首先利用電光晶體調制雷射光，使之成為具有適當差頻的外差光源。接著以此外差光源量測各種系統所引入s- 與p- 偏光間的相位差變化，並根據相位差的變化來進行各種參數的量測。針對待測物的待測量，量測系統可分為共光程與不共光程干涉儀兩種。
在不共光程干涉儀的結構中，以可調波長二極體雷射為光源的外差干涉術來做干涉信號之中心條紋的定位。此方法除了可定出中心條紋的位置外，還可判斷干涉儀兩臂何者較長。
而在共光程干涉儀的結構中，探討量測折射率的方法；其中包括有全反射法、相位差之極大值求折射率法，以及根據全反射法所設計的液體折射率計。並發展出旋光外差干涉術，來量測材料的布魯斯特角，進而求得折射率。另外還有複數折射率的量測，以及磁頭滑片的等效複數折射率與其飛行高度的量測。這些應用都是以外差干涉術量出相位差，然後代入菲涅爾方程式解出待測的物理量。
本論文所提出的量測方法有光學結構簡單、操作容易、高穩定度與快速量測等優點。而由於外差干涉術可精確地量出相位差，因此量測解析度亦高，使其具有實用的價值。

A laser light is modulated by an electro-optic modulator to become a heterodyne light source with a suitable frequency difference. This heterodyne light source is used to detect the phase difference variation between the s- and p- polarization, when light transmits through or is reflected from a medium. From the analysis of the phase difference variation, some parameters of the medium can be obtained. Depending on the characteristics of the test medium, the optical configuration can be divided into two types: a common-path heterodyne interferometer and a non-common-path heterodyne interferometer.
In the case of a non-common-path heterodyne interferometer, the laser is replaced by a tunable laser-diode. It can be used to identify the central fringe and is easy to judge which arm of the interferometer is longer.
In the case of a common-path heterodyne interferometer, the measurement methods of the refractive index are investigated. They include the total-internal-reflection (TIR), the maximum phase difference of TIR, and liquid refractometer. Besides, The circular heterodyne interferometry is developed to determine the Brewster''s angle. Moreover, the measurements of the complex refractive index, and the effective complex refractive index and the fly-height of the read-write head slider are introduced. In these methods, the phase difference is measured by the heterodyne interferometry firstly. Then it is substituted into Fresnel''s equations, and the refractive index of the test medium is obtained.
Because the heterodyne interferometry can determine the phase difference precisely, these methods have the high measurement accuracy. Besides, they have several merits such as simple optical setup, easy operation, and rapid measurement. Hence, it is suitable to applied these methods to industry.

第一章 緒論1
參考資料4
第二章 外差干涉術及s-與p-偏光間的相位差變化6
2.1 前言6
2.2 外差干涉術的原理6
2.3 外差光源7
2.3.1 各種外差調變技術7
2.3.2 使用電光晶體調制的外差光源8
2.4 s-與p-偏光間的相位差變化與其測量方法12
2.4.1 共光程干涉儀12
2.4.2 不共光程干涉儀18
2.4.3 相位差的測量方法19
2.5 外差干涉術的週期非線性誤差22
2.5.1 偏振旋轉誤差22
2.5.2 偏振混合誤差25
2.6 小結28
參考資料29
第三章 中心條紋的定位33
3.1 前言 33
3.2 一般定位的方法33
3.3 可調波長外差干涉術的定位方法36
3.3.1 使用雷射二極體為光源的外差干涉術36
3.3.2 中心條紋的定位原理38
3.3.3 雷射二極體的特性40
3.3.4 同一縱模態的定位方法43
3.3.5 不同縱模態的定位方法48
3.4 使用雷射二極體與穩頻雷射的定位方法52
3.4.1. 原理53
3.4.2 實驗與結果54
3.4.3 討論55
3.5 小結55
參考資料58
第四章 折射率量測61
4.1 前言 61
4.2 一般測量折射率的方法61
4.3 利用共光程外差干涉術的折射率測量法62
4.3.1 全反射法63
4.3.2 以全反射相位差之極大值求折射率71
4.3.3 液體折射率計73
4.3.4 旋光外差干涉術80
4.3.5 複數折射率的測量88
4.4 小結95
參考資料96
第五章 磁頭滑片等效複數折射率與飛行高度的模擬測試102
5.1 前言102
5.2 一般的量測方法103
5.2.1 偏振干涉術103
5.2.2 受抑全反射法103
5.3 外差干涉式等效複數折射率與飛行高度測量法106
5.3.1 多光束干涉所引起s-與p-偏光間的相位差106
5.3.2 等效複數折射率的求法108
5.3.3 以外差干涉術測量相位差變化112
5.4 小結116
參考資料118
第六章 結論120

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