| 摘要 |
1379904 EVR recording system RANK ORGANISATION Ltd 8 March 1972 [15 March 1971] 6866/71 Heading H4F In a storage retrieval system using a driven storage medium on which information is stored in blocks relative to timing signals, e.g. EVR film, wherein the blocks comprise picture information frames and the timing signals field synchronizing pulses, (a) retrieval of the information is controlled by a periodic reference signal (e.g. field scanning of the flying spot scanner is triggered, 16, by a 50 Hz mains signal on line 10), (b) timing signals derived from this reference signal are incorporated into the retrieved information output signals (e.g. the field sync. pulses are derived, 18, from the mains signal), and (c) the retrieved timing signals (e.g. field pulses from the film on line 22) are phase compared, 30, with the reference signal and in response thereto the retrieval (e.g. the flying spot scanner) is additionally controlled so as to reduce the effects in the output signals of variations in drive speed of the storage medium. Phase detector 30 gives a short duration output during the field blanking period which represents in polarity and magnitude the extent of any phase error representative of film speed error. This short duration output is stored, e.g., in a box-car lengthener 32, so that it may be applied as additional field deflection to the flying spot scanner during the raster scanning of the subsequent picture frame. The effect is to vary the scanning raster position from frame to frame to compensate for film speed variations. Conventional film transport drive synchronization is effected by phase comparison 20 of the retrieved field pulses and the reference signal. |
