Patent ID: 7199912

Claim:
A Fourier transform lens system, comprising: a first lens group having negative power, wherein the first lens group comprises two negative meniscus lenses each having negative power, and each of the negative meniscus lenses has a concave lens surface facing toward a concave lens surface of the other negative meniscus lens; and a second lens group having positive power disposed at a first side of the first lens group with the first lens group and the second lens group being arranged on a common optical axis, wherein the second lens group comprises a positive lens having a convex lens surface facing toward the first lens group; and wherein the Fourier transform lens system satisfies the following conditions (1)˜(3): 0.1 <R 1R /f< 0.4; (1) −0.4 <R 2F /f<− 0.1; and (2) 0.1 <d 12 /f< 0.3; (3) where, f is a total focal length of the Fourier transform lens system; R 1R and R 2F are radiuses of curvature of the concave lens surfaces of the two negative meniscus lenses respectively; and d 12 is an air space between the two negative meniscus lenses along a direction of the optical axis.