Evaluate LCD viewing angle by color saturation degradation

Viewing angle is a key parameter for the visual performance of a TFT-LCD. The conventional method of defining viewing angle, contrast ratio of luminance, however, fails to represent the color performance viewed at a larger angle. We propose a new metric of evaluating the viewing angle of a TFT-LCD by using degradation of color saturation. Three TFT-LCD panels of different viewing angles (conventional TN, OCB-parallel, and OCB-45) were characterized to collect their angular-dependent colorimetric parameters. The color saturation, defined as the ratio of chroma to lightness, is calculated by using the measured CIELUV coordinates. We found that color saturation is a superior metric of evaluating the TFT-LCD visual performance at different viewing angles. We applied the proposed metric to another three displays (TN, MVA, and PVA), and performed psychophysical experiments with 35 observers. The experimental results validate the efficacy of the proposed metric.