| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a variable power optical system that realizes a variable power ratio of about 2-3 while maintaining high optical performance, and enables imaging in a wide angle end without hindrance in spite of a small and simple configuration. <P>SOLUTION: The variable power optical system includes, in order from an object side: a first lens group G<SB POS="POST">11</SB>having negative refractive power; a second lens group G<SB POS="POST">12</SB>having positive refractive power; and a third lens group G<SB POS="POST">13</SB>having positive refractive power. In the variable power optical system, when power is varied from a wide angle end to a telephoto end, the distance between the first lens group G<SB POS="POST">11</SB>and the third lens group G<SB POS="POST">13</SB>is unchanged and the following conditional expression is satisfied: (1) 1.4<(Tw×Tt)<SP POS="POST">1/2</SP>/(fw×ft)<SP POS="POST">1/2</SP><2.0, where Tw is the entire length of the optical system at the wide angle end, Tt is the entire length of the optical system at the telephoto angle end, fw is the focal length of the whole system at the wide angle end, and ft is the focal length of the whole system at the telephoto angle end. <P>COPYRIGHT: (C)2012,JPO&INPIT |
