Patent ID: 9703080
Date: 2017-07-11
CPC Classifications: G02B,G03B

Claim:
1. An imaging optical system comprising, in order from an object side to an image side: a first lens group having positive refracting power, an aperture stop, and a second lens group having positive refracting power, wherein there is no lens group other than said first lens group and said second lens group, said first lens group consists of three lens subgroups, including in order from the object side to the image side, a first lens subgroup having positive refracting power, a second lens subgroup having negative refracting power, and a third lens subgroup having positive refracting power, said second lens group consists of two lens subgroups: in order from the object side to the image side, a fourth lens subgroup and a fifth lens subgroup, said first lens subgroup consists of one positive lens component convex on its image-side surface, said second lens subgroup consists of one negative lens component concave on its image-side surface, said third lens subgroup consists of one positive cemented lens component, said positive cemented lens component in said third lens subgroup includes a positive lens convex on its object-side surface and a negative lens concave on its object-side surface, said fourth lens subgroup consists of one cemented lens component, said cemented lens component in said fourth lens subgroup includes a double-convex positive lens and a double-concave negative lens, said fifth lens subgroup comprises a negative meniscus lens concave on its image-side surface and a double-convex lens, wherein each of the lens components is a lens block having only two refractive surfaces in on-axis contact with air, including an object side-surface and an image side-surface, the total number of negative lenses included in said imaging optical system is four, and upon focusing from an object at infinity to a near distance object, said first lens group remains stationary, and said second lens group moves to the object side.