| 摘要 |
A zoom lens comprising a first lens group having a positive refracting power and its position fixed, a second lens group having a negative refracting power and displacable mainly for magnification, a third lens group having a positive refracting power and its position fixed, and a fourth lens group having a positive refracting power and displacable mainly for correction of the focal position for magnification and focusing. The first lens group includes, viewed from an object, a cemented lens consisting of a first lens which is a concave meniscus lens having a convex surface facing the object side and a second lens which is a convex lens, and a third lens which is a convex meniscus lens having a convex surface facing the object side; the second lens group, viewed from an object, includes a fourth lens which is a concave meniscus lens having a convex surface facing the object side, and a cemented lens consisting of a fifth lens which is a both-side-concave lens, and a sixth lens which is a convex lens; the third lens group includes a seventh lens which is a convex lens; and the fourth lens group, viewed from an object, includes a cemented lens consisting of an eighth lens which is a convex lens having a convex surface facing the object side, a ninth lens which is a concave lens, and a tenth lens which is a convex lens, and wherein the third lens group includes at least one surface constituted by an aspherical surface and in the fourth lens group, at least the surface which is at the object side is constituted by an aspherical surface.
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