JPS58158611A - Image guide - Google Patents

Abstract

PURPOSE:To improve the sharpness of a transmitted picture by charging the support layer part and clad layer part of each optical blank wire which has the etched object-side end surface of an image guide with a light-shielding material. CONSTITUTION:The end surface part of the image guide is treated in a mixed acid solution which contains 10wt% fluoric acid, 10wt% sulfuric acid, and 10wt% acetic acid at room temperature for about 20min to etch the clad layer and support layer. The depth of the etching by the 20min treatment is several mum, which is normally enough. Then, said etched part is charged with the paste, etc., of the light-shielding material prepared by mixing a small amount of thermosetting resin as a binder with inorganic or organic black paint, metallic particulates, and inorganic particulates and after drying or baking, the end surface of the image guide is polished to remove the layer of the light-shielding material sticking to the top surface of a core.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of an image guide of the structure shown in the preamble of the claims.

The pure quartz core image guide above has excellent heat resistance and radiation resistance, reflecting the characteristics of pure quartz core.
Suitable for internal observation of high-temperature reactors and nuclear reactors.

Generally, the image guide described in "2" is manufactured by bundling and drawing a large number of preforms having a five-layer structure corresponding to the structure of the constituent optical fiber strands. Dopant-containing quartz, which is used as a component of the cladding layer, has an extremely low softening point and deformation resistance in the bulk state compared to pure quartz, so it tends to cause overflow during the above-mentioned wire drawing. In order to suppress this overflow, a sabot layer made of quartz, such as natural quartz or synthetic quartz, with a crystallization point as high as 4 or close to that of pure quartz is provided in the cladding layer '], (1111).

The image (light) entering from the object side end of the image guide is transmitted by the core of each optical fiber, but at this time, the light also enters the cladding layer and support layer of each optical fiber, and the light is transmitted through the core of each optical fiber. There is a problem in that the light becomes noise in image transmission, making the transmitted image unclear.

In the present invention, the end surface of the image guide on the objective side is filled with a light-shielding substance in the XABOTO layer and cladding layer of each processed and sown optical fiber. Since the incidence of light is blocked by the light-linking material, the above-mentioned noise problem is eliminated and the clarity of the transmitted image is improved.

The image guide of the present invention can be easily manufactured, for example, by the method shown below.

The end face of the image guide is treated with an aqueous mixed acid solution containing 10% hydrofluoric acid (same for the upper grades), 10% sulfuric acid, and 10% nitric acid at room temperature for about 20 minutes to form the crystal layer and support layer.・νching.

The depth of etching after 20 minutes of processing is several μm,
This level is usually sufficient. It may be etched more deeply if necessary. In this process, the cruciate layer, which is made of quartz and is easily etched because it contains dopants, is etched without breaking away at a faster rate than the core and sabot layers, and as a result, the core and support layer are left behind.

The core and support layer portions left behind by etching the cladding layer are also etched from their top and side surfaces, but since the support layer is generally thin, the surface area/volume ratio is lower than that of the core. The support layer, which has a large etch value, will etch faster than the core, resulting in selective etching of the cladding layer and the support layer as described above.

Next, a light-shielding substance such as an inorganic or organic black paint, a paste made by mixing fine metal powder or fine inorganic powder with a small amount of thermosetting resin as a binder is filled into the etched area, dried or baked, and finally the core is sealed. - Polishing the end face of the image guide to remove the layer of light-blocking material that has grown on the face.

[Brief explanation of the drawing]

The drawing is a partial cross-sectional view of the tip of the image guide of the present invention, in which 1 is an optical fiber, 11, 12, and 13 are the core, cruciate layer, support layer, and core of the optical fiber J, respectively. 2 is a light-shielding material filled in the etched portions of the cladding layer 12 and the support layer 3. Patent applicant: Dainichi Nippon Electric Cable Co., Ltd. Representative Director: Yukio Aoyama

Claims (1)

[Claims] An optical fiber having a three-layer structure, which has a core made of pure quartz, a crat layer made of quartz containing a dopant and having a lower refractive index than pure quartz, and a support layer made of quartz glass on top of that, is mutually fused. 1. An image guide comprising a support layer and a cladding layer of each etched optical fiber on the object side end surface of the image guide, wherein the support layer and cladding layer of each etched optical fiber are filled with a light-shielding material.