3-Primary-color LED illumination system based on freeform-surface lenses

The illumination system with 3-primary-color light emitting diodes (LEDs) and light rod has the advantages of wide color gamut and small volume. However, there is a problem of low brightness when combining the 3-primary-color LEDs with the light rod. Firstly, the LED light source was selected based on the etendue theory, and then a set of free-form collimating lenses and collecting lenses were designed. The simulation results show that the light emitted by the collimator lens is concentrated within ±7.5°, and the energy utilization rate within the ±30°at the exit of the light rod is about 51.7%. Moreover, the designed lenses were manufactured and tested. The practical results show that the projection illuminance of the designed lenses set without the anti-reflection film can be improved by 1.6% than the original system with the anti-reflection film. It is expected that a 9.8% improvement of the projection illuminance can be achieved after the designed lenses are coated with the anti-reflection film.