Computer modeling of LED light pipe systems for uniform display illumination

Computer modeling of distributive light pipe systems using light emitting diode (LED) sources to produce uniform illumination for liquid crystal displays (LCDs) is presented. Due to their small size, lower power consumption, and lower heat generation, LEDs are a natural source choice for display illumination. However, to be useful in display applications, LEDs must be made to produce uniform illumination over the display area. The conversion of an LED's output flux distribution to one that is uniform over a given area can be accomplished with plastic, injection-molded light pipes. Illustrative examples of LED light pipe display systems are presented. These systems compare output coupling surface geometry for two LED input coupling scenarios; direct and indirect input coupling. Computer modeling via commercial software packages is used to optimize and analyze system designs. It is critical in these simulations to have accurate source models. Therefore close attention is paid to the LED source model. The final simulation results are presented and uniformity and total light output is compared. The implications of these results for display applications are discussed.