Multi-color, single gun, single grid/cathode beam index crt display

Abstract

A multi-color display system employing a raster-scanned cathode ray tube having a single gun, single beam and without shadow mask. Vertical color stripe phosphor triads are carried on the face of the tube. During a predetermined one or ones of non-viewed raster lines, beam impingement on successive red stripes is optically detected and this sample pulse train is compared with a system clock defined reference pulse train which corresponds to red video on-times of the system. Center-line defining ones of the sample and reference pulses are phase compared to calculate a raster offset error for offset correction of the horizontal deflection signal for the ensuing raster frame, while pulse-pairs of respective ones of sample and reference pulses are examined for time-occurrence discrepancy and errors for successive pulse pairs are stored in corresponding digitally-defined horizontal sweep addresses for the pulse-pair for subsequently addressed readout of storage for horizontal sweep correction at each successive pulse pair address during ensuing lines of the raster frame. Digital correction means are utilized to correct both the horizontal and vertical beam deflection signals for tube geometry defined linearity errors on a continuous basis throughout each raster frame, while indexing for assurance of proper picture color content is accomplished on a sample basis prior to the viewable portion of each raster frame and determined horizontal deflection corrections imposed throughout that frame.