Patent ID: 7599122

Claim:
A microscope optical system comprising, in order from an object side to an image side, a first lens group, a second lens group, a stop, a third lens group, a fourth lens group and a sensor, each lens groups comprising at least one lens element, at least one of said lens elements of the lens groups having one aspheric surface, wherein when the microscope is zoomed from a wide-angle end to a telephoto end, the first and fourth lens groups are kept stationary, while the second and third lens groups are movable, and wherein the following condition is satisfied: 0.5 < F ⁢ ⁢ 1 F ⁢ ⁢ 2 < 1.0 where F 1 is combined focus of the first lens group and F 2 is combined focus of the second lens group.