外差干涉技術是一重要的精密量測方法，據此所發展的感測系統可以在量測變化時有極佳的線性、穩定性與精密度，其應用範圍十分廣泛。另一方面，由於人們對於雙折射特性日益感到興趣，相關的量測系統大多以外差干涉為基礎，然而目前所提及關於量測材料之雙折射特性的系統中，較少具有同時量測主軸變化與雙折射特性的功能。
因此本研究提出兩種創新的系統設計，首先利用相位光柵作週期性的弦波調變及二分之一波片設計出類似賽曼雷射具雙偏極化特性的光源系統，再配合簡易的光學架構設計出新型共路外差干涉儀 ( New Common-Path Heterodyne Interferometer ) ，另外一套系統則是利用電光調變器，結合類似的光學結構，設計出另一套量測系統。此外，為達到同時量測的目標，本研究中亦同時發展一套相配合的數位訊號處理技術。結合光學量測與訊號處理以實驗證實所發展的系統可應用於同時量測具雙折射特性物質主軸角度以及其雙折射性，且結構簡單、價格低廉。
最後對於所提出的二系統分別分析其主要誤差成因，發現皆為具週期性非線性的誤差。

This study demonstrates two methods for simultaneously measuring both the angle of principal axis and the phase retardation of the linear birefringence in optical materials. First one, a transversely moving grating is utilized to modulate the light source, and operated in coordination to a half-waveplate to compose a two orthogonal polarized light with a Doppler frequency shift, such as a Zeeman laser. The other one is used a circular common-path interferometer (polariscope) as the basic structure modulated by an electro-optic (EO) modulator. On the other hand, in order to simultaneously extract the wanted results, the principal axis and the phase retardation, an algorithm was developed to achieve the goal.
Through the experimental results, these two measuring structures are further confirmed their abilities. For the Zeeman-liked system, its average absolute error of the principal axis and phase retardation are respectively approximately 3.15 % and 1.09 %. For the other one, the average absolute error of the principal axis is approximately 4.8 %, and that of the phase retardation is approximately 1.09 %. For repeatability, the average deviation for the principal axis is 0.186º and the phase retardation 0.356º. For the stability, the average deviation for the principal axis is 0.405º and the phase retardation is 0.635º. The dynamic ranges of these two new systems for principal axis is 0 to 360 degreeand phase retardation is from 0 to 90 degree.
Finally, analyzing the main error source in these two heterodyne interferometers, the thermal drift of PZT stack and the principal angular misalignment of the electro-optic modulator are found respectively. Then, a nonlinear error is discovered.

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