JPH05158155A - Transmission type screen - Google Patents

Abstract

PURPOSE:To prevent generation of moire and to obtain a picture having glossy feeling. CONSTITUTION:The screen is constituted of combination of the lens sheet of a Fresnel lens sheet 11 and a lenticular lens sheet 12. The Fresnel lens sheet 11 is equipped with a circular Fresnel lens 11a in the incident side of projected light. A first lenticular lens 11b is formed in the horizontal direction in the whole surface of the outgoing side. The lenticular lens sheet 12 is equipped with a second lenticular lens 12a in the vertical direction in the whole surface of the incident side. 1/4 wavelength plate 12b and a polarization plate 12c are successively laminated in the outgoing side.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to transmissive screens. In particular, the present invention relates to a transmissive screen for a rear type liquid crystal projector configured by a TN type liquid crystal panel.

[0002]

2. Description of the Related Art A transmissive screen used in a TV projector has the best performance because it meets the requirements of screen brightness, uniformity, wide horizontal field of view, and low vertical light loss. As one of them, a Fresnel lens sheet and a lenticular lens sheet with a black stripe are often used.

The structure of a conventional transmissive screen is shown in FIG. 3 and described (see, for example, Japanese Patent Publication No. 3-52049). That is, two lens sheets, the Fresnel lens sheet 21 and the lenticular lens sheet 22 with a black stripe, are combined. The Fresnel lens sheet 21 includes a Fresnel lens 21a on the incident side and a hairline processed surface 21b on the emitting side. The hairline processed surface 21b is provided in place of the lenticular lens and imparts a diffusion characteristic in the vertical direction of the projection screen. The hairline processed surface 21b is formed with a vertical diffusion characteristic (αv) (which represents an angular range in which the luminance is 1/2 or more when the maximum luminance on the optical axis is 1) is ± 4 ° or less. .. On the other hand, the lenticular lens sheet 22
The lenticular lens 22a is formed on the incident side of the lenticular lens 22a with the direction orthogonal to the processing direction of the fair line of the hairline processing surface as the longitudinal direction of the lenticular lens. The lenticular lens 22a normally has a horizontal diffusion characteristic (αH)
Is ± 35 ° to ± 50 ° to widen the left and right visual fields.
On the emission side, a black stripe 22b is provided on the non-condensing part of the lenticular lens. Black stripe 2
2b has the function of blocking stray light and reducing the reflection of external light on the output side.

According to the above-mentioned structure, a transmissive screen is obtained in which the diffusion characteristics in the vertical direction as well as in the horizontal direction are restricted. Furthermore, the resolution does not decrease in any direction, and excellent image quality without moire and reflected images is obtained.

[0005]

When a transmissive screen of this kind is used for a liquid crystal projector, it has the following problems. That is, TN for liquid crystal projector
Since the type liquid crystal panel includes a thin film transistor and a driving wiring for each pixel, there is a region where the liquid crystal does not operate. A light-shielding layer called a black matrix is provided to shield this region from light. The problem is that moire occurs on the projection screen due to the interaction between the black matrix and the black stripes of the transmissive screen. Since the CRT type projector does not have a black matrix in the CRT, the above problem does not occur, and the problem newly occurs in the liquid crystal projector.

As a measure against the above problem, there is a method of making the pitch of the black stripe fine, but it is necessary to make the pitch of the lenticular lens small corresponding to the pitch of the black stripe. In this case, since the lenticular lens and the black stripe are molded, it is difficult to perform fine processing. For example, with a 40-inch screen and 640 horizontal pixels, the black matrix is projected on the scoop at a pitch of 1.3 mm. To prevent moire with the black stripe, 0.2 to
Fine pitch black stripes of 0.3 mm or less and lenticular lenses are required. Therefore, the processing cost becomes expensive. In addition, since the pitch is fine, there is a problem that the projection screen loses gloss and becomes a poorly sharp screen. The present invention solves the above-mentioned problems by focusing on the point that a TN type liquid crystal projector is composed of only polarization components. It is an object of the present invention to provide a transmissive screen which has a low processing cost and is capable of obtaining a projected image with gloss and good sharpness.

[0007]

In order to achieve the above object, a transmission screen according to the present invention comprises a combination of two lens sheets, a Fresnel lens sheet and a lenticular lens sheet, and the Fresnel lens sheet is The Fresnel lens is formed only on one surface, and the first lenticular lens or the hairline processed surface having directionality is provided on the surface opposite to the Fresnel lens forming surface of this Fresnel lens sheet, and the lenticular lens sheet is Forming a second lenticular lens having a longitudinal direction in a direction orthogonal to the longitudinal direction of the first lenticular lens on the surface facing the Fresnel lens sheet, and the surface opposite to the second lenticular lens is 1 / A four-wave plate and a polarizing plate are sequentially laminated.

[0008]

[Operation] The operation of this configuration is as follows. That is, in the liquid crystal projector using the TN liquid crystal, the projection light is usually a linearly polarized wave due to the characteristics of the liquid crystal. Therefore, the projection light of the liquid crystal projector is converted into right-handed circularly polarized light or left-handed circularly polarized light by using the quarter-wave plate in the projection optical system. For example, the case where the projection light is converted into left circularly polarized light will be described. The projected light is condensed by the Fresnel lens and is diffused by ± 5 ° on the first lenticular lens or the hairline processed surface.

Next, the second lenticular lens and the light diffusing agent diffuse the light horizontally and vertically. This transmitted light is converted into linearly polarized light again by passing through the quarter-wave plate, and is transmitted through a polarizing plate having a polarization axis that matches the polarization axis of the linearly polarized light. Therefore, the projection light can display the screen only with the loss on the transmittance of the polarizing plate.

On the other hand, since the external light is natural light, it is composed of right circularly polarized light and left circularly polarized light, and the amount of light is halved by passing through the polarizing plate. Then, if it is set to be converted to left circularly polarized light by the 1/4 wavelength plate, for example, external light reflected by the diffusing agent changes to right circularly polarized light, and again passes through the 1/4 wavelength plate and is then absorbed by the polarizing plate. External light is completely absorbed because it is converted into linearly polarized light having a polarization direction in the axial direction. Therefore, the projected image hardly shows the influence of external light.

With the above construction, since there is no black stripe, moire due to interaction with the black matrix of the liquid crystal panel does not occur. Furthermore, since the surface is made of a polarizing plate, the projected image is glossy and sharp.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a perspective view showing the structure of the present invention. The Fresnel lens sheet 11 has a circular Fresnel lens 11 formed on the incident side of projection light, and a first lenticular lens 11b formed horizontally on the entire emission side. The lenticular sheet 12 is in the direction perpendicular to the entire surface on the incident side, that is, the Fresnel lens sheet 11
The second lenticular lens 12a is formed in a direction orthogonal to the longitudinal direction of the first lenticular lens, and the quarter wavelength plate 12b and the polarizing plate 12c are sequentially laminated on the emission side. The lenticular lens sheet 12 has a light diffusing agent 12d provided therein for visualization (FIG. 2). The light diffusing agent 12d adjusts the addition amount of the diffusing agent and the surface light diffusing layer so that the vertical diffusion characteristic (αV) of the lenticular lens sheet 12 is controlled to ± 5 ° to ± 10 °. Further, in order to have the vertical diffusion characteristic of the lenticular lens sheet 12, as shown in FIG.
2d may be provided, or these may be used together.

With the above construction, the projection light from the liquid crystal panel was converted into circularly polarized light by the quarter-wave plate in advance and evaluated. As a result, no moire was generated and there was no black stripe, so that the projected image was transparent. Moreover, we were able to obtain sharp images. It was confirmed that even in black display, it was hardly affected by outside light. In this embodiment, a lenticular lens is used for the Fresnel lens sheet, but the same effect can be obtained by using a hairline processed surface.

Further, the image quality can be further improved by applying a non-reflective coating on the surface of the polarizing plate. Even if a hard coating is applied to protect the surface, there is no problem with the effect of the present invention.

[0016]

When the transmissive screen according to the present invention is used in a liquid crystal projector, it has no moire, is transparent, and is hardly affected by outside light. It has the effect of obtaining excellent image quality.

[Brief description of drawings]

FIG. 1 is a perspective view of a transmissive screen according to an embodiment of the present invention.

FIG. 2 is a sectional view of a lenticular lens sheet according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a conventional transmissive screen.

[Explanation of symbols]

 11 Fresnel lens sheet 11a Circular Fresnel lens 11b First Fresnel lens 12 Lenticular lens sheet 12a Second lenticular lens 12b 1/4 wavelength plate 12c Polarizing plate 12d Light diffusing layer 21 Fresnel lens sheet 21a Fresnel lens 21b Hairline processing surface 22 Lenticular Lens sheet 22a Lenticular lens 22b Light shielding layer (black stripe)

Claims (2)

[Claims] 1. A combination of two lens sheets, a Fresnel lens sheet and a lenticular lens sheet, wherein the Fresnel lens sheet has a Fresnel lens formed on only one surface thereof, and the Fresnel lens forming surface of the Fresnel lens sheet is formed. A first lenticular lens or a directional hairline processing surface is provided on a surface opposite to the surface, and the lenticular lens sheet has a surface opposite to the Fresnel lens sheet in a direction orthogonal to the longitudinal direction of the first lenticular lens. A transmissive screen characterized in that a second lenticular lens having a longitudinal direction is formed on the surface of the second lenticular lens, and a quarter-wave plate and a polarizing plate are sequentially laminated on the surface opposite to the second lenticular lens. 2. The transmissive screen according to claim 1, wherein the lenticular lens sheet has a light diffusing agent inside.