A differential interferometric heterodyne encoder with 30 picometer periodic nonlinearity and sub-nanometer stability |
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| Affiliation: | 1. School of Instrument Science and Opto-electronic Engineering, Hefei University of Technology, Hefei 230009, China;2. College of Control Science and Engineering, China University of Petroleum, Qingdao 266580, China |
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| Abstract: | A differential interferometric heterodyne encoder with spatially separated input beams was developed to minimize periodic nonlinearities resulting from polarization mixing. The laser beams with different frequencies were delivered by two polarization-maintaining fibers to the encoder head. Under laboratory conditions this encoder demonstrated a system stability of 38 pm (standard deviation) and 100 pm over 30 s and 1 h respectively. In a comparison measurement with a differential heterodyne interferometer, this encoder showed periodic nonlinearities of less than 30pm without any additional correction. |
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| Keywords: | Displacement measurement Interferometric heterodyne encoder Periodic nonlinearity Fiber-fed encoder |
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