I. Introduction
Sunlight readability is a desirable feature for displays to be used under strong ambient light. In a typical transflective LCD [1], [2], each pixel is divided into transmissive (T) and reflective (R) sub-pixels. Under weak ambient lighting condition, the T-mode plays the primary role and R-mode makes little contribution. As the ambient light gets brighter, the T-mode is gradually washed out and the R-mode is gradually dominating. The existence of R sub-pixels blocks the beam path of some backlight and reduces the effective aperture of T sub-pixels. To overcome this problem, microlens array [3] is an attractive option because it channels the backlight through the T sub-pixels more effectively. A 2D focusing cones device [4], [5] is also proposed to increase the backlight utilization efficiency.