Luminance signal producing circuits

Claim 1

A luminance signal producing circuit comprising; signal input means to which an image pickup signal is supplied from a solid-state image sensor which has an image pickup flat portion comprising a matrix of two-dimensionally arrayed rows and columns of picture units and provided thereon 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 to correspond to the picture units, respectively, said image pickup signal comprising red, green and blue signal components obtained respectively from the picture units forming each horizontal reading row in the image pickup flat portion, signal delaying means for delaying the image pickup signal supplied to said signal input means by one line period in stages, wide band luminance signal generating means for producing a wide band luminance signal based on delayed image pickup signals obtained from said signal delaying means, low frequency compensation luminance signal generating means for producing a low frequency compensation luminance signal based on both of the image pickup signal supplied to said signal input means and the delayed image pickup signals obtained from said signal delaying means, and signal synthesizing means for synthesizing the wide band luminance signal and the low frequency compensation luminance signal obtained respectively from said wide band luminance signal generating means and said low frequency compensation luminance signal generating means with each other to produce a luminance signal, wherein said low frequency compensation luminance signal generating means 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 based on signals obtained from a vertical low pass filter to which the image pickup signal supplied to said signal input means and the delayed image pickup signals obtained from said signal delaying means are supplied, 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 the average of 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 said horizontal low pass filter.