Patent ID: 6421086
Filing Date: 2002-07-16
Classification: H04N

Abstract:
An image pickup apparatus comprising:a solid state image device having changeable. time for which charges are stored therein; a timing generator for generating drive pulses for driving said solid state image device and changing pulse intervals between the drive pulses so as to adjust the storage time of said solid state image device; integrating means for calculating an integrated value of one frame or a portion of an image signal obtained from said solid state image device; and calculating means for determining the pulse intervals between the drive pulses generated by said timing generator in accordance with the integrated value obtained from said integrating means so as to control the charge storage time of said solid state image device, wherein said calculating means includes: a first LUT composed of table values of brightness of N subjects at addresses 0 to (Nâˆ’1) which can be expressed by an exponential function in the form of constant K2-th and address value n-th power of predetermined constant K1; and a second LUT composed of table values of N charge storage time periods determined in such a manner that a predetermined image signal level can be obtained to correspond to the table values of the brightness of N subjects, and wherein exposure of an electronic still camera is performed by repeating operations that when an image has been picked up with the charge storage time at the n-th address in said second LUT, the integrated value obtained from said integrating means is divided by the n-th charge storage time so that the brightness of the subject is calculated, charge storage time corresponding to the calculated brightness of the subject is selected from said second LUT, and a next image is picked up with the selected charge storage time.