Patent GB-788445-A (GB)
Title: Device for examination of inaccessible parts
IPC: A61B1/00
Filed: 1954-06-23
Abstract: 788,445. Television. SHELDON, E. E. June 23, 1954 [March 11, 1954], No. 18415/54. Class 40 (3). [Also in Groups VI and XL (a)] A television system arranged in the form of an endoscope for viewing inaccessible parts of the human body or machinery is characterized by the use of a flexible light conductor for conveying the image detail to the image-signal generator. Where the generator is in the form of camera pick-up tube, it is necessary to convey a complete image of the part under examination and the conductor is formed of a bundle of quartz, rutile, plastic or other light-conducting fibres, each of which in effect conveys one image point. The fibres are polished on their surfaces and preferably coated with a very thin layer of a material having an index of refraction lower than that of the fibre. The fibres are glued together only at their ends so that the conductor as a whole retains the maximum flexibility. In an alternative arrangement, the fibres are held together at their ends by threading each through an opening in a fine mesh screen. When it is necessary to restrict the cross-sectional area of the light conductor, reference is made to the use of an optical demagnifying system to form a reduced image of the part under examination on the end of the conductor. A magnifying system may be employed to restore the image at the other end before projecting it on to the camera tube. Where the signal generator is in the form of a photo-electric cell and operates in conjunction with a flying-spot scanner illuminating the part under examination; it is only necessary to convey detail of one image point at a time and the light conductor comprises a single flexible rod. Fig. 1 illustrates an endoscope incorporating a camera-type pick-up tube 55A. 51A is the light conductor together with optical systems 53A, 54A at each end, and 7 is a source of image illumination. The whole assembly is contained within a flexible housing 66 formed of a stainless steel spiral 66a covered with rubber tubing 66b and an outer cover (not shown) of neoprene. The end is formed with windows 12 and 18 for illuminating and viewing the part under examination and terminates in a conical rubber tip 67. Pump 44 communicating with a channel 44a permits the examined part to be distended by air or fluid. Channel 44a may also serve to evacuate the contents of the examined part. Power supplies 9, a scanning generator 32A, an amplifier 43a<SP>1</SP> and a cathode-ray display tube 37A for the pick-up tube signals remain external to the housing 66. To facilitate placing the endoscope in position through sharply curved passages, it may be constructed so that the housing may first be placed in position and the light conductor and pick-up tube introduced into the housing subsequently. The pick-up tube may also be formed in two parts of reduced length (see Group XL (b)) comprising respectively a cathode-ray tube flying-spot scanner and a signal-generating tube with aphoto-cathode responsive to the flying-spot scanner, which are introduced separately and then brought into working relationship. The Specification describes modifications, Figs. 5 and 6a (not shown), in which components of scanning for the signal-generating tube are performed optically. In another modification, Fig. 8 (not shown), the source 7 of image illumination is arranged at the pick-up tube end of the light conductor and transmits its light to the part under examination by way of the light conductor. The light conductor in this embodiment extends to a window in the tip of the endoscope, it being stated that the window may be opened mechanically and the end of the light conductor brought forward slightly so as to be close to the examined part. The Specification discusses in general terms a large number of additional details including the use of ultraviolet and infra-red responsive pick-up tubes and the adaption of the system for colour working. The source of illumination may be separate from the endoscope. Fig. 9 illustrates an endoscope incorporating photo-electric cells and operating in conjunction with a cathoderay tube flying-spot scanner 76A. The light conductor in this arrangement comprises only a single flexible rod 77A. The construction is otherwise similar to that shown in Fig. 1. As illustrated, three photo-electric cells 78a<SP>1</SP>, 78b<SP>1</SP> and 78c<SP>1</SP> are provided and operate in conjunction with crossed dichroic filters 80A for colour analysis. Reference is made, however, to the use of a single photo-electric cell in a black-andwhite system.