Optical density measurement of TFT-LCD by PMT coupled monochrome LED

A fast and innovative method using a monochromatic red LED to measure the optical density of black matrix is developed in this study. The results show that the 3-Watt monochromatic red LED performs better than that of the currently used 100-Watt halogen lamp by reducing the pumping speed by 40% and the 3-sigma standard deviation of the test samples is also superior by 40%. The measurement difference for average OD values is within 1% between both light sources. In addition, using standard glass, the monochromatic red LED demonstrates accuracy within 1.58%. Therefore, the monochromatic red LED can substitute the halogen lamp currently used the TFT-LCD industry to measure the optical density of BM layer.