Red, green, and blue LED based white light generation: issues and control

The recent improvements in high-power light-emitting diodes (LED) technology with 100+ lumens per LED chip and efficacy exceeding that of incandescent lamps, brings the solid-state lighting close to a reality. An LED light source made of red, green and blue (RGB) LEDs can provide a compact light source with unique features such as instant color variability. However, the white light generation using many compact, discrete RGB light sources has the following issues: uniform spatial light mixing and distribution, white color point maintenance and thermal management. Specifically, the white color point maintenance is a stringent requirement in many applications. Meeting this requirement is a severe challenge due to the variation in the optical characteristics of the RGB-LEDs with temperature, time and forward current and the spread in the LED performance. This results in (1) an unacceptably high variability in white light color point, and (2) difficulties in manufacturing reproducible LED lamps.