外部光反射参数对LED显示屏全视角对比度的影响

由于对比度计算方法的局限性使得计算得到的对比度值与LED显示屏在实际中的显示效果会出现不吻合的现象。针对此现象主要对两个方面的内容进行分析。首先,分析LED测量方法中对比度与视角之间的相互关系,在此基础上建立各视角对比度参数。并且利用实际测得的此参数结果与通过LED测量方法计算的数据作对比,表明利用计算方法计算得到的对比度值与实际上在复杂因素的影响下采集得到的对比度结果存在差异,证实各视角对比度参数的计算方法存在问题。其次,分析外部影响参数如测量角度、反射参数在简单光照明下的模型,利用此模型计算得到背景亮度函数曲线,并与实验测得的背景亮度结果作对比,证明了两者结果的一致性。在此基础上,就可以以此模型为背景亮度函数式建立新对比度函数表达式,通过此表达式模拟显示屏上各视角对比度,使得到的函数曲面与使用LED测量方法计算得到的函数曲线相比较,证实LED测量方法中对比度计算方法的理想化,并说明了产生上述不吻合现象的原因。

The Influence of the Reflection Parameters of the External Light on Contrast Distribution at any Visual Angle in Large-area LED Display Panel

The limitation of the original definition of the contrast brings about the misconstruing of computing method of panel contrast in some cases where the display effect of LED panel to be appraised. Because of the existing of the misconstruing in some cases, two problems have to be solved primarily in this paper.Generally, the display effect of the LED panel is influenced by many factors (indexes), such an stability, luminance, chromo-contrast, visual angle, etc. But the main indexes inducing the misconstruing mentioned above are contrast and visual angle. So, first of all, the relationship between the contrast calculated by the test method of the LED panel and the visual angle need to be analysed, and a new index, so-called the contrast distributed at any visual angle, must be established to present the relation of the both indexes. As the same act of other indexes, the new index will be used to evaluate the display effect of the LED panel. So at first, the maximal panel brightness and the minimal panel brightness at any visual angle can be measured by BM-7 under a certain illumination intensity, and the contrast at any visual angle will be calculated. On the other hand, the contrast can be calculated by the expression of the test method of LED panel. By comparison, the difference between the results calculated by the both methods mentioned above exists, and the difference is very obvious. The experimental results indicate that the values of the contrast at any visual angle between that computed by LED panel measurement method and that calculated by the real panel brightness are also diffe-rent, and it was also proved that the results from LED panel measurement method are out of accord with the real display effect of LED panel.Secondly, the reason why the computing method is out of accord with the real display effect is due to the complex factors in the real surroundings. So the model of the main external factors which effect the values of the contrast in the real conditions must be analysed in detail, such as the measurement angle and the reflection parameters of extraneous light. Using the module of the reflection parameters, the minimal brightness curve of the extraneous light can be obtained.And comparing with the values measured by BM-7, it is concluded that the main characteristic consistence of two kinds of the curves obtained by different methods exists. Based on the conclusion, using the mo-del of the external factors, a new expression of the contrast can be established to evaluate the display effect of LED panel. And by using this new function relation, the curved surface of the contrast at any visual angle can be simulated. In comparing with the curve of contrast computed by the test method of IED panel, it was proved that the computing method of contrast in the test method of LED panel, as without thinking of the influence of specular reflection of extraneous light, is so idealization, sometimes its result could be not agree with the real display effect of LED panel. Thus, the misconstruing problem can be explained and resolved.