Development of Six Degree-of-Freedom Heterodyne Speckle Interferometer

• Main Authors: Jun-Ting Wu, 吳鈞珽
• Other Authors: Hung-Lin Hsieh
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/6gwh3r

碩士 === 國立臺灣科技大學 === 機械工程系 === 105 === In this study, a novel six-degree-of-freedom (DOF) heterodyne speckle interferometer for displacement and rotation angle precision measurement is proposed. The proposed system is combines the advantages of heterodyne interferometry, speckle interferometry, symmetrical optical path design and beam splitting technique, and possesses high resolution, large measurement range and multi-dimensional measurement capability. The proposed six-DOF heterodyne speckle interferometer consists of a heterodyne light source and three sets of symmetrical measurement configurations, with each set providing two-DOF in-plane displacement information. The heterodyne light source is produced by means of an electro-optic modulator and a helium-neon laser, and the innovative symmetrical optical path configuration is constructed with a grating, a Wollaston prism, and a focusing lens, making the system easy to set up and calibrate. When the heterodyne light passes through the grating, WP and focusing lens, the reference and measurement light will be incident at a symmetrical angle and overlap on a measured plane to form scattering and interference, the intensity of which is then acquired by a photodetector. When in-plane motion occurs for the measure plane, its distance to the light source and the photodetector will change with the angle of incidence and the angle of observation, and the electric field of the beams will change due to the Doppler effect. The displacement and rotation angle of the measured plane can then be derived from the phase shift of the speckle pattern received by the photodetector. To verify the feasibility and performance of the system, we used a commercial six-DOF positioning stage and a long-stroke stepping stage to carry out a number of experiments, and the system measurement results are compared with the results of the built-in capacitive displacement sensor and the optical encoder of the stages. The results show that the six-DOF heterodyne speckle interferometer can accurately provide measurement data of six-DOFdisplacement and rotation, the measurement resolution is about 10 nm, the repeatability of the x, y and z-axis displacement is 0.4 nm, 0.4 nm, 1.8 nm, the repeatability of θx, θy and θz axis rotation is 2 μrad, 3.5 μrad 1.58 μrad, and the measurement speed limit of the system is about 110 μm/s. This system displays excellent measurement performance and can be widely applied in fields such as precision manufacturing, automated optical measurement and machine tool industry.