GB1582886A - Optical fibre bundle with end structure - Google Patents

Description

(54) OPTICAL FIBER BUNDLE WITH END STRUCTURE (71) We, FUJI PHOTO OPTICAL CO.

LTD., a Company incorporated under the laws of Japan, of 1-324 Uetake-cho, Omiya shi, Japan, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be perfomed to be particularly described in and by the following statement: This invention relates to an optical fibre bundle, and more particularly to an im provement in the end structure of an image transmitting optical fibre bundle (hereinaf ter referred to simply as an "im-age guide").

In an image guide composed of a number of thin optical fibres arranged in an orderly array with a close-packed structure, the outer fibres on the periphery of the image guide are liable to slacken and the arrange ment of the fibres is apt to become dis ordered. Particularly, in image guides which are combined with an optical system used for enlarging an image, any disordered arrangement of the fibres is also enlarged, which results in degradation in image quali ty. In order td avoid this problem, it has been generally known to provide a field stop between the end of the image guide and an eyepiece.

In an image guide as practically manufac tured, the end face of the image guide is precision finished to make an optically flat end face. In order to prevent the finished end from staining, weathering or dimming.

a face plate is generally.cemented to the finished end -of the image guide. In such conventional image guides, the face plate is fixed directly to the end of the image guide and a field stop is mounted on the face plate to provide a mask surrounding the image obtained by the image guide. An eyepiece is then provided beyond the field stop.

The above described conventional image guide has a defect in that the effective aperture size of the field stop is changed as the position of the pupil of an observing eye is moved along the optical axis of the eyepiece, since the field stop is separated from the end face of the image guide. -When a picture of the image viewed through the image guide is taken, the marginal boundary of the image defined by the field stop is apt to be blurred.

If the field stop were inserted between, the face plate and the end face of the image guide in order to preclude the above described defect caused by the distance made therebetween, there would occur the following problems. If the field stop is fixed to the end face of the image guide, an adhesive must be used. In this case, it is very difficult to remove bubbles contained in the adhesive. Any bubbles present in the adhesive will accelerate the staining, weathering or dimming of the end face of the image guide.

Since the inner edge of the field stop, which has a substantial thickness. works to accelerate the formation of bubbles when the field stop is pressed against the end face of the image guide with the adhesive sandwiched therebetween. the prevention of the bubble formation is difficult. If bubbles were to become fixedly formed in the adhesive, it would become necessary to remove the field stop from the end face to again polish the --end face.

In view of the above defects, it is the primary object of the present invention to provide an image guide in which a field stop is fixed to the end face thereof so as to be at substantially the same position on the optical axis of an eyepiece used to observe the end face as that of the end face, whereby the change of the effective aperture size of the field stop is prevented.

It is an advantage that the present invention in its preferred form provides an image guide in which the formation of bubbles in an adhesive used to affix a field stop to the end face thereof is effectively prevented.

It is still another object of the present invention to provide an image guide which incorporates a field stop substantially coplanar with an end face thereof and in which a thick face plate can be used at said end, whereby the degradation of image quality caused by dusts or stains on the surface of the end face is prevented.

The present invention provides an optical fibre bundle and end structure therefor, comprising a stack of optical fibres an end face of which is precisely polished to provide a flat end face, a field stop supported between a pair of thin transparent films one of the films being fixed to said end face by adhesive, and a flat transparent face plate being fixed by adhesive to the other of the films.

An embodiment of the present invention will be described in more detail by way of example only with reference to the accom paying drawing of which: Figure 1 is plan view of a field stop used in the image guide - in accordance with the present invention, and Figure 2 is an exploded longitudinal sectional view showing the end of the image guide in accordance with the present invention.

Figure 1 shows a field stop 1 employed in the image guide in accordance with the present invention. The field stop 1 has a square aperture la. The field stop is sandwiched between a pair of thin transparent plastic films 2a and 2b as shown in Figure 2 and fixed thereto by means of an adhesive.

Since the field stop 1 is fixed to the films 2a and 2b independently from the image guide 5, any bubbles formed in the adhesive can be removed by vacuum deforming.

Referring to Figure 2, an orderly array of optical fibres 4 is sealed in a sleeve 6. The end of the sleeve 6 and the end of the fibres 4 are polished precisely to provide a flat face 5a to which said field stop assembly is attached. The assembly consisting of the pair of plastic films 2a and 2b and the field stop 1 fixed therebetween is adhered to the end face 5a of the image guide 5. Since the surface of the film 2b is flat, the assembly can easily be fixed to the end face Sa of the image guide by means of an adhesive without forming bubbles therein. On the assembly thus affixed to the end face 5a of the image guide. a face plate 3 is adhered to the surface of the film 2a by an adhesive.

Since the surfaces of the film 2a and the face plate 3 are also flat. the face plate 3 can easily be fixed to the assembly without forming bubbles in the adhesive. Thus, an image guide free from the fear of staining.

weathering or dimming on the end face thereof can be obtained.

WHAT WE CLAIM IS: 1. An optical fibre bundle and end structure therefor. comprising a stack of optical fibres an end face of which is precisely polished to provide a flat end face, a field stop supported between a pair of thin transparent films one of the films being fixed to said end face by adhesive, and a flat transparent face plate being fixed by adhesive to the other of the films.

2. An optical fibre bundle and end structure according to Claim 1 in which the transparent films are attached to said field stop by adhesive and this adhesive and the adhesive attaching said film to said end face is substantially bubble free.

3. An optical fibre bundle and end structure according to Claim 2 assembled by first attaching a field stop by adhesive between the transparent films, then substantially removing any bubbles formed in the adhesive. and then attaching the said one film to said end face by adhesive and attaching said face plate to said other film by adhesive.

4. An optical fibre bundle and end structure according to Claim 1 or Claim 2 assembled by first forming a field stop assembly composed of a pair of thin transparent films sandwiching a field stop between them and fixed to the field stop by means of adhesive, then substantially removing any bubbles formed in the adhesive, then fixing the assembly between said end face and said face plate by adhesive.

5. An optical fibre bundle and end structure according to any of Claims 1 to 4 in which the end of the bundle of optical fibres is sealed in a rigid sleeve. and the end face of the optical fibres and the end face of the rigid sleeve are polished together to provide said flat end face on which said end structure is fixed.

6. An optical fibre bundle and end structure therefor substantially as described herein with reference to or as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. invention to provide an image guide which incorporates a field stop substantially coplanar with an end face thereof and in which a thick face plate can be used at said end, whereby the degradation of image quality caused by dusts or stains on the surface of the end face is prevented. The present invention provides an optical fibre bundle and end structure therefor, comprising a stack of optical fibres an end face of which is precisely polished to provide a flat end face, a field stop supported between a pair of thin transparent films one of the films being fixed to said end face by adhesive, and a flat transparent face plate being fixed by adhesive to the other of the films. An embodiment of the present invention will be described in more detail by way of example only with reference to the accom paying drawing of which: Figure 1 is plan view of a field stop used in the image guide - in accordance with the present invention, and Figure 2 is an exploded longitudinal sectional view showing the end of the image guide in accordance with the present invention. Figure 1 shows a field stop 1 employed in the image guide in accordance with the present invention. The field stop 1 has a square aperture la. The field stop is sandwiched between a pair of thin transparent plastic films 2a and 2b as shown in Figure 2 and fixed thereto by means of an adhesive. Since the field stop 1 is fixed to the films 2a and 2b independently from the image guide 5, any bubbles formed in the adhesive can be removed by vacuum deforming. Referring to Figure 2, an orderly array of optical fibres 4 is sealed in a sleeve 6. The end of the sleeve 6 and the end of the fibres 4 are polished precisely to provide a flat face 5a to which said field stop assembly is attached. The assembly consisting of the pair of plastic films 2a and 2b and the field stop 1 fixed therebetween is adhered to the end face 5a of the image guide 5. Since the surface of the film 2b is flat, the assembly can easily be fixed to the end face Sa of the image guide by means of an adhesive without forming bubbles therein. On the assembly thus affixed to the end face 5a of the image guide. a face plate 3 is adhered to the surface of the film 2a by an adhesive. Since the surfaces of the film 2a and the face plate 3 are also flat. the face plate 3 can easily be fixed to the assembly without forming bubbles in the adhesive. Thus, an image guide free from the fear of staining. weathering or dimming on the end face thereof can be obtained. WHAT WE CLAIM IS:

1. An optical fibre bundle and end structure therefor. comprising a stack of optical fibres an end face of which is precisely polished to provide a flat end face, a field stop supported between a pair of thin transparent films one of the films being fixed to said end face by adhesive, and a flat transparent face plate being fixed by adhesive to the other of the films.

2. An optical fibre bundle and end structure according to Claim 1 in which the transparent films are attached to said field stop by adhesive and this adhesive and the adhesive attaching said film to said end face is substantially bubble free.

3. An optical fibre bundle and end structure according to Claim 2 assembled by first attaching a field stop by adhesive between the transparent films, then substantially removing any bubbles formed in the adhesive. and then attaching the said one film to said end face by adhesive and attaching said face plate to said other film by adhesive.

4. An optical fibre bundle and end structure according to Claim 1 or Claim 2 assembled by first forming a field stop assembly composed of a pair of thin transparent films sandwiching a field stop between them and fixed to the field stop by means of adhesive, then substantially removing any bubbles formed in the adhesive, then fixing the assembly between said end face and said face plate by adhesive.

5. An optical fibre bundle and end structure according to any of Claims 1 to 4 in which the end of the bundle of optical fibres is sealed in a rigid sleeve. and the end face of the optical fibres and the end face of the rigid sleeve are polished together to provide said flat end face on which said end structure is fixed.

6. An optical fibre bundle and end structure therefor substantially as described herein with reference to or as illustrated in the accompanying drawings.