利用獨立成份分析法評估新型電子紙之色料特性

Abstract

電子紙是新型顯示器市場中極具潛力的產品。做為非自發光型的顯示器，電子紙具有類似印刷製品的閱讀感受，在強光下也能保持畫面對比度；與此同時，電子紙也具有電子製品的資料傳輸模式及可重複書寫的特性。更重要的是電子紙具有雙穩態的特性，因此能夠以低耗能維持相同畫面。這些特性使得電子紙在商業市場上具有廣大的應用範圍，如電子閱讀器、電子報、電子標籤、電子看板等等。 為了與其他傳統顯示設備進行良好的色彩重建，有必要針對電子紙建立一套精確的色彩特性化模型。但受限於複雜的混色特性，過去所習之特性化模型難以應用於新型電子紙的特性化。因此本論文提出盲訊號分離的研究方法，利用量測到的頻譜資訊評估電子紙的色料特性。 盲訊號分離中的獨立成份分析法是根據高階統計量的方法訂出獨立度的量測準則，再針對量測準則建立最佳化演算法找到轉換矩陣，並通過此轉換矩陣將混合訊號轉換至統計上獨立之向量空間。利用獨立成份分析法能夠從量測得到的頻譜資訊中找到新型電子紙潛在的獨立色料頻譜成份，並以此做為系統的特性矩陣，建立一套屬於新型電子紙的色彩模型。在本論文中將獨立成份分析法應用於單色與全彩電泳式電子紙，且成功地得到此複合混色系統的特徵頻譜，並以此建立能精確描述此電子紙顯色之色彩模型。

E-paper is a novel display with several appealing features. Since E-paper is a non-light-emitting display, it performs as hardcopy and holds fine contrast under sunlight, while at the same time, it can deliver or send electronic data as softcopy. Moreover, it has the bi-stable system which can hold the screen with low energy consumption. There are many available applications with these properties, such as E-reader, E-label and E-board. In order to complete color reproduction, it is necessary to characterize the color performance of E-paper. However, it is too complicated to characterize the hybrid color mixing system with physical model, which is accomplished according to the physical structure. In this paper, we introduce a methodology based on independent component analysis to complete the colorimetric characterization. The independent featuring spectra of E-paper can be found out by applying independent component analysis to the reflectance spectra. After that, the color mixing system can be represented as a linear combination process of featuring spectra. Two samples will be introduced in this paper: monochrome micro-cup electrophoretic display and full-color micro-encapsulated electrophoretic display. According to the experimental results, the featuring spectra can be successfully determined by ICA-based methodology. Consequently, a colorimetric characterization of the special EPD with high fidelity has been done.