Freeform illumination lens design with a predefined exit surface

We previously proposed an iterative wavefront tailoring (IWT) method [Optics Letters 44(9): 2274-2277] to solve the freeform lens design problem for irradiance tailoring, where the entrance surface can be predefined as a spherical, aspherical or freeform surface. Here, this method is adapted to address a more challenging design problem where the exit surface is predefined. We design a freeform lens with a fixed aspherical exit surface to demonstrate the effectiveness of the modified method.