Patent ID: 8314995

Claim:
A variable power optical system, comprising: a first lens group having a negative power, a position of the first lens group being fixed with respect to an image pickup plane; a second lens group having a positive power; and a third lens group having a positive power, the first, the second and the third lens groups being arranged in this order from an object side, the first lens group comprising a first deflecting element arranged therein to bend an optical path, wherein: at least one lens group selected from the first to third lens groups excepting the first lens group are moved to perform changing of power or focusing; the first lens group comprises a negative lens, a negative lens and a positive lens arranged in this order from the object side; the second lens group comprises a positive lens and a negative lens arranged in this order from the object side; the third lens group comprises a positive lens; and when d 12 w (unit: mm) denotes a distance between an image side principal point of the first lens group and an object side principal point of the second lens group at a short focal length end, d 12 t (unit: mm) denotes a distance between the image side principal point of the first lens group and the object side principal point of the second lens group at a long focal length end, fw (unit: mm) denotes a focal length of the entire variable power optical system at the short focal length end, ft (unit: mm) denotes a focal length of the entire variable power optical system at the long focal length end, and f 1 (unit: mm) denotes a focal length of the first lens group, the variable power optical system satisfies a condition: 2.5<( d 12 w/d 12 t )/| √{square root over (fw×ft)}/f 1|<4.0 (1).