Patent ID: 6025960
Filing Date: 2000-02-15
Classification: G02B

Abstract:
A zoom optical system consisting of, in order from an object side of said system:a first lens group having positive refracting power;a second lens group having positive refracting power; anda third lens group having negative refracting power,wherein said first, second and third lens groups move together toward said object side for zooming from a wide-angle end of said system to a telephoto end of said system while a space between said first lens group and said second lens group becomes wide and a space between said second lens group and said third lens group becomes narrow,said second lens group comprises, in order from an object side thereof, a front lens subgroup having negative refracting power and a rear lens subgroup having positive refracting power,an aperture stop is located between said front lens subgroup and said rear lens subgroup in said second lens group,an aspheric surface is used for at least one surface in said rear lens subgroup in said second lens group, andsaid zoom optical system satisfies the following condition (1):0.4<f.sub.W /f.sub.1G <1.0 (1)where f.sub.W is a focal length of said zoom optical system at said wide-angle end and f.sub.1G is a focal length of said first lens group.