Visual Displays Using Pseudorandom Dot Scan

Pseudorandom dot scan yields a visually tolerable smallarea flicker for low frame rate television as compared to the large-area flicker of a conventional scanning sequence. With a short-persistence phosphor, one can use 12 frames/s. With a long persistence (such as a P38), one can display 3 frames/s. The "drift illusion factors" of various scanning systems are calculated. If square-wave generators are used to cover a rectangle, different scanning sequences are possible; this is applied to the scrambling of pictures. Hybrid systems, which avoid some of the disadvantages of a square-wave scan, are described. The results of an audience-reaction experiment in determining effective resolution are given.