"Optical Design and Analysis of LCD Backlight Units Using ASAP," Optical Engineering Magazine (published in China)
Updated: Aug 12, 2014
Author(s): Jee-Gong Chang, Chung-Yi Lin, Chi-Chuan Hwang, Ruey-Jen Yang
"The optical simulation, analysis, and design of backlight units (BLU) of liquid crystal displays, using ASAP™ optical modeling software, are introduced in this article. Two major types of BLU, i.e. edge lighting and bottom lighting, and their respective optical components are reviewed. The concerns in optical design of those components, namely the light guide in edge lighting BLU and the diffusion and reflection sheets in the bottom lighting BLU, are discussed. A scattering pattern is usually screen printed under the light guide, on which smaller scattering dots are sparsely located near the light sources while larger scattering dots are more densely distributed away from the sources. A diffusion sheet can be a Lambertian surface or with more sophisticated bidirectional reflection distribution function. The cross section of a reflection sheet may look like a parabolic curve that can be optimized. The structure of ASAP consists of the pre-processor that creates models and specify optical properties, the processor that calculates optical interactions, and the post-processor that retrieves and manipulates data for more analyses. The general procedure of ASAP analyses and optimizations of both types of BLU is introduced. The ASAP scripting language is powerful enough in optimizing the shape and dimensions of the BLU optical components fore mentioned. Finally the results of a case study of the design analysis for equal irradiance in a bottom lighting BLU are given to depict how the ASAP scripting language is applied to obtain the optimal locations for lamps. ..."