| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a variable power optical system capable of suppressing performance degradation due to a temperature change and reducing the cost while maintaining a small size, a wide angle, a large aperture ratio and high performance. <P>SOLUTION: The variable power optical system includes a first negative lens group G1, a diaphragm and a second positive lens group G2 in this order from an object side to obtain desired variable power by changing an interval between the first lens group G1 and the second lens group G2 in an optical axis direction. The first lens group G1 has a negative plastic lens and the second lens group G2 has a positive plastic lens. When a focal length of the negative plastic lens of the first lens group G1 is defined as fpn, a focal length of the positive plastic lens of the second lens group G2 is defined as fpp, and a focal length of the entire system at a wide angle end is defined as fw, they satisfy conditional expressions (1) and (2). 5.0<fpp/fw<7.5 (1) -7.0<fpn/fw<-6.0 (2) <P>COPYRIGHT: (C)2012,JPO&INPIT |
