JPH0342642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light condensing device that condenses light and transmits it through an optical system.

[Conventional technology]

FIG. 4 is a configuration diagram showing an example of a conventional condensing device, in which 1 is an incident light beam, 2 is a small-diameter lens, 3 is an optical fiber or an optical system similar to this (hereinafter simply referred to as an optical fiber system), 4 is the optical axis.

A conventional condensing device uses a lens 2 with a small diameter, and only the paraxial rays of this lens 2 are introduced into the optical fiber system.

Therefore, as shown in FIG. 5, if a large-diameter lens 5 is used and the incident light 1L is introduced at a large angle greater than the critical angle θ for total internal reflection, it will exit the optical fiber system 3. It becomes a loss. In order to prevent this, a concave lens 6 is provided at the light receiving part of the optical fiber system 3 as shown in FIG.
It is refracted in the direction of. This concave lens 6 makes it possible to use a lens 5 with a large diameter, and increases the transmission energy density of the optical fiber system 3.

[Problem that the invention seeks to solve]

By the way, as shown in FIGS. 7 and 8, when the diameter of the Fresnel lens 11 used in a solar light condensing device becomes about 1.5 meters,
In a structure in which the concave lens 6 is used in the optical fiber system 3, the diameter of the concave lens 6 becomes large, making it expensive. Furthermore, if the concave lens 6 is not used, the light from the periphery of the Fresnel lens 11 will be transmitted at the critical angle θ of the optical fiber system 3.
, and goes out of the optical fiber system 3, resulting in loss. Furthermore, when the aperture of the Fresnel lens 11 is increased, as shown in FIGS. 7 and 8, in the case of a single focal point, the wall 13 of the saw-like protrusion 12 becomes an optical path obstruction in the peripheral area, and a proportion of the light concentrated at the focal point becomes There was a problem that the amount decreased toward the periphery.

[Means for solving problems]

The light condensing device according to the present invention includes a coaxial multifocal Fresnel lens whose focal point becomes gradually longer toward the periphery, and a coaxial multistage optical system in which each of the focal points of the Fresnel lens corresponds to the light receiving surface. The multi-stage optical system is formed such that the angle of incidence of the light incident from the light-receiving surface of each stage is within the range of the critical angle for total reflection inside the optical system.

[Effect]

A coaxial multifocal Fresnel lens is formed so that all the incident light incident on the Fresnel lens is incident on the light receiving surface of the multi-stage optical system, thereby eliminating loss of incident light.

〔Example〕

FIGS. 1a and 1b are schematic diagrams showing an embodiment of the present invention.

First, as shown in FIG. 1A, a large-diameter Fresnel lens 21 has, for example, four focal points f ₁ , f ₂ , f ₃ , and f ₄ depending on the radius of the Fresnel lens 21 . A multistage optical fiber system 22 corresponding to these focal points f ₁ to f ₄
Four stages of light receiving surfaces 22a, 22b, 22c, 22d
Therefore, it is possible to receive all of the incident light rays 1 that have entered the large-diameter Fresnel lens 21 at an incident angle within the critical angle for total reflection of the multi-stage optical fiber system 22. Note that 23 is a space where the incident light beam 1 is not irradiated, and this is indicated by a mesh. A schematic diagram of the multi-stage optical fiber system 22 having this light-receiving surface is shown in Figure 1b.
Shown below. In this figure, 22a, 22b, 22c, 2
2d are the respective focal points f ₁ , f ₂ , f ₃ , and
It is a circular or annular light-receiving surface corresponding to _f4 .
FIG. 2 is a sectional view of a condensing device formed by combining FIGS. 1a and 1b.

Furthermore, FIG. 3 is an explanatory diagram showing that by using the condensing device of the present invention, light from the periphery of the Fresnel lens 21 also enters the multistage optical fiber system 22, and the loss is reduced compared to the conventional example.

Note that although the above embodiment shows a case where the multi-stage optical fiber system 22 is used as a multi-stage optical system, the multi-stage optical system of the present invention does not necessarily have to be as thin, long, and flexible as a fiber. For example, if the Fresnel lens 21 has a diameter of about 10 m, the diameter of the multi-stage optical system will also be 30 cm. Furthermore, the multi-stage optical system may be a hollow light guide.

[Effects of the Invention] As explained above, the present invention comprises a coaxial multifocal Fresnel lens whose focal points become progressively longer toward the periphery, and a coaxial multistage optical system in which the light-receiving surface corresponds to each of the focal points of the Fresnel lens. The system is arranged so that the angle of incidence of the light incident on each stage of the multi-stage optical system is within the range of the critical angle for total reflection inside the multi-stage optical system. The optical connection with the multi-stage optical system is lossless based on the principle of geometrical optics, and it is possible to effectively transmit the amount of collected light to the multi-stage optical system.

Therefore, solar photoconcentration and transmission systems,
It has the following advantages when applied to a wide range of fields such as concentrating light from a large-area light source to a small-area light source and as a coupler in optical communication.

1. There is little optical loss in the light receiving section of the multi-stage optical system.

2. A large-diameter condensing Fresnel lens can be used.

3. A concave lens or the like is not required in the light receiving section.

4. Positioning of the Fresnel lens and the multi-stage optical system, etc., and countermeasures against secular errors can be taken without loss by fixing the Fresnel lens to the multi-stage optical system at the center.

5. Due to its simple structure, it is reliable and inexpensive.

[Brief explanation of drawings]

Figures 1a and b are schematic diagrams of this invention;
1b is a schematic diagram showing the shape of a multi-stage optical fiber system, FIG. 2 is a sectional view showing an embodiment of the present invention, and FIG. An explanatory diagram showing the characteristics, Fig. 4 is a configuration diagram showing an example of a conventional condensing device, Fig. 5 is a diagram showing the loss of incident light when a large diameter lens is used, and Fig. 6 is a diagram showing the loss of incident light when a large diameter lens is used. A diagram showing a case where a concave lens is provided in the light receiving part of an optical fiber system of an optical device, and FIGS. 7 and 8 are explanatory diagrams showing the loss of incident light in the peripheral part of the Fresnel lens when a Fresnel lens is used. . In the figure, 1 is an incident ray, 21 is a Fresnel lens,
22 is a multistage optical fiber system, 22a, 22b, 22
c and 22d are light receiving surfaces, and f ₁ , f ₂ , f ₃ and f ₄ are focal points.

Claims (1)

[Claims] 1. A coaxial multifocal Fresnel lens whose focal point becomes longer toward the periphery, and a coaxial multi-stage optical system whose light receiving surface corresponds to each of the focal points of this Fresnel lens, and each of the above-mentioned focal points of this multi-stage optical system A condensing device characterized in that the incident angle of all the light incident from the light-receiving surface of the stage is within a critical angle range for total reflection inside the multi-stage optical system.