Color imaging apparatus with closed-loop control means for producing color signal frequency and phase control signals from a reference color signal and two reference index signals stored in a memory

摘要

In a color imaging apparatus, an optical image is focused on a photoelectrical conversion target of a color image pickup tube through a color stripe filter and converted to an electrostatic image, the latter being scanned line-by-line in rectangular raster form by an electron beam to generate a color multiplexed video signal. First and second index stripe electrodes are located adjacent to edges of the raster area to be scanned at the beginning of each field and at the beginning of each line. A memory is provided to store field and line index signals generated by the index electrodes as well as a reference video signal generated by the target illuminated with light of a predetermined color. During normal viewing operations, the stored signals are retrieved from the memory for frequency and phase comparison with signals generated by the index electrodes and the target to control the phase relationship between the retrieved reference video signal with the color-multiplexed video signal to effect synchronous detection therebetween at proper timing to produce primary color signals. The retrieved index signals prevent the loss of proper timing when the target is dimly illuminated.