Automatic correction of centering and convergence errors in CRT displays

摘要

An improved system for the automatic correction of centering and convergence errors in a cathode ray tube display is disclosed. The system includes a first masked light sensor (12) positioned on the major axis of the display and a second masked light sensor (14) positioned on the minor axis of the display. A light blip generator (16) is responsive to the horizontal and vertical timing pulses for unblanking the video circuits during the horizontal and vertical blanking intervals in order to generate light pulses in the vicinities of said first and second light sensors. A microprocessor based feedback controller (10) is responsive to the outputs of the light sensors and programmed to iteratively generate correction signals whenever no output is received from one or both of the light sensors.