利用主視覺顯著區演算法建立影像色分離指標 應用於色序型顯示器

Image Content Adaptive Color Breakup Index for Field Sequential Color Displays Using a Dominant Visual Saliency Method

林映汝(Lin, Ying Ju)

指導教授 ： 黃乙白 ； 謝漢萍

國立交通大學/電機學院/光電工程系所/碩士(2019年)

摘要

色序型顯示器(Field Sequential Color Displays, FSC Displays)是一種具有高光效率、 廣色域的新型顯示器，然而高頻率快速切換色場會造成嚴重的色分離(Color Breakup)問 題，色分離不僅會影響影像品質，更會使觀察者產生視覺疲勞。目前已經有許多解決色 分離的演算法被提出，但這些演算法通常僅應用於評估固定的單色色塊或色塊組合，並 不能適用於各種自然影像內容中。色序型顯示器可以應用的範圍相當廣泛，例如低耗能 顯示器、微型投影機、虛擬實境等，因此能應用於各種影像內容的「色分離指標」是相 當有價值與重要的。
為了制定一個新的色分離指標，首先需要建立一個影像資料庫作為人因實驗與影像 分析的根據，由於先前幾乎沒有專門用於色分離的影像資料庫被提出，在本研究的一開 始先提出了一個資料庫，其包含二十五張具有不同圖像內容的參考影像，以及一百二十 五張具有各種色分離可見度表現的測試影像。接著，透過使用 240Hz 液晶顯示器進行人 因實驗來獲取測試影像的主觀色分離分數，同時利用電腦模擬視網膜成像去做影像比對 分析得到客觀評分。基於視覺顯著性理論，加上考慮到人眼動態視覺可能會導致視覺關 注區域被限制，本研究提出了「主要視覺顯著理論(Dominant Visual Saliency Theorem)」 以及構築於該理論之上的色分離可見度計算模型，意旨影像整體的色分離可見度應該由具有一定閾值的更顯著視覺區域決定，而非單純由視覺顯著區決定。
透過整合主、客觀兩方數據並根據所提出的理論，主、客觀間色分離可見度之線性 相關係數高達 0.82，表明了此理論的正確性及指標的可靠性。另外，此色分離評估指標 被用於預測當今主流 FSC 演算法之色分離可見度，以驗證各演算法在色分離抑制方面的 表現。這種嶄新色分離評估指標可以適應來自各種不同影像內容，並有望作為色序法顯 示器未來相關應用的實現標準。

關鍵字

色序型顯示器 ； 色分離指標 ； 視覺顯著區

並列摘要

Field sequential color (FSC) displays have advantages of high optical throughputs, high spatial resolution, and wide color gamut. However, the high frequency of sequentially flashing multiple color fields causes a fatal issue, called color breakup (CBU). Therefore, a number of studies have been dedicated to developing indices that can predict the perceptual visibility of color breakup for varying image content, while the current color breakup indices are usually for fixed colored blocks or patterns.
Because few image databases for color breakup research have been proposed, to solve this problem, an image database containing 25 reference images with diverse image contents and 125 test cases with various color breakup visibility was first established. Next, visual experiments were conducted to acquire the subjective color breakup scores of the test cases by using a 240 Hz liquid crystal display. By considering that the subject dynamic eye saccades may cause constrained visual saliency compared to static viewing, a new theorem, as dominant visual saliency theorem (DVS theorem), based on visual saliency theory (VS theory), was proposed and a computational model of color breakup visibility was also
developed based on the proposed DVS theorem. The main concept of the DVS theorem is that 3
the color breakup perception is mainly determined by the image regions with visual saliency values higher than a certain threshold.
According to the proposed theorem, an analysis of the objective and subjective results revealed a Pearson linear correlation coefficient as high as 0.82, which matches the top-level image quality assessment algorithms, revealing it to be a reliable index. In addition, the proposed color breakup index was used to benchmark against several mainstream FSC algorithms to determine their performances in color breakup suppression. Consequently, this unprecedented image-content-adaptive index for color breakup assessment is promising for being a criterion for FSC-related devices—low power displays, micro projectors and virtual/augmented reality devices, etc.

並列關鍵字

Field Sequential Color Display ； Color Breakup Index ； Visual Saliency

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