Luminance signal producing circuits

Abstract

A luminance signal producing circuit comprises a signal input portion to which an image pickup signal is supplied from a solid-state image sensor provided with a color filter array comprising a plurality of color filter units arrayed in the manner of a checkered green-line sequential red and blue arrangement, a wide band luminance signal generator, a low frequency compensation luminance signal generator and a signal synthesizer for synthesizing a wide band luminance signal and a low frequency compensation luminance signal obtained based on the image pickup signal respectively from the wide band luminance signal generator and the low frequency compensation luminance signal generator with each other to produce a luminance signal. The low frequency compensation luminance signal generator is operative to produce a first signal in which a vertical carrier signal component is cancelled and a second signal in which a horizontal carrier signal component is cancelled, then operative to extract one of the first and second signals having a smaller absolute value when the first and second signals have the same polarity and none of the first and second signals or a signal corresponding to an average to the first and second signals when the first and second signals have respective polarities different from each other so as to have an extracted signal, and further operative to supply a horizontal low pass filter with the extracted signal to obtain the low frequency compensation luminance signal from the horizontal low pass filter.