JPH03278027A - Illuminator - Google Patents

Abstract

PURPOSE:To obtain an illuminator that the use efficiency of light is high without using a complicated means by providing a light source and a transparent body having micro prism structure and outputting the light emitted from the light source through the transparent body. CONSTITUTION:The illuminator is constituted of the light source 101 and the transparent body 103 having the micro prism structure. Then, the light emitted from the light source 101 is condensed by a lens 102 and made to be incident almost perpendicularly on the transparent body 103 having the fine prism structure. At this time, the light is bent almost at a right angle by the action of the fine prism structure 106 and emitted from the transparent body 103. Thereafter, it is condensed by a lens 104 and it arrives at a substance to be illuminated 105. Thus, the illuminator having the use efficiency of light which is almost double in comparison with conventional practice is obtained by the simple means.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an illumination device suitable for use in overhead projectors, liquid 8 color projectors, and the like.

[Summary of the invention]

Conventionally known lighting devices consist of a combination of a concave mirror and a convex lens, so it is difficult to efficiently guide the luminous flux from a planar light-emitting area to an illuminated object using lenses and mirrors alone. Also. Considering that when used in liquid crystal projectors, etc., there was a problem that only one polarized light component could be used, resulting in darkness. The present invention provides an illumination device including a light source and a micro prism structure. Furthermore, in the present invention, by arranging the polarization splitting element, the local wavelength plate, and the mirror between these two, it is possible to realize a highly efficient and bright illumination device. The lighting device according to the present invention is particularly suitable for application to a projection display device. By implementing the present invention, not only can rectangular samples be efficiently illuminated, but also it can be used as a means of polarization synthesis. [Prior art] The configuration of a conventional lighting device is shown in Fig. 4 (A) and Fig. 4 (B).
), where FIG. 4(A) shows a concave mirror 401
This structure is a combination of a convex lens 402 and a convex lens 402. A light source 403 is located at the center of these (focal position). [Problems to be Solved by the Invention] However, conventional lighting devices have a problem of low light utilization efficiency. This makes it difficult to use for display purposes. The reason for this low light utilization efficiency is that lenses and mirrors alone cannot efficiently convert the luminous flux emitted from a light source with a planar light emitting area (for example, a white discharge lamp).
This is because it is difficult to guide the light to the object to be illuminated. Furthermore, for applications where one polarization component is not used, such as a liquid crystal projector, the present invention is intended to solve these problems, and its purpose is to The object of the present invention is to provide a lighting device with high utilization efficiency.

[Means for Solving the Problems] A first lighting device of the present invention is characterized by comprising a light source and a transparent body having a micro prism structure. In the second lighting device of the present invention, the shape of the transparent body having the micro prism structure is approximately a triangular prism, and one of the five horizontal sides forming the triangular prism has the micro prism structure; The light source is characterized in that one of the two planes whose surface normal line is in the same plane as the plane having the microprism structure faces the light source. A third lighting device of the present invention is characterized in that, in the first or second lighting device, a polarization splitting element, a half-wave plate, and a mirror are provided in the middle of the optical path from the light source to the transparent body having the micro prism structure. is characterized in that the half-wave plate and the mirror are arranged on the same optical path. A fourth lighting device of the present invention is characterized in that, in the first or second lighting device, a polarization splitting element, a half-wave plate, and a mirror are provided in the middle of the optical path from the light source to the transparent body having the micro prism structure. is characterized in that the half-wave plate and the mirror are arranged on different optical paths. A fifth lighting device of the present invention is characterized in that, in any one of the first to fourth lighting devices, the light source is composed of a plurality of light sources arranged two-dimensionally. A sixth lighting device of the present invention is any one of the first to fifth lighting devices, and is characterized in that it is used to illuminate a light bubble in a projection display device having a light bubble. [Examples] Hereinafter, the content of the present invention will be explained in detail based on Examples. FIG. 1(A) and FIG. 1(B) show an embodiment of the present invention. FIG. 1(A) and FIG. 1(B) are perspective views of one lighting device viewed from different directions. Light emitted from a light source 101 is condensed by a lens 102 and almost perpendicularly enters a transparent body 103 having a micro prism structure. Then, due to the action of the micro prism structure 106, the light is bent at a nearly right angle and exits from the transparent body 103. Thereafter, the light is focused by the lens 104 and
Reaching 05. The shape of the transparent body 103 is approximately a triangular prism,
Surface 103a and surface 103b are perpendicular to each other. Note that instead of the lens 102, an aspherical mirror is used as the light source 1.
It can also be used after 01. Further, the lens 104 is not necessarily required, and a Fresnel lens formed on the light emitting surface of the transparent body 103 may be used instead. FIG. 3 shows a micro prism structure 10 that the transparent body 103 has.
6 is shown. The apex angle of the transparent body 103 is a, and the angle that the incident light ray 301 and the outgoing light ray 302 make with respect to the normal 303 of the surface having the micro prism structure 106 is θ1, respectively.
．． Let θ be [Figure 3 (A)], and let β be the apex angle of the microprism, p be the period, and h be the height [Figure 3 (B)]
. The incident light ray 301 is totally reflected on the micro prism surface and becomes the output light ray 302. For these to be orthogonal. The apex angle β of the micro prism can be given by the following equation. β: π/4-a (1) From equation (1), the relationship between the height h and the period p of the micro prism is given by the following equation. h=ptan(x/4-a)-(2) Furthermore, the area ratio r between the bundle of incident light rays 301 and the bundle of output light rays is given by the following equation. r=cosθ, /cosθ+=tanα...(3
) If the shape of the illuminated object 105 is rectangular in FIG. 1,
If the area ratio r in equation (3) is small (taken), efficient illumination can be achieved.To do this, the apex angle a of the transparent body can be made small.Once the apex angle α of the transparent body is determined, the micro prism The apex angle β is determined from equation (1). The period p of the microprism is determined so that the influence of shadows is not large and the influence of diffraction is large. Depending on the emission conditions, a highly reflective metal film or dielectric film is formed on the interface 304 between the transparent body and the surroundings (air). By using a transparent body with such a micro prism structure, the light emitted from the light source Light can be efficiently guided to the object to be illuminated. Fig. 2 shows another embodiment of the present invention. Fig. 2 (A) and Fig. 2 (B) respectively show illumination with different configurations. Fig. 2 is a perspective view of the apparatus.
It is divided into two linearly polarized lights. One of these polarized lights passes through a half-wave plate 202 and a mirror 203, and then
The light enters a transparent body 103 having a micro prism structure. The other polarized light enters the transparent body 103 as it is. Both lights are bent almost perpendicularly to the direction of incidence by the action of the micro prism structure, and are reflected in the transparent body 103.
Emits more light. At this time, the polarization directions of the two linearly polarized lights are the same. Thereafter, the light is focused by the lens 104 and reaches the object 105 to be illuminated. The shape and structure of the transparent body 103 are the same as those shown in FIG. In Figure 2 (B), the arrangement of each element is as shown in Figure 2 (A).
different from. However, the basic function of converting the irregularly polarized light emitted from the light source 101 into linearly polarized light is shown in Figure 2 (
The same is true for ^). When such a lighting device is used in an application that utilizes linearly polarized light, such as a liquid crystal projector, it can provide about twice the brightness as compared to the conventional technology (see FIG. 4). Note that although the embodiment has been described here with respect to a single light source, similar effects can be obtained even in the case of a plurality of light sources arranged two-dimensionally.

【Effect of the invention】

As described above, according to the lighting device to which the present invention is applied, it is possible to achieve light utilization efficiency approximately twice as high as that of the conventional method using extremely simple means.

[Brief explanation of the drawing]

1(A) and 1(B) are perspective views of a lighting device according to one embodiment of the present invention, and FIG. 2(A) and FIG. 2(B) are respectively according to another embodiment of the present invention. 3(A) and 3(B) are perspective views of the lighting device, and FIG. 4(A) and FIG. (B) is a plan view of each conventional lighting device. 101... Light source, 102... Lens, 103... Transparent body, 103B... Surface, 103b... Surface, 104... Lens, 105... Illuminated object, 106... Minute Prism structure. 201... Polarizing beam splitter, 2θ2... Half wavelength plate, 203... Mirror 210... Undefined polarization, 211... Polarized light, 212... Polarized light, 301... Incident light beam, 302... Outgoing ray, 303... Normal to surface, 304... Interface, 401... Concave mirror 402... Convex lens. 403... Light source, 404... Elliptical mirror Figure (B) Figure (A) Figure 2 <8> σ Figure 3 (8) 03 Figure (8) 401: Concave mirror 402: Convex lens

Claims (1)

Claims: 1) An illumination device comprising a light source and a transparent body having a micro prism structure, and outputting light emitted from the light source through the transparent body. 2) The shape of the transparent body having the micro prism structure is approximately a triangular prism, and one of the five horizontal planes forming the triangular prism has the micro prism structure, and a flat surface having the micro prism structure. The lighting device according to claim 1, wherein one of the two planes whose surface normals lie within the same plane faces the light source. 3) A polarization separation element, a 1/2 wavelength plate, and a mirror are placed in the middle of the optical path from the light source to the transparent body having the micro prism structure, and the 1/2 wavelength plate and the mirror are placed on the same optical path. The lighting device according to claim 1 or 2, characterized in that the lighting device is arranged as follows. 4) A polarization separation element, a half-wave plate, and a mirror are placed in the middle of the optical path from the light source to the transparent body having the micro-prism structure, and the half-wave plate and the mirror are placed on different optical paths. The lighting device according to claim 1 or 2, characterized in that the lighting device is arranged as follows. 5) The lighting device according to claim 1, wherein a plurality of two-dimensionally arranged light sources are used as the light source. 6) The lighting device according to claim 1, wherein the light output from the transparent body is used to illuminate a light bubble of a projection display device.