JPH0310580B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing an image fiber, which is a direct transmission path for images. More particularly, the present invention relates to an improved method of manufacturing image fibers using a technique known as the circular multi-process.

Prior Art Image fibers function as image transmission paths that transmit images to remote locations by utilizing total internal reflection of light, and generally consist of a large number of optical fibers that contribute to image transmission. It consists of a pixel section and a jacket section surrounding the pixel section.

Incidentally, the jacket section is generally made of a quartz tube because of its weather resistance and chemical stability, and is therefore excellent as a member for protecting the pixel section, but it does not contribute anything to image transmission. do not.

Therefore, when such image fibers are used as unit fibers and a plurality of these are bundled together to transmit a large amount of image information, simply bundling the unit fibers leaves the jacket part as a dark part of the image, which deteriorates the image quality. cause a decline. This problem can be solved by the so-called acid elution method in which a predetermined number of unit fibers are bundled and then the jacket portion is melted, but this method is extremely expensive.

A known method for manufacturing image fibers is the circular mulch method, in which unit fibers are first manufactured. In this case, as shown in the attached Figure 2 (this figure corresponds to the case of 7 cores), seven glass rods 3 (light transmission rods) having a single core 1 are arranged concentrically in parallel and densely. , 19 or 37 fibers are inserted into the jacket tube 9 in such a number as to give a close-packed structure, and the fibers are collapsed to form a base material for the unit fiber, which is then drawn to produce the unit fiber. Ta.

However, when the unit fiber is manufactured, cracks occur when it collapses, and the jacket portion remains, so the image fiber manufactured using such a unit fiber has problems such as the above-mentioned and third-stage defects. As shown in the figure,
A large gap 10 may be formed between the units, resulting in various problems such as a decrease in transmission efficiency per unit area and a decrease in image quality.

Furthermore, as an alternative method, without using a jacket tube, a number of optical transmission rods such as 7, 19, or 37 rods can be bundled concentrically in parallel and densely to form a close-packed structure, and the rods can be drawn as they are. A method of forming a unit fiber is also known, but in this method as well, as shown in Fig. 4, the core of the drawn unit fiber is deformed and does not maintain a perfect circle, but in order to obtain even better image quality. leaves an unfavorable gap 11. Therefore, the image fiber obtained by this method still has serious problems in terms of transmission characteristics.

Problems to be Solved by the Invention As mentioned above, in the conventional circular mulching method known as a method for manufacturing image fibers, cracks occur when collapsing during the manufacture of unit fibers, and jacket portions remain. When an image fiber is manufactured using such a unit fiber, the image fiber has a large gap 1 between the units as shown in FIG.
0 is formed, which results in poor image quality, transmission efficiency, etc.

In addition, even in the method of manufacturing image fibers using unit fibers that do not use jacket tubes, the core of the unit fibers may deform when drawn, or the image fibers may not maintain a perfect circle, resulting in problems with the transmission characteristics of the image fibers. It had various harmful drawbacks.

Therefore, the present invention solves the above-mentioned drawbacks of the conventionally known circular multi-method, and provides an image using unit fibers that does not create special gaps between unit fibers and minimizes core deformation. It is an object of the present invention to provide a method for manufacturing a fiber.

Means for Solving the Problems In view of the above-mentioned current state of image fiber manufacturing methods, the present inventors have conducted various studies and researches in order to develop a new method that can overcome the drawbacks of the conventional methods. As a result, it is extremely effective to use a spacer that corresponds to the shape and size of the gap formed when the optical transmission rods consisting of a core and a cladding are arranged in parallel and closely together. We found this out and completed the present invention based on this new knowledge.

That is, in the method of manufacturing an image fiber of the present invention, a plurality of optical transmission rods each having a core and a cladding are arranged in parallel and densely, and in the gap formed between the transmission rods, a fiber having the same shape as the gap, The method is characterized in that a spacer of the same size is inserted, heated and drawn to form a unit fiber, and then a plurality of unit fibers thus obtained are bundled and heated and drawn.

In the method of the invention, at least two types of spacers are required. That is, a peripheral spacer and a central spacer. Further, these spacers are generally made of glass, and are preferably of the same quality as the cladding portion of the optical transmission rod. That is, as described below, they may be heated and fused together to function as a cladding for the core of the light transmission rod as a whole.

After inserting these spacers into the gaps between the arranged optical transmission rods, they are heated and wire-drawn.
It is also advantageous to heat-soften the array of light transmission rods and spacers to fuse their contacts before said hot drawing.

Hereinafter, the method for manufacturing an image fiber of the present invention will be explained in more detail with reference to the accompanying drawings.

First, as shown in Fig. 1a, glass rods 3 having a core 1 and a cladding 2 are bundled concentrically in parallel and densely in a number such as 7, 9, or 37 that gives a close-packed structure. . Next, each
Two spacers, a peripheral spacer 4 and a central spacer 5, having cross-sections as shown in FIG. 1C are inserted into the gaps (α and β) formed in the bundle of glass rods, and A solid array body 6 having a rounded hexagonal shape is formed. Next, as shown in FIG. 1d, one end of the array 6 is connected to a quartz rod 7 (dummy rod) to form a preform 8 with a dummy rod. Either the fiber is drawn as is and the cut fiber is used as a unit fiber, or after the array 6 is formed, it is heated to a temperature near the softening point in an electric resistance furnace, plasma flame, etc., as shown in Figure 1e. All the contact parts are fused and integrated to form a preform 8', which is heated above its softening point and drawn to a diameter of several hundred μm.
It may be cut to form a unit fiber.

A large number of unit fibers thus fabricated,
An image fiber of a predetermined diameter is obtained by bundling the fibers in a parallel and dense state, inserting the bundle into a jacket tube having a diameter that allows the bundle to be tightly attached, heating it to a temperature near its softening point, and stretching it.

The light transmission rod used in the method of the present invention can be obtained by various methods such as CVD method, VAD method, etc., and the manufacturing method is not limited. Also,
As already mentioned, the cladding portion of the light transmission rod is preferably of the same quality as the spacer material.

Effect According to the method for producing an image fiber of the present invention,
After arranging optical transmission rods consisting of multiple cores and claddings in parallel and densely, a glass spacer is inserted into the gap formed between them, and by drawing in this state, it can be easily formed into an image fiber later. It is possible to significantly reduce the gaps that may be left behind, and furthermore to minimize core deformation.

Therefore, by following the method of the present invention, which includes such a special configuration, it is possible to effectively eliminate the above-mentioned drawbacks of the image fiber obtained by the conventional circular multi-method. Become. That is, it is possible to obtain an image fiber in which the boundaries between the units are not noticeable and the deformation of the core is extremely small, so that it is possible to transmit clear images with good image quality using such an image fiber.

Further, in one aspect of the present invention, after forming an array of optical transmission rods and spacers, this is heated to a temperature near the softening point, and before wire drawing, the array is heated to near the softening point temperature, and the The transmission rod and spacer are fused together. This is because, as mentioned above, if a preform with dummy rods is drawn as is, it will fall apart in the initial stage of drawing, especially when there are a large number of optical transmission rods or when each optical transmission rod is thick. There is no point in going out of your way to fill in the gaps.

Therefore, this fusion step is highly preferred for efficiently carrying out the method of the present invention.

Examples Hereinafter, the method for manufacturing an image fiber of the present invention will be explained in more detail with reference to Examples. however,
The scope of the present invention is not limited in any way by these Examples.

Example 1 Seven silica-based glass rods manufactured by the VAD method with an outer diameter of 5.6 mm, core/cladding = 0.40, and Δn = 1.5% were placed concentrically in parallel and densely as shown in Figure 1a. Then, the glass spacers shown in FIG. 1b were inserted into the gaps formed between the glass rods to form the rounded hexagonal array shown in FIG. 1c. One end of this array was joined to a quartz rod (diameter 16.8 mm, length 800 mm) as a dummy rod to form a preform with a dummy rod. this
It was heated at 2100°C and drawn to produce a unit fiber with a diameter of 232 μm. This unit fiber
Cut the 17,500 pieces into lengths of 300 mm, with an outer diameter of 35 mm.
It is inserted into a quartz glass tube with a wall thickness of 1.5 mm, aligned using ultrasonic vibration, the inside of the tube is depressurized to 10 ^-2 mmHg, and heated and stretched at 2100°C to form a tube with an outer diameter of 4 mm and a pixel diameter.
3.7mm, core diameter 4.2μm, distance between cores 10.4μm Number of pixels
An image fiber with a diameter of 120,000 mm, a NA of 0.25, and a length of 10 m was fabricated.

The image fiber thus obtained had little core deformation, and provided extremely clear images with inconspicuous unit boundaries.

Example 2 Nineteen silica-based glass rods with an outer diameter of 5.6 mm, core/cladding = 0.40, and Δn = 1.5% manufactured by the VAD method were
As shown in FIG. 5a, which is similar to FIG. 1a, the glass rods are arranged concentrically in parallel and densely, and spacers as shown in FIG. An array (see FIG. 5b) was formed, and one end of the array was joined to a quartz rod (diameter 28 mm, length 800 mm) as shown in FIG. 1d, to form a preform with a dummy rod. This is further heated in an electric resistance furnace.
It was heated to 1700° C. to fuse the contact portion between the glass rod of the preform and the spacer to form a rounded hexagonal fused body as shown in FIG. 5c, which was used as a preform. This preform
It was heated to 2100°C and drawn to obtain a unit fiber with a diameter of 380 μm. The unit fibers thus obtained were cut into lengths of 300 mm, and 6,300 of them were cut into pieces with an outer diameter of 35 mm.
Insert into a quartz glass tube with a wall thickness of 1.5 mm and align using ultrasonic vibration, and the internal temperature is 10 ^-2 mmHg.
After reducing the pressure to
An image fiber with a pixel count of 120,000, NA=0.25, and a length of 10 m was obtained.

The thus obtained image fiber of the present invention had little core deformation and gave extremely clear images with inconspicuous unit boundaries.

Effects of the Invention Thus, according to the method for manufacturing an image fiber of the present invention, a spacer having the same shape and size as the gap is arranged in the gap formed between the light transmission rods of the raw material, and the spacer is drawn by heating. Due to the unique technical feature of forming a unit fiber and then operating it in the same manner as before to form an image fiber, the resulting image fiber has many problems seen in the conventional method, namely the problem of cracking when collapsing. It is possible to solve problems such as large gaps formed between units, deterioration of image quality and deformation of the core due to this, and deterioration of transmission characteristics due to this. That is, according to the present invention, it is possible to produce an image fiber with significantly less core deformation and capable of transmitting extremely clear images.

[Brief explanation of the drawing]

1A to 1E are diagrams for explaining the image fiber manufacturing method of the present invention, FIG. 2 is a diagram for explaining the conventional circular multi-method, and FIG.
The figure shows that the image fiber obtained by the conventional circular mulching method has a large gap between the units, and FIG. FIG. 5 is a diagram showing that the image fiber has been deformed and does not maintain a perfect circle; FIGS. (Main reference numbers), 1... Core, 2... Clad, 3... Optical transmission rod, 4... Peripheral spacer, 5...
...Central spacer, 6... Array, 7... Dummy rod, 8... Preform, 9... Jacket, 1
0...Unit gap, 11...Intra-unit gap.

Claims (1)

[Claims] 1. A plurality of optical transmission rods having a core and a cladding are arranged in parallel and densely, and a spacer having the same shape and size as the gap is provided in the gap formed between the optical transmission rods. is inserted to form an array of optical transmission rods and spacers, which is heated and drawn to form a unit fiber, and then a plurality of unit fibers thus obtained are bundled and heated and drawn. manufacturing method. 2. The method of claim 1, wherein the spacer is made of the same material as the cladding. 3. A patent characterized in that, before heating and drawing the array to form a unit fiber, the array is heated to a temperature near its softening point to fuse the contact portions between the light transmission rod and the spacer. Claim 1
The method described in Section or 2.