Patent ID: 6897899

Claim:
An electronic image pickup apparatus, comprising: a photographic optical system; solid state image pickup devices disposed on a plane where a subject image formed by subject beams which have passed through said photographic optical system is formed; a main mirror disposed between said photographic optical system and said solid state image pickup devices, wherein a part of said main mirror comprises a half mirror to divide the subject beams which have passed through said photographic optical system into an observing beam and a focus detecting beam; a sub-mirror for reflecting the subject beam which has passed through the part of said main mirror; a focus detecting optical system for forming an image of the subject beam reflected by said sub-mirror on partial areas of said solid state image pickup devices; and an electrical circuit for outputting focus detecting information based on image signals of the partial areas of said solid image pickup devices; wherein a first end of said main mirror is adapted to be turned to insert said main mirror and said sub-mirror into an optical path of said subject beams; and wherein the focus detecting optical system comprises: a view field mask for restricting an irradiation range of said subject beam which has passed through the part of said main mirror; a field lens for condensing a subject beam which has passed through said view field mask; a reflecting mirror for bending the optical path of a subject beam which has passed through said field lens to guide said subject beam to said solid state image pickup devices; a pupil mask having openings for splitting a subject beam which has been reflected by said reflecting mirror into two beams; and two image reforming lenses disposed behind said openings.