GB1471047A - Flexible light guide - Google Patents

Abstract

1471047 Light guides G NATH 28 June 1974 [29 June 1973] 28854/74 Heading G2J A flexible light guide, e.g. for an endoscope, comprises a single optical fibre 10 extending within a protective tubular shielding 18. At least one end of fibre 10 extends within the bore of a tubular end-fitting 14 which is made from a material, e.g. glass, which is fusible to the fibre, the extremity of the fibre 10 being fused to one end of end-fitting 14 while the remainder of the end portion of the fibre 10 is spaced from the wall of the bore of the end-fitting 14. In one embodiment, Fig. 1b, a homogeneous or clad-type fibre 10, e.g. of quartz glass, is fused at each thickened end inside an end-fitting 14 which is itself surrounded by a flexible liquidfilled 18, e.g. of ptfe, and rigid metal end-tubes 30 which may contain lenses 32. Inside tube 18 and surrounding the fibre 10 are provided glass spacers 20 which may be dielectrically coated. A flexible metal tube 26 may surround tube 18, metal rings being placed around tube 26 to define a safe minimum bending radius for the fibre. The ends of the fibre 10 may be polished flat. In a modification, Fig. 2 (not shown) the tube 18 is narrower and the flexible metal tube 26 and spacers 20 may be omitted. The rigid metal tube 30 is provided at the input end only and carries lenses; the exit end of the fibre is convex or concave to act as a lens. In another modification, Fig. 4a, the fibre 10a is a liquid filled capillary only one end of which is fused to its end-fitting 14, the other end being slidable inside its end-fitting 14. The fibre 10a is surrounded for most of its length by two coaxial flexible tubes 18, 18a which are spaced by a helical wire 44. The filling liquid is circulated through a heat exchanger by a pump entering the guide at 38 and leaving at 40. Liquid circulation and the free sliding of one end of the fibre within its suspension tube may be employed with a solid, homogeneous fibre.