Patent ID: 7164542
Filing Date: 2007-01-16
Classification: G02B

Abstract:
1. A variable magnification group m a zoom lens comprising: a first group having a negative focal length; a second group having a positive focal length in turn from an object side; and an iris disposed in the object side of the second group for moving integrally with the second group, wherein at the time of variation of magnification from a short focus end to a long focus end, at least one of said first and second groups is moved so that a space between the first and second groups is reduced, and wherein the second group substantially varies magnification and includes three elements of a positive lens of which a surface having a large curvature faces an object, a negative lens of which a surface having a large curvature faces an image, and a positive lens arranged in turn from the object side, a surface on the most image side of the second group has a convex shape, and a surface on the most object side and a surface on the most image side are aspherical surfaces, so that when a thickness of the second group in a direction of optical axis is L