of the LCD grating becomes finer, but due to limitations in processing technology, etc. There were restrictions on the combinations. Furthermore, when defocusing is used, there is a problem in that the resolution decreases.

In particular, the complex moiré caused by the lenticular lens, Fresnel lens, and LCD grating is
The grating is modulated by the pattern of the Fresnel lens, which is thought to cause moiré and lenticular lenses, so the conventional method of making the pitch finer alone could not solve the problem.

The present invention has been made to solve the above-mentioned problems, and includes a projection distance, an effective radius of the projection lens, and a vertical half-value angle (αV) of the diffuser plate between the Fresnel lens sheet and the lenticular lens sheet. The purpose is to reduce moiré caused by a combination of an LCD grating, a Fresnel lens, a lenticular lens, etc., without defocusing, by providing a gap determined from the above.

[0008]

A first means of solving the problems of the present invention is a projection screen that combines a lenticular lens sheet and a Fresnel lens sheet, the projection screen having a gap S between the Fresnel lens sheet and the lenticular lens sheet. The gap S is the effective radius of the projection lens, R is the projection distance from the projection lens to the lenticular lens surface on the incident side of the lenticular lens sheet, and the pitch of the Fresnel lens is P.
When, S≧P×L/R

...The configuration is as follows (1).

[0009] A second solution is that the (
1) A transparent plate having a thickness equal to the gap S determined by equation 1 is inserted.

A third solution is a projection screen that combines a lenticular lens sheet and a Fresnel lens sheet, and a diffusion plate is inserted between the Fresnel lens sheet and the lenticular lens sheet. A gap S1 is provided between the diffusion surface on the side closer to the Fresnel lens sheet and the lenticular lens sheet, and when the vertical half-value angle of the diffusion plate is T and the pitch of the Fresnel lens is P, S1 ≧P/tan(T)
...
The configuration is as follows (2).

A fourth solution may be such that the thickness of the diffusion plate is equal to the gap S determined by the equation (2).

A fifth solution is such that a transparent plate having a thickness equal to the gap S determined by the equation (2) is inserted between the lenticular lens sheet and the diffuser plate.

[0013]

According to the present invention, since a gap is provided between the Fresnel lens sheet and the lenticular lens sheet, the shadow caused by the modulation effect of the Fresnel lens sheet can be sufficiently blurred on the lenticular lens sheet.

[0014]

EXAMPLES The present invention will be described in detail below with reference to the drawings and the like. FIG. 1 is a diagram schematically showing a first embodiment of a projection screen according to the present invention, FIG. 2 is a diagram showing a projection optical system used in the screen of the first embodiment, and FIG. 3 is a diagram showing a Fresnel projection screen. FIG. 3 is a diagram for explaining the modulation effect of a lens.

The screen of the first embodiment is a combination of a Fresnel lens sheet 1 and a lenticular lens sheet 2, and a gap S is provided between the Fresnel lens sheet 1 and the lenticular lens sheet 2.

LCD grid of LCD panel 5 (FIG. 2), Fresnel lens sheet 1, and lenticular lens sheet 2
Moiré caused by a combination of the above is caused by the LCD grating being modulated by the Fresnel lens pattern, so it is sufficient to prevent the modulation by the Fresnel lens sheet 1 from reaching the lenticular lens sheet 2. That is, it is sufficient that the shadow of the Fresnel lens sheet 1 is sufficiently blurred on the lenticular lens sheet 2. Since the light projected from the projection lens 6 is slightly diffused, as shown in FIG. What is necessary is to arrange the lenticular lens sheet 2.

Here, the diffusion angle θ of the light incident on the Fresnel lens sheet 1 is calculated as shown in FIG. If the projection distance to the surface is L, then θ=arctan(R/L)
...(3
). Since the angle of diffusion of light emitted from the Fresnel lens sheet 1 is considered to be approximately equal to θ, the gap S when the Fresnel lens sheet 1 is shifted by one pitch is as follows, where P is the pitch of the Fresnel lens, S=P /
tan(θ)
...(4). Substituting equation (3) into equation (4), S=P×L
/R
...(5)
is obtained.

At this time, the lenticular lens sheet 2
If the image is formed on the lens surface, it will not affect the imaging system in any way, so the resolution will not be degraded.

FIG. 4 is a diagram schematically showing a second embodiment of the projection screen according to the present invention. In each of the embodiments described below, the same reference numerals are given to parts that perform the same functions as those in the first embodiment. The screen of the second embodiment has a transparent plate 3 inserted between the Fresnel lens sheet 1 and the lenticular lens sheet 2 and having the same thickness as the gap S obtained by the above-mentioned equation (5). In the second embodiment, by using the transparent plate 3, the gap S between the Fresnel lens sheet 1 and the lenticular lens sheet 2 can be kept uniform with a simple support structure.

FIG. 5 is a diagram schematically showing a third embodiment of the projection screen according to the present invention. In the screen of the third embodiment, a diffusion plate 4 is inserted between a Fresnel lens sheet 1 and a lenticular lens sheet 2.

If the gap S is calculated as in the first embodiment, it will be a relatively large value. Therefore, in the third embodiment, it was decided to further actively diffuse the light emitted from the Fresnel lens sheet 1. That is, by placing the diffuser plate 4 on the light exit surface of the Fresnel lens sheet 1, the shadow of the Fresnel lens on the lenticular lens sheet 2 is blurred by the shorter gap S1. At this time, if the vertical half-value angle (αV) of the diffuser plate 4 is set to T, and the same formula as (4) is used, S1=P/tan(T)
...
(6) is obtained.

At this time, if the gap S1 is within the depth of focus of the projection lens 6, the resolution will only decrease slightly, and if the diffuser plate 4 contains a small amount of transmitted light,
Furthermore, a decrease in resolution can be prevented.

FIG. 6 is a diagram schematically showing a fourth embodiment of the projection screen according to the present invention. In the fourth embodiment, a diffuser plate 4 having the same thickness as the gap S1 obtained by equation (6) is inserted between the Fresnel lens sheet 1 and the lenticular lens sheet 2. According to the fourth embodiment, the vertical half-value angle (αV) of the diffuser plate 4
Since =T becomes larger, the gap S1 can be made smaller and the gap S1 can be kept uniform.

FIG. 7 is a diagram schematically showing a fifth embodiment of the projection screen according to the present invention. In the fifth embodiment, a diffuser plate 4 having the same thickness as in the third embodiment is inserted between the Fresnel lens sheet 1 and the lenticular lens sheet 2, and a transparent plate 3 is further inserted.

The fifth embodiment will now be explained using a more specific manufacturing example. As the Fresnel lens sheet 1, the aspect ratio is 16:9 (high-definition specification), the focal length is 1500 mm with a diagonal of 55 inches, and the pitch P is 0.1.
A lenticular lens sheet 2 having a pitch P1 of 0.247 mm was used. Between the Fresnel lens sheet 1 and the lenticular lens sheet 2, there is a film-like diffuser plate 4 with a vertical half-value angle T=9°.
A transparent plate 3 made of acrylic and having a thickness of 3 mm was placed. A single-tube LCD projector 5 was used as the light source, with a projection distance L = 1530 mm, a focal length of 128 mm, and an F8.0.
The image was projected onto a screen using a projection lens 6. By using the diffuser plate 4 and the gap transparent plate 3 in this way, moiré can be significantly reduced.

[0026]

[Effects of the Invention] As explained above in detail, according to the present invention, since a gap is provided between the Fresnel lens sheet and the lenticular lens sheet, moire caused by the modulation effect of the Fresnel lens is defocused. image quality can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing a first embodiment of a projection screen according to the present invention.

FIG. 2 is a diagram showing a projection optical system used in the screen of the first embodiment.

FIG. 3 is a diagram for explaining the modulation effect of a Fresnel lens.

FIG. 4 is a diagram schematically showing a second embodiment of a projection screen according to the present invention.

FIG. 5 is a diagram schematically showing a third embodiment of a projection screen according to the present invention.

FIG. 6 is a diagram schematically showing a fourth embodiment of a projection screen according to the present invention.

FIG. 7 is a diagram schematically showing a fifth embodiment of a projection screen according to the present invention.

[Explanation of symbols]

1 Fresnel lens sheet 2. Lenticular lens sheet 3 Transparent plate 4 Diffusion plate 5 LCD panel 6. Projection lens

Claims (5)

[Claims] 1. A projection screen that combines a lenticular lens sheet and a Fresnel lens sheet, wherein a gap S is provided between the Fresnel lens sheet and the lenticular lens sheet,
When the gap S is the effective radius of the projection lens, R is the projection distance from the projection lens to the lenticular lens surface on the incident side of the lenticular lens sheet, and P is the pitch of the Fresnel lens, then S≧P×L/R

...(1) A projection screen characterized by the following. 2. The projection screen according to claim 1, wherein a transparent plate having a thickness equal to the gap S determined by the equation (1) is inserted between the lenticular lens sheet and the Fresnel lens sheet. 3. A projection screen that combines a lenticular lens sheet and a Fresnel lens sheet, wherein a diffusion plate is inserted between the Fresnel lens sheet and the lenticular lens sheet,
A gap S1 is provided between the diffusion surface of the diffusion plate on the side closer to the Fresnel lens sheet and the lenticular lens sheet, and the gap defines the vertical half-value angle of the diffusion plate as T and the pitch of the Fresnel lens as P. When I did,
S1≧P/tan(T)
...
(2) A projection screen characterized by: 4. The projection screen according to claim 3, wherein the thickness of the diffusion plate is equal to the gap S1 determined by the equation (2). 5. A gap S determined by the equation (2) between the lenticular lens sheet and the diffuser plate.
4. The projection screen according to claim 3, further comprising a transparent plate having a thickness equal to 1.