Freeform lens design for uniform illumination with extended source

Nonuniform illumination caused by extended source is one of the challenging points for high power Light-emitting diodes (LEDs) especially for LED array applications. A new design method to improve the uniformity of illuminance of extended source is presented. To obtain high uniformity at target plane, a feedback optimization method is introduced including target plane girds, light source girds and target plane and light source girds optimization algorithms. Monte Carlo ray tracing simulation results demonstrate that our feedback optimization algorithms are able to obviously increase the uniformity of illuminance at target plane. The uniformity increases from 0.53 to 0.9, 0.77 and 0.88 by our three different optimization algorithms respectively. This method would be a potential way in improving the uniformity of illuminance at target plane with little light pattern expansion.