A video display system



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The present digital image processing system in the Image Analysis Laboratory in the Electrical Engineering Department at the University of Houston lacked a fast method of displaying images that had been scanned from the closed circuit television system and stored in the Scientific Data System 92 (SDS92) computer. The method in use was a display on a storage oscilloscope that required a considerable amount of time (about 30 seconds) to complete. The Video Display System requires about 1.5 seconds to convert and display an image on the television screen. The image consists of 128 X 128 pixels5 each consisting of sixteen possible gray levels. The ability to superimpose two images as well as increase horizontal resolution to 256 is included. The Video Display System consists of six subroutines and the necessary hardware to display images on the television screen. The six subroutines are integrated into the operating system for the digital image processing system and can be called by a four character command from either SDS92 or Hewlett-Packard 2100 (HP2100). The software releases control of the SDS92 during vertical retrace of the television monitor to allow computation and possible alteration of the image. The hardware includes an analog multiplexer that automatically displays video information from the camera if the Video Display System is not in use. Both digital and analog memory were tried as a storage element in the Video Display System. Digital memory proved to be the most cost effective storage element as well as offering the best quality image display.