Reflections on Measurement Methods

摘要

Take a close look at two different reflective liquid-crystal-display (LCD) panels; which one shows the better contrast? It's a simple question, but one that proves to be difficult to answer. The way in which a panel is illuminated and observed has a major impact on the perceived visual results. At present, there is no broad agreement on how the illumination and measurement of reflective displays should be accomplished. In 1976, G. G. Barna first proposed a method for illuminating reflective LCDs during measurement by using a glass hemisphere that produced a multidirectional illumination that approximated diffuse lighting. This concept evolved into a commercial product in Germany in 1985, but despite the available knowledge and instrumentation there still is no international standard for reflective-LCD panels. In the December 1994 issue of Information Display, James Greeson contributed the article "Display Standards in Trouble." It seems that 8 years after the status analysis in the first paragraph of that article, little has changed for the better. But there is some cause for optimism.