Optical density measurement of thin-film transistor liquid crystal display by a monochrome light-emitting diode

A new method using a monochromatic light-emitting diode (LED) to measure the optical density (OD) of the black matrix of thin-film transistor liquid crystal display (LCD) is developed in this study. The measured results show that the average OD difference is within 1% between the proposed 3 W monochromatic LED and the currently adopted 100 W quartz halogen lamp. On the other hand, the monochromatic LED reduces the boosting time by 40% in establishing the baseline database. The 3sigma standard deviation of the OD of the test samples is from 0.1% to 0.6% for the LED, whereas it is from 0.5% to 1.2% for the halogen lamp. Using standard glass samples, the monochromatic LED demonstrates accuracy within 1.58%, better than that of the quartz halogen lamp. Therefore, it can substitute for the quartz halogen lamp currently used in the thin-film transistor LCD industry for OD measurement of the black matrix layer, as it is faster, is more accurate, is more reliable, and consumes less power.