JPH0518749Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] 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 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 continuous lens units form a lenticular lens. This rear projection screen with lenticular lenses is designed so that light entering from the back side and emitted to the front side is diffused by the lenticular lenses on the screen surface.
It has the advantage that the viewing angle of the projected image is larger than that of a flat screen.

[Problem that the invention attempts to solve]

By the way, conventionally, a rear projection screen with a lenticular lens formed on its surface has a top part as a lens part and sloped surfaces on both sides as total reflection surfaces that reflect incident light from the back side of the screen toward the lens part. It is known that a lenticular lens with continuous lens units is formed on the screen surface, but in conventional rear projection screens, the lens part of each lens unit of the lenticular lens is formed on a single spherical lens surface. In order to make it a reality,
The light diffusion range in the lens part of each lens unit is small, so the viewing angle cannot be made very large.Furthermore, conventional rear projection screens have a total reflection surface on both sides of each lens unit of the lenticular lens. Since the sloped surface is directly connected to the lens part, the angle of incidence of the light reflected from near the top of the total reflection surface towards the side edge of the lens part to the lens surface is close to the total reflection angle. There is also a problem in that this light is reflected by the lens surface toward the back of the screen, resulting in light loss on both sides of the lens portion of each lens unit.

This idea was created in view of the above-mentioned circumstances, and its purpose is to widen the viewing angle by diffusing light that enters from the back side and exits to the front side over a wide range on the screen surface. To provide a rear projection screen that can brighten the screen by eliminating light loss on both sides of each lens unit of a lenticular lens.

[Means to solve problems]

This idea is based on a rear projection screen that allows an optical image projected from the back side to be observed from the front side.The screen surface has a lens section at the top and a total reflection surface at both sides, and the ratio between the width w and the height h. A large number of lens units having a relationship of approximately 3:1 to 3.55:1 form a continuous lenticular lens, and the lens portion of each lens unit of the lenticular lens has a concave lens surface at its center. year,
Both sides have a convex lens surface that is continuous with the concave lens surface, and the light reflected by the total reflection surface is configured to exit from the convex lens surface on the total reflection surface side, and The total reflection surface has a rising angle of approximately 60°, and the upper end side of the total reflection surface is a rising surface rising at an angle of approximately 68° to 90°.

[Effect]

In other words, the rear projection screen of this invention is
The lens portion of each lens unit of the lenticular lens that diffuses light entering from the back side of the screen and exiting to the front side of the screen has a shape with a concave lens surface in the center and convex lens surfaces continuous with the concave lens surface on both sides. By doing so, the light is diffused over a wide range by the concave lens surface and the convex lens surface, and the upper end side of the total reflection surface on both sides of the lens unit of the lenticular lens is adjusted to the angle of inclination of the total reflection surface. By creating a rising surface that rises at a steeper angle, the reflected light from any position on the total reflection surface will enter the lens section at an angle that will not be reflected by that lens surface, and this light will not be reflected by the lens surface. In this lenticular lens, the ratio of the width w to the height h of each lens unit is approximately 3:1 to 3.55:1, and the rise of the total reflection surface on both sides of each lens unit is approximately 3:1 to 3.55:1. The angle is approximately 60°,
The rising angle of the upper end of this total reflection surface should be approximately 68° or
Optimal characteristics can be obtained when the angle is 90°.

For this reason, this lenticular lens has a relatively gentle shape in which the lens height is kept low relative to the lens width, and therefore, it can be made by hot pressing, extrusion molding, or injection molding. Manufacturing is easy because the molded screen can be removed from the mold smoothly without applying excessive force to the lens.
Furthermore, since the unevenness of the lenticular lens surface is small, the lens surface is less likely to be damaged by rubbing against other objects, and therefore has a long life.

Furthermore, since it is configured so that the light reflected by the total reflection surface is emitted from the convex lens surface on the side of the total reflection surface,
The light reflected on the total reflection surface will not be totally reflected again on the concave lens portion, or will not pass through the concave lens portion and further enter the convex lens on the opposite side.

〔Example〕

An embodiment of this invention will be described below with reference to the drawings.

Figure 1 shows a part of the rear projection screen, where 1 is the screen body made of a transparent resin sheet such as acrylic resin, and a lenticular lens 2 is integrated over the entire surface of the screen, that is, the viewing surface. is formed. 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 linear lens units 3, 3 with minute widths in parallel, and each lens unit 3, 3 has a width (maximum width of the base) w, for example. 1.2mm, height h is 0.4mm
It is said that the dimensions are . Each lens unit 3,3
has a lens part 4 at its top and total reflection surfaces 5, 5 on both sides, and the lens part 4 at the top
has a shape with a concave lens surface 4a in the center and convex lens surfaces 4b, 4b continuous with the concave lens surface 4a on both sides. The radius of curvature Ra of the concave lens surface 4a is 0.3 mm, and the radius of curvature Rb of the convex lens surfaces 4b, 4b is 0.58 mm.
4b is a curved surface whose apex is the outer edge of the lens portion. Further, total reflection surfaces 5, 5 on both sides of each lens unit 3, 3 reflect parallel light incident from the back side of the screen to convex lens surfaces 4b on both sides of the lens section 4,
It is an inclined surface rising at an angle θ of approximately 61° with respect to one surface of the screen body so as to reflect the light toward the surface of the screen body 4b. The straight rising surfaces 5a, 5a are substantially perpendicular to the surface. The height of the rising surfaces 5a, 5a, that is, from the upper end of the slope of the total reflection surface 5 to the top of the lens unit 3 (side edge of the lens surface 4)
The distance Δh is approximately 0.125 mm.

FIG. 2 shows the light diffusion state of one lens unit 3 of the lenticular lens 2. Among the parallel light incident on the lens unit 3 from the back side of the screen, it is directly reflected by the lens part 3 at the top of the lens unit. As shown in the figure, the light passing through is refracted and diffused by the concave lens surface 4a and convex lens surfaces 4b, 4b of this lens unit 4, and the parallel light incident on the inclined total reflection surfaces 5, 5 on both sides of the lens unit 3 is , the convex lens surfaces 4b, 4b of the lens portion 4 due to the total reflection surfaces 5, 5.
The light is reflected toward the convex lens surfaces 4b, 4b, and is refracted and diffused by the convex lens surfaces 4b, 4b as shown.

Therefore, in the above rear projection screen, the lens portions 4 of each lens unit 3, 3 of the lenticular lens 2 formed on the screen surface have a concave lens surface 4a at the center, and convex lenses continuous with the concave lens surfaces 4a on both sides. Since the surfaces 4b and 4b are shaped, the light that enters from the back side of the screen and exits to the front side can be diffused over a wide range by the concave lens surface 4a and the convex lens surfaces 4b, 4b. The viewing angle can be increased. Furthermore, in this rear projection screen, the upper end sides of the total reflection surfaces 5, 5 on both sides of the lens units 3, 3 of the lenticular lens 2 are made to stand up almost perpendicularly to one surface of the screen body. Therefore, light can be transmitted throughout the lens portions of the lens units 3, 3 without loss, and the screen can be brightened. That is, for example, lens unit 3,
If the upper ends of the total reflection surfaces 5, 5 on both sides of 3 directly connect the convex lens surfaces 4b, 4b of the lens part 4 as sloped surfaces, the convex lens surfaces 4b, 4b from near the upper ends of the total reflection surfaces 5, 5, A convex lens surface 4b that reflects light toward the side edge portion that is a horizontal surface,
4b approaches the total reflection angle, and this light is reflected toward the back of the screen by the convex lens surfaces 4b, 4b, resulting in light loss near both side edges of the lens portion 4. However, in the above example If the upper ends of the total reflection surfaces 5, 5 are made to stand up almost vertically as shown in FIG. This light can be made incident on the area and transmitted without being reflected by the convex lens surfaces 4b, 4b. Incidentally, the rising surfaces 5a, 5a on the upper end side of the total reflection surfaces 5, 5 are as follows:
These rising surfaces 5a, 5a are slightly tilted because they cannot be perfectly vertical due to die cutting during molding of the screen, and therefore, the rising surfaces 5a, 5a are tilted slightly from the back side of the screen to the rising surfaces 5a, 5a. The incident parallel light passes through these rising surfaces 5a, 5.
a and enters the vicinity of the side edges of the convex lens surfaces 4b, 4b, but since the rising surfaces 5a, 5a are steeper than the angle of inclination of the inclined total reflection surfaces 5, 5, this rising surface Since the angle of incidence of the light reflected by 5a, 5a on convex lens surfaces 4b, 4b is an angle that does not cause total internal reflection, the light is reflected by rising surfaces 5a, 5a and enters near the side edges of convex lens surfaces 4b, 4b. Light is not reflected by the convex lens surfaces 4b, 4b and no light loss occurs.

Note that there are two types of projection devices, such as rear projection projectors: 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. . Furthermore, even if it is a full-size image projection type, in the case of an oblique projection type, the light (parallel light) from the projection source enters the screen surface from an oblique direction, and in the case of an enlarged image projection type projection device, In this case, a Fresnel lens is placed on the back side of the screen to refract the light from the projection source into parallel light perpendicular to the screen surface, or The Fresnel lens described above may be integrally formed on the back surface of the screen, and the light from the projection source may be incident on the screen through the Fresnel lens.Furthermore, in the case of an enlarged image projection type and an oblique projection method, the rear surface of the screen may be used. On the side, there is a Fresnel lens that transforms the incident light into parallel light while another Fresnel lens that directs the light direction perpendicular to the screen surface (however, one Fresnel lens is formed on the back of the screen). The light from the projection source may be made into parallel light perpendicular to the screen surface and then incident on the screen. This also applies to other embodiments described later.

FIG. 3 and FIG. 4 show another embodiment of this invention, in which the lens parts 4, 4 of each lens unit 3, 3 of the lenticular lens 2 are
is shaped like the above embodiment, with a concave lens surface 4a in the center and convex lens surfaces 4b, 4b continuous with the concave lens surface 4a on both sides, and the upper ends of the inclined total reflection surfaces 5, 5 of the lens units 3, 3. The rising surfaces 5a, 5a formed on the sides are formed as inclined total reflection surfaces 5, 5.
The angle θa (for example, about 61°) is steeper than the inclination angle θ (about 61°).
68°), this rising surface 5a,
5a as well, the incident light is actively reflected toward the convex lens surfaces 4b, 4b of the lens portion 4 as shown in FIG. 4, and this embodiment is similar to the above embodiment. effect can be obtained. In addition, in FIG. 3, lens units 3, 3
The width w is 1.33 mm, the height h is 0.375 mm, the radius of curvature Ra of the concave lens surface 4a is 0.3 mm, the radius of curvature Rb of the convex lens surfaces 4b, 4b is 0.58 mm, and the upper end of the inclined total reflection surfaces 5, 5. The height Δh of the side rising surfaces 5a, 5a is 0.125 mm. In addition, a rising surface 5 formed on the upper end side of the total reflection surfaces 5, 5 of the lens units 3, 3.
The rising angles of a and 5a may be selected according to the arrangement pitch of the lens units 3, 3 and the width of the lens part at the top of the lens units 3, 3. For example, if the arrangement pitch of the lens units 3, 3 is made small and the lens If the width of the part is to be sufficiently large, the rising angles of the rising surfaces 5a, 5a may be made close to vertical.

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

[Effect of idea]

The rear projection screen of this invention is formed by forming a lenticular lens in which a large number of consecutive lens units are formed on the screen surface, and the lens portion of each lens unit of the lenticular lens has a concave lens surface at the center; Both sides have a convex lens surface that is continuous with the concave lens surface, and the light reflected by the total reflection surface is configured to exit from the convex lens surface on the total reflection surface side, and Since the upper end of the total reflection surface is a rising surface that rises at a steeper angle than the inclination angle of the total reflection surface, light that enters from the back side and exits to the front side is diffused over a wide range on the screen surface. In addition, the viewing angle can be increased by increasing the viewing angle, and the screen can be brightened by eliminating light loss on both sides of each lens unit of the lenticular lens.

Furthermore, in this invention, the ratio of the width w to the height h of each lens unit is approximately 3:1 to 3.55:
1. The rising angle of the total reflection surfaces on both sides of each lens unit is approximately 60°, and the top end of this total reflection surface is 68°.
Since the rising surface rises at a rising angle of 90°, the shape of each lens unit is a relatively gentle shape with a low lens height relative to the lens width. Manufacturing is easy because the lens can be smoothly removed from the mold without applying excessive force to the lens.Also, since the unevenness of the lenticular lens surface is small, it can be easily removed from the mold by rubbing against other objects. Since the lens surface is less likely to be damaged, it has the effect of a longer lifespan.

[Brief explanation of drawings]

1 and 2 are perspective views of a portion of a rear projection screen showing one embodiment of this invention, and FIG.
FIGS. 3 and 4 are perspective views of a portion of a rear projection screen and diagrams of light diffusion of one lens unit, respectively, showing other embodiments of the present invention. 1... Screen body, 2... Lenticular lens, 3... Lens unit, 4... Lens section, 4
a...Concave lens surface, 4b...Convex lens surface, 5...
Total reflection surface, 5a... rising surface.

Claims (1)

[Scope of utility model registration request] It is a rear projection screen that allows an optical image projected from the rear side to be observed from the front side, and the screen surface has a lens section at the top and total reflection surfaces at both sides, and the ratio of width w to height h is approximately 3. :1 to 3.55:
A large number of lens units having a relationship of 1 form a continuous lenticular lens, and the lens portion of each lens unit of the lenticular lens is
The center is a concave lens surface, and both sides are convex lens surfaces continuous with the concave lens surface, and the light reflected by the total reflection surface is configured to exit from the convex lens surface on the total reflection surface side, The rising angle of the total reflection surfaces on both sides of each lens unit is approximately 60°, and the upper end of this total reflection surface is approximately 60 degrees.
A rear projection screen characterized by having a rising surface rising at an angle of 68° to 90°.