An Improved Surround Adaptive Metric for Dynamic Range of Liquid Crystal Displays

摘要

The dynamic range and contrast performance of displays are usually specified as the maximum contrast ratio (CR) of displays. However, there are drawbacks in the theoretical and technological aspects of the measurement of the traditional CR in display industry. Recently, a metric for dynamic range of displays that closely corresponds with human perception has been developed by Greg Ward, which was called the Number of Distinguishable Grays (NDG). In this paper, a surround adaptive NDG metric (SNDG) was proposed for liquid crystal displays (LCDs). Comparing with the original NDG metric, the SNDG metric was improved in two aspects. Firstly, instead of measuring the gray level luminance response for all the identical RGB inputs of a LCD, the tone reproduction curve (TRC) of the LCD was measured for a few of identical RGB inputs with suitable intervals and modeled by the S-curve function to get the luminance difference between adjacent gray levels. Secondly, the just noticeable luminance or visual threshold at each luminance level under known ambient lighting was calculated based on the surround luminance adaptive contrast sensitivity function (CSF) modeled by Y. J. Kim so that the effect of surround on perception could be taken into account. Then the perceptible luminance steps were counted by the SNDG metric from the deepest black to the brightest white of the display. In the end, four LCDs, two TV displays and two mobile phone displays, were evaluated under varying ambient lighting using this new SNDG metric.