Patent ID: 7706085
Filing Date: 2010-04-27
Classification: G02B

Abstract:
1. An imaging optical system, comprising: an aperture stop for limiting an axial light beam, an object-side lens group that is located on an object side of said aperture stop and has negative refracting power, and an image-side lens group that is located on an image side of said aperture stop and has positive refracting power, wherein: said object-side lens group comprises, in order from its object side, an object-side positive meniscus lens that is convex on its object side and has positive refracting power and an object-side negative meniscus lens that is convex on its object side and has negative refracting power, said image-side lens group comprises, in order from its object side, an image-side negative lens, an image-side first positive lens and an image-side second positive lens, said image-side negative lens and said image-side first positive lens adjacent thereto form together a cemented doublet, and said imaging optical system has a total of five lenses, with satisfaction of the following conditions (1), (2) and (3): where f is a focal length of the whole imaging optical system, f f L is an axial distance from a vertex of the lens surface located in, and nearest to the object side of, said object-side lens group to a vertex of the lens surface located in, and nearest to the object side of, said image-side lens group.