Designing compact and ultra-efficient illumination lenses with prescribed irradiance properties for extended light sources

Direct design of illumination optics for extended light sources is challenging but rewarding. Most of the current direct methods, which are developed specifically for the treatment of prescribed intensity designs, usually cannot yield acceptable illumination in the near field where the influence of lens size on the irradiance distribution cannot be ignored. Here, for the first time, to the best of our knowledge, we develop a direct method for designing rotationally symmetric illumination lenses with prescribed irradiance properties for extended sources in geometry. The proposed method is valid in both near field and far field. The numerical and experimental results show that the final lenses are very compact and highly efficient, the spatial energy distribution of the extended source is well controlled even when the ratio of the lighting distance to the lens diameter only equals 1.38.