JPS6256331A - Production of image guide - Google Patents

Abstract

PURPOSE:To produce an image guide which can transmit an image with high quality by detecting the void in a base material made of quartz glass, locating the axial position thereof, specifying the position of the void in a secondary base material corresponding thereto and cutting off said part. CONSTITUTION:The void is recognized as a luminescent point 10 and the position of the void in the longitudinal direction of the base material 1 made of quartz glass is specified when a light beam is made incident on one end face of the material 1. The secondary base material 2 is produced by subjecting the base material 1 to wire drawing. The part of the secondary base material where the above-mentioned void is estimated to exist is cut away in this stage. The secondary base materials 2 sized and cut while the void parts are cut away in the above-mentioned manner are bundled and are drawn, by which an optical fiber 3 is produced. The image guide which can transmit the image with high quality is thus realized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing an image guide using a silica glass optical fiber, and more specifically, to a method for manufacturing an image guide using a silica glass optical fiber. We propose a method for removing voided material to eliminate alignment.

[Prior art]

An image guide is made up of a bundle-like assembly of a large number of optical fibers, and is used to transmit an image from one end to the other. Optical fibers constituting the image guide include those made of multi-component glass and those made of quartz glass. The former has a low drawing temperature (softening point), so it can be drawn to a fine diameter to obtain an optical fiber with a uniform outer diameter, and then it can be drawn using the box stacking method, in which a large number of these are aligned and focused, or # It can be produced by the I elution method. Although it is used for medical purposes such as gastrocameras, it has drawbacks such as high transmission loss and the inability to manufacture long ones, and low heat resistance that makes it impossible to use it for monitoring high-temperature objects.

On the other hand, the latter, made of quartz glass, has low transmission loss and has excellent heat resistance and even radiation resistance, and can be used in high heat and radiation environments such as steel melting furnaces and nuclear power plants. Yes, and long ones are in practical use.

However, since quartz glass has a high drawing temperature, it is difficult to draw it using a crucible method like multi-component glass, and it is difficult to obtain an optical fiber with a uniform fine diameter. Optical fibers with non-uniform diameters cannot be arranged even if they are arranged in a stack, and it is virtually impossible to arrange the optical fibers so that there are no gaps between them. The presence of such gaps is undesirable because it degrades the quality of transmitted images.

Therefore, as a manufacturing method for a silica glass image guide with a high density of pixels, as shown in Figure 2, a cylindrical base material l
A secondary base material 2 with a diameter of approximately 200 to 400 μm is obtained by melt drawing.
This secondary base material 2.2... is bundled into many pieces, each 2.
Next, the adjacent base materials 2, 2... are heated and drawn so that they are fused together, and the adjacent optical fibers 3, 3...
Methods are known to ensure that there are no gaps between them.

In the case of such a method, the optical fibers 3, 3, etc. obtained by further heating and drawing the secondary base materials 2, 2, etc. are sufficiently thin,
Since the optical fibers 3, 3, . . . are in close contact with each other, high-quality image transmission is possible without gaps.

[Problem that the invention seeks to solve]

However, conventional products sometimes have dark spots that appear locally, which causes problems such as poor manufacturing yield and impaired image quality.

Measures for Solving Problem c] The inventor of the present application has repeatedly conducted numerous tests and studies in order to investigate the cause of the phenomenon in which such dark spots appear, and has found that the main cause is the base material l or secondary base material. It was revealed that this was due to the void in 2.

This will be explained below. As shown in FIG. 3, the base material 1 has a core 11 at the center, and a cladding layer 12 on the outside thereof.
Furthermore, a support layer 13 is provided on the outer layer. The base material l having such a structure is, for example, a cylindrical support layer material made of quartz glass, and the inner circumference of the support layer material is coated with CVD.
A cladding layer is doped with B, F-based compounds, etc. using a cladding method, and a cylindrical core material made of pure silica glass is fitted inside the cladding layer, which is then integrally heat-sealed. be. Therefore, such a base material 1 may contain voids in the core 11, the core 11-cladding layer 12 interface, within the cladding layer 12, the cladding layer 12-support layer 13 interface, and within the support layer 13. It exists in large quantities in the support layer 13 and at the cladding layer 12-support layer 13 interface. Note that the base material 1 is 15 to 20 mφ and several hundred fins long, whereas the void is 1 μm = l f
It has a size of about l.

Since such a base material 1 is drawn into a secondary base material having a diameter of approximately 200 to 500 μm, a void having a diameter and length corresponding to the proportion thereof is formed. These voids distort the cross-sectional shape of the secondary base material 2 from a perfect circle, and are trapped between the optical fibers 3.3 in the next step of drawing the image guide.For these reasons, the distance between the cores of the image guide is reduced. In addition, the image quality is impaired due to irregularities in the image quality, and voids are present between adjacent support layers, causing inconveniences such as increased light attenuation in these areas and the appearance of the dark spots.

The inventor of the present application, who has investigated such causes, has: ■ Detected voids in the base material and located their positions; By identifying the position of the void in the corresponding secondary base material and cutting out that part, a secondary base material that is substantially free of voids is obtained, and by focusing and drawing it, the core can be made in an orderly manner. We have established a method for manufacturing an image guide that is aligned, has no dark areas, and has high transmission image quality.

The gist of the present invention is a method for manufacturing such an image guide, which includes the steps of detecting voids in the base material, locating at least their axial positions, and information on the oriented positions, etc. In both cases, based on the effective length information of the base material that was effectively used to draw the line of the secondary base material, the longitudinal position of the void in the secondary base material that was generated due to the voids in i; 1 is identified. It is characterized by including the step of.

[Explanation of the entire manufacturing process]

First, an outline of the entire manufacturing process will be explained below.

First, as shown in FIG. 4, a light beam having an appropriate diameter is incident on one end surface of the base material 1 from a high-intensity light source 41 such as a halogen lamp. Since the base material 1 has the same optical structure as a thin optical fiber, most of it passes through the core 11 and a part passes through the cladding layer 12. Light leaks through or from the support layer 13. And these cores 11. When voids IO exist in the cladding layer 12 and the support layer 13,
Light is reflected in this area and is perceived as a bright spot from the outside.

The bright spot or void lO detected in this way is the base material l
The longitudinal position of is determined.

The base material l has connecting rods l at the upper and lower ends as shown in Figure 5.
a and lb are connected, and while heating the lower end of the base material l, the connecting rod 1b at the lower end is gripped by a chuck (ryJ not shown) and pulled downward to draw a wire. The connecting rod ia at the upper end is supported by a chuck (not shown) to support the base material, and is lowered as the drawing progresses and is wound onto the winding drum 42.

Since the wire drawing reduction ((diameter of base material 1/diameter of secondary base material 2) 2) R is set to a predetermined value and the wire drawing operation is performed, the voids 10 in the base material 1 are removed from the base material 1. L from the bottom of material l
If the void 10 is located at position c, the position of the void 10 in the secondary base material 2 will be at a position RLc from the tip of the secondary base material. The portion of the secondary base material in which voids are estimated to exist in this way is cut and removed at the stage of cutting the secondary base material to size.

Note that when manufacturing the secondary base material 2, the lower end 1c shown with hatching in FIG. 5 does not reach the prescribed wire diameter and is discarded, and the upper end 1d is left undrawn. The length of the portion is taken into account when calculating the position of the void in the secondary base material 2.

Next, while cutting and removing the secondary base material portion in which voids exist as described above, the pieces cut to size are bundled and drawn as shown in FIG. 2. The secondary base materials 2, 2... subjected to this drawing process do not substantially contain voids, so that each optical fiber 3, 3... has a cross-sectional shape as shown in FIG. The structure is arranged as a hexagon, that is, in a regular honeycomb shape, with uniform core spacing, and i
An image guide without the dark areas mentioned above is completed.

〔Example〕

Hereinafter, a specific method for identifying voids in the base material 1 and voids in the secondary base material 2, which is the main part of the method of the present invention, will be described in detail with reference to FIGS. 6 and 7.

FIG. 6 is a drawing showing the position of voids in the base material 1,
In FIG. 5, for convenience of explanation, the void position is shown by taking the dimension from the lower end side of the base material 1, but in reality, for convenience of calculation, the position is specified by the dimension from the upper end side. As shown on the left side of Fig. 6, voids A, A2, . A3...
The dimensions from the top of the base material 1 of An are A, , J2, 13. I
Let n be the length of the base material l, and let β be the length of the base material l. The dimension of void An from the lower end of base material 1 is j! -1, .

Next, paying attention to the lower end of the base material 1, as shown on the right side of FIG. 6, there is no hatching 1. Since the length of s does not correspond to the required wire diameter at the start of drawing, the secondary base material 2,
It is not used as 2.

Further, when the drawing is completed, the lower end of the remaining base material 1 (indicated by hatching) has an inverted conical shape with a length hl, as shown in FIG. Above this conical section, a cylindrical (or original) section of length hl remains. (However, in the actual line drawing, hl is made as close to O as possible to avoid waste.) As shown, the hl part is 2
Next, the length of these parts in base material 1 is calculated, even though they are not part of the base material.

Furthermore, the secondary base material 2 from the apex X of the inverted conical portion with length hl to the drum 42 (see Figure 5) is also cut, but the length of the base material l corresponding to this portion is 1. Let it be p.

To summarize the above, the length part of the upper end Lo + Lp of the base material l and the length part of the lower end Ls are not used as the secondary base material 2, and the remaining length part with hunting is 2
The next base material will be 2. Then, from one end of the base material L, Lo +
Void A1+A2. from the position of Lp. The dimensions from A3...An to L, , L2... L3...[,;).

Furthermore, let the diameter of the base material 1 be Dfi, the bottom diameter of the inverted conical portion be [)1m, and the diameter of the remainder of the base material 1 having a length h2 be D2M. Note that if h2 is sufficiently long, the remaining portion is not affected by heat, so D''=D, -D2.

Now, during actual operation, 11, 12, 123-1n, l, and D are actually measured in the preceding void detection process, and hI, h2. Dl and D2 are actually measured and input into a computer programmed to perform the following calculations. The calculation is performed as follows.

The length L (m) of the base material l effectively becomes the secondary base material 2, but if that length is A (m), then L-A/Rxl,
It can be expressed as ooo ・(1). However, R is a line reduction as described above.

Further, if the volume of the remaining part of the base material I shown by the broken line in FIG. It is uniquely determined by the position of the drum 42 and can be given as a constant.

Therefore, Ls can be obtained from L+Lo obtained from equations (1) and (3) and the constants t and p in °C using equation (4) below.

L s = 1- (L + Lo + Lp)
=・<4) Void A+, A2 + A3 = 2 of An
For convenience of cutting and removal, it is preferable to specify the position on the next base material 2 by the number of turns on the drum 42 rather than by length information.

Drum 4 of these voids Ai (i-+, z...n)
Place ff1 counted from the end turn of the bee on 2 (lined end side)
(Turn) Ti is determined by the following equation (5), and the first turn (
The position (turn) ti counted from the beginning of line drawing is as follows (6)
It is expressed by the formula.

Ti or ti may be used depending on the need.

c　x　too.

R(Ji-2CX1000/R-Lo)c x to
o.

CX 1000 Also Formula for the example where Cm2.5m.

C is the subscript i of the circumference 1i of the drum 42 is 1, 2.3...'n R(L+Lo+Lp-Iln) R(L+Lo+2CX1000/R-In)c
x ioo.

X100O It is sufficient to cut and remove the Ti-th turn from the end of the winding or the Ti-th turn from the beginning of the winding determined in this way.

During actual operation, the rt+jtj will be adjusted to ensure a certain level of safety.
It is sufficient to remove an excess of the ltteen.

When the above calculations are summarized into two equations, Ti and ti become the following equations (?) and (8), respectively.

(Margin below) CX100O... (7) Similar to below Margin) In other words, you can set this formula and the values of R and C in advance and measure them on a certain calculator, or h2. D,,D2. By inputting D and zi, the secondary base material portion to be cut is expressed by the number of turns on the drum.

[Young fruit]

Figure 1 schematically shows a product manufactured using only the secondary base material from which the void-existing portions have been removed.

The diameter of the core 31 is 7.10 μm, the diameter of the circumscribed circle of the cladding layer 32 is 12.94 μm, and the diameter of the circumscribed circle of the support layer 33 is 13.75 μm.The optical fiber 3 is focused and fused for the number of pixels required, Pure quartz skin vibe 4
As can be understood from the figure 3, which is tightly fitted into Figure 3, these optical fibers 3, 3... are arranged in a regular hexagonal shape and are arranged in a regular stacked bale shape or a regular honeycomb structure. , the core spacing is made uniform and no arrangement disorder occurs. There are no dark areas as seen in FIG.

As described above, according to the present invention, an image guide capable of high-quality image transmission can be realized.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an image guide according to the present invention;
Figure 2 is a process diagram for explaining six manufacturing methods for silica glass image guides, Figure 3 is a cross-sectional view of base material I, Figure 4 is an explanatory diagram of the method for detecting voids in base material II, and Figure 5 is The explanatory diagrams at the time of manufacturing the secondary base material, FIGS. 6 and 7, are explanatory diagrams for identifying voids. 1... Base material 2... Secondary base material 3... Optical fiber 31... Core 32... Clad layer 33...
Support Layer AI, A2, A3-An-Void Patent Applicant Dainichi Nippon Cable Co., Ltd. Agent Patent Attorney Noboru Kono n 2 Figure/Q 4 Figure 1. Boar (Su No. 5! Figure 7 Figure 7 Procedural amendment voluntarily written) September 13, 1985 Image guide manufacturing method 3, Relationship to the case of the person who corrects 7+li Patent applicant location Higashimukojima Nishinocho, Amagasaki City, Hyogo Prefecture 8゛ Address name (
326) Dainichi Nippon Electric Cable Co., Ltd. Representative Junzo Yuki 4, Agent Address ■543 Nisshin Building 207-5, 1-14-22 Shitennoji, Tennoji-ku, Osaka City, Subject of amendment
---R (I - ・・＜7) Tico- Cxl Shingen

Claims (1)

[Claims] 1. A cylindrical base material made of quartz glass having a core at the center and a cladding layer and a support layer on the outer periphery is melt-drawn and 2.
A method for manufacturing an image guide by obtaining a secondary base material, converging a large number of secondary base materials, and fusing them together, the method comprising: detecting a void in the base material and locating at least its axial position; Based on information on the located position and at least information on the effective length of the base material that was effectively used to draw the line of the secondary base material, the voids in the secondary base material generated due to the voids are determined. A method for manufacturing an image guide, comprising: identifying a longitudinal position; and cutting and removing a portion including voids in a secondary base material.