本研究提出一套多自由度複合式散斑干涉儀，用以進行精密位移及旋轉角量測。此套干涉儀系統結合外差干涉術和散斑干涉術之優點，並透過分光技術建立一套可以進行精密位移及旋轉角量測的架構，同時具備高解析度、非接觸的量測性質以及簡易方便的系統架構。
此套多自由度複合式散斑干涉儀之基礎架構為一雙自由度複合式散斑干涉儀，由外差光源及創新的複合式散斑光路系統組成。該複合式散斑光路系統結合一能夠測量面內位移的對稱式散斑干涉儀系統以及一能夠測量面內與面外位移的非對稱式散斑干涉儀系統。此種架構可經訊號相減獨立測量面內與面外位移，同時僅需要三到雷射聚焦在測量平面上的一點上，是一個簡單而有效的設計。由從測量平面散射的光形成的干涉條紋由光感測器接收，當平面發生位移時，干涉條紋的相位將根據都普勒頻移的原理而改變。各軸之相位變化可使用光的偏振態以及偏振片分離，並可透過相位解調獲得各軸之位移量。此雙自由度複合式散斑干涉儀架構可進一步擴展為三至六自由度的量測系統，用以量測位移及旋轉角，並可根據量測需求選擇是當的量測系統。
為了驗證本研究所提出的複合式散斑干涉儀的量測性能，本研究分別使用商用長行程步進平台及三軸和六軸精密定位平台對所有量測系統進行了多項實驗。其中包含不同波形、不同行程之位移與旋轉、重複性和解析度試驗，以及最大測量範圍實驗，並將干涉儀系統的量測結果與商用位移感測器的量測結果做比較。實驗結果證明，本研究所開發的複合式散斑干涉儀系統皆能夠準確地進行多自由度位移和旋轉量測，同時具備有高階析度、優異的重複性、大測量範圍以及可靈活運用的系統設計。

In this study, a compound speckle interferometer for multi-degree-of-freedom measurement is proposed. By combining heterodyne interferometry, speckle interferometry and beam splitting techniques, the system can perform precision displacement and rotation measurement, while having the advantages of high resolution, long-range non-contact measurement and a relatively simple configuration.
The basic configuration is a two degree-of-freedom (2-DOF) compound speckle interferometer consisting of a heterodyne light source and an innovative compound speckle optical configuration. This speckle optical configuration combines a symmetrical speckle interferometer system capable of measuring in-plane displacement with a novel asymmetric speckle interferometer system capable of measuring both in-plane and out-of-plane displacement. This arrangement allows for the independent measurement of two modes of surface displacement through signal subtraction, while only requiring three laser beams to converge on a single point on the measured surface, making this a simple yet effective design. The interference patterns formed from the scattered light reflecting off the measured surface is received as intensity signals by photodetectors. When the surface undergoes displacement, the phases of the interference patterns will shift according to the principle of Doppler frequency shifting. The resulting phase variation data can be separated by displacement axis via polarization, then the displacement values can be obtained through phase demodulation. The 2-DOF compound speckle interferometer can be further expanded into 3-DOF, 4-DOF, 5-DOF, and 6-DOF measurement systems, allowing for a wide selection to suit the needs of the required task.
In order to verify the performance of the proposed compound speckle interferometer, a series of measurement tests were performed with commercial precision motion stages on all variants of the system. These include displacement and rotation measurement tests with various waveforms and ranges, repeatability and resolution tests, as well as measurement range experiments. By comparing the acquired results with data from the internal displacement sensors of the motion stages, it is demonstrated that all variants of the compound speckle interferometer have the ability to accurately measure displacement and rotation in multiple DOFs, while also possessing the high resolution, excellent repeatability, long measurement ranges and a flexible design.

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