Multiple-functional and cost-effective liquid-crystal cell parameter measurement system

For years, the technology of TFT-LCDs (thin-film-transistor liquid crystal displays) has grown very rapidly, especially in the market share and technical development of FPD industries. To effectively promote the industry's capacity for the mass production and quality control, it is urgent to design and develop LC cell optical parameter measurement systems. The goal of this paper is to develop a multiple-functional and cost-effective measurement system to lower the manufacturing cost for the industry. The optical parameters includes the pretilt angle, liquid crystal (LC) cell gap (or phase retardation), and twist angle, which highly influence the display quality. In this paper, we first study the past approaches and analyze their measurement performance. Then, a simple and cost-effective method is proposed to achieve the multiple functions. That is, in addition to the precise measurement of the three important optical parameters, the proposed system can measure the voltage-transmittance (V-T) curve. In our approach, the theoretical study, simulation, and experiment are performed to show the feasibility of the system implementation. Finally, the proposed system is developed to automatically measure the LC cell parameters. Experimental results indicate that the proposed measurement system gives a satisfactory result.