Color imaging apparatus with compensation for beam deflection

Abstract

In a single-tube color imaging apparatus, the pickup tube includes a photoelectrical conversion target and a filter having recurrent groups of different color stripes through which an optical image is passed to the target. The target is scanned by an electron beam to produce a video signal having a frequency inversely proportional to the intervals at which the recurrent groups are arranged. The video signal varies in phase with the relative values of primary color components contained in the image passing through the stripes of each group and in amplitude with the intensity of the primary color components. Prior to normal operation, the target is uniformly illuminated with light of a predetermined color to generate a reference video signal, which is stored in a field memory. During normal operation, the reference signal is repeatedly read out of the memory and compared by frequency and phase comparators with the video signal from the target. Frequency and phase control circuitry responds to the outputs of the comparators by controlling the frequency and phase relationships between the two signals so that they match in frequency and phase before being applied to synchronous detectors.