| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable power lens optical system with which successful image forming performance is obtained, while achieving smaller size and lighter weight with fewer number of lenses and with a simple constitution. SOLUTION: Variable power of 2.2 times or more is performed by comprising a variable power optical system of a first lens group 1 with negative power and a second lens group 2 with positive power, arranged in the order starting from the object side toward the side of an image surface S and varying the interval of each lens group. The first lens group 1 comprises a lens 1A, with negative power and a lens 1B with positive power having aspheric surfaces on both sides arranged, in the order starting from the object side toward the side of the image surface S. If refractive index with respect to a d line of the lens 1B is set as Nd1B, Abbe's number to the d line of the lens 1B is set as Vd1B, conditional expression (1): 1.55<Nd1B<1.60 and the conditional expression (2): 25<Vd1B<35 are satisfied. COPYRIGHT: (C)2007,JPO&INPIT
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