透鏡對於光束偏振狀態的影響

Study on Variation of Polarization due to Mounted Lens

楊穎暉(Ying-Hui Yang)

指導教授 ： 曹培熙

國立臺灣大學/理學院/物理研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.00616

摘要

摘要
本論文的相關研究工作，是以偏振光相關的實驗及原理，了解透鏡影響偏振狀態的程度。我們獲得下列成果：
一、 偏振的運用：
設計簡易的觀察程序，以分辨圓偏振鏡及線偏振鏡。規劃出一系列實驗，藉以鑑定光束通過圓偏振鏡後的旋性。利用偏振鏡呈現相機的拍照效果及拍攝全像。
二、 柱面透鏡實驗：
以裝水的量筒當成柱面透鏡使用時，其中沒有應力分布，所以光波通過後，偏振狀態沒有發生變化。但是，玻璃棒中有應力分布，所以線偏振光通過後，變成橢圓偏振光。
三、 球面透鏡實驗：
我們發現，以常見方式架設透鏡，會使其中產生應力，因而會改變光波的偏振型態。利用光測彈性圖案，定性觀察透鏡上的應力分布，再觀測有應力的位置影響偏振狀態的程度。主要的觀測結果有：透鏡中央沒有應力時，線偏振光以近軸子午光線方式入射，透射後仍是線偏振。迫緊螺絲稍加施力，透鏡的中央部份就會有應力分布，會使出射光轉變為右旋橢圓偏振。改變迫緊的施力，觀測透鏡應力影響偏振狀態的程度，以偏振橢圓的長軸、短軸之比值及方向定量地呈現出來。

關鍵字

偏振 ； 旋性 ； 應力雙折射 ； 透鏡 ； 光測彈性術 ； 全像

並列摘要

Abstract
This thesis describes the efforts we made for investigating the variation of polarization due to mounted lenses. The motivation, principles, experimental methods, and results of our research are reported.

The first part of our work is related to the application and characterization of polarized light. We developed a simple procedure for distinguishing circular polarizer from linear polarizer. A series of experiments was performed to obtain the helicity of the light passing through a circular polarizer. Polarizers of known specifications were then applied in photography and holography.

Then we studied the effects on polarization due to cylindrical lens. The samples were a measuring cylinder containing water and a cylindrical glass rod. The polarization state of light transmitted through the measuring cylider was found to be the same as that of the incident light. But, with linearly polarized light at incidence, the light transmitted through the glass rod was found to be elliptically polarized. The difference can be interpreted with the difference in the stress distribution built in both samples, as revealed by photoelasticity patterns.

Spherical lens is a widely employed optical element. Hence its influence on polarization has to be understood. For that purpose, we carried out systematic studies.It was found that mounted lenses would transform linearly polarized light into elliptically polarized. Photoelastic patterns observed with a polariscope served as a qualitative indicator of the stress induced in mounted lenses. Then the extent of influence on the polarization state was observed for positions of the lens with stress.

When there are force applied to the mounting screw, photoelasticity patterns are created even at the central part of lens. Such an indication of built-in stress would lead to variation of polarization. By varying the magnitude of the force exerted on the mounting screw, we observed the effect due to lenses under stress. The extent of influence can be expressed quantitatively in terms of parameters of the polarization ellipse, that is, the ratio of axial lengths or the orientation of the long axis relative to the initial direction of polarization.

並列關鍵字

polarization ； helicity ； stress birefringence ； lens ； photoelasticity ； hologram

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