應用同軸式全像術於資訊儲存與三維取像之研究

Abstract

本論文將Dennis Gabor所提出的同軸全像應用於光資訊儲存以及三維取像。 在光資訊儲存方面，首先介紹我們的同軸式偏振全像資訊儲存系統之概念，利用體積偏振全像的繞射特性，將讀取光過濾，只留下重建的資訊光，解決同軸式全像的孿生像問題，所以，我們從分析體積偏振全像繞射特性藉以完善系統的設計出發，提出以正交圓偏極化為主要儲存架構。然後，說明儲存媒體－PQ/PMMA感光高分子的研製，與系統中關鍵器件操作原理。此外，在光學實驗中，我們首先證實理論分析的想法，然後研究不同的記錄條件，對儲存結果的影響，將用通訊理論之誤碼率與頻道容量來評估，最後找出最佳儲存條件，以其估算系統的儲存容量可達單一碟片約16GB。 在三維取像方面，首先我們根據市售CCD的特性，設計相移曝光方法，進行同軸式數位全像的研究，設計一套系統，以進行三維物體斷層取像，數位重建。結果顯示，當物體放置於CCD前13公分時，取像景深皆能保留，並予重建，圖案解析度可達～35μm。接著，為改善動態取像速度，我們進行近似同軸之數位全像設計，藉由參考光與物體光有小角度的分隔，加上傅氏頻譜法則之分析，可以實現單次曝光記錄，就可以進行三維物體斷層取像與重建。接著，比較同軸式與近似同軸式的重建效果。分析兩者之差別，我們發現同軸式的方法解析度較高，但須多次拍攝取像，故適用於靜物全像，而近軸式安排，則解析度稍差，可適用於動態取像應用。最後，我們以重建畸變三維物體光波，展示同軸式數位全像的三維取像能力。

In this thesis, we present our studies on holographic data storage and 3D imaging using in-line holographic method. In holographic data storage part, we first describe the design of our in-line polarization holographic data storage system. Then, we introduce the diffraction light properties of polarization holography, and utilize these properties to filter out the reading beam in order to solve the conjugate image problem. We start with the design of volume polarization holographic data storage system, using orthogonal circular polarization of light as a major recording method. Then, we describe (i) the recording medium - PQ/PMMA photopolymer, made by us in our laboratory and (ii) the working principle of the writing and reading head in our data storage system. Besides the optical experiments, we prove the idea by theoretical analysis. As a final point, in order to find the best recording condition, we study the storage results using different reference patterns and recording planes, and estimate them by bit error rate and channel storage capacity using communicational theory. The evaluated storage capacity of our system is about 16 GB for 5 inch disk. For 3D imaging part, following the properties of commercial CCD, we use the phase-shifting method to study the in-line digital holography. We design an optical system to execute 3D imaging using digital reconstruction method. The result shows that the system can resolve into ~35 μm when the distance between the CCD and the object is 13 cm. In order to improve the dynamic imaging speed, we execute the design of quasi-in-line digital holography. We use a small angle between the object beam and the reference beam, and utilize the analysis of Fourier spectrum to achieve single exposure reconstruction and 3D imaging. After that, we compare the reconstructed images using in-line and quasi-in-line methods. The results show that in-line method has higher resolution but it requires to record 3 holograms. Therefore, we conclude that in-line method is suitable for static measurements. On the other hand, quasi-in-line method requires to record only 1 hologram, but it shows lower resolution. Therefore, it’s suitable for dynamic measurements. Finally, we reconstruct the dispersed object to demonstrate the 3D imaging ability of in-line digital holography.