Optical Design of Direct Illumination-type LED Backlight for LCD-TV

Tri-color LED backlight is one of the key technologies which makes LCD has a high quality display;it delivers a color gamut of over 150 % that typically achieved by conventional CCFL backlight.Today,direct illumination-type backlight which has a simple structure and makes good use of light becomes the first choice for large-size LCD backlight,but its light uniformity gets bad without light guide plate.In this paper,the LED with a new type of intensity distribution is designed after many types of LED's intensity distribution have been simulated and analyzed.Furthermore,66 cm(26 in)backlight that consists of those LEDs is simulated.When the backlight has no diffuser films and the light box is 20 mm to 28 mm thick,the brightness uniformity is over 83 % and the value of ΔU'V' is about 0.01;When the backlight has diffuser films and the light box is only 20 mm thick,the brightness uniformity reaches 89 % and the value of ΔU'V' reaches 0.004 1.