JPS56104593A - Automatic color balance device - Google Patents

Abstract

PURPOSE:To reduce erroneous correction to facilitate adjustment, by gating R, G and B signals of the TV camera or the like and by holding their peak values by negative peak value holding circuits and by using the held G signal as the reference to take out the difference signals between R and G and between B and G and by using these difference signals as control signals of color balance. CONSTITUTION:R, G and B signals from the color TV camera applied to input terminals 1-3 are compared with the hold value from black threshold determining circuit 7 by level comparators 4-6; and these signals are prescribed values or less, they are detected by AND gate 8 and are applied to gate circuits 101-103. Circuits 101-103 are opened by the output of gate 8 to hold R, G and B signals from terminal 1 in negative peak value holding circuits 104-106. The output of circuit 105 is used as reference to take out difference signals between R and G and between B and G by differential amplifiers 107 and 108, and the R black level control signal and B black level control signal are output from output terminals 109 and 110 and are sent to the black balance circuit of the camera main body to adjust automatically black balance.