Design of Ellipsoid and Spherical Combined Light Source for Uniform Flux and Color Mixing

In this letter, an ellipsoid-spherical combined light source structure is presented for the purpose of uniform flux and color mixing, when considering heat dissipation. To allow more rays couple into spherical chamber while keeping illumination uniformity, algebraic equations to estimate light spot size focused by ellipsoidal reflector are derived and then employed to decide input slot size of the chamber. Then Monte Carlo ray tracing simulation suggests that the most preferable output slot size is between 15% and 30% of the chamber radius when considering both uniformity and available test area. A prototype with a 150-W Xenon arc lamp is fabricated to demonstrate heat distribution for the system, and experiment about uniformity indicates that 89.4% of the test circle radius can reach 2% nonuniformity. Color mixing performance for the system is studied by equipped with three ellipsoidal reflectors to collect rays from different color LEDs, and experiment shows that the maximum root-mean-square error of the spectrum across 90% of output circle radius is 1.4%. Results demonstrate it is a structure with simplified design process and having less dependence with light source type.