| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-performance real image type variable power finder optical system realizing high variable power even though it is compact and yielding an excellent field image free from the occurrence of flare. SOLUTION: The real image type variable power finder optical system is equipped with a positive objective system 1 consisting of a negative lens group G<SB>1</SB>, a positive lens group G<SB>2</SB>, a negative lens group G<SB>3</SB>and a reflection member 5a, and a positive eyepiece system 2, and has an erect normal image system having reflection members 5a and 6a by which an intermediately formed image by the objective system 1 is changed to an erect normal image. In the optical system, the lens group G<SB>2</SB>is moved to an object side so as to perform variable power from a wide angle end to a telephoto end, and the lens group G<SB>2</SB>and the lens group G<SB>3</SB>are moved to the object side in the case of variable power from the wide angle end to the middle, and the lens group G<SB>1</SB>is moved to the eyepiece system side so as to correct the deviation of diopter. In the case of variable power from the middle to the telephoto end, the lens group G<SB>3</SB>is mainly moved to the eyepiece system side to correct the deviation of diopter, and the optical system satisfies following expressions. -2.5<f<SB>G3</SB>/f<SB>T</SB><-0.1, 0.2<f<SB>G2</SB>/f<SB>T</SB><0.41, provided that f<SB>T</SB>, f<SB>G3</SB>and f<SB>G2</SB>are the respective focal distances of the objective system 1, the lens group G<SB>3</SB>and the lens group G<SB>2</SB>at the telephoto time. COPYRIGHT: (C)2005,JPO&NCIPI
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