JPH08106009A - Light guide for illumination - Google Patents

Abstract

PURPOSE: To improve the reflection efficiency at a reflection surface and to brighten the ray arriving at an objective surface by forming an inclination on an incident surface in order to collimate the ray arriving at the reflection surface from the incident surface to approximately parallel rays. CONSTITUTION: This light guide 2 has the incident surface 21 which is formed of a transparent acrylic resin and receives the ray L1 from a light source 1, the reflection surface 22 which totally reflects the ray L2 from the incident surface 21 and the objective surface 23 which irradiates the ray L3 reflected by the reflection surface 22 to an illuminating object 3, such as switch or nameplate of instruments. The inclined part 21a is formed on the side further from the light source 1 of the incident surface 21. The angle d[ deg.] of the inclined part 21a is set at an angle at which the ray L2 arriving at the reflection surface 22 from the incident surface 21 can be collimated to the approximately parallel rays. As a result, the incident angle θ3 of the ray L2 with the reflection surface 22 attains the critical angle θ0 (about 42 [ deg.[) or above and the rate at which the ray L2 is totally reflected at the reflection surface 22 is increased. The ray L3 arriving at the objective surface 23 is thus brightened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a light guide for illumination, and more particularly, to improve the shape of the incident surface so that the light rays from the incident surface to the reflective surface of the light guide are made parallel.

[0002]

2. Description of the Related Art A conventional light guide 20 of this type has a structure shown in FIG. That is, the conventional light guide 20 has an incident surface 210 that receives the light rays L1 and L1 ′ from the light source 1 and light rays L2 and L2 ′ from the incident surface 210.
And a target surface 230 that irradiates a light ray L3 reflected by the reflection surface 220 toward an illumination target.

The light guide 20 is generally formed by molding a transparent acrylic resin. This acrylic resin has a so-called critical angle θ0 at which the light ray L2 starts total reflection on the reflecting surface 220, which is about 42 degrees. Therefore, the incident angle θ1 formed by the normal line K perpendicular to the reflecting surface 220 and the light ray L2 from the incident surface 210 is defined as the critical angle θ0 (about 4).
By setting it to 2 [degrees] or more, the light ray L2 can be totally reflected by the reflecting surface 220. Normally, the incident angle θ1 is set to 45 degrees. Incidentally, this type of technology is disclosed in Japanese Patent Publication No. 4-78124.

[0004]

However, in the above-described conventional light guide 20, the light ray L1 'obliquely incident on the incident surface 210 is reflected by the side surface 240 of the light guide 20. The reflected light ray L2 ′ is incident on the reflecting surface 220 at a relatively small incident angle θ2,
When incident at an incident angle θ2 that satisfies the relationship of incident angle θ2 <critical angle θ0 (about 42 [degrees]), the light ray L2 ′ is reflected by the reflecting surface 2
No total internal reflection at 20. Therefore, the reflection efficiency at the reflecting surface 220 becomes poor, and the light ray L3 reaching the objective surface 230 is reached.
There was a problem that it became dark.

[0005]

The present invention is to solve the above-mentioned problems, and by devising the shape of the incident surface to make the light rays from the incident surface to the reflective surface of the light guide parallel rays, The purpose is to improve the reflection efficiency on the reflecting surface and to make the light rays reaching the objective surface bright.

In order to achieve the above object, the present invention provides
In an illumination light guide having an incident surface for receiving a light ray from a light source, a reflecting surface for totally reflecting the light ray from the incident surface, and an objective surface for irradiating the light ray reflected by the reflecting surface toward an illumination target. , An illumination light guide is provided, wherein the incident surface has an inclination that makes the light rays substantially parallel rays.

Further, in the above invention, the light guide for illumination is provided, wherein the incident surface has an inclined portion on the side far from the light source.

Also, in the above invention, there is provided an illumination light guide in which the incident surface has a shape of a convex lens.

Also, in the above invention, there is provided an illumination light guide in which the incident surface has a shape of a Fresnel lens.

[0010]

[First Embodiment] A first embodiment of the present invention will be described with reference to FIG. The light guide 2 of the first embodiment is formed by molding a transparent acrylic resin, and has an incident surface 21 that receives the light ray L1 from the light source 1 and a reflecting surface 22 that totally reflects the light ray L2 from the incident surface 21. And an objective surface 23 for irradiating the light ray L3 reflected by the reflecting surface 22 toward the illumination target 3 such as a switch or a nameplate of instruments.

An inclined portion 21a is formed on the side of the incident surface 21 far from the light source 1. The angle α [degrees] of the inclined portion 21a is set to an angle at which the light ray L2 from the entrance surface 21 to the reflection surface 22 can be made substantially parallel.

As a result, the incident angle θ3 of the light ray L2 with respect to the reflecting surface 22 becomes equal to or greater than the critical angle θ0 (about 42 [degrees]), the light ray L2 has a higher total reflection rate on the reflecting surface 22, and the objective surface 23 The light ray L3 reaching to becomes bright.

[0013]

[Second Embodiment] A second embodiment according to the present invention will be described with reference to FIG. The second embodiment has substantially the same structure as the first embodiment described above, and the description of the common structure will be omitted.
In the case of the second embodiment, the entrance surface 21 has the shape of a convex lens, and the light source 1 is arranged at the focal point of the convex lens. As a result, the light ray L2 from the incident surface 21 to the reflecting surface 22 is made into a substantially parallel light ray.

[0014]

[Third Embodiment] A third embodiment of the present invention will be described with reference to FIG. The third embodiment has substantially the same structure as the first embodiment described above, and the description of the common structure will be omitted.
In the case of the third embodiment, the entrance surface 21 has the shape of a Fresnel lens, and the light source 1 is arranged at the focal point of the Fresnel lens. As a result, the light ray L2 from the incident surface 21 to the reflecting surface 22 is made into a substantially parallel light ray.

Needless to say, in the third and second embodiments, the light rays L2 can be made parallel rays more easily than the ones in the first embodiment, but in terms of formability. Therefore, it is slightly disadvantageous to that of the first embodiment. Therefore, which structure of the first, second, and third embodiments should be appropriately selected in view of required performance and the like. Further, the shape of the incident surface is not limited to the shape of the embodiment, and may be any shape that can achieve substantially the same effect.

[0016]

【The invention's effect】

(1) According to the present invention, since the incident surface is inclined so that the light ray from the incident surface to the reflective surface is made substantially parallel, the light ray from the incident surface to the reflective surface of the light guide can be made into a parallel light ray. As a result, the reflection efficiency at the reflecting surface is improved, and the light beam reaching the objective surface becomes bright. (2) In addition, the structure in which the inclined portion is formed on the side of the incident surface farther from the light source has a structure in which the mold for molding the light guide is as simple as the conventional one, but the incident surface of the light guide is changed to the reflecting surface. It is possible to make the light rays reaching to the parallel light rays to some extent and improve the reflection efficiency on the reflection surface. (3) In addition, in the structure in which the shape of the incident surface is a convex lens or Fresnel lens, the light rays from the incident surface of the light guide to the reflecting surface can be made into parallel rays without limit, and the reflection efficiency at the reflecting surface can be improved. It can be improved sufficiently.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of the present invention.

FIG. 2 is a side view showing a second embodiment of the present invention.

FIG. 3 is a side view showing a third embodiment of the present invention.

FIG. 4 is a side view showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Light guide 3 Illumination object 21 Incident surface 21a Inclined part 22 Reflective surface 23 Objective surface 24 Side surface L1, L2, L3 Light ray

Claims (4)

[Claims] 1. An incident surface (21) for receiving a light ray (L1) from a light source (1) and a light ray (L) emitted from the incident surface (21).
A reflection surface (22) that totally reflects 2) and the reflection surface (22)
In the illumination light guide having an objective surface (23) that irradiates the light ray (L3) reflected by the object toward the illumination target (3), the incident surface (21) is a substantially parallel light ray of the light ray (L2). A light guide for illumination having an inclination. 2. The light guide for illumination according to claim 1, wherein the incident surface (21) has an inclined portion (21a) on a side far from the light source (1). 3. The illumination light guide according to claim 1, wherein the incident surface (21) has a convex lens shape. 4. The illumination light guide according to claim 1 or 3, wherein the incident surface (21) has a Fresnel lens shape.