| 摘要 |
PROBLEM TO BE SOLVED: To obtain a relay type finder optical system of a single-lens reflex camera which form an image, formed on a primary imaging plane at a position optically, equivalent to an image plane of a photographic optical system on a secondary imaging plate in a vertically and horizontally inverted state, and comprises a condenser lens group, a prism, and a relay lens group, wherein aberrations are properly corrected and miniaturization is attained. SOLUTION: The relay type finder optical system has the relay lens group comprising a front group with positive refracting power, a middle group with negative refractive power, and a rear group with positive refractive power, the most-eye-side lens of the rear group being made of a positive lens and satisfying conditional expressions (1): 1<SF and (2)-6<f/fM<-3, where SF=(r1+r2)/(r1-r2)r1 is the radius of curvature of the object-side surface of the most-eye-side positive lens of the rear group, r2 the radius of curvature of the eye-side surface of the most-eye-side positive lens of the rear group, (f) the focal length of the relay time finder optical system, and fM the focal length of the middle group, respectively. COPYRIGHT: (C)2009,JPO&INPIT
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