Patent ID: 8630045

Claim:
A zoom lens comprising: a first lens group having positive refractive power, and which is fixed with respect to the direction of an optical axis during zooming; a second lens group having negative refractive power, and which is moved in the direction of the optical axis during zooming; a third lens group having positive refractive power, and which is fixed with respect to the direction of the optical axis during zooming; and a fourth lens group having positive refractive power, and which is moved in the direction of the optical axis during zooming in such a manner that a fluctuation of the position of an image plane caused by zooming is corrected so that the zoom lens is focused, and the first lens group, the second lens group, the third lens group and the fourth lens group being arranged in this order from the object side of the zoom lens, wherein the first lens group consists of four lenses of a first-group first lens having negative refractive power, a first-group second lens having positive refractive power, a first-group third lens having positive refractive power, and a first-group fourth lens having positive refractive power, which are arranged in this order from the object side, and wherein the first-group first lens and the first-group second lens are arranged in such a manner that a space is formed therebetween, and wherein the following formulae (1′) and (6′) are satisfied: −1.9<( R 11 r+R 11 f )/( R 11 r−R 11 f )<−0.4 (1′) 0.13 <D 2 /TL 1<0.38 (6′), where R11f is a radius of curvature of an object-side surface of the first-group first lens, R11r is a radius of curvature of an image-side surface of the first-group first lens, D2 is a spatial interval between the first group first lens and the first group second lens, and TL1 is the thickness of the first lens group, wherein the following formula (4) is satisfied: −2.9 <f 2 /fw<− 1.8 (4), where fw is the focal length of the entire system of the zoom lens at wide angle end, and f2 is the focal length of the second lens group.