Freeform lens design for light-emitting diode uniform illumination by using a method of source-target luminous intensity mapping.

We present a freeform lens for application to LED uniform illumination. This lens, which is designed with a method of simple source-target luminous intensity mapping, can produce irradiance uniformity of greater than 0.8 and optical efficiency above 90% with an arbitrary half-beam angle greater than 45 deg. Typically, as compared with a conventional source-target energy mapping method, this design method can achieve better optical performance of lenses for general LED lighting. When a non-Lambertian-type light source is employed, for example, the chip on board LED, the use of the method can result in a compact LED lens without losing the optical performances of high irradiance uniformity and high optical efficiency as yielded by lenses for Lambertian-type LED light sources.