Scanning beam interference lithography (SBIL) technology is applied to produce large-area grating with nanoscale phase accuracy. One of the greatest challenges of SBIL is locking interference fringe to a moving substrate with nanometer spatial phase error, which requires measuring the fringe phase with subnanometer precision. We are developing a novel homodyne phase-locking interferometer (HPLI) to meet the harsh measurement requirements. The HPLI offers high precision phase measurements as well as the direction recognition of the interference fringe drift with a four-orthogonal detection system. However, nonlinearity error impacts the phase measurement accuracy of HPLI with nanometer scale, which is mainly due to polarization mixing. In this paper, we present a method to estimate and compensate nonlinearity error in real time by applying an extended Kalman filter algorithm. The simulation results show that the method can effectively eliminate the nonlinearity error.
Real-Time Correction of Nonlinearity Error in Homodyne Phase-Locking Interferometer
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Lu, S, Yang, KM, Zhu, Y, Wang, LJ, & Zhang, M. "Real-Time Correction of Nonlinearity Error in Homodyne Phase-Locking Interferometer." Proceedings of the ASME 2017 International Mechanical Engineering Congress and Exposition. Volume 2: Advanced Manufacturing. Tampa, Florida, USA. November 3–9, 2017. V002T02A096. ASME. https://doi.org/10.1115/IMECE2017-70914
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