Abstract
Liquid crystal display is currently the most widely used flat panel display device in the consumer market. Although with highly appreciated image performance, such as viewing angle, contrast and color saturation, the efficiency remains a serious issue to be resolved. With the increasing concern on the global environment issue, the development of green technology for liquid crystal displays becomes an important topic in display technology. The major efficiency loss in liquid crystal displays happens at down polarizer and color filter, which in concept will take away one half and two thirds of the energy respectively for unpolarized illumination light sources such as cold cathode fluorescent lamp (CCFL) and light-emitting diode (LED). The work described in this thesis introduces a backlight architecture with the combinational function of polarization recycling and pixelized illumination to resolve both energy loss mechanism in the mean time. For polarization recycling, a wire grid polarizer (WGP) is used as the reflective polarizer to split the light path of two orthogonal polarizations and a quarter wave retarder as the phase plate to rotate one polarization state by 90 degree. For pixelized illumination, the spatial arrangement of red, green and blue LED at the edge of the light guide will be turned into color sub-pixel separation by dedicatedly designed reflecting cup, collimating lens and lenticular array. The target specification of the work is a 3.7-inch WVGA display panel for smart phone application. Light path design and ray tracing simulation with ZEMAX and LightTools are being done firstly for verifying the performance, and the compatibility between the proposed polarization recycling and pixelized illumination scheme has also been studied. Finally, a prototype is built for measurement and evaluation. The pixelized illumination is clearly visible through microscope, and the outgoing light is highly polarized based on the visual checking with an analyzer. The overall light utilization efficiency without considering aperture ratio of LCD measures 36%, roughly 10% higher than traditional solutions, which indicates the effectiveness of the proposed backlight architecture.