VIDEO SYNTHESIZER FOR A DIGITAL VIDEO DISPLAY SYSTEM EMPLOYING A PLURALITY OF GRAYSCALE LEVELS DISPLAYED IN DISCRETE STEPS OF LUMINANCE

摘要

A digital video display system wherein the various characters to be displayed are displayed in the form of images of the complete character rather than the standard dot-matrix pattern of the prior art. A character generator in the display system stores signals representing the various characters to be displayed which are retrieved from storage in response to a character code. The signals are in the form of a binary code having a sufficient number of bits to represent a different number of levels of grayscale or luminance values for the various picture elements making up the character image. The binary codes thus retrieved from storage are supplied to a video synthesizer that generates the video signal to display the character images which may be displayed in a number of different modes including white-on-black, black-on-white, black-on-gray, and white-on-gray as well as different combinations of such modes to represent a cursor. The video synthesizer can generate output voltage levels in discrete stops for the different luminances to be employed. The voltage output signals differ from level to level in accordance with the 2.2 root of luminance.