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This thesis researches the measurement methods of cell gaps of LCDs employed commonly. We establish simple and precise cell- gap measurements of a transmissive twisted nematic LC cell anreflective twisted nematic and non-twisted LC cells. The experimental method we use is to place the LC cell between two polarizers and then rotating the polarizers to get transmittance and reflectance.In a LCD ( liquid crystal display ), the cell gap plays an important role in determining its performances, such as brightness, contrast ratio, and response time. In parti cular, a reflective LCD cell gap is usually smaller than a transmissive LCD one, so a little deviation of the cell gap from the desired one leads to poor performances. Dur ing the device fabrication, the LC cell gap may deviate from its designed value. Accurate cell gap can be obtained by fitting the experiment value with the calculation using Jones Matrix. For optimizing the performances of LCDs in the manufacturing process, simple, precise, and fast methods to measure the cell gap is required.
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