Focus detection device, focus detection method and imaging apparatus

摘要

A focus detection device comprises: image shift detection means for detecting a relative shift amount of a pair of images formed by a pair of light fluxes having passed through an optical system; and conversion means for converting the shift amount to the defocus amount based upon dimensional information of exit pupil corresponding to an aperture restricting light flux in the optical system and distance information of the exit pupil indicating distances to the exit pupil from a predetermined imaging plane of the optical system.