Servo Control of the Position and Size of an Optical Scanning System

A method of controlling the position and size of a television-type raster relative to arbitrary references by means of four servo mechanisms is described. One of the applications of such a system is that of a reading device for punched cards. A system for reading any one of a stack of cards without removing the selected card has been developed using the servo-controlled raster. The design of the servo mechanisms for this application is described in detail.