Patent ID: 7206137

Claim:
A taking optical system for focusing light from a subject on an image sensor, the taking optical system comprising at least, from a subject side, a first lens group having a positive optical power, a second lens group having a negative optical power, a third lens grouphaving a positive optical power, and a fourth lens group having a positive optical power, the taking optical system achieving zooming by varying at least one distance between the lens groups, wherein the following conditions are fulfilled: 0.05<f3/f4<0.95, 7.0≦f1/fw≦20.0, and −0.12≦f2/ft≦−0.05, where f 3 represents a focal length of the third lens group; f 4 represents a focal length of the fourth lens group; f 1 represents a focal length of the first lens group; fw represents a focal length of the entire taking optical system at a wide-angle end thereof; f 2 represents a focal length of the second lens group; and ft represents a focal lenath of the entire taking optical system at a telephoto end thereof.