Small-sized, large-aperture, wide-angle zoom lens

Abstract

A small-sized, large-aperture, wide-angle zoom lens, having three lens groups of negative, positive, and positive refractive power, respectively, in order from the object side, is disclosed. The FNO of the zoom lens remains constant during zooming. The second lens group includes, in order from the object side, a biconvex lens element, a negative lens element having a concave surface on the object side, a positive lens element having a convex surface on the image side, and a biconvex lens element. The first and second lens groups are moved along the optical axis during zooming, and the third lens group is fixed in position during zooming and includes a stop. Specified conditions are preferably satisfied in order to keep the focal length of the zoom lens short, to correct aberrations, and to keep manufacturing of the zoom lens practicable. Thus, bright, well-corrected images are obtained over the entire range of zoom.

Dependencies are inferred from the claim text.