| 摘要 |
784,856. Television. SOC. NOUVELLE DE L'OUTILLAGE R.B.V. ET DE LA RADIOINDUSTRIE. Feb. 12, 1954 [Feb. 21, 1953; March 16, 1953], No. 4249/54. Class 40 (3). In an arrangement for recording interlaced television images on intermittently moving kinematographic film by exposing the film during alternate field scans of the cathode-ray tube 6 which reproduces the images the fields which occur when the film is obturated being photographically effective (due to the " afterglow " of the tube) in the subsequent exposure period the gain of the video amplifier 3 which supplies the television signals to the tube 6 is controlled in accordance with a gain control voltage having the waveform shown at J (Fig. 4), the positively-going portions occurring during the non-exposure and the negatively going portions occurring during the exposure of the film in order to compensate for the light decay characteristic of the screen of tube 6. As shown, the gain of amplifier 3 is controlled by clamping its control grid to the potential of waveform J by means of a clamp circuit 11 controlled by clamping pulses occurring during line retrace periods so that its gain remains constant during line-trace periods but varies from one line to the next in accordance with the variation of waveform J. The output of amplifier 3 is then supplied to the tube 6 via a second amplifier 14 the control grid of which is clamped to a reference potential (to restore the D.C. level) by means of a second clamp circuit 15 also controlled by pulses occurring during the line retrace periods. To compensate for the " gamma " effect of tube 6 the signals are initially (prior to input amplifier 3) amplified in an amplifier having a suitable characteristic and the gain of which is controlled in similar manner to that of amplifier 3 (Fig. 8, not shown). Specification 640,186 is referred to. |
