本論文提出一種利用外差干涉術量測面內微小位移量的方法。外差干涉術是一種測量光相位變化的方法，它對於雜訊擾動有良好的抑制能力，而傳統的干涉儀的實際應用之中往往會受限於這一缺點。目前光干涉儀之位移監控大多利用不共光程的方式來達成，而外界環境的擾動將會造成監控上穩定度之困難。本文以外差干涉技術為基礎，設計一特殊的光學架構，量測光柵位移時所引入的相位變化，並且將經由鎖相放大器測得的相位變化換算為面內之位移量。當實驗中的環境雜訊很大時，鎖相放大器不易受到雜訊的影響，仍可量測到實驗中所需要的微小AC訊號，再經過內部的電路運算後將可獲得我們所需的相位差。由目前的理論計算結果與實驗量測實驗驗証，此技術的測量範圍可達1毫米，且其解析度可達1皮米。因為外差干涉術具有高靈敏度的優點，本技術同時具有高精確性及寬量測範圍，將可應用於高精密移動平台之位移及定位之感測等。 A heterodyne interferometry for measurement of the in-plane displacement is proposed. The measurement system includes a heterodyne light source, a moving grating and a lock-in amplifier for phase measurement. The in-plane displacement means that the direction of the measuring object displacement and the direction of the measuring light beam become vertical relation each other. The phase variation, which resulted from the displacement of grating movement, is measured by the heterodyne interferometry, and it is converted into the small in-plane displacement. Proved by the present experiment, the measurement range is about 1 millimeter, and its resolution is about 1 picometer.This method has some advantages, such as high sensitivity, high accuracy and large measurement range. It can apply to sense the small displacement, localization of the platform with high-accuracy, and so on.
