寬頻譜極化眼鏡式3D立體投影系統的設計與實現

Abstract

偏極化式眼鏡的立體影像系統已廣泛應用於商業電影中，一般常見的偏極化式眼鏡僅使用一片線偏振極化片與一片四分之一波長相位延遲片的組合，相位延遲片是用來將線偏振光轉成圓偏振光，如此可解決頭偏帶來的問題，但市面上的相位延遲片的延遲量並非在可見光波段維持在π/2。這使得在某些波長下延遲片無法將線偏振極化光轉成圓偏振光，導致觀賞者在頭偏在頭轉動的時候影像會有漏光的情形，也就是左眼可能收到部分右眼的影像，反之亦然，也就是所謂的交互干擾值(Crosstalk)會升高。 在本論文中，在投影機端與眼鏡端分別添增一片四分之一波長相位延遲片作為補償以達到寬頻的效果，並於三種評價指標：交互干擾 (Crosstalk)、錯誤值 (Error value)與色差 (color-shift)分別作討論，並使用發光二極體 (LED)光源與未來預計系統中會使用的投影機光源，針對我們購入的線偏振極化片與相位延遲片分析，針對不同的頭偏角度去找到線偏振極化片與相位延遲片的最佳角度關係，並透過模擬與實驗的對照確認此方法為可行。 為了評價此方法的改變，提出了錯誤縮減改善比例，在四片延遲片的情況下，我們分別對可見光波段與窄波段優化，窄波段可以得到可以較佳的優化效果，相較寬的可見光波段則也有一定程度的優化，透過實驗也佐證在多片堆疊的情況下可以達到較為寬頻的效果，改善了頭偏帶來的問題。 使用多片堆疊確實可以減少錯誤值或交互干擾的影響並且改善色差的現象，但減少錯誤值或交互干擾值得到的結果卻不一定適用於色差優化後的結果，錯誤值與交互干擾優化得到的角度造成的色差對於色差的造成甚小，反過來，色差優化後的角度卻嚴重地增加錯誤值與交互干擾值甚值大幅降低我們應該要接受的影像，對我們所購入的材料而言，相位延遲片角度的選擇會以優化交互干擾值為優先，色差的影響相較之下是較小的。

Polarization glasses type 3D stereoscopic projection system has been used widely in commercial movies. Common polarization glasses is combined with only one linear polarizer and a quarter waveplate. Retarder is used to transfer linear polarization into circular polarization, which can solve the problems caused by head-rotation. However, the retardation of retarder in market not all are π/2 in visible wave band. So retarder under some wavelengthes can’t transfer linear polarization into circular polarization, which can cause light leakage of image under head-rotation. That is to say, left eye might receive partial image of right eye, and vice versa, which means that crosstalk will rise. This thesis added a quarter waveplate both at the projector and glasses for compensation to fulfill broadband retarder, and make discussion under the three criterion：error value, crosstalk, and color-shift ,respectively. This paper used LED source and projector light, which is planned to be used in future system, to analyze the purchased linear polarizer and retarder. We focused on different angles of head-rotation to find the optimal angle relation between linear polarizer and retarder, and compare the simulation and experiment results to make sure this method is workable. To evaluate the performance of the parameter change, we proposed the error reduction ratio. Under the situation of four retarders, we optimize the whole visible wave band and narrow wave band respectively. Narrow wave band can get better results of optimization, and broader visible wave band also can be optimized up to certain error reduction ratio. Our experiment proved that the purpose of broadband can be reached under several stacks, and it can solve the problems cause by head-rotation. Using more retarders indeed can decrease the effect of error value and crosstalk and reduce the phenomenon of color-shift, however the result of decreasing error value and crosstalk may not suit for the result of reducing color-shift. The optimal angle of error value and crosstalk cause small effect of color-shift, conversely, the optimal angle of color-shift will increase error value and crosstalk seriously, and even decrease the image that we can accept. The materials that we purchased will take optimal error value and crosstalk as priority to choose the angels of retarders, the effect of color-shift will be less in comparison.