| 摘要 |
PURPOSE:To deflect the outermost part of a distance measuring luminous flux on the outside of the optical axis toward the optical axis to improve the focusing precision by making the diameter of a pair of stop aperture parts, which are provided in focus detecting blocks on the outside of the optical axis, in the direction perpendicular to the arrangement direction smaller than that of a pair of stop aperture parts, which are provided in a focus detecting block on the optical axis, in the direction perpendicular to the arrangement direction. CONSTITUTION:Photographic lenses TL1 and TL2 of a focus detecting optical device are arranged lengths PZ1 and PZ2 apart from a predeterminate image surface FP respectively and a visual field mask FM is provided near the image surface FP. A transversely long and rectangular aperture part E0 is provided in the center of the mask FM, and longitudinally long and rectangular aperture parts E01 and E02 are provided on both sides, and luminous fluxes which pass them are converged through condenser lenses L0, L01, and L02. Pairs of image reforming lenses L1, L2, and L3-L6 arrayed in the transverse direction and the longitudinal direction are arranged in the center part. A stop mask AM is arranged and stop aperture parts A1-A6 are formed correspondingly to these lenses L1-L6, and outermost parts of distance measuring luminous fluxes on the outside of the optical axis are deflected toward the optical axis,thus improving the focusing precision.
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