The Fine Structure of Television Images

There are described the necessary or preferred relations in the fine structure of television scanning, so chosen as to yield a system which is both theoretically ideal and practically optimum. The relations involve the width and spacing of the lines and the intensity distribution of circular scanning spots in both transmitter and receiver, which are correlated with the filter characteristics and the required width of the frequency band. A "flat" field of scanning, as distinguished from a "half-tone" field, is required at both ends, especially in the transmitter to suppress spurious large patterns otherwise generated in the scanning process. For equal horizontal and vertical "width of confusion," the nominal cutoff frequency of the system is found to be f. = fpN.' R/ V2N2 in which fp= frame frequency Ns= number of scanning lines, and R = aspect ratio. The over-all electrical characteristics require distortionless reproduction up to fcand permit a gradual cutoff between fcand 2fc. The "quadratic-sum rule" is derived for a special case and is offered as a generally approximate expression of the image width of confusion w in terms of the width of confusion of the respective individual components (object, optical, scanning, electrical): W = VWi2 + Wo2 + ± wn2. Based on the proposed television system of 30 frames per second, the full utilization of 441 lines requires a separation of 5.5 megacycles between picture and sound carriers. A separation of 4.