JPS62150205A - Image fiber - Google Patents

Abstract

PURPOSE:To extremely lower the optical coupling between the outermost peripheral part of a core and a jacket layer covering the core so as to make transmission of a picture whose picture quality is not deteriorated at its peripheral part and uniformly excellent over the whole area, by providing a light leakage preventing layer between the outermost clad and the jacket layer. CONSTITUTION:Numerous pure quartz cores 1 are arranged in a clad 2 made of fluorine-added quartz having a refractive index which is lower than that of the pure quartz at prescribed intervals 2t and a light leakage preventing layer 4 having a thickness (t) is formed inside a jacket layer 3 which covers the clad 2 and is made of the same pure quartz as that forming the cores 1. In other words, the light leakage preventing layer 4 whose refractive index is smaller than that of the clad 2 exists between the outermost cores 1 and jacket layer 3 of an image fiber. In addition, the interval between the cores 1 and jacket layer 3 is set at the distance 2t between the cores 1 or more by providing the light leakage preventing layer 4. Therefore, the optical coupling between the outermost ores 1 and jacket layer 3 hardly takes place and deterioration of picture quality at the peripheral part can be remarkably prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image fiber that can prevent light leakage from the outermost core adjacent to the jacket layer and improve the image quality in the peripheral area. .

<Conventional technology> Multi-core image fibers having depressed-type pixels with a refractive index of I [made of pure quartz in the core and a pixel with a refractive index lower than that of pure quartz, such as fluorine-doped quartz, in the cladding, are generally made of pure quartz, which is called a jacket layer. A layer is formed on its outermost periphery.

As shown in Figure 3, which shows the cross-sectional shape of a conventional multi-core image fiber having pixels with a depressed refractive index distribution, the multi-core image fiber has a core 1 spaced apart from a cladding 2 having a lower refractive index at a fixed interval. The outermost periphery is surrounded by a jacket layer 3.

As shown in FIG. 4, which shows the same refractive index 11 of this multi-core image fiber, if the refractive index of the cladding 2 is used as a reference, the refractive index increase Δn of the core 1 (the thickness 2 of the rad portion 2
It appears peripherally across t. The refractive index increase of the shirt layer 3 roughly surrounding the pixel part of the image fiber is 0 minutes △
n or the outermost periphery] A1 with a gap t in between.

<Problems to be Solved by the Invention> As is clear from the knockdown ratio of a conventional multi-core image fiber using Hetun quartz for the core and jacket layer, the core surrounded by a cladding with a thickness of t is Since the image fiber is formed by reddening the pixels, the spacing between adjacent cores is set at 2t, or the spacing between the jacket layer and the outermost core 1 adjacent to this layer 1 is set to ℃. Since the jacket layer 3 and the core 1 have the same refractive index, the optical coupling effect between the outermost core 1 and the jacket layer 3 is large. It easily leaks into the image, creating a contrast problem.

The present invention has been made in view of the problems of the prior art, and it is an object of the present invention to provide an image fiber having holes in the periphery with less deterioration in image quality.

Means for Solving the Problems> The image fiber according to the present invention has a large number of aligned cores and a cladding that is interposed around these cores and has a refractive index lower than that of the cores. In the image fiber surrounded by a jacket layer, a light leakage prevention pattern having a refractive index less than or equal to the refractive index of the cladding is provided between the jacket layer and the outermost cladding inscribed in the cyanoget layer. It is characterized in that the thickness is greater than the thickness of the outermost crut between the outermost core and the jacket figure which are close to the core.

A light leakage prevention layer formed between a jacket having a refractive index equivalent to that of the core and the outermost cladding, and having a refractive index equal to or lower than that of the cladding, is formed between the core and the peripheral core of the image fiber. It acts to weaken the optical coupling effect with the jacket layer, and prevents light from leaking from peripheral pixels to the jacket layer.

<Embodiment> As shown in FIG. 1, which shows the structure of an embodiment of the image fiber according to the present invention, a large number of pure quartz cores 1 are arranged in a fluorine-doped quartz cladding 2 having a refractive index lower than that of pure quartz. A jacket layer 3 made of pure quartz, which is the same material as the core 1, surrounds the core 1 and is arranged at a predetermined interval of 2t.
A light leakage prevention figure 4 with a thickness of ↑ is formed on the inside of the . The light leakage prevention layer 4 is made of a material that is the same as the material of the cladding 2 or has a lower refractive index than that material.

As shown in FIG. 2, which shows an example of the refractive index distribution of this image fiber, there is a light leakage prevention diagram 4 having a smaller refractive index than the cladding 2 between the outermost core 1 of the image fiber and the layers 21 to 3. is intervening. Further, the distance between the core 1 and the layer 3 to the jacket 1 is set to be equal to or greater than the inter-core pressure i1t2t by the intervention of the light leakage prevention diagram 4. Therefore, the outermost core 1 and the jacket h b'f
3, and the deterioration of image quality in the peripheral area can be significantly prevented.

Table 1 below shows a comparison of the combined image fiber according to the present invention as shown in FIGS. 1 and 2 with the conventional example having the configuration shown in FIGS. 3 and 4. but,
The image fiber according to the present invention has a core: pure quartz cladding, two fluorine-doped quartz jacket layers; pure quartz light leakage prevention layer, and two fluorine-doped quartz layers. :Uses pure quartz. Then, the image quality of the periphery and center is adjusted by MT.
F (Modulation Transfer F
Evaluation was made in terms of line pairs per millimeter when the resolution was 50%.

As shown in Table 1, it was found that there was no deterioration in image quality at the periphery of the image fiber J3 according to the *invention.

<Effects of the Invention> According to the image fiber of the present invention, optical coupling between the outermost core and the jacket layer is significantly reduced by providing a light leakage prevention diagram between the outermost crat and the jacket layer. However, it is now possible to transmit images with uniform, submerged image quality over the entire surface without deterioration of image quality in the peripheral areas.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of an image fiber according to the present invention, FIG. 2 is a refractive index distribution diagram thereof, FIG. 3 is a sectional view of a conventional image fiber, and FIG. 14 is a refractive index distribution diagram thereof. Must have. In the drawing, 1 is a core, 2 is a craat, 3 is a jacket layer,
4 is a light leakage prevention diagram. Patent applicant Sumitomo Electric Industries Co., Ltd. Agent Patent attorney Mitsuyuki Dobe (and 1 other person) Figure 1 Figure 3 Figure 2 Figure 4

Claims (1)

[Claims] In an image fiber in which a jacket layer surrounds a large number of aligned cores and a cladding that is interposed around these cores and has a refractive index lower than the refractive index of the cores,
A light leakage prevention pattern having a refractive index lower than the refractive index of the cladding is provided between the jacket layer and the outermost cladding inscribed in the jacket layer and the outermost core adjacent to the jacket layer and the jacket layer. An image fiber characterized in that the image fiber is provided with a thickness greater than the thickness of the outermost cladding between the outermost peripheries.