Patent GB-954629-A (GB)
Title: Improvements in or relating to optical systems
IPC: A61B1/002
Filed: 1959-07-16
Abstract: 954,629. Endoscopes. H. H. HOPKINS. July 15, 1960 [July 16, 1959], No. 24539/59. Heading A5R. [Also in Division G2] An optical system for conveying and/or forming an optical image, which system comprising at least two rodlike biconvex lenses arranged end to end in separated relationship, the refractive index of the rod-like lenses being greater than that of a medium separating them, and the axial length of each of the said rod-like lenses being greater than the axial length of the said medium. As shown in Fig. 2 the optical system is embodied in an endoscope consisting of a tubular sheath 11 having an oblique extension 14 containing a lamp 15 for illuminating the cavity wall 19 into which the tubular sheath is to be inserted. Within the sheath is mounted a telescope 13 the hollow cylindrical casing 18 of which is sealed at one end by an oblique plate 21 having an aperture 22 aligned with an aperture 23 in the sheath 11 so that both apertures face on to the part of the cavity wall 19 which is illuminated by the lamp 15. This casing 18 contains rod-like glass biconvex lenses 24-29 which are spaced apart by annular spacers 31- 35 enclosing air. The outside edges of the lenses are made non-reflecting by coating with an optically black paint. The lenses and the annular spacers therebetween are a sliding fit within the casing 18, the lenses being of greater axial length than the spaces. The objective of this system is formed by the lenses 24 and 25 which forms at 43 an image of the internal cavity wall 19. This image is relayed by lenses 26 and 27 to a position at 49 and the last two lenses 28 and 29 form a final image at 54. Optical data are given in the Specification for one example of this optical system. A sleeve 55 is sealed to the rear end of the telescope casing and has threaded thereon a cylindrical casing 62. The casing 62 is, as best shown in Fig. 1a, open at one end and contains a slidable eyepiece mounting 72, the eyepiece comprising lenses 75 and 76 and prisms 78, 79 disposed therebetween. This eyepiece mounting is slidable by a rack and pinion mechanism and can be attached at 88 to  another casing which terminates in an aperture at 71. In this aperture is mounted a graticule or cross wire and in use the eyepiece mounting is first moved until the eyepiece is focused upon the graticule and then by means of the knob 88, the two casings are secured together so that they can be moved by the rack and pinion until the cross wire is in the plane of the final image 54. Also carried in the casing supporting the cross wire is a reflector 103 which is slidable into the light path so as to direct the final image downwardly through a lens system in a mount 91 into a photographic camera 65 attached to a downwardly extending neck 93 of the chamber 62. As shown in Fig. 3 this reflector 103 is on a bracket 104 which is movable along rails 98 against the action of a spring 99, the movement being effected by a push rod 101 having a handle 106 which when the prism moves into the light path, contacts a shutter release 108 and therefore thus operates the shutter of the camera. In another form, one or more prisms may be disposed between the rod-like lenses so that the optical system may be angled. (Fig. 5, not shown). In Fig. 7 a modified camera and eyepiece assembly is shown attached to the telescope casing 18. This assembly includes a camera lens 223 adjustable by rack and pinion mechanism so that it may be focused on the final image formed by the optical system of the telescope. The light from the camera lens is directed by a prism 236 on to a glass plate 239 which has a silvered portion 244 and a clear portion 245. This glass plate is carried by a pivoted arm linked to the camera shutter 243 so that when the unsilvered part 245 is brought into the light path from the prism an image is formed on the camera film 246. When however the silvered part 244 is in the light path the light is directed back on to the prism 236 and thence to a graticule 218 and to an eyepiece 234. This eyepiece is slidable and in use is first focused on the graticule 218. Thereafter the camera lens is adjusted until the image reflected by the silvered portion 244 of the glass plate is focused on the graticule 218. Optical data are given in the Specification for the camera lens 223 and for the eyepiece 234.