Abstract: Apparatus and methods are herein disclosed for use in conjuction with a standard monochrome closed-circuit television system for the generation, display, and manipulation of geometrical patterns upon the screen of the video monitor for the purpose of quantifying the irregularities in an interference pattern displayed on the screen of the video monitor. The invention comprises, in one embodiment, a control unit connected between the television camera and the video monitor of a standard closed circuit television system. The control unit includes the control means, switches, and electronic circuitry for the generation, manipulation, and control of video signals which are superposed onto the video signals from the camera and which are to be displayed on the screen of the video monitor.