Patent ID: 7589764

Claim:
A focus detection device comprising: an AF sensor which converts received object light into electrical charges, integrates said electrical charges, and outputs said integrated electrical charges as a video signal in pixel units; a photometering sensor which converts received light into an electrical signal to output said electrical signal as a photometering signal; a flicker repetition period determiner that determines a flicker repetition period of said received object light from fluctuations of said photometering signal of said photometering sensor, wherein said flicker repetition period determiner detects one of bottom or peak values of said photometering signal of said photometering sensor, an output level of which fluctuates periodically, to determine said flicker repetition period from a time interval between said detected one of bottom and peak values; and a controller which causes said AF sensor to start integrating said electrical charges in synchronization with said flicker repetition period, wherein said controller sets an integration cycle reference point, at which a predetermined period of time elapses from the time at which said one of bottom and peak values is detected, and causes said AF sensor to start integrating said electrical charges upon an elapsed time from said integration cycle reference point reaching an integer multiple of said flicker repetition period determined by said flicker repetition period determiner.