To detect a focal point without causing the missing of a frame.

This imaging apparatus includes: a switching means for selectively forming a first aperture, a second aperture and a third aperture different from each other in an optical path of a light beam passed through an optical system; a control means for forming the second aperture or the third aperture at the time interval of repeatedly forming the first aperture by the switching means and alternately forming the second aperture and the third aperture at repeatedly generated time intervals; a light receiving means for receiving a light beam through one of the first to third apertures formed by the switching means; an imaging means for obtaining image information based on the output of the light receiving means on receiving a light beam through the first aperture; and a focal point detecting means for detecting the focusing state of the optical system based on the output of the light receiving means on receiving a light beam through the second aperture and the output of the light receiving means on receiving a light beam through the third aperture.

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