Patent ID: 7593171

Claim:
A zoom lens comprising: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; a third lens unit having a negative refractive power; and a fourth lens unit having a positive refractive power, wherein the first lens unit, the second lens unit, the third lens unit, and the fourth lens unit are arranged in order from the object side to the image side, wherein, a distance between the first lens unit and the second lens unit at the telephoto end is smaller than that at the wide-angle end, a distance between the second lens unit and the third lens unit at the telephoto end is larger than that at the wide-angle end, and a distance between the third lens unit and the fourth lens unit at the telephoto end is smaller than that at the wide-angle end, and wherein the following conditions are satisfied: ν1n>70 θ1 n −(0.651−0.00168·ν1 n )>0 25<ν1p<50 θ1 p −(0.644−0.00168·ν1 p )<0 −0.2 <N 1 p− 1.77<0 1.2 <|f 1 /fw|< 1.6 where ν1n and θ1n are an Abbe number and a partial dispersion ratio, respectively, of a material of at least one negative lens included in the first lens unit, ν1p, θ1p, and N1p are an Abbe number, a partial dispersion ratio, and a refractive index, respectively, of a material of at least one positive lens included in the first lens unit, f1 is a focal length of the first lens unit, and fw is a focal length of the entire zoom lens at the wide-angle end.