| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable power optical system realizing both of miniaturization and high definition by properly allotting variable power action to a plurality of lens groups while optical entire length is constant at the time of variable magnification, and to provide an imaging lens device equipped with the variable power optical system and digital equipment on which the imaging lens device is mounted. SOLUTION: The variable power optical system includes a 1st lens group having positive optical power and fixed at the time of variable magnification, a 2nd lens group having negative optical power and a 3rd lens group having positive optical power, which are arranged in order from an object side. Whenβ<SB>3W</SB>,β<SB>3T</SB>are defined as the lateral magnification of the 3rd lens group at a wide angle end or a telephoto end respectively, and Z is defined as a variable power ratio, the 3rd lens group satisfies a following conditional expression; 0.4<(β<SB>3T</SB>/β<SB>3W</SB>)/Z<0.9. COPYRIGHT: (C)2006,JPO&NCIPI |
