Brightness management in a direct LED backlight for LCD TVs

Abstract

Abstract— A method of calculating the luminance and luminance uniformity of a bottom LED backlight is proposed and demonstrated. Both the power consumption and brightness uniformity as a function of screen brightness, screen size, backlight thickness, transmittance of the LCD panel, reflective cavity efficiency, gain, cone angle of the enhancement films, LED array configuration, and the average luminous flux, radiation pattern, and input power of individual LEDs. Moreover, a 42‐in. LCD TV using this backlight design approach was fabricated. The bottom backlight incorporates an array of RGGB 4‐in‐1 multi‐chip LEDs within a highly reflective box behind a diffuser and a dual brightness‐enhancement film. The brightness uniformity can be predicted within an accuracy of 94% and the luminance level within an accuracy of 96%.

Enhanced light-extraction from hierarchical surfaces consisting of p-GaN microdomes and SiO2 nanorods for GaN-based light-emitting diodes

“…Enhanced light-extraction from hierarchical surfaces consisting of p-GaN microdomes and SiO 2 nanorods for GaN-based light-emitting diodes Nitride-based light emitting diodes (LEDs) have drawn intensive research efforts due to their huge commercial success in various applications, such as displays, cell phones, and general lighting. 1 However, to further enhance the efficiency, challenges still remain. One challenge urgently needed to be overcome is to liberate trapped light inside the LEDs, which occurs due to the large difference in refractive index (n) between air (n ¼ 1) and GaN (n $ 2.5), causing considerable Fresnel loss and total internal reflection (TIR) at the abrupt interface.…”

Creating a desired lighting pattern with an LED array

“…In LCD TV applications a uniform background is desired. 11 In order to ensure uniform illumination, a slightly larger targetarray distance could blur the discrete spots into a smoothly varying field. However, the trade-off between illumination uniformity and rendering accuracy is small because when increasing the working distance the NCC decreases slowly after the peak value.…”

High-Uniformity Planar Mini-Chip-Scale Packaged LEDs with Quantum Dot Converter for White Light Source

“…In addition, it needs to have good optical quality, resulting in high cost. Direct-lit does not use a light guide; the LED array is evenly placed directly below the LCD panel, which provides outstanding performance in brightness uniformity and good optical efficiency [34][35][36]. The BLU brightness and uniformity has a great influence on the display module uniformity.…”