FOCUS DETECTING APPARATUS

A focus detecting apparatus has, an imaging optical system for forming an image of an object on a predetermined plane, an array having a plurality of photoelectric conversion elements arranged at predetermined interval, a focus detecting optical system for directing to the photoelectric conversion element array the light beam from the object passed through the imaging optical system, and discrimination apparatus for discriminating the imaged condition of the image of the object on the predetermined plane on the basis of the signal output of the image of the object spatially sampled at a predetermined sampling interval by the focus detecting optical system and the photoelectric conversion element array. The focus detecting optical system and the photoelectric conversion element array are disposed a predetermined distance in the direction of the optical axis from the predetermined plane so that the imaged condition of the image of the object on the predetermined plane is different from the imaged condition of the image of the object spatially sampled by the photoelectric conversion element array.