JPH06175229A - Transmission type screen - Google Patents

Abstract

PURPOSE:To obtain good display quality without the abnormal exit light resembling ghosts even from an extremely close distance by constituting the transmission type screen in such a manner that the absorptivity of the substrate of a Fresnel lens is distributed according to the intensity of the reflected light reflected by prism surfaces. CONSTITUTION:A part of the incident image light 1 on the Fresnel lens 2 is reflected by the prism surfaces and the reflected light 3 thereof passes the inside of the substrate 2a while refracting or reflecting therein. The absorptivity 2a of the Fresnel lens 2 is constituted by dispersing light absorbing materials 4 to have the absorptivity A adjusted in such a manner that the reflected light passing the substrate attenuates while the light is absorbed. The intensity of the reflected light 3 is higher nearer the peripheral part where the inclination thetafrom the prism surfaces is large. Then, the absorptivity A is so adjusted that as to be as high as, for example, 20% in the peripheral part of the Fresnel lens 2 as the inclination theta of the prism surfaces is large in this part, to continuously decrease toward the center where the inclination theta of the prism faces is small and to be 0%, i.e., colorless and transparent in the central part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive screen, a rear projection display device capable of observing an abnormal outgoing light reflected by a prism surface in a lens and observing it with a good display quality even at a short distance. Regarding

In recent years, the importance of display devices in the information processing field has been increasing more and more, and liquid crystal display devices that are thin, lightweight, and capable of high-definition display have made remarkable progress in place of conventional CRT display devices. However, it is difficult for a liquid crystal display device to form a large screen with full color. Therefore, a projection type display device using a liquid crystal display panel as a light valve has been developed.

The projection type display device includes a front projection type suitable for displaying a large screen of 100 inches or more and a medium size of 50 to 70 inches, and is used as a display device for information processing terminals such as OA equipment and CAD terminals. There is a rear projection type suitable for viewing.

When used as an information processing terminal, the rear projection type display device can reach the display surface unlike the case where the rear projection type display device is viewed from a relatively long distance like a TV (television). Often viewed from a distance close to. Therefore, there is a problem caused by viewing a relatively large screen at a close range, and improvement is desired.

[0005]

2. Description of the Related Art Conventionally, a projection type display device has a type in which a CRT is projected on a screen as a projection tube and is divided into a front projection type and a rear projection type. Among them, the front projection type is suitable for a large screen, while the rear projection type can be made small, and is suitable for a display device of an information processing terminal such as an OA device or a CAD terminal. Moreover, if a liquid crystal display panel is used instead of the CRT as the original image display means, a smaller device can be obtained and a high-definition display screen can be obtained.

FIG. 3 is a block diagram showing an example of a rear projection type display device using a liquid crystal display panel, and FIG. 4 is a schematic block diagram showing an example of a conventional transmission screen. In the figure, 1
Is image light, 2 is a Fresnel lens, 2a is a substrate, 2b is a prism surface, 6 is a diffusion plate, 7 is a lenticular lens, 10 is a transmissive screen, 20 is a rear projection display device, 21 is a liquid crystal display panel, and 22 is A light source, a projection lens 23, a reflecting mirror 24, and a driving device 25.

In FIG. 3, the rear projection display device 20 is
This is a projection device using the liquid crystal display panel 21 as a light valve. The light emitted from the light source 22 is spatially modulated by the liquid crystal display panel 21 to become the image light 1. Then, the image light 1 is enlarged by the projection lens 23, the optical path is bent in multiple layers by the plurality of reflecting mirrors 24, and projected on the rear surface of the transmissive screen 10. The viewer sees the image light 1 from the front through the transmissive screen 10. The liquid crystal display panel 21 and the light source 22 are controlled by a driving device 25.

The liquid crystal display panel 21 is significantly thinner and lighter than a conventional CRT. Further, when performing color display, high-definition panels each having a single color of B (blue), G (green), and R (red) can be combined by an optical system.

Therefore, with the transmissive screen 10 thus constructed, it is possible to obtain a high-quality color display screen having thousands of pixels. In FIG. 4, the transmission screen 10 has a structure in which a Fresnel lens 2, a diffusion plate 6 and a lenticular lens 7 are stacked.

The Fresnel lens 2 is formed, for example, on a substrate 2a made of acrylic plastic, such as PMMA, on a lens portion composed of prisms arranged in a concentric pattern.
2b is provided, and the image light refracted by the prism surface 2b and magnified and projected is made incident on the diffusion plate 6 as a light ray which is parallel or converged with respect to the optical axis.

The diffusing plate 6 diffuses the incident image light to determine the viewing angle in the horizontal / vertical directions. The viewing angle set here is the same in all directions in the radial direction. There is.

When viewed as a display device, the viewing angle in the horizontal direction is generally wider than the viewing angle in the vertical direction. Therefore, the light beam emitted from the diffusion plate 6 is again diffused in the horizontal direction by using the lenticular lens 7 to widen the horizontal viewing angle.

Rear projection display device having such a configuration
20 is conventionally used for enlarged projection of TV images,
The viewer was looking at the screen from a position relatively far from the screen. For example, in the case of a TV, the viewing distance is 6 to 8 times the height of the screen, and it is viewed from a position several meters away. Therefore, the inclination of the prism surface 2b of the Fresnel lens 2 is:
θ may be relatively small.

On the other hand, in recent years, in place of the CRT display device, a rear projection type display device which is thinner and can realize a large screen is CA.
It has been required to be used as a display terminal such as a D or EWS (workstation). However, the display device used for CAD, EWS, etc. is used at a viewing distance of at most about twice the height of the screen, that is, at a distance that can be reached by reaching out, depending on the usage pattern.

Therefore, in order to significantly shorten the focal length of the Fresnel lens 2, that is, to largely bend the incident light entering the Fresnel lens 2, it is necessary to increase the inclination: θ of the prism surface 2b. However, the inclination of the prism surface 2b: θ
When is increased, the component of light reflected by the prism surface 2b is also increased, which causes a problem.

[0016]

FIG. 5 is a diagram for explaining the behavior of light in the Fresnel lens. In the figure,
2 is a Fresnel lens, 2b is a prism surface, 3 is reflected light, 1
1, 11a, 11b and 11c are incident light, 12 is normal output light, 13a
, 13b and 13c are extraordinary emitted lights.

As can be seen from FIG. 5, the Fresnel lens 2
The incident light 11 that is incident on is divided into a normal output light 12 that is refracted and emitted by the prism surface 2b and a reflected light 3 that is reflected by the prism surface 2b. Then, the reflected light 3 enters the lens,
The reflection is repeated and the light is emitted from another position different from the normal emission position.

Refraction and reflection of the incident light 11 on the prism surface 2b depend on the angle between the incident light 11 and the prism surface 2b. When the incident angle of the incident light 11 is constant, the prism surface
2b slope: Determined by θ.

Therefore, in order to shorten the viewing distance and use the rear projection display device for CAD, EWS, etc., if the inclination: θ of the prism surface 2b is increased, the reflected light 3 also increases. Then, if the intensity of the reflected light 3 is small, it will not be visually recognized, but as the intensity increases, for example, the incident light 11a shown by the solid line will be the abnormal outgoing light 13a, and the incident light 11b shown by the dashed line will be the abnormal outgoing light 13b. The incident light 11c indicated by the broken line is emitted as abnormal emission light 13c at an abnormal position distant from the predetermined position.

The abnormal emitted lights 13a, 13b and 13c are
Like a ghost seen on a TV, a number of regular images are overlapped with each other to significantly deteriorate the display quality and cause unevenness in brightness on the screen.

Therefore, the present invention provides a rear projection type display device in which abnormal emission light reflected by the prism surface of a Fresnel lens is dimmed within the lens and can be viewed with good display quality even from a close distance. Has an aim.

[0022]

The above-mentioned problem is a transmissive screen for observing the image light projected from the back from the front side, which has a Fresnel lens, and the Fresnel lens is a transparent substrate. And a prism surface concentrically engraved on the substrate, wherein the absorptance A of the substrate is distributed according to the intensity of the reflected light reflected by the prism surface. Is solved by a transmissive screen configured as follows.

[0023]

In the transmission screen using the Fresnel lens, it is inevitable that the image light is reflected by the prism surface and emitted from a position outside the predetermined range. However, in the present invention,
The reflected light is dimmed or extinguished.

That is, the light absorbing material is dispersed in the Fresnel lens through which the reflected light passes, corresponding to the intensity of the reflected light reflected by the prism surface. Then, the absorption coefficient A of the Fresnel lens is adjusted.

By the way, when viewing from a transmissive screen at a very short distance, it is necessary to increase the inclination θ of the prism surface of the Fresnel lens toward the periphery, and therefore the intensity of reflected light is also high. Therefore, if the extinction coefficient A of the peripheral portion of the Fresnel lens is made large and the central portion is made small, the reflected light reflected by each prism surface can be appropriately absorbed and dimmed or extinguished.

In this way, it is possible to reduce the image light emitted from a non-predetermined position such as a ghost of TV, and prevent a problem that the quality of the displayed image is deteriorated. As a result, it is possible to obtain good display quality even when viewed at a very short distance from the transmissive screen.

[0027]

1 is an explanatory view of a first embodiment of the present invention, and FIG. 1 (A) is a schematic sectional view of a transmissive screen.
(B) is a diagram showing a distribution state of absorptance: A, FIG. 2 is an explanatory diagram of a second embodiment of the present invention, and FIG. 2 (A) is a schematic sectional view of a main part of a transmissive screen, FIG. 2 (B) shows the absorptance:
It is a figure which shows the distribution state of A. In the figure, 1 is image light, 2 is a Fresnel lens, 2a is a substrate, 2b is a prism surface,
3 is reflected light, 4 is a light absorbing material, 5 is a light absorbing plate, and 10 is a transmissive screen.

Embodiment 1 In FIG. 1, the transmission screen 10 is a Fresnel lens 2
The diffuser plate 6 and the lenticular lens 7 are superposed on each other, and the Fresnel lens 2 is made of an acrylic plastic molded product such as PMMA.

Most of the image light 1 that has entered the Fresnel lens 2 passes through the substrate 2a of the Fresnel lens 2 and the prism surface
The light is refracted at 2b, emitted, and enters the diffusion plate 6. A part of the image light 1 is reflected by the prism surface 2b, and the reflected light 3 passes through the substrate 2a while being refracted and reflected. The substrate 2a of the Fresnel lens 2 has a configuration in which the light absorption material 4 is dispersed so that the reflected light 3 thus passing is absorbed and attenuated, and the absorptivity: A is adjusted. The light absorbing material 4 is preferably an achromatic pigment so that the displayed image does not become colored, and carbon black, for example, is used.

On the other hand, the intensity of the reflected light 3 becomes larger in the peripheral portion where the inclination: θ of the prism surface 2b is larger. Therefore, FIG.
As shown in (B), since the inclination: θ of the prism surface 2b is large in the peripheral portion of the Fresnel lens 2, the absorptance: A is large, for example, 20%, and the inclination: θ of the prism surface 2b becomes small at the center. It decreases continuously toward 0% in the center
That is, it is adjusted to be colorless and transparent. The Fresnel lens 2 having such a configuration can be manufactured by, for example, molding a plastic which is dry-colored with the light absorbing material 4 by a double molding method.

In this way, particularly in the peripheral portion where the reflected light 3 is strong, the reflected light 3 is absorbed and dimmed while passing through the substrate 2a, and disappears in the substrate 2a or the prism surface 2b. Even if the light is refracted at the outside and goes out, the trouble of disturbing the display screen does not occur.

Embodiment 2 In FIG. 2, the light absorption plate 5 is bonded to the substrate 2a of the Fresnel lens 2. This light absorption plate 5 is shown in FIG.
As shown in (B), the absorptance: A is large in the peripheral portion of the Fresnel lens 2, and the absorptance: A is reduced stepwise toward the central portion.

By the way, the reflected light 3 which has passed through the substrate 2a
However, if the light-absorbing plate 5 reflects from the bonding surface between the substrate 2a and the light-absorbing plate 5, it does not work effectively. Therefore, the light absorption plate 5 is the substrate 2a.
It is better to use acrylic plastic with the same refractive index as Further, it is preferable that the adhesive surface is so-called solvent-bonded with, for example, ethylene tetrachloride so that the substrate 2a and the light-absorbing plate 5 are integrally formed without the adhesive surface.

In order to change the absorptance: A of the light-absorbing plate 5 in a stepwise manner, for example, an appropriate amount of the absorptive material 4 made of an achromatic pigment such as carbon black is dispersed to form a ring with the absorptance: A adjusted. It can be made by sequentially fitting them concentrically.

In the Fresnel lens 2 to which the light-absorbing plate 5 is bonded in this manner, especially in the peripheral portion where the reflected light 3 is strong, when the reflected light 3 passes through the substrate 2a and enters the light-absorbing plate 5, it is absorbed and dimmed. Then, even if it disappears or is reflected again and refracted by the prism surface 2b and goes out, the problem of disturbing the display screen does not occur.

What is the maximum absorptivity A of the Fresnel lens 2 peripheral part: A, and how is the absorptance aA toward the center part?
Various modifications can be made as to how to reduce the angle depending on the image light forming means shown in FIG. 3 and the inclination: θ of the prism surface 2b related to the viewing distance from the transmissive screen.

[0037]

EFFECTS OF THE INVENTION In the rear projection type display device, when viewed from a close range, abnormal emission light appears like a ghost of a TV. According to the present invention, such a defect is suppressed and a good display quality is obtained. Obtainable.

As a result, if a liquid crystal display panel is used instead of the CRT as the original image display means, it is possible to realize a small-sized display device which can be applied to CAD or EWS and which is capable of high-definition and color display.

[Brief description of drawings]

FIG. 1 is an explanatory view of a first embodiment of the present invention, (A) is a schematic sectional view of a transmissive screen, and (B) is an absorptivity:
It is a figure which shows the distribution state of A.

2A and 2B are explanatory views of a second embodiment of the present invention, FIG. 2A is a schematic sectional view of a main part of a transmission screen, and FIG. 2B is a diagram showing a distribution state of absorptance: A. .

FIG. 3 is a configuration diagram of an example of a rear projection display device using a liquid crystal display panel.

FIG. 4 is a schematic configuration sectional view of an example of a conventional transmission screen.

FIG. 5 is a diagram for explaining the behavior of light in a Fresnel lens.

[Explanation of symbols]

1 image light 2 Fresnel lens 2a substrate 2b
Prism surface 3 Reflected light 4 Light absorbing material 5 Light absorbing plate 10 Transmissive screen

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Hamada 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Yoshinori Tanaka, 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (4)

[Claims] 1. A transmissive screen for observing image light (1) projected from the rear from the front, comprising a Fresnel lens.
(2), wherein the Fresnel lens (2) includes a transparent substrate (2a) and the substrate.
A prism surface (2b) engraved concentrically on (2a), wherein the absorptance of the substrate (2a): A is the reflected light (3) reflected by the prism surface (2b). ) The transmission screen is characterized in that it is distributed according to the intensity. 2. The Fresnel lens (2) has an absorptivity: A
2. The transmission screen according to claim 1, wherein the distribution of the distributions is dependent on the concentration of the light absorbing material (4) dispersed on the substrate (2a). 3. A Fresnel lens (2) comprising: a light-absorbing plate (5), wherein the light-absorbing plate (5) is based on the concentration of the light-absorbing material (4) in which the distribution of absorptance: A is dispersed. Is the light absorption plate (5) on the substrate (2a)
The transmissive screen according to claim 1, wherein the transparent screen is adhered. 4. The transmissive screen according to claim 1, wherein the light absorbing material (4) is made of an achromatic pigment.