Patent GB-477775-A (GB)
Title: Invisible ray vision system
IPC: H04N5/33
Filed: 1936-07-03
Abstract: 477,775. Viewing objects by use of infra - red and like rays; television. STURDY-CAGE PROJECTS, Inc. July 3, 1936, No. 18475. Convention date, July 6, 1935. [Classes 39 (i), 40 (iii), and 40 (v)] A method of producing a fluorescent light image of a field of view comprises simultaneously subjecting a fluorescent screen to the influence of two beams of radiant energy, one of which is of a nature to cause the screen to fluoresce and the other, which does not itself cause the screen to fluoresce, being of a nature to modify fluorescence of the screen by the first beam, and forming the second beam into the pattern of the field of view as it impinges on the screen, whereby an image is formed in differential values of fluorescent light due to modified fluorescence over the image area on the screen by action of the modifying beam. As shown in the Figure, the fluorescent screen 13 of a cathode-ray tube 10 is scanned by a beam emitted from the cathode 20 and an image of the field of view is thrown on to the screen by an objective lens combination 80a arranged within a casing 82a mounted on a shoulder 16 of the tube 10. A filter 83a designed to pass only infra-red rays is preferably mounted in the casing 82a in front of lens 80a. The fluorescent coating 14 on the screen 13 may consist of zinc sulphide (Sidot Blende), barium sulphide, strontium sulphide, calcium sulphide or Balmain's paint. Since the fluorescent light image thus produced on the screen 13 may be very faint, a lens 80 may be arranged opposite the screen to focus the light rays emanating from the screen on to a photo-electric cell 82, a filter 81 being provided as shown to prevent after-glow of the fluorescent screen and infrared rays from reaching the cell 82. The currents generated in this cell are fed through amplifiers 85, 87 to the control grid 36 of a second cathode-ray tube 30 operating synchronously with the tube 10, an intensified image being thus produced on the screen 33. The contrasts of the image on the screen 13 may be increased by employing a regenerative system consisting in capacitatively or inductively coupling the output of amplifier 85 to the control grid 22 of tube 10, control of the regeneration being obtained either by means of the variable resistance 99 or by regulation of the gain of the amplifier 85. When such a regenerative system is employed, the tube 30 may be dispensed with. Alternatively, a regenerative system may also be provided for the tube 30 and a portion of the picture current from this tube utilized to control the beam intensity of a third cathoderay tube, the screen of which is designed to be viewed directly. Both the tubes 10 and 30 may be arranged at,the transmitting station and a further tube or tubes provided at one or more receiving stations. A regenerative system may be employed in connection with a tube-at the receiving station and the image produced on the screen of this tube may be reproduced as an intensified image on the screen of a further cathode-ray tube, Fig. la (not shown). Fig. 2 shows a modified transmitting arrangement employing ultra-violet, violet or X-rays in place of a cathode ray. As shown, light from a glow lamp 261 capable of producing a beam of ultra-violet rays is projected by a lens combination 263 on to a mirror 266 which reflects it on to a fluorescent screen 252. The mirror is mounted so as to be oscillated about vertical and horizontal axes, Figs. 4-6 (not shown) by a pair of moving coil systems, one of which is fed with current having a frequency of 3000 cycles a second whilst the other is fed with current having a frequency of 20 cycles a second. The screen 252 which is thus scanned by the beam of ultra-violet light has an image of the object or field of view projected thereon by means of an objective lens 255, a filter 258 designed to pass only infra-red rays being preferably provided as shown. Fig. 3 shows a receiver for use with the transmitter shown in Fig. 2, comprising a glow lamp 327 light from which is projected by a lens 329 on to a mirror 330 adapted to oscillate about vertical and horizontal axes in synchronism with the mirror 266 and to reflect the light on to a screen 321. Fig. 7 shows a circuit arrangement employing the transmitter and receiver of Figs. 2 and 3, in which the light from the screen 252 is projected through a filter 356a (corresponding to filter 81, Fig. 1) on to a photo cell 357 the currents from which after amplification in amplifiers 360, 364 are fed to the receiving lamp 327. A regenerative system may be associated with the transmitter by inductively coupling the output of amplifier 360 as shown at 371, 372 with the input to the lamp 261. If desired, an amplifying and regenerative system may be associated with the receiver, the final image being viewed on a further screen scanned by an additional mirror operating in synchronism with the mirror 330, Fig. 7a (not shown). The receiver, Fig. 3, may be used in association with the cathoderay tube transmitter 10, Fig. 1 whilst the ultra-violet transmitter unit, Fig. 2, may be used with the cathode-ray receiver tube 30, Fig. 1. According to a modification of the transmitter arrangement shown in Fig. 2, the whole of the screen 252 may be flooded with light from the lamp 261 so as to become uniformly fluorescent, the image of the field being cast on the screen in infra-red rays as before. The image so produced may then be divided into picture elements by a scanning disc and transmitted to a distant station Fig. 2a, (not shown). If desired, the radiation or reflection of infra-red rays from the field of view may be increased artificially. Thus, if the system is used for enabling aeroplanes to find landing fields in darkness or in fog, such fields may be equipped with infra-red ray generators.