US Patent 7450318 Zoom lens and optical apparatus having the same

A zoom lens, including, in order from an object side to an image side (a) a first lens unit of negative optical power, (b) a second lens unit of positive optical power, and (c) a third lens unit of positive optical power, wherein a separation between the first lens unit and the second lens unit and a separation between the second lens unit and the third lens unit are varied to effect variation of magnification, and wherein the zoom lens satisfies the following conditions: ndp3<1.5 and νdp3>70.0, where ndp3 and νdp3 are a refractive index and Abbe number, respectively, of material of the positive lens in the third lens unit.