| 摘要 |
PROBLEM TO BE SOLVED: To realize compactness and high resolution by specifying the power of each lens group in a three group zoom lens having a variable magnification exceeding three and consisting of a negative lens, a positive lens, and a negative lens arranged in this order from the object side. SOLUTION: This zoom lens consists of a negative lens, a positive lens, and a negative lens disposed in this order from the side of an object. When changing the power, it moves the first lens group G<SB>1</SB>relatively close to the second lens group G<SB>2</SB>, and the second lens group G<SB>2</SB>simply to the object side, and moves the third lens group G<SB>3</SB>in a way its moving locus makes a convex arc against the object, and its wide angle position is set closer to the object side than the telescope position when the object distance is made infinitive. When focusing, the third lens group G<SB>3</SB>is moved to the object side. Conditional expressions (1) and (2) are satisfied. (1) 2.0 <¾f<SB>1</SB>¾/f<SB>w</SB><2.4, (2) 0.29<f<SB>2</SB>/f<SB>3</SB><0.37 (f<SB>w</SB>: focal length of the whole system in the wide angle position. f<SB>1</SB>: Focal length of the first lens group, f<SB>2</SB>: Focal length of the second lens group, and f<SB>3</SB>: Focal length of the third lens group). COPYRIGHT: (C)2005,JPO&NCIPI
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