JPH03184035A - rear projection screen - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a rear projection screen used in a projection device.

[Conventional technology]

The observation surface, that is, the screen surface, is used as a rear projection screen used in projection devices such as rear projection type projectors that project a light image onto a translucent screen from the back side and observe the projected image from the front side of the screen. Another type of lens is known in which a large number of lens units form a continuous lenticular lens. This rear projection screen with lenticular lenses is designed so that the light that enters from the back side and exits to the front side is diffused by the lenticular lens on the screen surface, and this screen has a better projection than a flat screen. It has the advantage that the viewing angle of the image is large.

[Problem to be solved by the invention]

By the way, a conventional rear projection screen with a lenticular lens formed on its surface is a lens unit in which the top part is a lens part and the inclined surfaces on both sides are total reflection surfaces that reflect incident light from the back side of the screen toward the lens part. It is known that continuous lenticular lenses are formed on the screen surface, but in conventional rear projection screens, the total reflection surfaces on both sides of each lens unit of the lenticular lens are linear inclined surfaces. Among the light reflected toward the lens section by this total reflection surface, the light that is incident on the lens surface of the lens section at an angle close to the total reflection angle is reflected by the lens surface toward the back of the screen. Therefore, there was a problem that there was a lot of light loss and the screen became dark.

This invention was made in view of the above-mentioned circumstances, and its purpose is to diffuse the light that enters from the back side and exits to the front side using the lenticular lens on the screen surface, thereby increasing the viewing angle. Although it is designed to be large, this rear projection screen can brighten the screen by transmitting the light reflected toward the lens part by the total reflection surface of each lens unit of the lenticular lens to the screen surface side without loss. Our goal is to provide the following.

[Means for Solving the Problems] The present invention forms a lenticular lens in which a large number of continuous lens units each having a top portion as a lens portion and both side surfaces as total reflection surfaces is formed on a screen surface, and that the lenticular lens is The lens portion of each lens unit is formed with a linear surface that faces the total reflection surfaces on both sides of the lens unit, and the total reflection surface is used to reflect and collect incident light from the back side of the screen toward the linear surface. It is characterized by a curved surface that emits light.

[Effect]

That is, in the rear projection screen of the present invention, the total reflection surfaces on both sides of each lens unit of the lenticular lens, which diffuses light incident from the rear side and exiting to the front side, are curved as described above. All of the light reflected by the total reflection surface is focused onto a straight line formed in the lens section, and since the straight line faces the total reflection surface, the light reflected by the total reflection surface is Since the light that is reflected and enters the linear surface is transmitted through this linear surface without being reflected, according to this rear projection screen, the light is reflected toward the lens section by the total reflection surface of each lens unit of the lenticular lens. The screen can be brightened by transmitting light to the front surface of the screen without loss.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Figure 1 shows a portion of the rear projection screen.
Reference numeral 1 denotes a screen body made of a transparent resin sheet such as acrylic resin, and a lenticular lens 2 is integrally formed over the entire surface of the screen body, that is, the viewing surface.

Note that this rear projection screen is manufactured by hot pressing a transparent resin sheet, extrusion molding, or injection molding of a transparent resin.

The above-mentioned lenticular lens 2 is formed by continuously forming a large number of microscopic linear lens units 3.3 in parallel.
Each lens unit 3, 3 has, for example, its width (maximum middle of the base)
The dimensions are W is 1.2 mm and height h is 0.675 cm. Each lens unit 3.3 has a lens section 4 at its top and a total reflection surface 5.5 at both sides. The bottom surface of the recess is a convex lens surface 4a, and both side surfaces are inclined linear surfaces 4b, 4b facing the total reflection surface 5. Aspherical lens surface 4c.

4C, and furthermore, convex lens surfaces 4d, 4d having the outer edge of the lens part as their vertices are formed on both side edges of the lens part. Note that the convex lens surface 4 at the center of the lens portion
The width ΔW of a is 0.07--, the radius of curvature of this convex lens surface 4a is 0.05 mm, and the aspheric lens surfaces 4c, 4c are aspheric surfaces expressed by the 10th order equation,
The radius of curvature R of the convex lens surfaces 4d, 4d on both side edges is 0.1
It is said to be mm.

In addition, the total reflection surfaces 5°5 on both sides of each lens unit 3, 3 are as follows:
It is formed into a paraboloid that reflects and condenses parallel light incident from the back side of the screen toward the central linear surfaces 4b, 4b of the lens section 4, and this paraboloid has its focal point directed toward the linear surfaces 4b, 4b. 4b, a curved surface (in this example, a curved surface expressed by y m O, 4x2) that connects to 4b.

Furthermore, the upper end side of these total reflection surfaces 5, 5 is a total reflection surface 5.5.
The straight rising surface 5a rises at a steeper angle. These rising surfaces 5a, 5a direct parallel light incident from the back side of the screen to convex lens surfaces 4 on both sides of the lens section 4.
d, 4d, and this rising surface 5a
, 5a, that is, the distance Δh from the upper end of the parabolic part of the total reflection surface 5 to the top of the lens unit 3 (side edge of the convex lens surface 4d) is approximately 0.215 mm, and this rising surface 5a
, 5a with respect to one surface of the screen body is approximately 70°.

Figure 2 shows the light diffusion state of one lens unit 3 of the lenticular lens 2, in which parallel light incident on the lens unit 3 from the back side of the screen is directly transmitted through the lens unit 4 at the top of the lens unit. The light is refracted and diffused by each lens surface 4a, 4c, and 4d of this lens portion 4 as shown in the figure.

Further, the parallel light incident on the parabolic total reflection surfaces 5.5 on both sides of the lens unit 3 is reflected by the straight lines on both sides of the convex lens surface 4a formed at the center of the lens portion 4 by the total reflection surfaces 5.5. 4
The light is reflected and focused toward the straight surfaces 4b and 4b.
The light passes through and is refracted and diffused as shown. Further, the parallel light incident on the rising surfaces 5a, 5a on the upper end side of the total reflection surfaces 5, 5 is reflected by the rising surfaces 5a, 5a toward the convex lens surfaces 4d, 4d formed on both side edges of the lens portion 4. , passes through these convex lens surfaces 4d, 4d, and is refracted and diffused as shown.

Therefore, in this rear projection screen, the total reflection surfaces 5, 5 on both sides of each lens unit 3.3 of the lenticular lens 2, which diffuses light entering from the back side and exiting to the front side, are arranged as described above. By making it a paraboloid, all the light reflected by the total reflection surface 5.5 is focused on the linear surfaces 4b, 4b formed at the center of the lens portion 4, and the linear surfaces 4b, 4b is opposed to the total reflection surface 5.5, the light reflected by the total reflection surface 5, 5 and incident on the straight line surfaces 4b, 4b is transmitted through the straight line surfaces 4b, 4b without being reflected. Therefore, according to this rear projection screen, the light reflected toward the lens portion 4 by the total reflection surfaces 5, 5 of each lens unit 3.3 is transmitted to the screen surface side without loss, thereby brightening the screen. I can do it.

In addition, in this embodiment, the parabolic total reflection surface 5° 5 is a curved surface that focuses on the straight line surfaces 4b, 4b because the reflection from the paraboloid total reflection surfaces 5, 5 Linear plane of light 4
This is to maximize the diffusion angle at b and 4b. Also, among the parallel light incident on the screen from the back side, the linear surface 4b.

Depending on the inclination angle of the linear surface 4b, the light incident on the linear surface 4b is reflected to the aspherical lens surface 4C, and depending on the angle of incidence on the aspherical lens surface 4C, the light is reflected on the aspherical lens surface 4C. However, since the width (height) of the linear surfaces 4b, 4b is quite small, the loss of light due to light reflection on these linear surfaces 4b, 4b is small, and this loss of light In comparison, the effect of allowing all the reflected light from the total reflection surfaces 5, 5 to be transmitted from the linear surfaces 4b, 4b to the screen surface side is much greater, so the loss of light due to the linear surfaces 4b, 4b is significantly greater. can be ignored. Furthermore, in the above embodiment, the linear surfaces 4b, 4b
Since a convex lens surface 4a is formed in between, when the screen is viewed from the front, the linear surfaces 4b and 4b become dark due to the reflection of incident parallel light, which is compensated for by light diffusion on the convex lens surface 4a. I can do it.

Moreover, in the above embodiment, the linear rising surfaces 5a rising at a steeper angle than the total reflection surfaces 5.5 on both sides of the lens units 3, 3 of the lenticular lens 2
, 5a, the light is reflected from near the top of the total reflection surface toward the side edge of the lens section 4, as in the case where the top ends of the total reflection surfaces 5, 5 are directly connected to the lens section 4. The light enters the lens surface of the lens section 4 from the direction of its total reflection angle and is not reflected by this lens surface toward the back of the screen, thus reducing light loss even near both side edges of the lens section 4. It will never occur. Further, in this embodiment, the portion between the center and both side edges of the lens unit 4 of the lens unit 3.3 of the lenticular lens 2 is aspherical lens surfaces 4c, 4c having a larger light diffusion angle than a spherical lens. Therefore, the viewing angle can be increased by diffusing light over a wide range on the screen surface.

Projection devices such as rear projection projectors include full-size image projection types that project the image onto a screen without enlarging it, and enlarged image projection types that use a projection lens to magnify the image and project it onto the screen. Furthermore, there are two types of projection devices: vertical projection type, which projects images from a direction perpendicular to the screen surface, and oblique projection type, which projects images from an oblique direction to the screen surface. However, in the case of a full-size image projection type and vertical projection type projection device, the projection light from the projection source is parallel light perpendicular to the screen surface, so it is sufficient to let this light enter the screen as it is. . In addition, even if it is a full-size image projection type, in the case of an oblique projection type, light from the projection source (parallel light)
In the case of an enlarged image projection type projection device, the light from the projection source enters the screen while being spread, but in this case, the projection source is on the back side of the screen. A Fresnel lens that refracts the light from the projection source into parallel light perpendicular to the screen surface is placed, or the Fresnel lens is integrally formed on the back of the screen so that the light from the projection source passes through the Fresnel lens and reaches the screen. In addition, in the case of an enlarged image projection type and an oblique projection type, a Fresnel lens is installed on the back side of the screen to turn the incident light into parallel light while spreading, and the direction of the light is directed relative to the screen surface. A Fresnel lens is placed vertically (however, one Fresnel lens may be formed on the back of the screen), and the light from the projection source is made into parallel light perpendicular to the screen surface and incident on the screen. Just do it. This also applies to other embodiments described later.

3 and 4 show another embodiment of the present invention, in which the lens portion 4.4 of each lens unit 3.3 of the lenticular lens 2 is constructed in the same manner as in the above embodiment. A convex lens surface 4a and linear surfaces 4b, 4b are formed in the center, convex lens-like aspherical lens surfaces 4c, 4c are formed on both sides, and convex lens surfaces 4d, 4d are formed on both side edges. The total reflection surfaces 5.5 on both sides of the lens unit 3.3 are formed into paraboloids that reflect and condense parallel light incident from the back side of the screen toward the linear surfaces 4b, 4b at the center of the lens portion, and This total reflection surface 5.5
A linear rising surface 5a that rises at a steeper angle than the inclination angle of the total reflection surface 5.5 is formed on the upper end side. At the same time, the outer edges of the convex lens surfaces 4d, 4d on both sides of the lens portion are extended approximately horizontally to form horizontal surfaces 4e, 4e that are approximately perpendicular to the rising surfaces 5a, 5a. There is. In addition, the dimensions w, h, ΔW, Δh of each part of the lens unit 3.3 in this example
, R are the same as in the above embodiment.

The rear projection screen of this embodiment also has a lenticular lens 2 on the surface of the screen that diffuses the light that enters from the rear side and passes through the screen, as shown in FIG. 4, each lens surface 4a, 4c.

The light that passes through the screen 4d is refracted and diffused as shown, and the light that passes through the horizontal surfaces 4e and 4e on the outer edge is refracted due to the difference in the optical refractive index between the material of the screen (for example, acrylic resin) and the air. Therefore, in this embodiment as well, the light reflected toward the lens portion 4 by the total reflection surfaces 5, 5 of each lens unit 3.3 can be transmitted to the screen surface side without loss, thereby making the screen brighter. Also, lens unit 3
Since the substantially vertical rising surfaces 5a, 5a are formed on the upper end sides of the total reflection surfaces 5, 5 of 3 degrees, light loss near the side edges of the lens portion 4 can also be eliminated. Incidentally, the rising surfaces 5a, 5a on the upper end side of the total reflection surfaces 5, 5 cannot be perfectly vertical surfaces due to die cutting in molding the screen, so these rising surfaces 5a, 5a are slightly inclined. Therefore, parallel light incident from the rear side of the screen toward the rising surfaces 5a, 5a is reflected by the rising surfaces 5a, 5a and enters near both side edges of the lens section 4, but the above-mentioned rising surfaces 5a, The light reflected by 5a reaches the horizontal surface 4e on both side edges of the lens portion.

Since it is incident on 4e and passes through the horizontal planes 4e and 4e,
The light reflected by the rising surfaces 5a, 5a and incident near the side edges of the lens portion 4 will not be reflected by the lens surface and no loss of light will occur.

In the above embodiment, the total reflection surfaces 5, 5 on both sides of each lens unit 3, 3 of the lenticular lens 2 are paraboloids, but the total reflection surfaces 5.5 reflect the incident light from the back side of the screen. For example, a curved surface such as an elliptical surface may be used as long as it reflects and condenses light toward the straight surfaces 4b, 4b at the center of the lens portion.

Furthermore, in the above embodiment, the screen is made of transparent resin such as acrylic resin, but this rear projection screen is
It may be formed of a transparent resin mixed with light-diffusing fine particles or a transparent resin sheet with a light-diffusing layer formed on the negative side.

〔Effect of the invention〕

In the rear projection screen of the present invention, the lens portion of each lens unit of the lenticular lens that diffuses light that enters from the back side and exits to the front side has a linear surface that faces the total reflection surfaces on both sides of this lens unit. At the same time, since the total reflection surface is a curved surface that reflects and condenses incident light from the back side of the screen toward the straight surface, the total reflection surface of each lens unit of the lenticular lens is used as a lens portion. The screen can be made brighter by transmitting the light reflected toward the screen to the screen surface side without loss.

[Brief explanation of drawings]

1 and 2 are perspective views of a portion of a rear projection screen and a state diagram of light diffusion of one lens unit showing one embodiment of the present invention, and FIGS. 3 and 4 are other embodiments of the present invention. FIG. 2 is a perspective view of a portion of a rear projection screen and a light diffusion state diagram of one lens unit; DESCRIPTION OF SYMBOLS 1... Screen body, 2... Lenticular lens, 3... Lens unit, 4... Lens part, b... Linear surface, 5... Total reflection surface.

Claims (1)

[Claims] This is a rear projection screen that allows an optical image projected from the rear side to be observed from the front side, and a lenticular lens is formed on the screen surface in which a number of continuous lens units each having a lens portion at the top and total reflection surfaces at both sides form a lenticular lens. In addition, the lens portion of each lens unit of the lenticular lens is formed with a linear surface that faces the total reflection surfaces on both sides of the lens unit, and the total reflection surface is configured to reflect incident light from the back side of the screen. A rear projection screen characterized by having a curved surface that reflects and focuses light toward the straight surface.