本文提出一波長移相雙繞射干涉儀，此位移量測系統分為兩部分，在光學架構部分，由於光柵的繞射效應可以將光柵位移的訊息轉換成光的相位訊息，利用鏡子反射繞射光，使含有光柵位移相位的繞射光再一次反射回光柵產生繞射，因為通過了兩次光柵，產生兩次繞射提高了相位對應光柵位移的靈敏度，並且在反射鏡部分設計一個固定的光程差，使波長的變化可以轉換成相位變化。
在相位解析系統中，以雷射二極體搭配訊號產生器調制波長，並調整調制訊號所需的振幅，使量測訊號在高點與低點因為波長的不同有90度的相位差，此相位差使得量測訊號在訊號高點與低點位置有一個正餘弦關係存在，將量測訊號送入開發出的相位解析程式，即可求出相位值，最後推算出光柵位移量，免去了使用昂貴的鎖相放大器進行相位解析，降低了系統的成本，使得本系統的利用價值大大提高。實驗結果顯示出此系統具有良好的穩定性及重復性，在考慮高頻雜訊的情況下，系統的解析度達1.5 nm，靈敏度為g/d=0.72 ˚/nm。優於市售的位移感測器，本系統可應用於精密位移量測、精密位移平台的震動量測、微動定位系統。

In this paper, we present a wavelength phase-shifted double diffraction interferometer for measuring displacement. This displacement measurement system is divided into two sections, in the optical configuration section, according to the optical phase variation resulting from the moving grating, we design a light path, it can be used to increase the sensitivity of the phase change, and using the wavelength-modulated laser beam which passing through an unequal-path-length optical configuration by two mirrors, it can change the system phase.
On the other hand, using the wavelength-modulated laser produce two signals that phase difference of 90 degrees can be sent into a phase analyze system. The phase analysis system obtained grating displacement by the relationship between the sine position light intensity and cosine position light intensity, eliminating the need for a lock-in amplifier, which makes utilization value of the system greatly, the experimental results show that the system has high stability and repeatability, if only high frequency noises are considered, the measurement resolution of our system is about 1.5 nm, the sensitivity is 0.72 ˚/nm and the measureable speed is 5.5 um/s. The system can be a useful sensor to monitor the displacement and vibration of the precision motorized stage using in wide scientific research.

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