JPS61205634A - Production of image guide - Google Patents

Abstract

PURPOSE:To produce an image guide having well aligned elements, easily, by heat-treating the surface of a preform made of a core and a clad added with fluorine, drawing the treated preform, bundling the obtained filaments and fusing and integrating the filaments. CONSTITUTION:The surface part of a preform consisting of a core made of pure quartz, etc. and a clad having a refractive index decreased by the addition of fluorine to quartz, etc., is heat-treated to evaporate the fluorine near the surface. A high-melting glass skin having decreased fluorine concentration can be produced thereby. The heat-treatment is carried out preferably by rotating the preform, and igniting with an oxyhydrogen flame at a temperature lower than the melting point of the clad glass. The heat-treated preform is drawn and the obtained filaments are bundled and fused together. The flow of the clad 13 can be prevented and an image guide free from the disturbance of the arrangement of the cores 12 and having high resolution power can be produced by this process.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of manufacturing an image guide, and in particular, performs a surface heat treatment on a base material before drawing the strands constituting the image guide, so that the surface portion The present invention relates to a method of manufacturing an image guide in which a high melting point glass shell with a low fluorine content is formed.

[Prior Art] In radiation-resistant image guides and high numerical aperture image guides, fluorine is often added to the cladding of the wires constituting the pixels of the image guide. this is,
For radiation-resistant image guides, pure quartz with good irradiation properties is used as the core material, so the cladding is made of fluorine,
This is because it is necessary to lower the refractive index by adding boron or the like.

In addition, for high numerical aperture image guides, dopants such as germanium and phosphorus are added to the core to increase the refractive index, and fluorine is added to the cladding to lower the refractive index. This is to increase the difference and increase the numerical aperture.

FIGS. 3 and 4 show the refractive index distributions of the base materials of the radiation-resistant image guide and the high numerical aperture image guide before wire drawing, respectively. In FIG. 3, 1 is a core portion made of pure quartz, and 2 is a cladding portion doped with fluorine. Further, in FIG. 4, numeral 3 is a core portion doped with germanium, and numeral 4 is a cladding portion doped with fluorine.

In manufacturing an image guide, a large number of wires having the same chevron-shaped refractive index distribution as the base material produced by drawing the base material are bundled and fused together to form a single body.

[Problems to be Solved by the Invention] However, since fluorine is added to the cladding of the wire, the cladding is a low-melting glass. Therefore,
Even if the cable wires are regularly bundled and arranged and fused together, the cladding 5 melts and becomes fluid during fusion, and the arrangement of the core 6 becomes irregular, as shown in FIG. In many cases, the resolution of the image guide decreases.

In order to prevent this arrangement of the cores 6 from being disturbed, there is a method of covering the outside of the cladding of the base material with a quartz tube 7, as shown by broken lines in FIGS. 3 and 4.

However, in order to cover the quartz tube 7, it is necessary to use the rod-in-tube method, and in some cases, H
It is also necessary to perform F processing, which requires a great deal of knowledge.

[Object of the Invention] This invention was devised to solve the problems of the prior art described above, and an object of the invention is to provide a method for manufacturing an image guide that can easily manufacture an image guide without disordered arrangement. Our goal is to provide the following.

[Summary of the Invention] In order to achieve the above object, the present invention provides a surface portion of a base material of a strand of wire, which is made up of a core and a fluorine-doped cladding, before being drawn. is heated to volatilize the fluorine near the surface of the base material, which is the outermost layer of the cladding of the wire, to form a high melting point glass acid with a low fluorine concentration. This prevents the arrangement from being disturbed due to the flow of the clad during fusion of the strands.

The core material may be pure quartz or a suitable dopant, such as Ge or P.

It may be quartz containing one or more of M, i, Sb, etc.

In addition, the cladding is made of quartz containing at least F,
Other dopants, such as B, if desired.

It may contain Ge and P@.

Further, as a heating method for the base material, an oxyhydrogen flame, a plasma flame, an electric furnace, etc. are used, but the method is not limited to these. The heating temperature varies depending on the composition of the cladding, so it cannot be determined unconditionally, but it is preferable to ignite at a temperature lower than the melting point of the cladding glass. However, if it is heated too much, fluorine will volatilize violently, and the entire cladding will become close to quartz, reducing the difference in refractive index between the core and the cladding.
A lot of light seeps out from the core, resulting in poor image contrast.

[Examples] Examples of the present invention will be described in detail below with reference to the accompanying drawings.

First, it consists of a core made of pure quartz and a cladding made of quartz doped with fluorine, and the difference in refractive index between the core and cladding is 1%. A base material (having a cylindrical shape with an outer diameter iea* and a ratio of the radius of the core part to the thickness of the cladding part of 5:3) with a ratio distribution is prepared.

Next, this base material is mounted on a glass lathe, and while being rotated slowly at 50 rpm, it is fed in the axial direction at 80 M/min, and the surface of the base material is heat-treated two to three times with an oxyhydrogen burner.

By this heat treatment, as shown in FIG. 1, the fluorine on the surface of the cladding portion 9 of the base material 8 is volatilized, and an outer shell 11 whose glass composition is close to that of pure quartz of the core portion 10 is formed.

Next, the base material 8 having the outer shell 11 made of quartz glass having a high melting point is drawn to produce a wire. The refractive index distribution of this wire also had the same W-shape as the refractive index distribution of the base material 8.

Finally, these strands are bundled and arranged regularly and fused together to form an image guide.

The obtained image guide is core 1 as shown in Figure 2.
2 were arranged regularly. This is because when the strands are fused together, the outermost layer of the strands is made of high melting point glass, so this outermost layer functions as a hard shell, and the clad 13
This is because it prevents fluidization due to melting.

[Effects of the Invention] In summary, the present invention provides the following excellent effects.

(1) A high melting point glass shell is formed on the surface of the base material by surface heating treatment, and therefore a high melting point glass shell similar to quartz is formed in the outermost layer of the wire, so that the cladding during welding of the wire is An image guide with high resolution and no disturbance in the core arrangement can be obtained.

(2) It is only necessary to heat-treat the surface of the base material, which is extremely simple compared to the method of attaching a quartz tube to the outside of the cladding portion of the base material.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the refractive index distribution of the base material obtained by the method of the present invention, Fig. 2 is a partial cross-sectional view of an image guide manufactured from the same base material, and Fig. 3 is a diagram showing a conventional radiation-resistant image guide. Figure 4 is a diagram showing the refractive index distribution of the base material for conventional high numerical aperture image guides, and Figure 5 is an image of the base material manufactured from the base material for conventional image guides. FIG. 3 is a partial cross-sectional view of the guide. In the figure, 8 is the base material, 9 is the cladding part, 10 is the core part, 11
is an outer shell, 12 is a core, and 13 is a cladding.

Claims (2)

[Claims] (1) In manufacturing the base material before drawing the strands, which is performed prior to manufacturing an image guide formed by bundling and fusing strands of strands consisting of a core and a fluorine-doped cladding, A method for manufacturing an image guide, characterized in that the surface portion of the base material is heat-treated to volatilize fluorine near the surface of the base material, which will become the outermost layer of the cladding, thereby reducing the fluorine concentration. (2) The method for manufacturing an image guide according to claim 1, wherein the heat treatment of the surface portion of the base material is performed while rotating the base material using an oxyhydrogen flame.