JPH0459606B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is applicable to light transmission materials, particularly when transmitting sunlight (including artificial sunlight such as xenon lamps) concentrated by an optical system over long distances for purposes such as lighting. The present invention relates to an extremely useful optical transmission material.

Conventionally, it has been proposed to transmit concentrated sunlight using a light transmission material formed by converging a large number of optical fibers. However, in such optical fiber type optical transmission materials, sunlight enters the cladding part and the gap between the fibers at the light receiving end surface, and the effective light receiving cross section of the light receiving end surface is only about 70%. , the light receiving loss at the light receiving end face is large. In order to solve this problem, it has been proposed to expand the effective light-receiving cross-sectional gap by deforming the vicinity of the light-receiving end face and eliminating the gap between the cladding part and the fibers. Even if light is forcibly taken in through such deformation, a considerable portion of the taken in light escapes when it transfers to each fiber in the undeformed part, so it is actually not very effective, and the problem of light reception loss has been solved. Can not.

In addition, as is said in the field of optical communications, a light guide has a critical angle determined by its refractive index (the limit angle at which it can be transmitted relative to the angle of oblique incidence; light incident at an angle larger than this is rapidly attenuated). ), and the critical angle θc of the optical fiber is usually 20
It is said to be ~30°. Therefore, in an optical fiber, ideally all of the light incident within this critical angle should be transmitted without loss.
In reality, it is conceivable that minute scratches, dirt, etc. on the core surface cause a slight amount of surface scattering for each reflection, and that this scattering generates a component that protrudes outside the critical angle and is attenuated. The inventor discovered that when the optical fiber is incident perpendicularly to the end face and transmitted without reflection (θ
= 0°), compared to the amount of transmitted light at oblique incidence (however, 0<
The angle at which the amount of transmission for θ<θc) is 80% is the “acceptance angle”
When considering the acceptance angle, we found that when the light source is a laser, as in the field of optical communications, the distinction between the critical angle and the acceptance angle is not very important, but when the light source is sunlight, , the acceptance angle decreases considerably compared to the critical angle, and the degree of this decrease increases as the transmission distance increases, and in the case of long-distance transmission, even light incident within the critical angle can cause considerable transmission loss. found. The reason for this is not clear, but if the light source is a laser, the angle of light incident on the end face of the optical fiber is usually within 10°, which is much smaller than the critical angle (20 to 30°). In addition to the fact that there are almost no components that protrude outside the critical angle, the number of reflections that cause such surface scattering (per unit transmission distance)
On the other hand, in the case of sunlight, the angle of incidence expands to the critical angle, and light that is incident at an angle close to the critical angle will be attenuated due to surface scattering that occurs with each reflection. In addition to this, it is presumed that the fact that the number of reflections (per unit transmission distance) that causes such attenuation increases as the angle approaches the critical angle is considered to be a major influence.

The present invention has been made for the purpose of providing a high-quality, high-performance optical transmission material that has no light reception loss as seen in optical fiber systems and can significantly improve the light reception angle. teeth,
The diameter D is 10mm<D, which are connected sequentially in the length direction through transparent elastic connecting parts made of silicone rubber.
It is characterized by having a core made of a single transparent synthetic quartz rod with a diameter of <30 mm, which is given flexibility and stretchability by the elasticity of the silicone rubber constituting the connection part. Related to optical transmission materials.

In the present invention, since the core part is particularly composed of a single quartz rod (diameter D10mm<D<30mm),
There are no cruds or gaps on the light receiving end surface that would cause light receiving loss, resulting in a 100% effective light receiving cross section, and this effective light receiving cross section can be maintained throughout the entire length, eliminating the problem of light receiving loss. . Furthermore, as is clear from the graph shown in FIG. 5, the acceptance angle can be significantly improved, and the transmission loss seen in long-distance transmission can also be greatly reduced. There are various possible reasons for this, but since the number of reflections (per unit transmission distance) of light transmitted through the core is inversely proportional to the diameter of the core, as in the present invention, the diameter D is 10 mm.
If the diameter of the core is increased by using a quartz rod with <D<30 mm, the number of reflections will be reduced accordingly, which is thought to greatly contribute to improving the acceptance angle.

Furthermore, although the core part is composed of transparent synthetic quartz rods with a diameter of 10 to 30 mm, it has flexibility and stretchability at appropriate intervals in the length direction, for example, about 0.5 to 10 m. . This flexibility and stretchability improves workability when attaching to buildings, etc., and also absorbs the difference in thermal expansion that occurs between the building and the temperature difference between winter and summer, or between day and night, and there is a risk of damage to the optical transmission material. You can wipe out sexuality.

In this way, the optical transmission material of the present invention has a 100% effective light-receiving cross-sectional area and no light-receiving loss, and also has low transmission loss due to the improvement of the light-receiving angle, and has high quality and high performance. It is flexible and stretchable, can be bent freely, and there are no restrictions on installation, making it extremely useful for applications such as transmitting sunlight collected on a rooftop as illumination light into a basement.

An embodiment of the present invention will be described below based on the accompanying drawings.

As shown in FIG. 1, the optical transmission material A of the present invention consists of a core part 1 and a clad part 2 covering the core part 1, like a conventional optical fiber.In particular, the core part 1 is made of a single transparent synthetic quartz rod. It is characterized by being composed of.

The quartz rod is not particularly limited as long as it is synthesized to be transparent, but it is preferable to use one with as little absorption coefficient and surface flaws as possible, such as transparent synthetic quartz molded from silicon tetrachloride as a starting material. Rod (extinction coefficient: 1.08×10 ^-5 cm ^-1 (λ=632.8nm refractive index: 1.46)
can be used to advantage. If the diameter D of the quartz rod is too small, not only will it not be possible to expect much improvement in the acceptance angle, but the light source image focused by the optical system will protrude beyond the acceptance end face, making it impossible to receive the entire light source image. , and even if this is too large, we cannot expect much improvement in quality and performance considering the rising price, so 10 mm <
It is necessary that D<30mm, especially 10
It is preferable that mm<D<20mm.

The quartz rods are successively connected together in the longitudinal direction via transparent elastic connections 3, as shown in FIG. 2, in order to impart stretchability and flexibility to the product. The spacing between the connecting portions 3 is not particularly limited, but if the spacing is too small, the number of connecting portions 3 may increase unnecessarily, resulting in undesirable results in terms of optical transmission efficiency, or conversely, if the spacing is too large Therefore, the distance between the connecting parts 3 and 3 should be set at 0.5.
About 10 m, particularly about 1 to 4 m is suitable.

Silicone rubber is used as the rubber constituting the connecting portion 3. Silicone rubber is transparent and has appropriate elasticity, and this elasticity allows it to impart flexibility and stretchability to the core portion. Silicone rubber has an extinction coefficient of 3×10 ^-3 ~5×10 ^-3 cm ^-1 and a refractive index of 1.4 ~
1.5, which is close to that of quartz, so optical transmission loss at the connection portion 3 can be reduced as much as possible. Furthermore, silicone rubber has good mechanical properties and light resistance to visible light and ultraviolet light, and is also excellent in durability.

It is desirable that the connecting portion 3 is formed to have the same diameter as the quartz rod, as shown in FIG. 4a. If the connecting part 3 is made of silicone rubber, since silicone rubber is relatively weak against infrared rays with a wavelength of 0.9μ or more, such infrared rays should be removed in front of the receiving end using, for example, a hot ray cut film. It is preferable to do so. In the present invention, such a connecting portion 3 may be formed not only during factory production but also at a construction site.

A cladding section 2 is provided to protect the peripheral side of the core section 1 from dust and other contaminants in the air. The material of the cladding part 2 may be any material that has high transparency, has as low a light refractive index as possible, and is optically and mechanically durable, such as fluororesin, silicone resin, inorganic fluoride, etc. can. Among these, fluororesin is the most suitable because it is transparent over a wide range from ultraviolet to infrared rays, has a low optical refractive index of about 1.34, has high light resistance, and has an excellent mechanical protection effect.

As shown in FIGS. 2 to 4, in the present invention, the optical transmission material A is protected using a protective tube 4 such as a metal tube or a hard synthetic resin tube that has been subjected to anti-rust treatment as necessary. It's okay. In this case, if a circumference 6 based on the spacer 5 is formed between the protective tube 4 and the optical transmission material A, this circumference 6 can buffer mechanical shocks and absorb deformation of the protective tube 4. This is advantageous because it allows you to Further, by sealing the periphery 6 with the spacer 5, it is possible to prevent dust, rainwater, etc. from entering the periphery 6. The spacer 5 is usually made of the same material as the cladding part 2. In the figure, 7 is a pipe joint that connects the protective tube 4 to each connection part 3 of the quartz rod, and as the pipe joint 7, a flexible one such as a bellows type as shown in Fig. 4 should be used. is preferred.

Figure 5 shows a quartz rod (diameter 11mmφ, length 16mm).
m) and quartz fiber (diameter 1mmφ, length 16m)
This is a graph showing the relationship between the incident angle (horizontal axis) and the light transmittance (vertical axis) at the light-receiving end surface of the quartz rod.

The graph in Figure 5 is based on actual measurement data for quartz rods (wavelength used: H _e −N _e laser λ = 632.8n).
m), and the quartz fiber was created based on estimated data. The estimation method was as follows. In other words, the actual measurement data for the quartz rod is that the diameter of the rod is d (cm) and the length is l.
(cm), the transmittance (Tint) corrected for end face reflection is -log Tint=l/cosγ(β/dsin ² γ+α) with α and β as parameters for the angle of incidence (θ), where sinγ=sinθ /1.46 (refractive index = 1.46). Here, α means the extinction coefficient of the quartz material used, and β means the surface scattering factor, and they have the values of α=1.08×10 ⁻⁵ (cm ⁻¹ ) and β=5.38×10 ⁻⁴ , respectively. In the case of quartz fiber, assuming that the quartz material and surface condition are the same,
α and β are the same values as the rod, the difference is the diameter d
Therefore, it can be estimated using these values.

In the graph of Figure 5, the broken line c indicates the amount of transmitted light is 80%.
In other words, this acceptance angle is approximately 28 degrees in half angle in the case of quartz rod.
In the case of quartz fiber, the angle is approximately 9°, and it can be seen that the acceptance angle can be significantly improved by using a quartz rod as the core as in the present invention.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view showing an embodiment of the present invention, Fig. 2 is a longitudinal cross-sectional view showing an example of a modification thereof, and Fig. 3 is a cross-sectional view taken along line I-I in Fig. 2. , FIG. 4 is an enlarged sectional view showing the structure of the connection part in FIG. 2,
FIG. 5 is a graph showing a comparison of the acceptance angles of quartz rod and quartz fiber. In the figure, 1 is the core part, 2 is the clad part, and 3
4 is a connection part, 4 is a protection tube, 5 is a spacer, 6 is a circumference, and 7 is a pipe joint.

Claims (1)

[Scope of Claims] 1. Diameter D is 10 mm, which are sequentially connected integrally in the length direction via transparent elastic connecting parts made of silicone rubber.
It has a core made of a single transparent synthetic quartz rod with <D<30 mm, and the core has flexibility and stretchability due to the elasticity of the silicone rubber that makes up the connection part. Optical transmission material. 2. The optical transmission material according to claim 1, wherein the single transparent synthetic quartz rod constituting the core portion is covered with a clad portion made of fluororesin. 3 A single transparent synthetic quartz rod constituting the core part is loosely inserted and held in a protective tube under the application of a spacer, and the protective tube has a flexible and stretchable rod at a position that coincides with the transparent elastic connection part of the core part. 3. The optical transmission material according to claim 1 or 2, wherein the optical transmission material is provided with a flexible pipe joint portion.