GB1232133A - - Google Patents

Abstract

1,232,133. Television. BRITISH BROADCASTING CORP. 16 Jan., 1970 [20 Feb., 1969], No. 9329/69. Heading H4F. Two adjacent frames of a motion picture film 16 which is intermittently pulled down one frame by a mechanism 18 are scanned simultaneously by a flying spot scanner comprising a cathode-ray tube 12, twin lenses 14, 14 and 20, 20, and photodetectors 22, 24 and a switch 34 connected to an output 32 is synchronized with the mechanism 18 to pass the direct signal from detector 22 when the film is stationary and the signal from detector 24, delayed 30 for a substantially integral number of fields, when the film is moving. In a preferred embodiment, the line 30 provides a delay of one field Πone half line period, and the spacing of the two flying spot images at the film is one film frame pitch Πone picture line pitch. In a modification, the switch may be arranged to pass both the signals at 26, 28 to a combining circuit, except when either signal is unusable due to pull down, when only the other signal is passed. The separation of the lenses 14 may be servo-controlled, e.g. by arranging that, during field blanking periods, the line scan of the tube 12 is perturbed to scan the film sprocket holes, when the outputs 26, 28 should be time coincident.