外差干涉術在中央條紋法的應用與誤差分析

Abstract

外差式中央條紋定位法，是一種利用可調波長雷射結合外差干涉術與中央條紋定位法，進行定位的絕對距離量測技術。具有光學架構簡單、定位方便、測量範圍大、準確度高、準確度不易受到波長擾動影響等優點。本研究設法將外差式中央條紋定位法應用在塊規厚度、透明平板厚度及多階高樣本量測，其中多階高樣本的量測是使用相機取樣的全場外差量測架構。 研究中，提出了外差式中央條紋定位法的快速定位步驟，並且發現外差式中央條紋定位法原理中應考慮的初始相位問題；當系統的相位重複性較差時，也提出了快速定位步驟中的波長選擇條件。另外整理了出外差干涉術可能有的20多種誤差來源，並以程式模擬分析部分誤差對干涉信號相位項的影響，結果歸納出最佳化的取樣參數設定。經由此研究可解決從前使用外差干涉術時不知道如何設定最佳取樣參數的窘境，也能夠直接根據誤差來源強度推論出相位誤差的大小，或是藉此評估實驗中最迫切需要改善的誤差來源。

Heterodyne central fringe identification technique is an absolute distance metrology technique, which combined the heterodyne interferometry and the central fringe identification method with a wavelength tunable laser. It has some merits such as simple optical configuration, easy operation, wide measurable range, high precision and the accuracy isn’t easily affected by wavelength fluctuation. In this research, the heterodyne central fringe identification technique is applied on the gauge block, thickness of a parallel transparent plate, and multi-step height measurements. In the multi-step height measurement, the data is acquired by one camera with the full-field heterodyne central fringe identification configuration. In this research, we propose fast identification procedures, and discover that the initial phase condition must be taken into account in the principle of heterodyne central fringe identification. As the phase repeatability is not good, the best wavelength suggestion is also proposed to the fast identification procedures. Besides, more than 20 kinds of error sources of the heterodyne interferometry are arranged. Then, we use simulation programs to analysis the phase error from some of the error sources. As a result, the optimal sampling conditions are induced. By this research, we solve the question of how to setup the sampling conditions in heterodyne interferometry, and induce phase error formulas to estimate the most important error in systems.