| Summary: | 碩士 === 國立臺北科技大學 === 自動化科技研究所 === 107 === To develop a compact fiber-based displacement measuring probe for the realization of detection on a nanoscale linear displacement with a range of few hundreds of millimeters, especially for precise positioning in a 3-axis wafer stage. The objective is realized by proposing a compact fiber-based probe with Fizeau interferometry to measure nanoscale displacement using simultaneous phase-shifting interferometry. In the design, the phase-shifting module can simultaneously produce two interfering signals with an orthogonal phase difference by using fiber-configured quarter wave plates and linear polarizers to achieve simultaneous phase shifting signal processing, so the displacement can be detected in a high speed. Two-axis polarization-maintenance optical fibers compatible in infrared light range and multi photodetectors are employed as light signal carriers and receivers. Free space optical components were all replaced with fiber-configured optic circulator and multi couplers for system integration. The fiber-based design is in its advantage on minimizing of the effect of depolarization and wavefront distortion caused by any potential ambient light turbulence. Meanwhile, another advantage can be obtained in its highly flexible and compact fiber-based structure for good space compatibility in various industrial applications. To achieve a displacement measurement speed of up to 200 mm/s, a FPGA firmware design was employed to process interfered light signals for onboard processing and a pre-processing circuit system was developed to correct Lissajous circles. To attest the measurement accuracy, the developed measuring probe and simultaneous phase shifting module was tested on a 3-axis NTU-developed wafer stage. As seen from its tested results, a displacement measurement with one standard deviation of 117 nm in the 300 mm range of measurement with a resolution of 1.0 nm can be achieved when a pre-calibrated high accuracy laser interferometric measuring system was applied for accuracy calibration. After the cosine error correction of the data, an accuracy error of less than 269 nm can be obtained. The successful development of an optical probe in a compact size of 25.4×25.4×38.9 mm3 has a good potential to be further integrated with 3-axis measuring stages for high accuracy in-situ displacement positioning.
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