Patent ID: 7873267

Claim:
A focus detection device, comprising: focus detection elements that include a plurality of micro-lenses and light-receiving elements that generate a pair of signals corresponding to a pair of light fluxes each passing through an imaging optical system that includes a lens and an aperture stop, each of the light-receiving elements being disposed in correspondence to one of the micro-lenses and receiving the light fluxes from the imaging optical system via the micro-lenses; a focus detector that determines a first focus adjustment state of the imaging optical system with a full-aperture of the imaging optical system, based upon the pair of signals; and a condition judging unit that judges whether or not the first focus adjustment state satisfies a specific condition, wherein: if the condition judging unit judges that the first focus adjustment state satisfies the specific condition, the focus detector determines a second focus adjustment state with an f-number slower than the full-aperture of the imaging optical system.