用於擴增實境之側光源穿透式電腦全像顯示器的設計

本論文研究如何將全像技術應用於擴增實境之設計，我們不但利用全像光學元件整合系統成為輕薄型的穿戴裝置，同時研究電腦全像技術作為顯示軟體，來實現虛擬擴增實境的三維影像顯示。在穿戴裝置的硬體方面，我們提出使用了體積全像片，並利用其可以多工紀錄的特性，實現僅在一片體積全像片中完成輕薄型的穿戴裝置。為了實現以上設計，我們先對紀錄材料的側面表面進行研磨，使其變成像是毛玻璃的表面，藉此可以讓原先光線孔徑過小的雷射光源散射並且在記錄材料內進行全反射，同時用材料記錄下此散射的光與另一道從紀錄材料正面入射平面波的干涉條紋，即可以用雷射的小孔徑光源來提供與顯示器尺寸相符的光源。再來用材料記錄一道平面波從顯示器到體積全像片與另一道平面波指向使用者眼睛方向的干涉條紋，藉由此干涉條紋可以將顯示器的資訊光導向眼睛與現實環境結合，如此一來這兩次的干涉條紋紀錄可以實現輕薄體積全像片整合上述的三個功能。在電腦全像片設計方面，我們提出使用可以藉由快速傅立葉加速的菲涅斯轉換來計算電腦全像片，藉此獲得更好的電腦全像片運算速度表現，但是菲涅斯轉換本身只能計算平面對平面的光波傳播，所以這邊我們先用三維列表機軟體Cura，將三維投影物體轉換成物體切層的輪廓並存取在文字檔中，之後再用開源軟體python讀取文字檔還原成輪廓並進一步的轉換成欲投影的物體切層平面，再來因為顯示器本身只有相位調控的因素，我們使用了迭代菲涅斯轉換演算法，來提升只使用相位調控顯示的純相位電腦全像片的重建品質。

關鍵字

擴增實境；體積全像光學元件；全像顯示器

並列摘要

In the thesis, we study the design of see-through edge-lit Computer-Generated Hologram (CGH) for Augmented Reality (AR). First, we propose to use two volume holographic optical elements to integrate an optical system for a wearable AR device, meanwhile use a reflective phase-modulate liquid crystal on silicon(LCos) for displaying Computer Generate Hologram(CGH) that bring the feature of three-dimension(3D) object on wearable AR device. In order to realize the volume-hologram based AR device, we first grind the side surface of the recording material to make the surface like ground glass, so that the laser light source can be scattered and totally internal reflected in the whole recording medium for beam expansion. Using another plane wave that incident from the front surface of recording medium, a beam expander device can be achieved. Then, using the same recording material to record a second reflection hologram whose reference beam is reflected beam from spatial light modulator and signal plane wave is pointed to user’s eye. These two cascaded holograms can guide the information light from display to the eyes and combine with the reality. For the design of the CGH, we propose to use the Fresnel transform which can be boosted by Fast-Fourier Transform(FFT) to calculate the CGH, by the algorithm we can get a better speed performance on calculating CGH. But Fresnel transform can only calculate the wave propagation from plane to plane, so we use the 3D printer software Cura to convert the 3D object into each section’s contour and store the information in the text file. Later using python to read the data and turn it into the image we want to display. Considering the problem that display can only modulate the phase part, so we use the iterative Fresnel transform algorithm(IFrTA) to improve the quality of reconstruction displayed by phase-only CGH.