Patent ID: 7852381

Claim:
An image signal processor, comprising: an image signal receiver that receives an image signal generated by an imaging device when said imaging device captures an optical image of an object through a photographic optical system, the photographic optical system having a focus optical system that focuses said optical image on a light receiving surface of said imaging device, and the photographic optical system being housed in a lens unit having a detector that determines an object distance based on a location of said focus optical system in said photographic optical system; a white balance processor that performs a white balance process for said image signal, based on a photographing magnification of said photographic optical system, said object distance, and light intensity of said optical image as said image signal is generated by said imaging device; a color separator that separates said image signal into primary color signal components for each picture element forming a light receiving surface of said imaging device, and a signal converter that converts said primary color signal components into first and second color difference signals; a plurality of predicting-areas, on a two dimensional coordinate plane of said first and said second color difference signals, are predetermined for predicting an actual light source illuminating said object; said white balance processor calculates a white balance gain used for multiplying said image signal, based on average values of said first color difference signals of said picture elements and said second color difference signals of said picture elements, and performing said white balance process for said image signal with said white balance gain; and said white balance processor calculates said white balance gain, based on average values of said first and said second color difference signals whose color combination for said picture elements are included only in one of said predicting-areas that is selected, from said plurality of predicting areas, based upon including the most of said color combinations.