Patent ID: 8797410

Claim:
A method for driving an image pickup apparatus including a pixel configured to output a pixel signal, and an AD conversion unit configured to convert the pixel signal into a digital signal, the AD conversion unit including a comparator configured to compare a reference signal with a signal based on the pixel signal and output a comparison result signal, the method comprising: determining signal values of higher-order bits of the digital signal based on the pixel signal by operating the AD conversion unit as one of a successive approximation AD conversion circuit and a ramp AD conversion circuit; and after the signal values of the higher-order bits are determined, determining signal values of lower-order bits of the digital signal based on the pixel signal by operating the AD conversion unit as the other one of the successive approximation AD conversion circuit and the ramp AD conversion circuit, wherein, when the AD conversion unit is operated as the ramp AD conversion circuit, the AD conversion unit generates a first digital signal on the basis of the comparison result signal which is output by the comparator supplied with a first ramp signal as the reference signal and a comparison signal and comparing the first ramp signal with the comparison signal, the AD conversion unit generates a second digital signal on the basis of the comparison result signal which is output by the comparator supplied with a second ramp signal as the reference signal and the comparison signal and comparing the second ramp signal with the comparison signal, the second ramp signal having a ramp start potential different from a ramp start potential of the first ramp signal, the image pickup apparatus generates a correction value on the basis of the first digital signal and the second digital signal, a first correction operation of correcting a reference potential on the basis of the correction value is performed, the reference potential being used when the AD conversion unit is operated as the successive approximation AD conversion circuit, and a second correction operation of correcting the digital signal based on the pixel signal on the basis of the correction value is performed.