Virtual source simultaneous dual-surface method for uniform illumination.

We present a new simultaneous dual-surface design method for uniform illumination by introducing a virtual light source. This method is a combination of the equal optical path length condition and the tailored method. It can be applied to an extended light source after some optimization processes with a negative feedback algorithm. A solid lens to yield a circular uniform irradiance distribution is designed by using our method. Both optical simulation and experiment have been carried out to show that the experimental irradiance map is close to both the simulation result and the desired distribution, and the uniformity is higher than 0.9 while the light source is a 5050 LED chip with SMD package. The rays from the outside lens surface are of good topological invariance, which can give the potential to design more than two smooth freeform optical surfaces simultaneously by introducing multiple virtual point sources.