Television film transmitters using apertured scanning discs

This paper outlines various methods which can be used for the production of interlaced signals by apertured-disc film scanners. A novel arrangement using an intermittent-magnification optical system is described, and details are given of a complete transmitter according to this method. The continuously moving film is illuminated by a split optical system to remove picture flicker, and a device is included for the exact compensation of film shrinkage. Comprehensive details are given of the construction of highspeed discs, and of punches and dies for the production of scanning holes only 30¿40 microns in diameter. It is shown that, for a given noise level at the input of the vision channel, the scanning resolution obtainable is proportional to the strength/density ratio of the disc material, and the limit is well above present television standards. Synchronizing signals are all derived from the disc, and various mechanical arrangements are shown by which multiple and sub-multiple frequency signals are available for control purposes.