JPS6338682B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coating an image transmission path with a light shield, which is designed to bundle optical fibers and transmit high-contrast images with little light leakage.

The image transmission path that transmits images and patterns consists of a large number of aligned optical fiber wires that form pixels and are made up of a core with a high refractive index and a cladding with a low refractive index surrounding the core. Due to the refractive index difference between the core and cladding, the light incident on the core undergoes repeated total reflection at the boundary between the core and cladding, and is transmitted through the core. ing. Therefore, when the angle of incidence of light exceeds the critical angle determined by the refractive index ratio between the core and cladding, the light that has entered the core will pass through the cladding and leak to the outside. However, if there are bubbles, impurities, or irregularities between the optical fiber strands or at the boundary between the core and cladding,
A part of the leaked light is diffusely reflected here and mixed into the information light transmitted through the core, reducing the contrast of the transmitted image. In addition, some of the light incident on the cladding section also strays into the core section, making the contrast of the transmitted image even greater. It is clear that even by simply blocking this, it is possible to expect a significant increase in the contrast of the transmitted image.

The present invention is based on the above-mentioned findings, and an object of the present invention is to provide a method for coating an image transmission path with a light-shielding material, which can transmit clear images with high contrast by shielding parts other than the core portion at least on the incident end face. do.

The structure of the light shielding coating method for an image transmission path of the present invention that achieves this purpose is composed of a core portion through which light is transmitted and a cladding portion surrounding the core portion and having a lower refractive index than the core portion. In a method of coating a light-shielding material on at least a portion other than the core portion of an end face on the incident side of an image transmission line in which a large number of optical fibers are bundled in an aligned state, a photosensitive emulsion is applied to the end face of the image transmission line to be coated with the light-shielding member. After coating, uniform illumination light is applied to the image transmission path from the end face on the reflection side to expose the photosensitive emulsion at the position facing the core part, and after the photosensitive emulsion is developed, the photosensitive emulsion facing the part other than the core part is exposed. , then coating the end face of the image transmission path to be coated with the light shielding material, and removing the light-sensitive emulsion in the core portion, leaving the light shielding material in areas other than the core portion. It is.

That is, as shown in FIG. 1, which shows the principle structure by enlarging a part of the input side end of the image transmission line according to the present invention, the input side of the image transmission line 2 other than the core part 1 through which light is transmitted is shown in FIG. By coating the end face with the light shield 3, the light enters the image transmission path 2 only from the core part 1 located on the incident side end face, so only the light that enters each core part 1 within the critical angle remains unchanged. The image is transmitted to the exit side end face of the image transmission path 2. Therefore, the cladding portion 4 surrounding the core portion 1
Only the light that is incident on the core part 1 at a critical angle or more is incident on the core part 1, and between each optical fiber strand composed of the core part 1 and the clad part 4, or between the core part 1 and the clad part 4. As long as there are no bubbles, impurities, or irregularities at the boundary between the core section 1 and the core section 1, there is no risk that this light will leak out of the image transmission path 2 and be mixed into the information light transmitted through the core section 1 as noise. High contrast image information can be transmitted to the exit side end face of the image transmission path 2. in this case,
By coating a portion of the exit side end surface other than the core portion with a light shielding material, it is possible to achieve even higher contrast in the transmitted image, transmission pattern, etc.

By the way, if the thickness of the light shielding body 3 is too thick, part of the obliquely incident light to the core part 1 will be eclipsed, so it is desirable to make it as thin as possible, and generally a thin film of metal such as aluminum or various materials is used. It is possible that For example, as shown in FIG. 2, which shows an example of the manufacturing procedure, a photosensitive emulsion 5 is uniformly applied to the incident side end surface of the image transmission path 2 which has been polished smooth.
(see Figure 2 a), image transmission path 2
Illumination light of uniform brightness is transmitted from the exit side end face of the image transmission path 2 to expose the photosensitive emulsion 5 at a position facing the core portion 1 on the entrance side end face, and this is developed to expose the light-sensitive emulsion 5 on the entrance side end face of the image transmission path 2. The photosensitive emulsion 5 facing the portion other than the core portion 1 is removed (see FIG. 2b). in this case,
By using a parallel light beam as illumination light, making it obliquely incident on the exit side end face, and furthermore keeping the image transmission path 2 in a straight line, the light leaking from the cladding part 4 on the entrance side end face can be significantly reduced. can do. Next, after coating the light shielding body 3 by vacuum evaporation method, ion sputtering method, etc. (see FIG. 2c), the light-sensitive emulsion 5 adhering to the core part 1 is removed, and the incident side The light shielding body 3 remains on the end face at a portion other than the core portion 1. If the light shield 3 is too thin, it is possible to increase the thickness of the light shield 3 by using metal as an electrode and plating it. If the light shielding body 3 is also to be coated on the exit side end face of the image transmission path 2, it can be done in the same manner as the above-mentioned procedure. Further, the image transmission path 2 is usually surrounded by a jacket, and it is desirable to coat the end face of this jacket with a light shielding material.

As described above, according to the method of coating a light shielding material for an image transmission path of the present invention, the light shielding material is coated on the portion other than the core portion located on the incident end surface of the image transmission path, thereby preventing light from entering from this portion. Since only information light is transmitted within the core, it is possible to send clear images and patterns with high contrast.

Furthermore, according to the method of the present invention, in order to expose only the part of the photosensitive emulsion facing the core part, the illumination light is incident on the image transmission path from the end surface opposite to the end surface coated with the photosensitive emulsion. Therefore, there is no need for a special mask to separate the core part from other parts, and there is no need to align the mask.
The workability is extremely good, especially when the image transmission path is in a straight line as in the example and the parallel light beam is incident from the opposite end face, the advantage is that the leakage of light that exposes the photosensitive emulsion in the cladding area is significantly reduced. be.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the cross-sectional structure of the incident side end of the image transmission path according to the present invention, and FIGS. 2 a to 2 c are work principle diagrams showing the coating procedure of the light shielding body. is the core part, 2 is the image transmission path,
3 is a light shielding body, 4 is a cladding portion, and 5 is a photosensitive emulsion.

Claims (1)

[Scope of Claims] 1. An image transmission path in which a large number of optical fiber wires are bundled in an aligned state, each consisting of a core portion through which light is transmitted and a cladding portion surrounding the core portion and having a refractive index lower than that of the core portion. In the method of coating a light shielding material on at least a part other than the core part of the incident side end face of the image transmission line, the light-sensitive emulsion is applied to the end face of the image transmission path to be coated with the light shielding body, and the emulsion is uniformly applied to the image transmission path from the opposite end face. In image transmission, the photosensitive emulsion at a position facing the core is exposed by inputting illumination light, the photosensitive emulsion is developed, the photosensitive emulsion facing the area other than the core is removed, and then a light shielding member is coated. A method for coating an image transmission path with a light shielding material, the method comprising coating the end face of the path with a light shielding material, removing the photosensitive emulsion in the core portion, and leaving the light shielding material in a portion other than the core portion. 2. An image transmission path according to claim 1, characterized in that a parallel light beam is used as the illumination light, and the illumination light is incident obliquely to the end face while the image transmission path is in a straight line. Light blocking coating method.