JPH058686A - Brake lamp for vehicle - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a brake light for a vehicle, which can display to the rear of the vehicle without hindering the driver's rear view. [Structure] A light source 2 that is turned on in association with a brake operation of a vehicle and a structure in which two types of transparent bodies a and b having different refractive indexes are alternately laminated are provided. , A light guide 3 which is transmitted through the transparent body toward the other end while being totally reflected at the boundary surface with the outside, and which is reflected at each joint surface of the two kinds of transparent bodies and radiates in a fixed direction. Prepared configuration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake light that informs a following vehicle that a vehicle brake has been activated.

[0002]

2. Description of the Related Art Conventionally, generally used brake lights are
It was a lamp attached to a bumper or fender at the rear of the vehicle, but recently, in order to improve visibility from the following vehicle, a large-sized light emitting element etc. is located at a relatively high position on the rear of the vehicle, for example, near the rear window. The technology of providing a display (so-called high-mount stop lamp) has been put into practical use. As a vehicle brake light as described above,
For example, there is one described in Japanese Utility Model Publication No. 64-24647.

[0003]

However, in the conventional vehicle brake light as described above, a light diffusing region is provided in a part of the light guide, and the light incident from the side surface is diffused to the rear of the vehicle. Since the display is configured, there is a problem in that the diffusion region becomes frosted glass and becomes opaque, which hinders the driver's backward vision.

The present invention has been made to solve the problems of the prior art as described above, and provides a vehicular brake light capable of displaying the rear of the vehicle without obstructing the rear view of the driver. The purpose is to

[0005]

In order to achieve the above object, the present invention is constructed as described in the claims. That is, the present invention has a structure in which two kinds of transparent bodies having different refractive indexes are alternately laminated, and the light of the light source incident from one end is totally reflected at the boundary surface with the outside while Transmitted towards the edge, and 2
Provided with a light guide that is reflected by each joint surface of the transparent body of the seed and radiates in a certain direction, so that the light of the light source that is turned on in conjunction with the brake operation is emitted to the rear of the vehicle through the light guide. It is composed.

[0006]

As will be described later in detail in FIG. 2, a light guide having a structure in which two kinds of transparent bodies having different refractive indexes are alternately laminated is used, and the total reflection condition is satisfied from one end of the light guide. When the light is introduced at an angle, the light is transmitted toward the other end of the light guide while repeating total reflection at the boundary surface between the light guide and the outside. Then, in the middle of the transmission, a part is reflected on each of the joint surfaces of the two kinds of transparent bodies and is radiated in a constant direction. If the above-mentioned light guide body is installed so that the emitted direction is directed to the rear of the vehicle, the light of the light source that is turned on in association with the brake operation can be emitted to the rear of the vehicle.

Since the light guide of the present invention has a structure in which two kinds of transparent bodies having different refractive indexes are alternately laminated, the light from the rear of the vehicle is slightly refracted. However, it does not become opaque like the conventional ground glass, and the driver's rear view can be sufficiently secured.

[0008]

1 is a sectional view of an embodiment of the present invention.
First, the structure will be explained. 1 is rear window glass, 2
Is a light source (for example, a red light lamp), 3 is a transparent light guide, and a has a refractive index n ₁ and a b has a refractive index n ₂ .
Composed of a transparent body of seeds. Reference numeral 4 is light transmitted through the transparent light guide, 5 is reflected light reflected by the boundary surface between the transparent bodies a and b, 6 is a switch linked with the brake, and 7 is a power source. The light guide 3 is installed along the rear window glass 1, and the light source 2 is installed close to one end of the light guide 3. The light guide 3 is made of, for example, a transparent resin material (plastic) having a different refractive index as shown in FIG.
It can be manufactured by alternately laminating a and b, adhering them, and cutting from the broken line.

Next, the operation will be described. The red light source 2 is turned on by a switch 6 which is turned on / off in conjunction with a brake. The light from the light source 2 is incident on one end of the transparent light guide 3. The positional relationship between the light source 2 and the light guide 3 is such that the incident light satisfies the condition of total reflection at the boundary surface between the light guide 3 and the outside. Light incident under such conditions is transmitted toward the other end while repeating total reflection inside the light guide 3. Then, a part of the transmitted light 4 is reflected by the boundary surface between the transparent body a and the transparent body b, and emitted toward the rear of the vehicle.

Next, FIG. 2 is a cross-sectional view for explaining the state of light in the light guide 3 described above. Hereinafter, the operation in the light guide 3 will be described in detail with reference to FIG. Figure 2
A is a transparent body having a refractive index n _a , b is a transparent body having _a refractive index n _b , 3 is a light guide body composed of transparent bodies a and b, 11 is an incident light beam, and 12 is a transparent body a and b. A transmitted light ray transmitted through the boundary surface, a reflected light ray 13 reflected at the boundary surface between the transparent bodies a and b, a refracted light ray 14 reflected by the reflected light ray 13 at the boundary surface between the light guide 3 and the outside air, Reference numeral 15 is a boundary surface between the transparent body a and the transparent body b.

Hereinafter, the directions of the respective light rays will be described by giving specific numbers. For example, the refractive index n of the transparent body a
_{It is} assumed that _a = 1.4 and the refractive index nb of the transparent body _b = 1.6. Also,
The outside of the transparent body is air, and the refractive index is n _air = 1.0. The inclination of the rear window glass is 70 ° with respect to the horizontal line, and the light guide 3 is assumed to be installed in parallel with it. First, according to Snell's law, sin ~ ¹ (1 / 1.4) = 45.6 ° ∴ α <90- is the condition that the incident ray 11 is totally reflected at the point A (the boundary surface between the transparent body a and the air). 45.6 = 44.4 ° must be met. Here, for example, α = 14 °. It is desirable that the optical axis emitted from the vehicle high-mount stop lamp, that is, the emission direction of the refracted light beam 14 in FIG. Therefore, the reflected light ray 13 is set to be horizontal in consideration of the refraction at the point D. From this condition, β ″ = α + 70 = 84 ° ∴β = β ′ = 90−84 / 2 = 48 ° δ = 180−α−β = 118 °, and the boundary surface 15 between the transparent body a and the transparent body b guides light. The angle should be 118 ° with respect to the plane of the body 3. At this time, the refracted ray 14 radiated rearward of the vehicle has an angle θ with respect to the horizontal line of θ = 7 ° from Snell's law. On the other hand, the transmitted ray 12 that has passed through the boundary surface 15 between the transparent bodies a and b is refracted by γ = 38.7 ° according to Snell's law. it is readily apparent to meet. that is, for 180-δ-γ '= 180 -δ- of a (90-γ) = 10.7 ° , the critical angle ^{sin ~ 1 (1 / 1.6)} = 38.7 °, which satisfies the condition sufficiently.As described above, the incident ray 11 is partially reflected by the boundary surface 15. And the rest of the light 12 is sequentially transmitted through the inside of the light guide 3 while satisfying the condition of total reflection. Note that the light is incident from the transparent body b to the transparent body a under the opposite conditions. It can be handled in the same way as above, and the same operation as above is achieved.

Next, the amount of light reflected by the boundary surface 15 between the transparent bodies a and b will be described.

This amount of light can be immediately obtained by obtaining the Fresnel coefficient. That is,

[0014]

[Equation 1]

Therefore, it is 1.2 in one pass through the boundary surface.
% Of the light will be reflected. For example, if the reflectance for one time is x, the amount of incident light is P, and there are 100 boundary surfaces, the amount of reflected light is as shown in the following (Equation 2).

[0016]

[Equation 2]

In the above equation (2), n = 100 and x = 0.
If 012 is substituted for the calculation, the reflected light quantity becomes approximately 0.7P. That is, when there are 100 boundary surfaces, about 70% of the light incident from the light source is emitted rearward.

Next, FIG. 4 is a perspective view of another embodiment of the present invention. In this embodiment, one kind of transparent body 21 is laminated at intervals so that a thin air layer 22 is provided therebetween. The spacer 23 (resin plate or the like) is provided to leave the above-mentioned interval. In the above configuration, the transparent body 21 corresponds to the transparent body a in FIG. 1 and the air layer 22 corresponds to the transparent body b. In this case, since it is easy to increase the difference between the refractive index of the transparent body 21 and the refractive index of air,
The reflectance on the boundary surface can be increased.

[0019]

As described above, according to the present invention, the structure has a structure in which two kinds of transparent bodies having different refractive indexes are alternately laminated, and the light from the light source incident from one end is separated from the outside. By using a light guide that transmits in the above-mentioned transparent body toward the other end while being totally reflected by the surface, and is reflected by each joint surface of the two types of transparent bodies and radiates in a fixed direction, The fact that the brake has been activated can be displayed to the rear of the vehicle without hindering it. Further, since the light of the light source is configured to be transmitted by total internal reflection, it is sufficient to provide the light source at one end of the light guide body, which is excellent in space.
And so on.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view for explaining the internal operation of the embodiment shown in FIG.

FIG. 3 is a perspective view showing a method of manufacturing the light guide body of FIG.

FIG. 4 is a perspective view of another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rear window glass 2 ... Light source 3 ... Light guide a is a transparent body with a refractive index n ₁ , b is a transparent body with a refractive index n ₂ 4 ... Light transmitted in a transparent light guide body 5 ... Transparent body a, Reflected light reflected on the boundary surface of b 6 ... Switch interlocked with the brake 7 ... Power source 11 ... Incident light ray 12 ... Transmitted light ray transmitted through the boundary surface between the transparent bodies a and b 13 ... Boundary between the transparent bodies a and b Reflected light ray 14 reflected by the surface ... Reflected light ray 13 is a refracted light ray that is refracted at the boundary surface between the light guide 3 and the outside air 15 ... Boundary surface between transparent body a and transparent body 21 ... Transparent body 22 ... Thin Air layer 23 ... Spacer

Claims (1)

Claim: What is claimed is: 1. A brake light for a vehicle, which informs a succeeding vehicle that a brake of the vehicle has been operated, a light source that is turned on in association with a brake operation of the vehicle, and two types of transparent materials having different refractive indexes. It has a structure in which the bodies are alternately laminated, and transmits the light of the light source incident from one end toward the other end in the transparent body while totally reflecting at the boundary surface with the outside, and also includes two types of transparent bodies. A brake light for a vehicle, comprising: a light guide body that reflects at each joint surface and emits light in a fixed direction.