Method to design two aspheric surfaces for a wide field of view imaging system with low distortion

This paper presents a distortion correction method for designing a wide field of view (FOV) lens for an imaging system. The lens is composed of two aspheric surfaces and several spheres. In the preliminary design, profiles of the aspheric surfaces can be obtained according to aplanatism, refraction law, and polynomial fitting methods, where the numeric computation, the differential geometry computation, and the polynomial fitting algorithm are stated in detail. Then the lens is optimized by the damped least squares method. Theoretically, this method cannot eliminate aberrations absolutely but can balance some kinds of aberrations to the image well. Furthermore, a projector lens with a wide FOV, low distortion, and low throw ratio [TR = (projection distance)/(image diagonal size)] is designed successfully by this method.