近年來各類型的雷射干涉儀已被廣泛地應用在眾多的科學研究及工程領域中，藉由提供精準的位移或旋轉角度的量測資訊使定位系統或載具能維持高精度的定位性能，以期能準確完成製造程序、元件對位、幾何誤差量測與系統校正等目的，可見其扮演著舉足輕重的角色，相關的研究團隊或量測設備製造商(如Agilent, Zygo, Renishaw, SIOS)紛紛提出各式干涉儀技術，顯見其深具發展潛力及寬廣的應用前景。有鑑於此，本研究提出一套可用以進行六自由度位移及旋轉角度量測的新式共路徑式散斑干涉儀，主要是以「散斑干涉」做為核心技術，同時輔以「外差調制技術」、「對稱與非對稱式光路」、「共路徑式光路」、「共面偵測光路」及「自混雙頻技術」等設計概念進行系統開發，賦予系統具備優異的量測性能。
此套「共路徑式散斑干涉儀」使用電光調制技術來產生外差光源，用以降低環境低頻振動對量測結果所造成的影響，透過平行分束器及聚焦透鏡的搭配使每個偵測架構皆形成對稱式與非對稱式散斑光路架構，除了可使系統於單一偵測架構下即具備同時量測面內及面外位移的量測能力之外，亦能形成創新的共路徑式光路架構，使參考光束及量測光束行經相同的元件，當環境存在擾動時，參考與量測光束將感受到相同的擾動訊息，環境擾動對系統所造成的影響將於干涉訊號中被相互抵銷或補償，使系統具備優異的穩定性。此外，為了進一步延伸此套共路徑式散斑干涉儀的量測能力，本研究亦藉由自混雙頻技術與共面偵測技術的運用建構出三組偵測架構（每組皆具備面內及面外位移量測能力），而後透過比對每組偵測架構之間的量測結果，即可回推出待測粗糙面於三個旋轉軸向的角度變化量。
由實驗結果證明本研究所開發的「共路徑式散斑干涉儀」可在不改變光學架構下，同時提供六自由度位移及旋轉角的量測資訊，其面內、面外位移及旋轉角解析度分別為2.1 nm、5.5 nm及205 nrad，且位移及旋轉角於10分鐘之量測穩定度分別優於15.2 nm及750 nrad，重複性分別優於4.6 nm及240 nrad，證明具備優異的量測性能。

In recent years, various types of laser interferometers have been widely used in many fields of scientific research and engineering. By providing accurate measurement information of displacement or rotation angle, the positioning system can maintain high-precision positioning performance, so as to accurately complete the purposes of manufacturing process, component alignment, geometric error measurement and system correction. Relevant research teams or measurement equipment manufacturers such as Agilent, Zygo, Renishaw and SIOs have proposed various interferometer techniques, which shows that it has deep development potential and broad application prospects. In view of this, this study proposes a novel common path speckle interferometer for six-degree-of-freedom displacement and rotation angle measurement. It takes “speckle interferometry” as the core technique, supplemented by “heterodyne modulation”, “symmetric and asymmetric optical path”, “common optical path”, “co-planar detection configuration” and “self-mixing modulation” techniques, which gives the system excellent measurement performance.
This set of “common path speckle interferometer” is used electro-optic modulation technique to generate heterodyne light source to reduce the impact of environmental low-frequency vibration on measurement results. Through the combination of beam displacer and focusing lens, each detection configuration forms symmetrical and asymmetric speckle optical path configuration. In addition to the measurement ability of measuring in-plane and out-of-plane displacement at the same time under a single detection configuration, it can also form an innovative common optical path configuration, so that the reference beam and the measurement beam are passed through the same elements. When the environment is disturbed, the reference and measurement beams woulf receive the same disturbance information. The influence of the environmental disturbance on the system will be offset or compensated for each other in the interference signal, so that the system has excellent stability. In addition, in order to further extend the measurement capability of this set of common path speckle interferometer, this study also constructs three groups of detection configurations by using self-mixing dual frequency technique and coplanar detection technique (each group has in-plane and out of plane displacement measurement capability), and then compares the measurement results between each group of detection configurations, the angular variation of the rough surface in three rotating axes can be obtained.
The experimental results show that the “common path speckle interferometer” developed in this study can provide the measurement information of six-degree-of-freedom displacement and rotation angle without changing the optical configuration. The in-plane, out-of-plane displacement and rotation angle resolutions are 2.1 nm, 5.5 nm and 205 nrad respectively while the measurement stability of displacement and rotation angle is better than 15.2 nm and 750 nrad in 10 minutes, respectively and repeatability is better than 4.6 nm and 240 nrad, respectively, proving that the proposed system has excellent performance.

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