Patent ID: 7667740

Claim:
A method for use in a digital imaging device having an image sensor, an electronic rolling shutter, a processor and firmware for implementing the method, the method comprising: detecting the presence of light modulation and the frequency of the light modulation using an exposure time that is synchronous to possible line frequencies used to generate the light modulation; and synchronizing the exposure times to the modulation cycle time; wherein the presence of light modulation and frequency is detected by: capturing a set of images using exposure times that are not synchronous with possible light modulation frequencies to be detected; performing a discrete Fourier transform (DFT) on columns of images of the set to measure the presence of the effects of light modulation frequency modulation, the largest DFT indicating the frequency of the light modulation; and wherein, once the presence and frequency of light modulation are determined, the exposure times of all image captures is forced to be an integer multiple of the modulation cycle time.