Design optimization for optical patterns in a light-guide panel to improve illuminance and uniformity of the liquid-crystal display

Abstract

Design of an optical pattern in a light-guide panel (LGP) has relied on empirical methods. However, the characteristics of developing liquid-crystal display (LCD) products such as frequent design modifications, various design conditions, and a short development period make it difficult for the empirical design approach to cope with various design requirements for size, shape, and optical performance of the LCD products. The most important tasks for the design of LGPs are improving average illuminance and the uniformity of the backlight unit. To meet these requirements, a design for an incoupling and an outcoupling part of the LGP is presented. These two parts can be designed in two separate phases: the first for the incoupling part and the second for the outcoupling part. The shape of serration in the incoupling part was first determined by design of experiments, and the dot patterns in the outcoupling part were subsequently determined by a density-based approach with progressive quadratic response surface modeling. Using this design approach, the illuminance was increased from 2241 lx in the initial design to 2299 lx in the optimal design, and its uniformity also increased from 38% to 82%.