Patent GB-540403-A (GB)
Title: Improvements in or relating to means for taking stereoscopic x-ray photographs
IPC: A61B6/02
Filed: 1940-01-09
Abstract: 540,403. R÷ntgen-ray apparatus. JACKSON, L. MELLERSH-. (Power X-Ray Products, Inc.). Jan. 9, 1940, No. 27547/39. [Class 98 (i)] Apparatus for producing stereoscopic X-ray photographs comprises means for successively forming on a fluorescent screen images produced by X-radiation from two spaced-apart points and a camera arranged to photograph the two images successively on two exposure areas of photosensitive material, means being associated with the camera for bringing the second area of the material into operation after taking the first photograph. In the apparatus shown in Fig. 1, the subject is supported over a horizontal fluorescent screen 10, above which the X-ray tube is carried on a platform 14 which is supported on guide rails 16 and moved by a link 18 connected to an eccentric pin 19 radially adjustable on a rotatable disc 20, in order to impart the necessary stereoscopic shift to the tube. The screen image is photographed by a camera 22 having a large aperture lens, to which the image is reflected by a mirror or prism 33, and a film feeding device comprising a reciprocable gripper 28 which is operated by a connecting rod 30 from an eccentric pin on a wheel 57 and engages the film in one direction of movement only. A hood 35 excludes visible light from the space between the fluorescent screen and camera. The apparatus is operated by a motor 40 through gearing including a Geneva mechanism 44, 95 which causes the tube 12 to be rapidly moved from one position to the other, and at the same time actuates the film feed mechanism, after which the tube and film are stationary during the photographing of the image. An illuminated counter 60 is included near one edge of the field of view of the camera to identify the photographs, is actuated after every second exposure by the Geneva mechanism. The shafts 46, 49 by which the film feed and counter mechanisms are driven are telescopic. A switch 82 momentarily closed by two pins 81 on the driving disc 44 of the Geneva mechanism completes the circuit of a conventional X-ray timer 80 which closes the supply circuit to the X-ray tube for a predetermined time when the tube is in each of its end positions. Where the driving motor 40 is started by closure of a switch 78 its circuit is maintained by a switch 77 until a pair of photographs have been taken, when the switch 77 is opened by a cam projection 79 on the disc 20 and the apparatus is stopped. In the form shown in Fig. 3, two spaced-apart X-ray tubes 100, 101 are used for giving a stereoscopic pair of image, and their terminals 105 are alternatively connected to the high-tension supply leads by switch members 106 connected by a bar 107 operated by solenoids 115, 116. The camera 112 contains two holders 110 for cut films on to one or other of which the image is projected by a mirror 111 which is rotated through 90 degrees between exposures by the action of solenoids 120, 121. The taking of a pair of photographs proceeds automatically on closure of a switch 78. This energizes the clutch winding 131 of an X-ray timer 130, the motor 135 of which closes a switch 132 which energizes a holding relay 152 to establish a circuit through contacts 154 so that the switch button 78 may be released. The closure of the switch 132 also energizes a solenoid 84 which closes a switch 75, high tension current being thereby supplied to the X-ray tube by way of leads 74 in order to effect an exposure. The relay 152 also closes contacts 160 establishing a circuit through a relay 156 which closes contacts 163 completing a holding circuit including a resistance 162 by which the relay 156 is maintained energized. The timer now opens the switch 132, de-energizing the solenoid 84 to break the high-tension supply to the tube and so terminate the exposure, and to allow a contact 166 to move to the left so energizing the solenoid 121. This causes movement of a pivoted arm 123 to the right which rocks the mirror 111 to the broken-line position. Simultaneously the solenoid 116 is energized to connect the hightension supply to the right-hand tube. The arm 123 when moved to the right closes contacts which complete a circuit through the clutch winding 131 of the timer, which again closes switch 75 to make the second exposure and energizes relay 152. The arm 123 also closes contacts completing a circuit through a relay 180, which opens contacts 171 and closes contacts 181, thereby de-energizing solenoids 121 and 116 and energizing a relay 183. The latter closes contacts 184, 185, the former holding relay 183 energized until the timer opens the switch 132, when relays 183, 152 are de-energized and the switch 75 is opened, terminating the exposure. De-energization of the relay 152 causes contacts 166 to short-circuit relay 156 through a circuit including the closed contacts 185, so that contacts 164 close to energize solenoids 115, 120 to return the switch 106 to the position in which the left-hand tube is energized, and to return the mirror 111 to the full-line position. At the same time a solenoid 187 is energized to operate the counter 60. The parts are now in their original positions, ready for making another pair of exposures. In a modification, the two images are taken by two lenses, alternately brought into use by a shutter operated by the solenoids 120, 121. Other forms of apparatus are referred to in one of which the two exposure areas in the camera are perpendicular to one another, one being exposed by reflection from a diagonally arranged mirror, and the other directly, the mirror being moved out of the image path. Or, a mirror or totally-reflecting prism may be moved in front of the lens to reflect the two images on to the two half-widths of the film. Alternatively, the lens or the film may be moved, or the camera may be swung about a pivot intermediate the lens and film, the fluorescent screen being also swung to maintain it parallel to the film.