| 摘要 |
933,246. Television systems for viewing by X-rays. GENERAL ELECTRIC CO. March 30, 1961 [April 26, 1960], No. 11740/61. Class 40 (3). In a television system utilizing an X-ray responsive pick-up device 11 scanned by a scanning beam, to produce signals representative of an object 14 exposed to X-rays from a source 31, the source is pulsed in synchronism with the scanning operation so as to produce X-rays only during the period when the scanning beam is blanked for retrace. In the system illustrated, which operates at a frame rate of one frame per second, the source 31 is pulsed on by negative frame blanking pulses obtained from scanning generator 20 which are differentiated at 43, limited to the negative transient pulses at 45 and then applied to control a pulse generator 47. The final pulses 48a control a relay 49 which short-circuits a cut-off bias source 39 and allows the grid 33 of the X-ray tube, which comprises source 31, to assume a potential at which discharge takes place between cathode 32 and anode 34. Pulse generator 47 may comprise a mono-stable multivibrator whose trigger time is made adjustable so as to provide control of the pulse duration. Reference is made to a system which operates at a higher frame scanning rate, e.g. 15, 30 or 60 frames per second, and the pulse produced by generator 47 controls the grid 33 of source 31 through a step-up transformer. The signal produced by pick-up device 11 is applied through an amplifier 19 to a mixer 24 where it is combined with scanning- control signals obtained from generators 20, 21 and then applied to a conventional magnetic tape recorder 23. For play-back purposes, the tape may be formed into an endless loop and mounted in a conventional magnetic tape reproducer, the signal from which is separated into the picture and scanning-control components and applied to control a cathode-ray picture-reproducing tube, Fig. 2 (not shown). The pick-up device has storage properties and utilizes a photo-conductive material for the X-ray responsive target 12. The invention, which permits a desired X-ray dose to be given by high intensity radiation pulses of short duration, prevents blurring of the viewed images due to the current lag phenomenon of the photo-conductor. |
