Patent ID: 6665131
Filing Date: 2003-12-16
Classification: G02B

Abstract:
An imaging optical system comprising, in order from an object:a front lens group with a positive refractive power; an aperture stop; and a rear lens group with a positive refractive power; and wherein the front lens group includes, at the most object side thereof, a double convex positive lens; wherein at least one of the front lens group and the rear lens group includes a triple cemented lens being adjacent to the aperture stop having a negative refractive power as a whole composed of a first positive lens, a negative lens, and a second positive lens; and wherein the following conditional expression is satisfied; 0.3<5.0â€ƒâ€ƒ(1) where fs denotes the focal length of the cemented lens at e-line (&lgr;=546.07 nm) and f denotes the focal length of the imaging optical system at e-line.