Patent ID: 8149325

Claim:
An exposure control apparatus for exposure control of an electronic digital camera installed on a vehicle, said camera disposed to periodically capture respective images of an external scene ahead of said vehicle, each of said images comprising an array of picture elements having respective luminance values, and said exposure control apparatus comprising circuitry configured to convert said luminance values to corresponding brightness values of said external scene in accordance with a predetermined relationship between an exposure condition of said camera, said luminance values and said brightness values; wherein said exposure control apparatus comprises: extraction circuitry configured to extract from each of said images a plurality of groups of picture elements to constitute a brightness measurement region, calculation circuitry configured to calculate respective average brightness values of said plurality of picture element groups and, for each of said groups, apply time-axis filter processing to successively obtained average brightness values obtained for said group, to thereby effect smoothing of variations in said average brightness values, measurement circuitry configured to calculate a capture-objective brightness value based on respective average brightness values obtained for said picture element groups following said time-axis filter processing, and exposure control circuitry configured to perform exposure control of said camera in accordance with said capture-objective brightness value.