Optical design of a compact multispectral LED light source with high irradiance and uniformity.

As light-emitting diodes (LEDs) become dominating solutions in general lighting, their applications are also penetrating into biomedical engineering, especially light therapies. These new applications usually require much higher light power density at a shorter working distance than general lighting. Besides the high power, uniformity in power distribution is another important factor in such applications to illuminate samples with equal irradiance. These factors require designing a compact optical system to transmit light from a highly integrated high-power LED light source. While existing designs mainly focus on providing the desired illuminance in a much larger target space, little work has been devoted to the optical design to achieve a high irradiance that is uniformly distributed onto a target area at a short distance away from the light source. This work proposes a design method to solve such a problem, based on a highly integrated LED module, a mixing rod, and a pair of aspheric lenses. Both numerical simulations and experiments with a prototype are performed, which have verified the effectiveness of the proposed method.