JP2705830B2 - Light guide - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber bundle type light guide for transmitting illumination light from a light source device to an object to be observed, and particularly to improving durability thereof. It is a hurry.

"Conventional technology" The optical fiber bundle type light guide transmits image fiber illumination light that transmits images in a constant temperature environment or a vacuum environment such as in an LNG tank that cannot be observed directly by humans. It is used for.

FIG. 1 and FIG. 2 show examples of a conventional optical fiber bundle type light guide.

In FIG. 1, the light guide comprises a plurality of optical fibers 1,
1, a terminal casing 2, a metal sleeve 3, and a metal flexible tube 4.

A large number of optical fibers 1, 1,... Are bundled and placed in a metal flexible tube 4 for protecting them. The ends 5, 5,... Of these optical fibers 1, 1,... Are aligned and inserted into the annular metal sleeve 3, and
The gaps formed between the metal sleeves 3 are filled with an adhesive 6 made of epoxy resin and fixed. The optical fiber 1, 1,... And the end face 8 composed of the adhesive 6 are mirror-polished.
Further, the metal sleeve 3 and the end 4a of the metal flexible tube 4 are accommodated and fixed in the terminal casing 2 made of metal or resin. Such an optical fiber bundle type light guide can be obtained by the following steps.

First, after removing the protective coating of the ends 5, 5,... Of the optical fibers 1, 1,... From the tips 7, 7,. Are bundled and aligned, and then the ends 5,5 of each of the aligned optical fibers 1,1 ...
Are immersed in the adhesive 6, and the aligned optical fibers 1, 1
Are sufficiently impregnated with the adhesive 6 in the gaps formed between. After that, the ends 5, 5,... Of these optical fibers 1, 1,.
, And inserted into the metal sleeve 3. Then, the adhesive 6 is cured by heating, and the optical fibers 1 and 2 are hardened.
.. Are fixed in the metal sleeve 3.

Next, the ends 7, 7,... Of the optical fibers 1, 1,.
The cut end surface 8 is polished to a mirror surface state by an optical polisher. Then, the optical fibers 1, 1,... Are put into the metal flexible tube 4, and the metal sleeve 3 and the end 4a of the metal flexible tube 4 are accommodated and fixed in the terminal casing 2 made of metal or resin.

FIG. 2 is a cross-sectional view of the terminal portion 9 on the light source side of the light guide.

As shown in FIG. 2, the terminal portion 9 of the light guide has a metal sleeve 3 held by a terminal casing 2, and a large number of optical fibers 1, 1
Are fixed with an adhesive 6 made of an epoxy resin.

However, in the above-described optical fiber bundle type light guide, light from a light source such as a xenon lamp is made to enter the optical fibers 1, 1. Although light is transmitted, when the amount of light incident on the end face 8 of the light guide is large, the gap formed between the ends 5, 5,... Of the optical fibers 1, 1,. Since the adhesive 6 made of an epoxy resin is colored pale yellow or yellow,
The coloring causes problems such as absorption of incident light, especially infrared energy, to generate heat, and sometimes, the adhesive 6 is ignited to burn the light guide.

Therefore, it was necessary to reduce the amount of incident light or to attach an infrared cut filter to the light source to cut off heat rays.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a durable light guide which does not generate heat or ignite even when high energy density light is incident thereon. .

`` Means for solving the problem''A light guide of the present invention is a light guide in which a number of optical fibers are aligned, and ends of these optical fibers are fixed in a fixing member by a heat-resistant transparent adhesive, The above problem was solved by using a heat-resistant transparent adhesive having the following heat resistance and transparency.

Heat resistance: For the adhesive after curing, temperature 250 ° C, time 24
The decrease in light transmittance at a wavelength of 0.38 μm to 0.78 μm by heating for a time is less than 5%.

Transparency: The cured adhesive is colorless and transparent, and has a wavelength of 0.
In the range of 4 μm to 5.0 μm, the light transmittance is 90% or less.

[Operation] In the light guide having such a configuration, since the ends of a large number of optical fibers are fixed in the fixing member by the above-mentioned heat-resistant transparent adhesive, a high energy density is obtained from the end face of the light guide. Even if the light is incident, the adhesive fixing the end of the optical fiber does not absorb the infrared energy of the incident light, and thus does not generate heat or ignite.

Embodiment The difference between the light guide of the present invention and the conventional light guide shown in FIGS. 1 and 2 is that the ends 5, 5,... Of the optical fibers 1, 1,. Is that a heat-resistant transparent adhesive 10 is used to fix the adhesive.

Here, the heat-resistant transparent adhesive 10 is obtained by heating the cured adhesive at a temperature of 250 ° C. for 24 hours to obtain a wavelength of 0.38.
a decrease in light transmittance of less than 5% at μm to 0.78 μm;
Shows heat resistance, is colorless and transparent and has a visible to infrared range (wavelength
(0.4 μm to 5 μm) refers to a transparent adhesive having a light transmittance of 90% or more.

As a specific example of the heat-resistant transparent adhesive 10 that satisfies such conditions, a silicone resin-based adhesive that does not include a filler and a coloring agent can be given. Silicone resin-based adhesives have a siloxane bond (-Si-O-Si-O-) in the molecular structure.
This siloxane bond is stable to heat, and has a property that a color-forming center causing absorption loss of light energy, particularly infrared rays, is not formed.

In such a light guide, even if high-energy light is incident on the end, the light energy is converted into heat energy because the adhesive layer at the end is made of a heat-resistant transparent adhesive having the above-described characteristics. The conversion ratio is significantly reduced, and the adhesive does not generate heat or ignite.

For example, a light guide similar to that shown in FIGS. 1 and 2 is manufactured using a silicone resin as the heat-resistant transparent adhesive 10, and an Xe lamp is used as a light source, and an output 30 is used.
When 0 W light was incident on this light guide, no heat was generated or fired at the terminal portion 9.

Further, the heat-resistant transparent adhesive 10 of the present invention is not limited to the silicone resin described above, but may be any material that satisfies the above-mentioned properties.

As described above, the light guide of the present invention aligns a large number of optical fibers and fixes the ends of these optical fibers in the fixing member with the heat-resistant transparent adhesive described above. Even when high energy density visible light is incident, the end does not generate heat or ignite, and the durability of the light guide can be improved.

[Brief description of the drawings]

1 and 2 show examples of a light guide according to the present invention. FIG. 1 is a longitudinal sectional view, and FIG. 2 is a transverse sectional view of a terminal portion. 1 ... optical fiber, 3 ... metal sleeve (fixing member), 5 ... end of optical fiber, 10 ... heat-resistant transparent adhesive.

Claims (1)

(57) [Claims] 1. A light guide in which a number of optical fibers are aligned and the ends of these optical fibers are fixed in a fixing member with a heat-resistant transparent adhesive, wherein the heat-resistant transparent adhesive has the following heat resistance and transparency. A light guide characterized by having a characteristic. Heat resistance: For the adhesive after curing, temperature 250 ° C, time 24
The decrease in light transmittance at a wavelength of 0.38 μm to 0.78 μm by heating for a time is less than 5%. Transparency: The cured adhesive is colorless and transparent, and has a wavelength of 0.
In the range of 4 μm to 5.0 μm, the light transmittance is 90% or more.