液晶顯示器基於人眼偏好的影像品質調整迦瑪曲線及反射式液晶顯示器白色色偏之研究

Abstract

顯示器元件在設計及規格之制定上通常會以人眼的視覺感知為基礎，因此人類的視覺特性在顯示器的發展上扮演著重要的角色。本論文主要的研究方向有二：一是對液晶顯示器迦瑪曲線的校正達到人眼喜好的影像品質，傳統對CRT迦瑪的研究只單純改變系統迦瑪的數值乘積來達到喜好的影像品質，然而液晶顯示器由於在輸出光的方式的不同，因此在液晶顯示器無法以數值方式逼近液晶螢幕本身非線性的輸出關係。因此本論文設計的主觀視覺實驗，以使用者主觀的調整曲線來達到偏好的影像品質，此方法的最大優點之一就是評估的結果與人眼的主觀感知相符，找出gamma有效的提高影像品質，評估的結果可以對主觀的影像品質制定出最佳化的顯示參數，實驗結果可以應用於制定驅動IC規格的參考。 另一方面是研究反射式液晶顯示器背景白色純度不足，造成顯示器影像品質降低，在本論文中以模擬可見光波長範圍內反射頻譜與人眼視覺特性結合產生的顏色，可以了解在不同液晶形式下所造成的白色偏移的程度，並提出可行的方式來補償偏移，達到理想中的白色背景。

Human perception is the basis for defining specification of display devices. Consequently, human visual characteristics play an important role in the development of display devices. There are two subjects studied in this thesis. First, the subjective adjustment of LCDs’ gamma relation is to achieve users’ preferred image quality. Conventional method of gamma correction for a CRT display system only modulates the numerical multiplication of overall gamma to evaluate the image quality. However, LCDs have different illuminant method to reproduce output luminance. Therefore, the intrinsic non-linearity of LCDs cannot be approached by a numerical relation. The optimized gamma relation to reproduce the perceived image quality is conducted via a psychophysical experiment. The major advantage of this evaluative method is that the results are well correlated with subjective human perception. As a consequence, optimal display parameters for subjective image quality can be specified and the experimental results can then be utilized to specify the characteristics of driving IC. On the other hand, the impure whiteness of reflective LCDs degrades the image quality. In order to comprehend the degree of white shift caused by LC layer, the spectral distribution of reflected light is integrated with the characteristic of human vision functions to calculate the chrominance on the reflective panel. Further a feasible method to compensate the impurity of whiteness is proposed in this thesis.