JPS6427381A - White balance setting circuit for video camera - Google Patents

Abstract

PURPOSE:To set automatically always accurate white balance inexpensively by providing a lens drive control means, a mean value forming means of a color difference signal of an object, a control means talking white balance while adjusting the level of a color difference signal so as to make its mean value zero and a setting start means of the white balance. CONSTITUTION:A control signal 300 is supplied from a counter zoom control circuit 20 to a zoom motor drive circuit 18 to drive a zoom lens to the wide edge. R-Y, B-Y signals are integrated by low pass filters 14, 15, become mean DC voltages respectively and inputted to comparators 7, 8. Up-down counters 9, 10 increment their counts when the output of comparators 7, 8 goes to a high level. Gain control amplifiers 1, 2 decrease the gain to approach the level of the R-Y, B-Y signals to zero. When the output of the comparators 7, 8 goes to a low level, the level of both the signals is made close to zero in reverse operation to above. Thus, while a setting control signal 100 is outputted in this way, the white balance is taken automatically.