JPH0157763B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a leakage light transmitting body that can be used as a linear light emitter.

Conventionally, this type of linear light emitting material is of a type that emits light by itself as a light source, so it is not only almost impossible to make one with a long length and a small diameter, but also as a means of emitting light. It is necessary to provide electrodes or the like at least at both ends, and as a result, the range of its use is also limited and extremely narrow.

In view of these conventional problems, the present invention eliminates the conventional idea of requiring the light source itself, and
The aim is to obtain a linear light emitting body that seeks light from an external light source, and for this purpose, it was originally designed to completely reflect light at the interface between the core and the cladding that surrounds it, confining it within the core. Focusing on the optical transmission body configured to transmit light, the light transmitted within the core is leaked to the outside via the cladding by utilizing the relationship between the angle of incidence of light on the boundary surface and its critical angle. , all of the above problems have been solved by utilizing the leaked light for external illumination.

This configuration will be explained below based on the drawings. First, as is known, the configuration in Figure 1 is made of a dielectric material with good light transmittance, such as quartz glass, and has a refractive index n ₁ .
This optical transmission body is constructed by wrapping a core 1 in a cladding 2 made of a dielectric material with a smaller refractive index _n2 , and forming an interface 3 between the core 1 and the cladding 2. In the embodiment, the diameters of the core 1 and the cladding 2 remain unchanged in the longitudinal direction, and therefore the diameter of the interface 3 also remains unchanged in the same direction, but the refractive index n ₁ of the core 1 and Kuratsudo 2
By changing one or both of the refractive indices n ₂ within the range n ₁ > n ₂ , the ratio of n ₁ and n ₂ is set to gradually decrease from the input end 4 side to the output end 5 side. , As a result, the critical angle αc of the boundary surface 3 given by the following equation (h) is set so as to gradually increase in the above direction as shown in FIG.

αc=sin ^-1 (n ₂ /n ₁ ) ...(h) Therefore, in the case of this embodiment, as shown in FIG. travels through the core 1 toward the output end 5 side while undergoing total reflection at the boundary surface 3 at an incident angle α and an equal reflection angle α (α=π/2−θ), and this incident angle α is the critical angle mentioned above. When it becomes smaller than αc, it is refracted toward the cladding 2, and further leaks to the outside via the cladding 2.

In this case, let us consider the position of a point I at the entrance end of the core 1, where light incident from a point P separated by y from the optical axis is refracted toward the cladding 2 at the boundary surface 3. Now, let the diameter of core 1 be d, and the number of total reflections of light to reach point I be i(0
or an integer greater than or equal to 1), and if we take the x-axis on the optical axis from the input end 4 to the output end 5 side, the x-coordinate of the i-th total reflection point xi and the x-coordinate of the I point xi+
1 is given by the following equations (i) and (j), respectively.

xi=(di+d/2-y)cotθ...(i) xi+1={d(i+1)+d/2-y}cotθ=(di+2/3d-y)cotθ...(j) Here, the critical angle αc of x is Since it is a function, it can be expressed as α=f(x), and at x=xi, αc<α=π/2−θ, and at x=xi+1, αc>α=π/2−θ. (xi)<π/2-θ<f(xi+1), that is, f{(di+d/2-y)cotθ}<π/2-θ<f{(di+3d/2-y)cotθ}, and by this inequality, i is found. Thus, by substituting this value into the above equation (j), the value of xi+1, that is, the distance from the incident end 4 to point I can be obtained.

In the above description, the case where the diameter of the core 1 is not changed has been described, but it is also possible to use a combination of methods of reducing the diameter of the core 1 from the incident end side to the output end side, if necessary. Furthermore, in the above embodiment, for convenience of explanation, the critical angle of the boundary surface 3 is changed over the entire length of the optical transmission body, but such a change is set only in a part of the optical transmission body, and it is not applied to other parts. It is of course possible to set a different change in the critical angle of the boundary surface 3 as needed.

Furthermore, by providing a light scattering layer on the outer periphery of the cladding 2 that allows light to scatter and pass through, it is possible to uniformly scatter and emit light leaking to the outside in multiple directions.
As this scattering layer, opalescent glass formed by turbidizing calcium fluoride or sodium fluoride in glass or the like can be used.

As explained above, in the present invention, in an optical transmission body in which a cladding 2 having a smaller refractive index is provided around the outer periphery of a core 1, the core 1 is provided along the entire length or part of the cladding 2 from the input end side to the output end side. By setting a change in which the critical angle of the interface 3 between the core 1 and the cladding 2 gradually increases, the light incident from the input end 4 side at an arbitrary angle to the optical axis of the core 1 is directed to the output end 5 side. In the process of transmission, the boundary surface 3
Since the light is refracted toward the clad 2 side and leaks to the outside, the light is spread over the entire surface of the incident end of the core 1.
If light is incident at an unspecified angle with respect to the optical axis, light can be leaked from all around the entire length of the light transmitting body, making it possible to use the light transmitting body as if it were a linear light emitter. Moreover, since the light transmitting body itself is long and small in diameter, it is not only possible to completely compensate for the drawbacks of conventionally used linear light emitters of this kind, but also to be able to transmit light only at the input end. All you have to do is connect a light source, etc., which simplifies the equipment and reduces the installation space.Also, since it does not generate heat itself, there is no need to directly install electrical equipment, so for example, if flammable gas etc. This significantly expands the scope of its use, as it can be used in places where there is a risk of explosion.

Furthermore, if light is incident at a specific angle with respect to the optical axis from a specific position of the input end of the core 1, the light can be leaked from a specific position of the optical transmission body in accordance with this, so that the light can be locally transmitted. It can also be used for light extraction or illumination, and in this respect as well, it is possible to provide a leakage light transmitting body that can be used in an extremely wide range of applications.

[Brief explanation of drawings]

FIG. 1A is a vertical cross-sectional explanatory view showing one embodiment of the present invention, and FIG. 1...Core, 2...Clad, 3...Boundary surface.

Claims (1)

[Scope of Claims] 1. In an optical transmission body in which a cladding having a smaller refractive index is provided around the outer periphery of the core, the boundary between the core and the cladding extends along the entire length or part of the core from the input end side to the output end side. By setting a change in which the critical angle of the surface gradually increases, light incident from the input end at an arbitrary angle to the optical axis of the core is transmitted from the boundary surface to the cladding side in the process of being transmitted to the output end. 1. A leakage light transmitting body characterized in that the light is refracted to the outside and leaks to the outside. 2. The leakage light transmission body according to claim 1, wherein a light scattering layer is provided on the outer peripheral side of the cladding.