Programmable interlace with skip and contrast enhancement in long

Abstract

Disclosed are systems and techniques for image generation applicable in general to any long persistence display device, particularly one in which contrast builds over a number of frames. The display device disclosed in detail by way of example herein is a high resolution cathodochromic CRT (CCRT) in a projection system. The system includes a deflection generator for the display device capable of writing to at least individual image lines in any order and, in some embodiments, to individually-addressed pixels. In raster-scanned embodiments, an image memory is included, capable of storing pixel data on a line-by-line basis. An image controller serves to read particular lines from the image memory and to write corresponding image lines on the display device. In one embodiment, those scan lines which have no picture information (e.g. all white lines in the case of a CCRT) are skipped as lines are read from the image memory and written to the display device, substantially increasing the frame refresh rate in the time-critical operation of writing to a CCRT. The skipping of lines is perferably implemented by storing a 'skip word' with each line of pixel data in the image memory, each skip word indicating a particular successive line to scan, and thus which lines to skip. The use of 'skip words' also permits programmable interlace to be implemented. 'Rolling writing' techniques of the invention facilitate display of partial raster images which become available line-by-line over a period of time, as well as point writing for annotation.