基於鏡頭陣列之區域化高動態範圍影像處理技術與其系統實現

Abstract

隨著科技快速的進步，消費者對於影像畫質的要求越來越高，接近人眼所看之影像越發重要，另外，目前的影像感測裝置與影像顯示設備無法完整將真實場景中的動態範圍保存下來。因此在各種視訊影像應用當中，可以提供更高的動態範圍以及更好的影像品質的高動態範圍影像技術開始蓬勃發展。 高動態範圍影像處理技術已發展多年，大致可以分為單張影像增強技術與多張不同曝光合成技術，但大多為各自發展，很少有結合兩者優點之技術被討論，因此本論文提出了一結合兩種單一技術之優點的高動態範圍影像技術，不僅能針對真實場景中極端亮度區域的細節保留，也能提升正常亮度範圍但對比度不足的情況 在取得高動態範圍影像後，須將影像映射至較低的動態範圍以供一般顯示裝置播放，因此本論文也提出了一結合全域映射與區域映射之優點的技術，有效將高動態範圍影像映射至一般顯示器可以播放的低動態範圍，並且保留場景中的細節。本論文利用羅技視訊鏡頭組成的鏡頭陣列來取得輸入影像，並將整體系統實作在Adlink MXC-6300平台上，可達到每秒約20張畫面之處理速度。

With the rapid advance of technology, the demands of consumers for quality of image are increasing. It is important that images preserve scenes close to human eyes. In addition, the current image sensor and display device cannot preserve the whole dynamic range of the real scene completely. Therefore, in the application of image technique in different field, the image techniques with both higher dynamic range and image quality are prospering. High dynamic range image techniques can be roughly classified into two categories: single image enhancement and merging different exposure images. These two categories of methods are improved respectively. The method merging the advantages of these two different categories of methods is seldom to be discussed. Ergo, this thesis proposes a new method combining these two kinds of methods. It can not only preserve details in the extreme high luminance region of real scene but also enhance the contrast of the area under normal brightness. In order to display the image contents on common devices, it is necessary to compress the high dynamic range image into low dynamic range one. Therefore, this thesis proposes a mapping function merging the advantages of global and local tone mapping. It is effective to compress the HDR image to lower dynamic range for common displays and preserve details in the scene. The thesis uses camera array being composed of Logitech webcams to capture input images. The system is implemented on platform called Adlink MXC-6300 and reaches 20 frames per second processing speed for VGA video.