基於全內反射波長調制外差干涉術小角度測量

Small-angle Measurement Based on Total Internal Reflection Using Wavelength-modulated Heterodyne Interferometry

吳啟斌(Qi-bin Wu)

指導教授 ： 李朱育

國立中央大學/工學院/機械工程學系/碩士(2015年)

摘要

光學測角法中，光學內反射相位法運用的是偏振光的特性，具有對環境要求不高、測量範圍可調與體積小等優點，在生產線即時測量與空間受限的場合具有潛在的運用價值。但是目前的光學內反射相位測角法的研究由於普遍使用昂貴的電光調制器等移頻器件，限制了它的應用。鑑於此研究動機，本文通過直接對雷射波長進行調制，以達到外差干涉的效果，實驗驗證了其可行性外並開發了一新型差分共光路光學架構，具有體積小、架構簡單與成本低等優點。
論文中主要進行了兩個光學架構的研究，一個為以驗證性為目的的單光路光學架構，另一個為新型差分共光路光學架構，即在單光路光學架構的基礎上，僅增加一個1/4波片和反射鏡就實現差分光路的效果。研究中通過函數發生器產生調制訊號直接調制雷射波長，旋轉平台角度變化訊息載入全反射相位變化效應下具有光程差的P光和S光的相位，最後運用示波器直接擷取外差訊號相位。
實驗測量結果與理論基本相符合，測量特性分析主要包括靈敏度、解析度、線性化處理、相對折射率因素、相位穩定性與誤差分析。差分共光路光學架構中，除去正入射零點測量，測量範圍約達到10度，靈敏度達到700，解析度達到0.0014度。

關鍵字

全內反射 ； 波長調制 ； 外差干涉 ； 小角度測量

並列摘要

Taking the advantages of polarized light’s characteristics, the method of measuring small angle based on total internal reflection has the advantages of being susceptible to environmental impact, adjustable measuring range and small size in the field of optical angle measurement which could make it possess the potential applications in on-line measurement and space-constrained fields. However, the widespread use of electro-optic modulator devices such as the expensive frequency shift which limits its applications. In order to solve this problem, the thesis develops a new method to modulate the wavelength of laser directly called wavelength-modulated heterodyne interferometry , the validity of this method is demonstrated. What’s more, a new differential common-path optical configuration has been developed, and it has the advantages of simple structure, small size and low cost.
There are two optical configurations studyed in the thesis. One is called single optical path configuration studied to verify the method of wavelength-modulated heterodyne interferometry’s feasibility. The other configuration called differential common-path optical configuration adds one quarter-wave plate and a mirror on the basis of a single path configuration. The modulated signals produced by the FG(function generator) is used to modulate the wavelength of laser. Due to the total reflection effect, the angular variations of the rotation stage is loaded in the phases of P light and S light which own the optical path difference. Finally, an oscilloscope is used to measure the phases of the heterodyne signals.
The experimental results are in agreement with the theoretical analysis. The analysis of the measurement characteristics include sensitivity, resolution, linearization, relative refractive index factors, the stability of the phases and the error analysis. In regard to the differential common-path optical configuration, the measurement range is about 10 degrees except the nomal incidence, the best sensitivity is 700 and the best resolution is 0.0014 degrees.

並列關鍵字

The total internal reflection ； Wavelength-modulated ； Heterodyne interferometry ； Small angle measurement

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