| 摘要 |
Zoom lens comprising, in order from its object side, a first lens unit (U1) having positive power and that does not move for zooming, a second lens unit (U2) having negative power and that moves for zooming, a third lens unit (U3) having positive power and that moves for zooming and a fourth lens unit (U4) having positive power and that does not move for zooming, the third lens unit (U3) moving first towards the image side and then towards the object side for zooming from the wide-angle end to the telephoto end, wherein the inequalities -3.2 < f1/f2 < -1.0, -0.55 < f2/f3 < -0.20 and -0.7 < 1/²3w < 0.5 are satisfied (f1, f2 and f3 denoting the focal lengths of the first, second and third lens units, respectively and ²3w denoting the lateral magnification of the third lens unit at the wide angle end with an incident beam at infinity). The first lens unit (U1) further comprises a first sub-unit (U1a) having positive power and that does not move for focusing, a second sub-unit (U1b) having negative power and that moves for focusing and a third sub-unit (U1c) having positive power and that does not move for focusing. |
