Patent ID: 8670063

Claim:
A focus detection apparatus, comprising: an image sensor that receives light of respective images that are formed by light that passes through different pupil regions of a photographing optical system including a focus lens, and outputs a pair of image signals; a control unit that controls so as to acquire a pair of image signals from said image sensor at each of a first lens position and a second lens position, that are different positions to each other, of said focus lens; a conversion unit that, by multiplying a shift amount between a pair of images representing the pair of image signals that are output from said image sensor by a conversion coefficient, converts the shift amount to a defocus amount of said photographing optical system; and a calculation unit that calculates the conversion coefficient based on displacement amounts of respective ones of the pair of images representing the pair of image signals that are acquired at the first lens position and the second lens position, and a displacement amount of said focus lens from the first lens position to the second lens position.