Patent ID: 8797656

Claim:
A zoom lens, comprising: a first lens group having a positive refracting power and normally positioned at a fixed position; a second lens group having a negative refracting power and movable in the direction of an optical axis for zooming; a third lens group having a positive refracting power; and a fourth lens group movable in the direction of the optical axis for correction of a focal position by zooming and for focusing; the first, second, third and fourth lens groups being disposed in order from the object side to the image side; the first lens group comprising three lenses including a negative lens, a positive lens and another positive lens disposed in order from the object side to the image side and satisfying the following conditional expressions (1), (2) and (3) 15.0< ft/fw <31.0 (1) 7.0< f 1/ fw <13.0 (2) −8.5 <fL 1/ fw <−4.0 (3) where fw is the focal length of the entire lens system in a wide angle end state, ft is the focal length of the entire lens system in a telephoto end state, f1 is the focal length of the first lens group, and fL1 is the focal length of the negative lens of the first lens group.