JPH0782195B2 - Rear projection screen - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rear projection screen used in a projection device.

[Conventional technology]

As a rear projection screen used for a projection device such as a rear projection type projector that projects a light image from the rear side on a translucent screen and observes this screen projection image from the screen front side, that is, the observation surface, that is, the screen surface. It is known that a lenticular lens in which a large number of lens units are continuous is formed. The rear projection screen with this lenticular lens is designed so that the light that enters from the back side and goes out to the front side is diffused by the lenticular lens on the screen surface. It has the advantage that the viewing angle of the image is large.

[Problems to be Solved by the Invention]

By the way, as a rear projection screen having a lenticular lens formed on its surface, conventionally, a lens unit having a top as a lens part and inclined surfaces on both sides as a total reflection surface for reflecting incident light from the back side of the screen toward the lens part It is known that a continuous lenticular lens is formed on the screen surface, but in the conventional rear projection screen, since the total reflection surfaces on both sides of each lens unit of the lenticular lens are linear inclined surfaces, Of the light reflected toward the lens section by this total reflection surface, the light that enters the lens surface of the lens section at an angle close to the total reflection angle will be reflected by the lens surface in the screen back direction. However, there was a problem that the screen became dark due to a lot of light loss.

The present invention has been made in view of the above situation, and its purpose is to diffuse the light incident from the back side and emitted to the front side by the lenticular lens on the screen surface to increase the viewing angle. A rear projection screen that is large in size, but allows the light reflected toward the lens to be transmitted through the total reflection surface of each lens unit of the lenticular lens to the screen surface side without loss to make the screen brighter. To provide.

[Means for Solving the Problems]

The rear projection screen of the present invention, on the screen surface,
A lenticular lens in which a large number of lens units each having a top portion as a lens portion and left and right side surfaces as total reflection surfaces are continuous is formed, and the central portion of the lens portion of each lens unit of the lenticular lens is recessed, The pair of left and right linear emission surfaces facing the total reflection surfaces on both sides of the lens unit are formed by the both side surfaces of the recessed portion, and the left side total reflection surface of the both side total reflection surfaces is from the screen back side. Is a curved surface that reflects and condenses the incident light toward approximately one point on the left side linear emission surface, and the right total reflection surface is an approximately one point on the right side linear emission surface that is the incident light from the back side of the screen. It is characterized by having a curved surface that reflects and focuses the light toward.

[Action]

In the rear projection screen of the present invention, of the light that is incident on each lens unit from the rear surface, the light that directly passes through the lens unit at the top of the lens unit is refracted and diffused by this lens unit, and total reflection surfaces on both sides of the lens unit are provided. The light that is incident on and reflected by the total reflection surface toward the top of the lens unit is emitted from a linear emission surface formed by recessing the central portion of the lens portion.

In this rear projection screen, the central portion of the lens unit of the lens unit is recessed to form a pair of left and right linear emission surfaces facing the total reflection surfaces on both sides of the lens unit by the both side surfaces of the recessed section. , Of the total reflection surfaces on both sides, the left total reflection surface is a curved surface for reflecting and condensing the incident light from the back side toward almost one point of the left linear emission surface, and the right total reflection surface is Since the incident light from the back side is a curved surface that reflects and focuses the light toward almost one point on the right linear emission surface, the light reflected by any of the left and right total reflection surfaces is incident on the linear emission surface.

Since the left and right linear emission surfaces face the left and right total reflection surfaces, respectively, the light reflected by the total reflection surface and condensed on the linear emission surface is not reflected by this straight line. The light is transmitted through the light emitting surface and emitted.

Therefore, according to the rear projection screen of the present invention,
By the total reflection surfaces on both sides of each lens unit of the lenticular lens, the light reflected toward the lens portion at the top of the lens unit can be transmitted to the screen surface side without loss to brighten the screen.

〔Example〕

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

FIG. 1 shows a part 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, that is, an observation surface.
The rear projection screen is manufactured by hot pressing a transparent resin sheet or by extrusion molding or injection molding of a transparent resin.

The lenticular lens 2 is formed by connecting a large number of linear lens units 3 and 3 having a small width in parallel, and each lens unit 3 and 3 has, for example, its width (maximum width at the base) w.
The dimensions are 1.2 mm and the height h is 0.675 mm. Each of the lens units 3 and 3 has a lens portion 4 at the top thereof and total reflection surfaces 5 and 5 on both side surfaces thereof.
The central portion is recessed, the bottom surface of the recessed portion is a convex lens surface 4a, and both side surfaces are inclined linear emission surfaces (hereinafter, referred to as linear surfaces) 4b facing the total reflection surfaces 5 and 5, respectively, 4b
Along with both sides of the concave portion, convex lens-shaped aspherical lens surfaces 4c, 4c having the apex on the center side of the lens portion are formed, and further on the both side edge portions of the lens portion, a convex lens with the outer edge of the lens portion as the apex It has a shape in which the surfaces 4d, 4d are formed.
The width Δw of the convex lens surface 4a at the center of the lens portion is 0.07.
mm, the radius of curvature of the convex lens surface 4a is 0.05 mm, the aspherical lens surfaces 4c and 4c are aspherical surfaces represented by the tenth order equation, and the radius of curvature R of the convex lens surfaces 4d and 4d at both edges is R. Is 0.1 mm.

Further, the total reflection surfaces 5, 5 on both sides of each lens unit 3, 3 are curved surfaces for collecting and collimating the parallel light incident from the back side of the screen toward the central straight surfaces 4b, 4b of the lens portion 4. It is said that. That is, of the left and right reflection surfaces 5, 5 of the lens units 3, 3, the left total reflection surface 5 is a curved surface for reflecting and condensing incident light from the back side toward the left straight surface 4b. The right total reflection surface 5 is a curved surface that reflects and condenses the incident light from the back surface toward the right straight surface 4b. This curved surface is, for example, a parabolic surface, and this parabolic surface is a curved surface (the curved surface represented by y = 0.4X ² in this embodiment) that connects its focal point to the straight surfaces 4b, 4b. There is. That is, the total reflection surface 5, 5 is formed into a curved surface for converging the incident light from the back side of the screen toward almost one point of the straight surfaces 4b, 4b facing the total reflection surface 5, 5, respectively. ing. Further, the upper end side of the total reflection surface 5,5 is a straight rising surface 5 rising at a steeper angle than the total reflection surface 5,5.
It is said to be a. The rising surfaces 5a, 5a reflect the parallel light incident from the back side of the screen toward the convex lens surfaces 4d, 4d on both sides of the lens portion 4, and the rising surfaces 5a, 5a.
The height of a, 5a, that is, the distance Δh from the upper end of the parabolic surface of the total reflection surface 5 to the top of the lens unit 3 (side edge of the convex lens surface 4d).
Is about 0.215 mm, and the rising angle θa of the rising surfaces 5a, 5a with respect to the surface of the screen body 1 is about 70 °.

FIG. 2 shows a light diffusing state of one lens unit 3 of the lenticular lens 2. Of the parallel light incident on the lens unit 3 from the back side of the screen, it is directly transmitted through the lens unit 4 at the top of the lens unit. The light to be reflected is refracted and diffused by each lens surface 4a, 4c, 4d of the lens portion 4 as shown in the figure. In addition, parabolic total reflection surfaces 5, 5 on both sides of the lens unit 3
Of the parallel light incident on, the light incident on the left total reflection surface 5 is reflected and condensed toward almost one point on the left straight surface 4b,
The light incident on the right total reflection surface 5 is reflected and condensed toward almost one point on the right straight surface 4b. Then, the total reflection surface 5,
The light reflected and condensed by 5 and incident on the linear surfaces 4b, 4b is refracted and diffused as shown in the drawing. Further, the parallel light incident on the rising surfaces 5a, 5a on the upper end side of the total reflection surfaces 5, 5 is
Convex lens surfaces formed on both side edges of the lens portion 4 by a and 5a
It is reflected toward 4d, 4d, transmitted through these convex lens surfaces 4d, 4d, and refracted and diffused as shown in the figure.

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 for diffusing the light that enters from the back surface and goes out to the front surface side are as described above. By making it a paraboloid, all the light reflected by the total reflection surfaces 5, 5 is condensed on the linear surfaces 4b, 4b formed in the central part of the lens portion 4, and the linear surfaces 4b, 4b, Since 4b is opposed to the total reflection surfaces 5 and 5, the light reflected by the total reflection surfaces 5 and 5 and incident on the linear surfaces 4b and 4b can be transmitted through the linear surfaces 4b and 4b without being reflected. And therefore according to this rear projection screen,
It is possible to brighten the screen by transmitting the light reflected toward the lens unit 4 to the screen surface side without loss by the total reflection surfaces 5 and 5 of each lens unit 3 and 3. In this embodiment, the parabolic total reflection surface 5,5 is a curved surface that focuses on the linear surfaces 4b, 4b is reflected by the parabolic total reflection surface 5,5. This is for maximizing the diffusion angle of the light on the straight surfaces 4b, 4b. Further, among the parallel light incident on the screen from the back side, the light incident on the linear surface 4b, 4b is an aspherical lens surface on the linear surface 4b depending on the inclination angle of the linear surface 4b.
It is reflected to the 4c side and further reflected to the back side of the screen by the aspherical lens surface 4c depending on the incident angle to the aspherical lens surface 4c, but the width (height) of the linear surfaces 4b and 4b is quite small. In addition, the loss of light due to the light reflection on the straight surfaces 4b, 4b is small, and compared with this loss of light, the total reflection surface 5,
Since the effect that all the reflected light from 5 is transmitted from the straight surfaces 4b, 4b to the screen surface side is much larger,
The loss of light due to the straight surfaces 4b, 4b can be ignored. Furthermore, in the above embodiment, since the convex lens surface 4a is formed between the straight surfaces 4b, 4b, when the screen is viewed from the front, the straight surfaces 4b, 4b are darkened due to reflection of incident parallel light. , Can be compensated for by light diffusion on the convex lens surface 4a.

Moreover, in the above-mentioned embodiment, the total reflection surface is provided on the upper end side of the total reflection surfaces 5, 5 on both sides of the lens unit 3, 3 of the lenticular lens 2.
Since the straight rising surfaces 5a, 5a that rise at a steeper angle than 5, 5a are formed, the upper end of the total reflection surface is the same as when the upper ends of the total reflection surfaces 5, 5 are directly connected to the lens unit 4. Light reflected from near to the side edge of the lens unit 4 does not enter the lens surface of the lens unit 4 from the direction of the angle of total reflection thereof and is not reflected by the lens surface in the rear direction of the screen. There is no light loss near both side edges of the lens unit 4. Further, in this embodiment, the lenticular lens 2
Since the portion between the central portion and both side edge portions of the lens unit 4 of the lens unit 3 of 3 is an aspherical lens surface 4c, 4c having a light diffusion angle larger than that of the spherical lens, the light is not reflected on the screen surface. The viewing angle can be increased by diffusing over a wide range.

Note that there are two types of projection devices, such as a rear projection type projector, which are a full-size image projection type that projects an image on a screen without enlarging it and a magnified image projection type that magnifies an image with a projection lens and projects it on the screen. In addition, any of the projection devices includes a vertical projection system that projects an image from a direction perpendicular to the screen surface and an oblique projection system that projects an image from a diagonal direction to the screen surface. However, in the case of a full-size image projection type and vertical projection type projection device, since the projection light from the projection source is parallel light perpendicular to the screen surface, this light may be directly incident on the screen. . Even if it is a full-scale image projection type, if it is an oblique projection method, light from the projection source (parallel light)
Is incident on the screen surface from an oblique direction, and in the case of a magnified image projection type projection device, the light from the projection source is incident on the screen while spreading, but in this case, the projection source is on the back side of the screen. Arrange a Fresnel lens that refracts the light from the parallel light perpendicular to the screen surface, or integrally form the Fresnel lens on the back surface of the screen, and pass the light from the projection source to the screen through the Fresnel lens. In the case of a magnified image projection type and an oblique projection type, a Fresnel lens that collimates the light that is incident while spreading is provided on the back side of the screen and the direction of the light with respect to the screen surface. Position the Fresnel lens to be vertical (though one Fresnel lens may be formed on the back of the screen) to block the light from the projection source. It may do it by entering the screen in the vertical parallel light to the lean side. This also applies to other embodiments described later.

FIGS. 3 and 4 show another embodiment of the present invention. In this embodiment, the lens portions 4, 4 of each lens unit 3, 3 of the lenticular lens 2 are arranged in the same manner as in the above embodiment. Forming a convex lens surface 4a and straight surfaces 4b, 4b in the central portion, and forming convex lens-shaped aspherical lens surfaces 4c, 4c on both sides,
The convex lens surfaces 4d, 4d are formed on both side edges, and the total reflection surfaces 5, 5 on both sides of each lens unit 3, 3 are used to direct parallel light incident from the back side of the screen to the straight surface 4 at the center of the lens portion.
It is formed on a parabolic surface that reflects and collects light toward b and 4b, and on the upper end side of the total reflection surfaces 5 and 5, a straight rising surface that rises at a steeper angle than the inclination angle of the total reflection surfaces 5 and 5. 5a is formed, and in this embodiment, the rising surfaces 5a, 5a are vertical surfaces that rise substantially perpendicular to the surface of the screen body 1, and the outer edge sides of the convex lens surfaces 4d, 4d on both sides of the lens portion are The surfaces are extended substantially horizontally to form horizontal planes 4e, 4e substantially perpendicular to the rising surfaces 5a, 5a. The dimensions w, h, Δw, Δh, R of each part of the lens units 3, 3 in this embodiment are the same as those in the above embodiment.

Also in the rear projection screen of this embodiment, the light that enters from the rear side and passes through the screen is diffused by the lenticular lens 2 on the screen surface as shown in FIG. Of the four, the light that passes through each lens surface 4a, 4c, 4d is refracted and diffused as shown in the figure, and the light that passes through the horizontal planes 4e, 4e at the outer edges is formed by the material of the screen (for example, acrylic resin) and air. It is refracted due to the difference in light refractive index. In this embodiment also, 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 to brighten the screen. Lens unit
Rising surfaces 5a, 5 that are almost vertical to the upper end side of the total reflection surfaces 5, 5 of 3, 3.
Since a is formed, it is possible to eliminate light loss near the side edge of the lens unit 4. The total reflection surface 5,5
Since the rising surfaces 5a, 5a on the upper end side of the screen cannot be a completely vertical surface due to die cutting in the molding of the screen, the rising surfaces 5a, 5a are slightly inclined, and therefore the rear surface side of the screen is The parallel light incident from the rising surfaces 5a, 5a toward the rising surfaces 5a, 5a is reflected by the rising surfaces 5a, 5a and enters near both side edges of the lens portion 4.
The light reflected by 5a and 5a is horizontal planes 4e and 4e at both edges of the lens.
Since it is incident on the horizontal plane 4e, 4e and penetrates,
The light reflected by a and 5a and incident on the side edge portion of the lens unit 4 is not reflected by the lens surface to cause a loss of light.

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 are incident light from the back side of the screen. May be a curved surface such as an elliptic surface as long as it is reflected and condensed toward the straight surfaces 4b, 4b in the center of the lens portion. Further, in the above embodiment, the screen is made of a transparent resin such as an acrylic resin, but this rear projection screen is made of a transparent resin mixed with light-diffusing fine particles or a transparent resin sheet having a light-diffusing layer formed on one surface. You may form.

〔The invention's effect〕

The rear projection screen of the present invention has a lenticular lens on the surface of the screen in which the central portion of the lens unit of each lens unit is recessed, and the left and right pair of left and right facing the total reflection surfaces on both sides of the lens unit are formed by both side surfaces of the recessed portion. Forming a linear emission surface of, of the total reflection surface of the both sides,
The total reflection surface on the left side is a curved surface that reflects and collects the incident light from the back side of the screen toward almost one point of the linear emission surface on the left side, and the total reflection surface on the right side is the incident light from the back side of the screen. Since it is a curved surface that reflects and focuses light toward almost one point on the right side of the linear emission surface, it is reflected by the total reflection surfaces on both sides of each lens unit of the lenticular lens toward the lens portion at the top of the lens unit. The light can be transmitted to the screen surface side without loss to brighten the screen. Moreover, according to the present invention, since the emission surface of the light reflected by the total reflection surface is a linear surface, the design of this emission surface is easy.

[Brief description of drawings]

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

Claims (1)

[Claims] 1. A rear projection screen for observing an optical image projected from the rear side from the front side, wherein a large number of lens units having lens parts on the top and total reflection surfaces on the left and right sides are continuous on the screen surface. A lenticular lens for forming a lenticular lens, and a concave portion is formed in the center of the lens portion of each lens unit of the lenticular lens, and a pair of left and right sides that face the total reflection surfaces on both sides of the lens unit are formed by the side surfaces of the concave portion. Of the two total reflection surfaces on both sides, the left total reflection surface reflects and condenses the incident light from the back side of the screen toward almost one point of the left linear emission surface. The right total reflection surface is a curved surface that reflects and condenses the incident light from the back side of the screen toward almost one point of the straight emission surface on the right side. Surface projection screen.