GB705953A - Improvements in or relating to picture analysis and recording devices - Google Patents

Abstract

705,953. Television. RADIO-INDUSTRIE SOC. ANON. Oct. 8, 1951 [Oct. 14, 1950; Nov. 18, 1950], No. 23401/51. Class 40 (3) In a system for the recording of television images upon or for the generation of television signals from kinema film, there are provided means for deriving a correcting signal from the frame synchronizing pulses and further means employing the correcting signal to compensate for flicker occurring at the picture repetition frequency due to non-uniform illumination of the film gate. In an arrangement to which the invention is applied wherein television signals are generated by the scanning of kinema film, light rays from a scanning raster formed upon the screen 2 pass through two separate optical paths comprising prisms 4 and 5 and the lens 6 so that, were the shutter 15 removed, a pair of images of the scanning raster would be formed one above the other upon the film 3 in the film gate 7. The shutter 15 exposes the upper and lower halves of the gate alternately in synchronism with the scanning of odd and even frames and the film 3 passes continuously through the gate at such a rate that interlaced scanning of the film results. Light passing through the film is focused upon a photo-electric cell 10 which consequently develops a signal which is then passed to suitable utilization circuits. It is found in such a system, or in a similar system for recording images derived from received television signals upon film, that a flicker effect occurs due to non-uniform illumination of the film gate. In order to compensate for this a correcting voltage at one half the frame-recurrence frequency is obtained by applying the framesynchronizing pulses to an Eccles-Jordan circuit and shaping the output square-waves therefrom by means of one or more stages of integrating circuits. The correcting voltage may be applied to a control electrode of the cathode-ray tube on to one or more stages of the circuits conveying the television signals to or from the apparatus. In the case of a transmitter circuit, as illustrated, the correcting may alternatively be applied to the photo-cell 10, particularly when this incorporates a cascade-type electron multiplier.