Chrominance signal processing circuit, chrominance signal processing method and camera using them

摘要

In white balance adjustment adopting a feedback control technique, after white balance has been established at a certain color temperature, a lead-in limiting frame may be shifted following the establishment of the white balance, causing an incorrect operation to be carried out for a next change in color temperature. In order to solve the problem described above, the present invention provides a chrominance signal processing circuit which comprises: white balance amplifiers with relative gains among R, G and B primary color signals thereof adjusted by using a feedback control technique; an integration circuit for computing chrominance difference signals R−G and B−G from the R, G and B primary color signals and integrating the chrominance difference signals R−G and B−G to produce integrated values for each field of the chrominance signals; and a controller for setting a lead-in limiting frame for limiting a range for establishing white balance with a reference point at a predetermined color temperature taken as a base and for continuously monitoring the magnitude of a shift of said integrated values output by said integration circuit from said reference point and, for integrated values existing inside said lead-in limiting frame after the shift, controlling the relative gains of the white balance amplifiers in accordance with the integrated values.