| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens easily adopting constitution to bend an optical path by a catoptric member, having such high optical performance that a variable power ratio is about 3.4 while keeping a wide angle, and made very thin in a depth direction and inexpensive. SOLUTION: The zoom lens comprises a first positive lens group G1, a second negative lens group G2, a third positive lens group G3, a fourth positive lens group G4, and a fifth negative lens group G5. When varying power from a wide angle end to a telephoto end, the first lens group G1 is nearly fixed relative to an image plane I, and at least the second lens group G2 and the fourth lens group G4 move. The first lens group G1 includes a catoptric element P for bending an optical path, and its object side from the reflection surface has negative refractive power. The zoom lens satisfies a conditional expression (1): 1.5<¾f5/fw¾<2.7 (wherein f5 is the focal length of the fifth lens group G5 and fw is the focal length of the entire system at the wide angle end) concerning the focal length of the fifth lens group G5. COPYRIGHT: (C)2008,JPO&INPIT
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