Patent ID: 7545581
Filing Date: 2009-06-09
Classification: G02B

Abstract:
1. A zoom lens comprising, in the following order from a magnifying side, a first lens group having a negative refractive power as a whole, a second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole, wherein changing the magnification of a whole lens system of the zoom lens is attained through a configuration in which, while a magnification varying operation is in effect, the third lens group is left fixed, the first lens group is made to move on an optical axis in such a manner as to move in a direction from a magnifying side to a contracting side over a range from a wide angle end to an intermediate area and to move in a direction from the contracting side to the magnifying side over a range from the intermediate area to a telephoto end, and the second lens group is made to move on the optical axis in such a manner as to move in a direction from the contracting side to the magnifying side over a range from the wide angle end to the telephoto end, wherein the first lens group is made up by disposing, in the following order from the magnifying side, a first a lens group and a first b lens group, wherein the first a lens group is made up by disposing, in the following order from the magnifying side, a negative lens element having a meniscus shape protruding towards the magnifying side, a negative lens element and a positive lens element, and wherein the first b lens group is made up by disposing one to three lens elements, and comprises (i) a refracting surface on a side lying closest to the magnifying side, said surface being made heavily concave towards the contracting side, and (ii) a refracting surface on a side lying closest to the contracting side, said surface being made convex towards the contracting side, and wherein the following conditional expression (1) is satisfied with respect to a power set on the first lens group, the following conditional expression (2) is satisfied with respect to a power set on the second lens group, the following conditional expression (3) is satisfied with respect to a positional relationship at the wide angle end between the second lens group and the third lens group, the following conditional expression (4) is satisfied with respect to a power set on the first a lens group, the following conditional expression (5) is satisfied with respect to a power set on the first b lens group, and the following conditional expression (6) is satisfied with respect to a size of the first lens group on the optical axis:  where: