Patent ID: 7920781

Claim:
An image capturing apparatus comprising: an image sensor in which a plurality of focus detection portions each of which is pupil-divided into a first focus detection pixel and a second focus detection pixel along a first direction are arranged along a second direction perpendicular to the first direction in each of a plurality of sections; a composition unit which composites signals output from the first focus detection pixels to obtain a first composite signal, and composites signals output from the second focus detection pixels to obtain a second composite signal in each of the plurality of sections; a coupling unit which couples first composite signals each of which is composited in each of the plurality of sections to obtain a first coupled signal, and couples second composite signals each of which is composited in each of the plurality of sections to obtain a second coupled signal; and an arithmetic unit which calculates a defocus amount of an image forming optical system on the basis of the first coupled signal and the second coupled signal.