JPS6115104A - Optical diffuser - Google Patents

Abstract

PURPOSE:To realize easily a surface illumination whose luminance is nearly uniform by forming a stepped part by superposing plural pieces of optical transmission bodies having a light incident end and a light emitting end, and also providing an optical diffusion plate so as to cover the stepped part. CONSTITUTION:A stepped part 4 is formed by superposing plural pieces of transparent plate-shaped bodies 2 of 0.5mm. thick having a light incident end face 6 and a light emitting end face 3, and fixed by an adhesive agent. On the upper part of this stepped part 4, an optical diffusion plate 11 is placed, and a light source 13 such as a long-sized fluorescent lamp, etc. is placed along the light incident end face 6 of an optical diffuser 1. The light which is made incident on the plate-shaped body 2 repeats a reflection and is emitted from the end face 3, and thereafter, subjected to a reflection or refraction by a prism 12 and emitted from the diffusion plate 11. Therefore, when a light of an equivalent quantity is made incident from the end face 6, an equivalent quantity is emitted, and even if a length of the plate-shaped body 2 is different, a surface illumination whose luminance is roughly uniform can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a light diffuser used as a surface illumination device.

BACKGROUND OF THE INVENTION Conventional surface illumination devices are widely used in large formats as billboards and various display devices, and in small formats as display devices for various devices and liquid crystal watches. Among these lighting devices, large signboards and display devices are illuminated by a large number of fluorescent lamps, which are line light sources, or incandescent lamps, which are point light sources, on the back of a light diffuser plate. It was common.

However, in order to make the illumination intensity (brightness) uniform in such a surface lighting device, it is necessary to considerably increase the distance between the light diffuser plate and the light source, or to arrange a large number of light sources densely. be. For this reason, the device becomes larger, the number of light sources increases, and it is necessary to design the device each time according to the size of the light emitting surface, resulting in high prices and low power consumption. There were problems such as increased maintenance costs.

In order to improve this point, a proposal has already been made to use a single light guide plate to guide light from its side edge, thereby obtaining surface illumination, and some have put it into practical use.

When such a light guide plate is used, substantially uniform area illumination can be obtained when the light introduced from the light source is parallel to the reflective surface of the light guide plate. However, since the light from the light source actually spreads radially, a large amount of light is emitted from the light guide plate near the light source, and a small amount of light is emitted from the light guide plate at a position away from the light source.

For this reason, there was a problem in that the amount of light decreased as the distance from the light source increased, making it impossible to obtain uniform surface illumination.

Furthermore, in order to solve these problems, attempts were made to make the distribution of the emitted light as uniform as possible by applying reflective processing, roughening the back side of a single light guide plate, or designing it into a special curved shape. Attempts are being made to do so.

However, even with these methods, there remain problems such as the need to design the device each time depending on the size of the light emitting surface, and it is difficult to say that these methods are necessarily satisfactory.

Purpose of the Invention In view of the above-mentioned problems, the present invention makes it possible to easily obtain surface illumination with approximately uniform brightness and direction of emitted light, and to perform individual optical design for surface illumination of various sizes. The objective is to provide a light diffuser that can be obtained without

Structure of the Invention In the light diffuser according to the present invention, a plurality of light transmitting bodies each having a light incident end face and a light emitting end face are arranged so as to form a staircase portion by the light emitting end face, and a light diffusing plate It is arranged so as to cover the stairs.

Embodiments Hereinafter, first and second embodiments of the present invention will be described with reference to FIGS. 1 to 3.

1 and 2 show a first embodiment of the invention. In the light diffuser 1 of this embodiment, a large number of transparent and homogeneous plate-like bodies 2 (thickness 0.5
mm) are arranged in a layered manner so as to form a stepped portion 4 by the light emitting end surface 3 which is one end surface of each, and
They are fixed to each other by adhesive (not shown) applied to both side end surfaces 5.

The light output end surface 3 is perpendicular to the spreading surface of the plate-like body 2, while the other end face, the light-incidence end face 6, is perpendicular to the spreading surface of the plate-like body 2.
are inclined with respect to the widening surface of the surface, and are flush with each other. Therefore, the light output end faces 3 and the light input end faces 6 have the same area.

Note that it is desirable that both of these end surfaces 3 and 6 be mirror-finished.

Each staircase portion 4 is covered with a light diffusing plate 11. The light diffusing plate 11 has triangular prisms 12 arranged in a plate shape.
and the light emitting end surface 3 are arranged so as to be parallel to each other.

In the light diffuser 1 as described above, when a long light source 13 such as a fluorescent lamp is arranged along the light entrance end surface 6, the light entrance end surface 6
The light incident on the plate-like body 2 travels through the plate-like body 2 in the direction of the arrow in FIG. 2 and exits from the light-emitting end surface 3. At this time, light parallel to the layered surface travels straight, and light inclined to the layered surface is repeatedly reflected by the opposing layered surface and reaches the light emitting end surface 3.

A part of the light emitted from the light emitting end surface 3 is directly transmitted to the light diffusing plate 1.
1, and the other part reaches the light diffusing plate 11 after being reflected by the surface 7 of the plate-like body 2 arranged so as to be continuous with the light emitting end face 3. The light reaching the light diffusing plate 11 is reflected and refracted by the prism 12 and then exits from the light diffusing plate 11.

Although FIG. 2 shows the traveling state of light only for one plate-like body 2, the same applies to other plate-like bodies 2.

As described above, in the light diffuser 1, a plurality of transparent plate-like bodies 2 are arranged in layers, so that not only light parallel to the layer plane but also light oblique to the layer plane is detected. The light reaches the light emitting end face 3 of the plate-like body 2. In other words, if an equal amount of light is incident on each plate-shaped body 2 from the light input end surface 6, approximately the same amount of light will be emitted from any of the light output end surfaces 3 whose distances from the light input end surface 6 are different from each other. Since the light is emitted, surface illumination with approximately uniform brightness can be obtained.

In addition, if each staircase part 4 is in a constant pinch, the light diffusing plate 11
The amounts of light reaching the portions corresponding to the respective staircase portions 4 are also approximately equal to each other, making it possible to obtain surface illumination with even more uniform brightness.

Further, the traveling direction of the light emitted from the light emitting end face 3 is biased toward the direction in which the plate-like body 2 spreads, but in the light diffuser 1, the step portion 4 of the plate-like body 20 is covered with the light diffusing plate 11. Therefore, the light emitted from the light emitting end surface 3 is transmitted to the light diffusing plate 11.
spread by.

Therefore, the light emitted from the light diffusing plate 11 has little directionality,
It is possible to obtain surface illumination in which the direction of the emitted light is approximately uniform.

In addition, the light diffuser 1 includes a plurality of plate-like bodies 2 arranged in a layered manner so that a staircase section 4 is formed by the light emitting end surface 3.
Since the light diffusing plate 11 can be disposed so as to cover the light diffusing plate 11, no special processing is required and manufacturing is easy.

Note that in the light diffuser 1, the light entrance end surface 6 is an inclined surface, but as shown by the dashed line in FIG. If this is done, it is sufficient to simply arrange the rectangular plate-like bodies 2 in a layered manner, which further facilitates production.

In addition, in the light diffuser 1, the staircase portion 4 is
Therefore, by simply changing the pitch of the staircase portion 4, surface illumination of various sizes can be obtained without performing individual optical design.

In other words, if the stairway portion 4 is widened, the light emitting end faces 3 are further spaced apart from each other, so that large area illumination can be obtained with a small number of light sources. On the other hand, if the pitch of the staircase part 4 is reduced,
Although the magnification ratio is small, surface illumination with more uniform brightness can be obtained. In addition, in order to obtain surface illumination with even more uniform brightness,
The plate-like body 2 may be made thinner.

FIG. 3 shows a second embodiment of the invention.

In the light diffuser 14 of this embodiment, the light diffuser plate 11 is further covered with a milky white light diffuser plate 15, and the light incident end face 6 is covered with a plano-convex cylindrical lens 16 made of a translucent material. 1 shown in FIGS. 1 and 2, except that
It may have substantially the same configuration as the light diffuser 1 of the embodiment.

In such a light diffuser 14, since the boundary line between the light emitting end face 3 and the surface 7 can be erased by the milky white light diffuser plate 15, more uniform area illumination can be obtained.

Further, in the light diffuser 14, light from the light source 13 is transmitted to the lens 16.
Since the light is condensed by and effectively enters each plate-like body 2, an efficient surface illumination device can be provided.

Although the present invention has been described above based on the first and second embodiments, it goes without saying that the present invention is not limited to these embodiments.

For example, in any of the above embodiments, the transparent plate-like body 2
Although the plates are directly arranged in a layered manner, a substance having a lower refractive index than the plate-shaped bodies 2, such as air, water, resin, or oligomer, is interposed between the plate-shaped bodies 2. may be arranged in layers. In that case, the light incident on the layered surface at an angle equal to or greater than the critical angle of total reflection reaches the light output end face 3 without external leakage, so the distance from the light input end face 6 to the light output end face 3 is long. Also, there is less reduction in the amount of light, and more uniform surface illumination can be obtained.

Further, by applying an adhesive having a refractive index lower than that of the plate-like bodies 2 to the entire layered surface, the plate-like bodies 2 can be more firmly fixed to each other.

In addition, if a metal vapor deposited film such as ^1 is interposed between the plate-like bodies 2, all of the light that is inclined with respect to the layer plane will be reflected regardless of the angle of incidence on the layer plane. Since the light reaches the light emitting end face 3 without any external leakage, more uniform surface illumination can be obtained.

Further, in each of the above embodiments, a homogeneous plate made of polymethyl methacrylate was used as each plate 2, but instead of arranging the plate 2 in layers, a large number of optical fibers were used. may be arranged vertically and horizontally, or so-called optical sheets on which optical waveguides are formed may be arranged in layers. In that case, the light entering the optical fiber or guide waveguide is confined within these optical fibers or optical waveguides,
Since the light reaches the light output end face 3 with almost no external leakage, even if the distance from the light input end face 6 to the light output end face 3 is long, there is almost no decrease in the amount of light, and more uniform surface illumination can be obtained.

Further, the homogeneous plate-like body 2 does not need to be made of polymethyl methacrylate, and may be made of either an inorganic material or an organic material as long as it has translucency.

Further, the light diffusing plate 11 is not limited to the prism 12, and may be made of other optical elements that diffuse light.

The light diffuser according to the present invention as described above can be applied to display signboards, displays, design surface lighting, liquid crystal bank lights, and the like.

Effects of the Invention As mentioned above, the light diffuser according to the present invention has: Since the number of light transmitting members jf is arranged so that light is transmitted from each light input end face to the light output end face, surface illumination with approximately uniform brightness can be obtained.

Furthermore, in the light diffuser according to the present invention, the step portion formed by the light output end face of the light transmitting body is covered with the light diffusion plate, so that the light emitted from the light output end face is diffused by the light diffusion plate. , it is possible to obtain surface illumination in which the direction of the emitted light is approximately uniform.

In addition, the light diffuser according to the present invention can be manufactured by arranging a plurality of light transmitting bodies so as to form a staircase part with the light emitting end face, and disposing a light diffusing plate so as to cover the staircase part. No processing is required and manufacturing is easy.

In addition, in the light diffuser according to the present invention, since the staircase part is formed by the light output end face of the light transmitting body, it is possible to easily change the pinch of the staircase part without having to perform an individual optical design. Area illumination of various sizes can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic enlarged side view showing the first embodiment of the present invention, FIG. 2 is a schematic perspective view showing the first embodiment with the light diffusing plate removed, and FIG. FIG. 3 is a schematic side view showing a second embodiment of the present invention. In addition, in the symbols used in the drawings, 1.14−−−−−−−−−−・Light diffuser 2−−−−
----------Plate body 3--------- Binary output end face 4 ------- Single step part 6------ Binary entrance end face 11--- ---Two-dimensional diffuser plate 15-----Light diffuser plate 16-----One plano-convex cylindrical lens.

Claims (1)

[Scope of Claims] 1. A plurality of light transmitting bodies each having a light incident end face and a light emitting end face and arranged so as to form a staircase portion by the light exit end face, and a structure that covers the staircase portion. A light diffuser comprising a light diffuser plate disposed on each of the light diffusers. 2. The light diffuser according to claim 1, wherein the light transmitting body is a homogeneous plate-like body having translucency. 3. The light diffuser according to claim 2, wherein a substance having a lower refractive index than the plate-like bodies is interposed between the plurality of plate-like bodies. 4. The light diffuser according to claim 2, wherein a metal vapor deposited film is interposed between the plurality of plate-like bodies. 5. The light diffuser according to claim 1, wherein the light transmission body is an optical fiber. 6. The light diffuser according to claim 1, wherein the light transmission body is an optical sheet having an optical waveguide formed therein. 7. Claims 1 to 7, characterized in that the light diffusing plate is further covered with another milky white light diffusing plate.
The light diffuser according to any one of item 6. 8. The light diffuser according to any one of claims 1 to 7, characterized in that a condenser lens body is disposed near the light incident end face.