Focus detecting system detecting position of images formed from the center and periphery of the optical axis

A focus detecting system comprising:

• (a) first optical means;
• (b) light shielding means having a plurality of apertures, said light shielding means being disposed near an imaging plane of said first optical means;
• (c) second optical means for forming a plurality of first object images based on light fluxes transmitted through a center area around an optical axis of said first optical means and forming a plurality of second object images based on light fluxes transmitted through a peripheral area of said first optical means, said second optical means being disposed behind the imaging plane of said first optical means;
• (d) first photo-sensing means arranged to receive both said first object images and said second object images formed through one of the apertures of said light shielding means;
• (e) second photo-sensing means arranged to receive only said first object images formed through another aperture of said light shielding means;
• and
• (f) discrimination means for discriminating a focusing state of said first optical means by a signal outputted from one of said first photo-sensing means and said second photo-sensing means.