Optical cable with bending mechanism

Abstract: An optical cable of the present invention comprises: an optical fiber sensor (1), the optical fiber sensor (1) having an optical fiber having an external circumferential wall portion and a flexible coating film covering the external circumferential wall portion; and a tube member (3) with a good flexibility, the tube member (3) having an axis and an internal circumferential wall portion and receiving the optical fiber sensor (1) along the axis such that the coating film faces the internal circumferential wall portion of the tube member, the tube member (3) having a portion where the axis is bent; wherein fluid (2) is sealed in between the coating film and the internal circumferential wall portion of the tube member with its pressure being changeable.

Description: BACKGROUND OF THE INVENTION This invention relates to a cable with a bending mechanism, and more particularly to a cable usefully applicable to an optical fibre sensor such as a medical or industrial endoscope or to a laser beam surgical catheter. In the optical fibre sensor such as a medical or industrial endoscope, it is often required to externally operate the fibre sensor such that the fibre sensor is bent at its end portion to let an image pickup portion provided at the end portion face in a desired direction so as to pick up a desired image. To meet this demand, it is known that an optical fibre sensor shown in Fig. 1 has been developed. As shown in Fig. 1, a plurality of knuckle rings 6 are provided to encircle the fibre sensor body 8. The knuckle rings 6 come into contact with one another at protruded support portions 7 provided in the centre portions of the rings 6. Several operating wires 5 are provided at the peripheral portions of the knuckle rings 6 in a symmetrical manner. According to such a structure of the optical fibre sensor, be tightening or pulling up one or ones of the wires 5 but extending other one or ones of the wires, the end portion of the fibre is bent to let the image pickup portion at the end portion thereof face in a desired direction. However, the conventional optical fibre sensor having the above-described structure has such a problem that the fibre sensor as a whole is made thick by the use of the knuckle rings 6. To the contrary, recently it becomes possible to produce a very long but very thin image fibre which is used as a body of the optical fibre sensor. On the other hand, a fibrescope is known from document EP-A-164623 wherein, instead of knuckle rings encircling the fibre sensor body, a flexible tube member is used. However, operating wires still have to be threaded through the tube via cylindrical casted sections provided at the tips of the fibrescope and although there is no increase in the thickness of the fibrescope and there is a reduction in the weight of the bending portion nevertheless, the arrangement is complicated with the use of operating wires and there is still a need for a smaller sized device as well as more flexibility and the ease of use. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the conventional optical fibre sensor. That is, the object of the present invention is to provide an optical fibre sensor with a bending mechanism which has a small diameter and a relatively simple structure and is operable to bend at its tip end. In order to achieve the above-mentioned object and other objects, an optical cable of the present invention comprises: An optical cable, comprising: a flexible tube member; an optical fibre sensor body having an optical fibre and a flexible coating film covering an external circumferential wall portion of the fibre, the sensor body being coaxially arranged in the tube member such that the coating film faces an internal circumferential wall portion of the tube member, characterised in that a fluid is provided in between the coating film and the internal circumferential wall portion of the tube member, and in that the tube member is bent at an end portion and comprises a sealing means at the end portion for sealing the fluid in between the coating film and the tube member so that when pressure is applied to the fluid the degree of bending (a) of the tube member at the end portion is changed. BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an explanatory view of a conventional optical fibre sensor; FIG. 2 is a vertical sectional view of an optical fibre sensor cable of an embodiment of the present invention; FIG. 3 is a view showing externally the fibre sensor cable of FIG. 2; FIG. 4 is a view illustrating an end portion of the optical fibre cable of FIG. 2; and FIG. 5 is a front view of the end portion of the optical fibre cable of FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An optical cable with bending mechanism of an embodiment of the present invention will be described in detail hereunder, with reference to the accompanying drawings. FIG. 2 is a vertically sectional view outlining the optical cable with bending mechanism of an embodiment of the present invention. FIG. 3 is a perspective view showing a tip end portion of the optical cable of FIG. 2. In FIG. 2, the optical fiber sensor body 1 is inserted into a tube 3 having excellent bending characteristic or flexibility made of plastic such as polyethylene, rubber such as silicone rubber, or the like. The optical fiber sensor 1 is previously bent at its end portion with a desired radius of curvature, so that the tube 3 is in a shape indicated by a solid line in FIG. 2. When a space 2 is filled with liquid or gas, since the space 2 is closed at its tip end with a stopper or plug 4, the internal pressure of the space 2 is increased to thereby bend the tube 3 and stopper 4 in a direction a in FIG. 2. According to the optical fiber sensor of the present invention, by the above-described structure, the degree of bending of the fiber sensor 1 is changeable with controlling the internal pressure of the space 2. The above description is made to an embodiment of the present invention applied to an optical fiber sensor having an image sensor as its body. The above-described bending mechanism is further applicable to an optical cable in which an energy fiber made of AgBr, AgCl which transmit CO₂ laser beam therethrough, or the like is inserted with or without the image fiber. If the bending mechanism of the present invention is applied to the end portion of the cable having such an energy transmitting fiber therein, it becomes possible to freely change the laser beam irradiation direction so that it makes possible to apply the laser beam to any affected part on a body as a laser beam medical treatment. FIG. 4 shows one example of the optical fiber cable of the embodiment of the present invention used as a medical endoscope. FIG. 5 shows the end portion of the optical fiber cable of FIG. 4. In FIG. 4, a tube made of polyurethane resin having stainless braided wires therein is used for the tube 3. The optical fiber sensor 1 comprises a group of elemental fibers coated with polyurethane resin 14. The group of elemental fibers includes an image transmitting bundle fiber 10, an objective lens group 11 provided at the end portion of the image transmitting bundle fiber 10, an illumination light transmitting fiber 12 and a laser beam transmission fiber 13, as shown in FIG. 5. As shown in FIG. 4, the stopper 4 made of polyurethan resin is provided at the end of the optical fiber cable. The illumination light transmission fiber 12 is made of silicone resin. The image transmission bundle fiber 10 comprises a bundle of three thousand elemental fibers of multi-compound glass, at the end portion of which a lens 11 made of optical glass is provided and held at an optical position with a holding sleeve. As the laser beam transmission fiber 13, an optical fiber of pure quartz series having a core diameter of 200 micron is used. As described above, according to the bending mechanism of the optical cable of the present invention, it becomes possible to freely let the tip end of the fiber sensor face in a desired direction. The optical cable of the present invention is made simple in construction and has a small diameter. Various modifications and variations could be made in the invention without departing from the scope as defined in the claims.

Claims: An optical cable, comprising: a flexible tube member (3); an optical fibre sensor body (1) having an optical fibre (10;12;13) and a flexible coating film (14) covering an external circumferential wall portion of said fibre (10;12;13), said sensor body being coaxially arranged in said tube member (3) such that said coating film (14) faces an internal circumferential wall portion of said tube member (3), characterised in that a fluid is provided in between said coating film (14) and said internal circumferential wall portion of said tube member (3), and in that said tube member (3) is bent at an end portion and comprises a sealing means at said end portion for sealing said fluid in between said coating film (14) and said tube member (3) so that when pressure is applied to said fluid the degree of bending (a) of said tube member at said end portion is changed. An optical cable according to claim 1, wherein said sealing means comprises a stopper member (4). An optical cable according to claim 1, wherein said optical fibre sensor body (1) has an image transmission portion (10,11) and an irradiation beam transmission portion (13). An optical cable according to claim 1 or 3, wherein said optical fibre is selected from an image fibre and/or an energy fibre. An optical cable according to claim 1, wherein the fluid is selected from liquid and gas.

Inventors: AWAZU KUNIO C O OSAKA WORKS, OHKAWA SHINICHI C O OSAKA WORK, AWAZU, KUNIO C/O OSAKA WORKS, OHKAWA, SHINICHI C/O OSAKA WORKS
Applicants: SUMITOMO ELECTRIC INDUSTRIES, SUMITOMO ELECTRIC INDUSTRIES LIMITED
Application year: 1987
Main classification: G02B23
IPC codes: A61B1, G02B6, G02B23