JPH05229841A - Image fiber - Google Patents

Abstract

PURPOSE:To provide an image fiber capable of satisfying three elements of radiation resistance, multiple picture elements and flexibility. CONSTITUTION:The objective image fiber is composed of a core 12 constituting picture elements, comprising an iodine doped quartz glass and a clad 14 consisting of a fluorine-doped quartz glass. Iodine raises the refractive index of the quartz glass without impairing the radiation resistant characteristics. As a result, difference in the specific refractive indices between the core and the fluorine-doped quartz glass to be the clad is made large and an image is sufficiently vivid even if the picture element diameter is made small and multiple picture elements are formed without impairing flexibility when the diameter is same as that of conventional fibers, thus finer diameter can be formed and flexibility can be improved when the picture element number is same as that of conventional fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in image fiber, which can satisfy the three conditions of being capable of having a large number of pixels, being excellent in radiation resistance and being excellent in flexibility. To do.

[0002]

2. Description of the Related Art As an image fiber having excellent radiation resistance, a fiber made of pure silica glass as a core and fluorine-doped silica glass as a clad is known. However, there is a limit in the manufacturing method for doping a large amount of fluorine into the quartz glass, and the relative refractive index difference between the core and the cladding is 1.2% at best.

[0003]

However, in recent years, there has been a strong demand for an image fiber used in a radiation atmosphere to have a large number of pixels, and the conventional fiber composition remains the same, and flexibility is maintained while the number of pixels is increased. However, there is a problem that the image becomes unclear due to a small relative refractive index difference between the core and the clad. Based on the above, the inventors of the present invention consider that the above problems can be solved if there is a dopant that does not impair the radiation resistance and that raises the refractive index of silica glass, and makes the present invention. It came to.

[0004]

The present invention has been made from the above viewpoint, and the invention according to claim 1 is characterized in that the core constituting the pixel is made of iodine-doped quartz and the cladding is made of fluorine. It consists of doped quartz.
It should be noted that iodine is used as a dopant because it is known that among the halogen elements, when fluorine is doped into the quartz glass as described above, its refractive index is lowered, and chlorine and bromine, on the contrary, raise the refractive index. However, the degree thereof is slight and only rises by about 1/100, whereas iodine can be raised by about 1/10.

[0005]

By using the quartz glass doped with iodine for the core forming the pixel, the refractive index of the core is increased, and the relative refractive index difference between the core and the fluorine-doped quartz glass as the clad is increased. In addition, the pixel diameter can be reduced and the overall diameter of the image fiber can be suppressed from increasing, so that the image fiber has a large number of pixels and is highly flexible and has excellent radiation resistance.

[0006]

EXAMPLE 1 FIG. 1 is a sectional view of an image fiber according to the present invention.
Reference numeral 1 is an image circle, and 2 is a quartz jacket surrounding the image circle. A large number of pixels 10 form an image circle, and a fluorine-doped quartz glass clad 14 is formed around an iodine-doped quartz core 12. In practice, adjacent claddings (shown by dotted lines) are melt-integrated and are not distinguished from each other. The refractive index of the core 2 is about 2.5% increased by doping with iodine, and the refractive index of the clad is 1.
It decreased by about 2%, and the relative refractive index between the core and the clad is eventually set to about 3.7%. This image fiber was prepared by the following method. First, the normal V
A soot preform made of quartz glass and having a diameter of 45 mm was obtained by the AD method. Using SiClI ₃ (melting point 3 ° C., boiling point 234 ° C.) in place of SiCl ₄ in the starting material gas, 200 sccm it in the center of the concentric multi-tube burner,
Ar is 300 sccm for the second layer and H ₂ is 100 for the third layer
O ₂ was supplied at 0 sccm and 1500 sccm to the fourth layer. Next, the maximum temperature of this soot preform is 1800
Put it in a heating furnace at ℃ and put SiI ₄ gas in the furnace at 20 cc /
Gradient sintering was performed while supplying min to obtain a iodine-doped SiO ₂ transparent glass rod having a diameter of 20 mm. The refractive index of this glass was 1,495. Then, a soot layer of SiO ₂ is formed around the iodine-doped SiO ₂ transparent glass rod by an external method.
It was formed into a thickness of mm and placed in a heating furnace having a maximum temperature of 1800 ° C., and SiF ₄ gas was supplied into the furnace at a rate of 50 cc / min to perform gradient sintering to dope transparent fluorine having a refractive index of 1,440. A core-clad type rod having an outer diameter of 30 mm and having a SiO ₂ clad layer (difference in relative refractive index of both Δ = 3.
7%). The rod thus obtained was introduced into a drawing furnace, and its tip was heated to 2000 ° C. to form a fiber, which was used as an image fiber element wire having a diameter of 200 μm. 10,000 of these image fiber strands have an inner diameter of 21 mm and an outer diameter of 23 m.
It was put in a quartz glass tube of m to form an image fiber base material, and this was introduced into a drawing furnace, and its tip was 2000 ° C.
It was heated and drawn to obtain an image fiber having a diameter of 650 μm. Although the number of pixels of this image fiber is 10,000, which is about four times as large as that of the conventional one, the relative refractive index difference between the core and the cladding is about three times as large as that of the conventional one, so that the whole diameter is made larger than that of the conventional one. It could be stopped at the same level, the decrease in flexibility could be prevented, and the radiation resistance was stable.

[0007]

In the image fiber according to the present invention, the core is doped with iodine to increase its refractive index more than that of silica glass without deteriorating the radiation resistance characteristics. A large rate difference can be obtained, and a stable image can be obtained even if the pixel diameter is reduced, so that it is possible to increase the number of pixels without impairing flexibility.

[Brief description of drawings]

FIG. 1 is a sectional view of an image fiber of the present invention.

[Explanation of reference numerals] 1 image circle 2 jacket 10 pixels 12 iodine dove quartz core 14 fluorine dove quartz clad

Claims (1)

[Claims] 1. An image fiber, wherein a core constituting a pixel is made of iodine-doped quartz and a clad is made of fluorine-doped quartz.