| 摘要 |
PURPOSE:To obtain a finder optical system which is provided with a diopter adjustable eyepiece and has aberrations corrected well, by constituting the eyepiece with lenses of 3 groups, namely, positive, negative, and positive groups arranged in order form the side of a pentagonal roof prism and satisfying prescribed conditions. CONSTITUTION:A finder optical system consists of a focus plate 1, a condenser lens 2, a roof prism 3, a positive first lens group 4, a negative second lens group 5, a positive third lens group 6, and an eye point 7, and the first lens group 4 and the second lens group 5 are fixed, and the second lens group 6 is moved on the optical axis to adjust the diopter. When focal lengths of the first and the third lens groups are denoted as f1 and f3, respectively, f1>f3 is satisfied to correct aberrations well. Further, when radiuses of curvatures of respective lens surfaces of the third lens group 6 are denoted as R11 and R12 in order from the roof prism side, R11<¦R12¦and R12<0 are satisfied to correct aberrations better. |
