Patent ID: RE38771

Claim:
An exposure controller comprising: a lens, a solid-state image pickup device for picking up the image of light having passed through said lens, an AD converter for converting said image picked up by said solid-state image pickup device into a digital signal, a luminance level detector circuit for detecting the luminance level of said image signal digitized by said AD converter, a subtracter for calculating the difference between said luminance level detected by said luminance level detector circuit and a target value of said luminance level stored in a register inside said controller, a discharge pulse calculation circuit for calculating a discharge pulse count to be output to said solid-state image pickup device within one field period, an absolute value circuit for calculating the absolute value of said difference between said luminance level and said target value of said luminance level to be output from said subtracter, a coring circuit for defining a quotient obtained from said discharge pulse count divided by a predetermined setting value and plus 1 as a coring value, for setting said discharge pulse hold signal at H when said coring value is larger than said luminance level error, or at L in other cases, and for outputting said discharge pulse hold signal, and a drive pulse generator circuit for converting said discharge pulse count into a discharge pulse signal and for outputting said discharge pulse signal to said solid-state image pickup device, wherein said discharge pulse calculation circuit calculates said discharge pulse count to be output to said solid-state image pickup device within one field period on the basis of the polarity of said difference between said luminance level and said target value of said luminance level to be output by said subtracter and said discharge pulse hold signal to be output from said coring circuit without changing said discharge pulse count when said discharge pulse hold signal is H, or depending on the polarity of said difference between said luminance level and said target value of said luminance level to be output from said subtracter when said discharge pulse hold signal is L, and outputs said discharge pulse count.