Scanning Sequence and Repetition Rate of Television Images

This paper considers factors which affect the apparent steadiness of television images: namely, line flicker, flicker of the image as a whole, alternating-current ripple in the defecting circuits, alternating-current ripple in the video frequency signal, and various kinds of beating of the alternating-current ripple with the various scanning frequencies. It is concluded that an integer ratio between alternating-current ripple frequency and frame frequency is very desirable for progressive scanning and is almost imperative for interlaced scanning. Interlaced scanning with a frame frequency of thirty per second and a field frequency of sixty per second fulfills the requirements in regard to flicker and the relations to alternating-current ripple frequency for a sixty-cycle power source, and offers considerable net gain over other scanning procedures considered. The problems of both odd- and evenline methods of interlacing are discussed and the odd-line method is found preferable.