Patent GB-1267614-A (GB)
Title: An image pickup system using a laser beam
Inventor: TAKAOKA TAKASHI
IPC: G03B15/00
Filed: 1970-03-02
Abstract: 1,267,614. Aerial television; laser ranging. TOKYO SHIBAURA ELECTRIC CO. Ltd. 2 March, 1970 [28 Feb., 1969 (2); 1 March, 1969], No. 9824/70. Headings H4F and H4D. An aircraft 21, Figs. 4A, 4B scans a pulsed fan laser beam through an angle 20 transversely of its direction of movement V, the direction of greatest width # of the beam being in said direction of movement. Reflections from the scanned strip of land 22 are detected and cause variations in the brilliance of a strip of light from a modulated source, the strip of light being laterally scanned is synchronous with the beam across a roll of photosensitive material, moving at a rate corresponding to that of the aircraft. The variations in brilliance may be proportional to the reflected light, to give a photographic type image on the material, or may be proportional to the echo time of an emitted laser pulse, to give an image having gradations of luminance proportional to the height of the land. The beam from the laser, 2, Fig. 2, pulsed at a repetition period t 0 , Fig. 3A is converted into a fan beam by cylindrical optical system 6, and laterally scanned by rotating mirror drum scanning device 5, the drum rotating at such a speed that T/t 0  = N pulses are transmitted in one scan. The reflected laser pulses from the moving strip 22, Figs. 6, 7 are collected by a mirror system 26/27, Fig. 6, or a lens system, Fig. 7, and directed on to the wide input end of a stack of tapering light guides 28, the stacking being in the direction of the strip, and the reflected light appearing at the narrow output end 28 of the stack, irrespective of the lateral position of the strip 22. The strip, distributed between n light guide ends 28-1 to 28-n, is imaged on an image intensifier tube 9, Fig. 2, or on n respective photodetectors 39-1 to 39-n, Fig. 14. In Fig. 2, the intensifier tube 9 is only enabled, by a source 10 synchronized by the laser pulse generator 1, during a period t 2 , Fig. 3D, extending from the minimum expected range time t 1  to the maximum expected range time t 4 . This stops receptions of interfering scattered light from intervening dust particles. Amplifiers 50-1 to 50-n in Fig. 14 receiving the outputs of the photodetectors are similarly gated on for period t 2 . The intensified strip of light appearing at the outport of the tube 9 is laterally scanned across the moving material 14, Fig. 8, by a mirror drum 13 rotating in synchronism with drum 5. In Fig. 14 the amplified photodetector outputs cause proportional brightness of respective lamps 43-1 to 43-a, and the strip of light so produced is scanned in the described manner across the material 14. The pulse outputs of amplifiers 50-1 to 50-n are fed to respective counters 51-1 to 51-n which are started by the transmission of the laser pulse and stopped by the receptions of the echo. Their output is thus proportional to the scanning slant range. These are converted to a vertical range measurements by correctors 52-1 to 52-n in accordance with the scanning angle of the laser beam. Signals indicative of the height of the scanned strip are thus produced and cause proportional brightness of lamps 53-1 to 53-n. The strip light from these lamps is scanned across a second moving material in the same manner as described for the light from lamps 43-1 to 43-n.