本研究以光柵干涉術作為主要的量測基礎，提出了一套新式的微型化雙繞射共路徑式線性光學尺，其系統架構簡單，架設及校正容易，可用以進行精密的大行程位移量測。我們利用自行設計的稜鏡配合反射式光柵建構出「共路徑式光路」，即相干涉的參考及量測光束於系統中均行經相同的光學元件，此兩道光將感受到相同的環境擾動訊息，環境擾動的影響量將於干涉訊號中相互補償抵銷，故能使光學尺具備較高的系統穩定度。而後，我們透過反射鏡使參考及量測繞射光沿原路徑再次入射相同的光柵，形成「雙繞射光路」，可引入加倍的相位變化量，提升系統的靈敏度及解析度。最後再藉由IC光偵測器擷取干涉訊號中的相位變化，用以回推待測光柵的位移變化量。
本研究將雙繞射共路徑式線性光學尺架設於商用微定位平台及長行程電控位移平台上進行多項驗證實驗，並將此套雙繞射共路徑式線性光學尺的量測結果與平台內建感測器所測得的結果相比較，用以驗證此套系統的可行性及量測性能。由實驗結果顯示，此套雙繞射共路徑式線性光學尺可精準量測規則及不規則的位移運動，其位移量測解析度可達10 nm，於總行程100 nm的步階運動中，重複度優於1.1 nm，穩定度於10分鐘內之飄移量優於15 nm，量測速度極限可達4.3 mm/s，驗證此套雙繞射共路徑式線性光學尺可廣泛應用於各式需精密位移量測的場合中，深具發展及應用潛力。

In this study, an innovative miniaturized double-diffraction common path linear encoder is proposed, which is used grating interferometry as the main measurement basis. The architecture of the system is simple and easy to be set up and adjusted. In addition, it has capability of precision long-range measurement. We constructed “common optical path” by using self-designed prism which is combined with the reflective grating. In other words, the corresponding interference reference and measuring beams pass through the same optical elements, which are under the same environment and the influence of the external disturbance will be offset by mutual compensation in the interference signal, so that the linear encoder would have a higher system stability. Then, the reference and measuring diffraction beams are incident to the same grating along the original optical path to form “double-diffraction”, which induce the double phase variation and improve the sensitivity and resolution of the system. Finally, the displacement can be obtained by capturing phase variation of the interference signal received by IC.
The proposed linear encoder is placed on the commercial positioning stage and long-range precision motion stage to conduct several experiments. And the measurement results are compared with the results of built-in capacitive sensor to verify the feasibility and performance of the proposed system. It can be shown from the experimental results that the proposed linear encoder can measure regular and irregular motion precisely, where the resolution can reach 10 nm, the repeatability is better than 1.1 nm within the step motion of 100 nm total range, the stability is better than 15 nm within 10 minutes experiment, and the speed limit can reach 4.3 mm/s, respectively, proving that the proposed double-diffraction common path linear encoder can be widely used in various fields requiring precise displacement measurement, and has great development and application potential.

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