Dynamic Doppler Frequency Shift Errors: Measurement, Characterization, and Compensation
Dynamic Doppler Frequency Shift Errors: Measurement, Characterization, and Compensation
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DOI：
10.1109/tim.2014.2377991
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发表时间：
2015-01
影响因子：
5.6
通讯作者：
Chen Wang;J. Ellis
中科院分区：
文献类型：
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作者：
Chen Wang;J. Ellis
动态条件下的定位校准对于高精度领域（诸如增材制造和半导体光刻）正变得越来越受关注。外差干涉测量法通常用于校准载物台的位置，因为干涉测量法具有高动态范围和对仪表的直接可追溯性。当使用外差干涉测量法时，常规地执行滤波以处理和确定所测量的相位变化，所测量的相位变化与从一个目标位置到另一个目标位置的位移成比例。信号处理中的滤波引入了取决于检测频率的相位延迟，这在目标速度不恒定时（如在动态校准中的情况）导致位移误差。提出了一种通过测量瞬时检测频率，并在现场可编程门阵列（FPGA）中真实的实时求解相应相位延迟的相位延迟补偿方法。FPGA硬件在环仿真表明，该方法在动态情况下可将位移误差从±100 nm减小到±3 nm，在准静态标定时仍能保持亚纳米级的精度。
Positioning calibration under dynamic conditions is becoming increasingly of interest for high precision fields, such as additive manufacturing and semiconductor lithography. Heterodyne interferometry is often used to calibrate a stage's position because interferometry has a high dynamic range and direct traceability to the meter. When using heterodyne interferometry, filtering is routinely performed to process and determine the measured phase change, which is proportional to the displacement from one target location to another. The filtering in the signal processing introduces a phase delay dependent on the detection frequency, which leads to displacement errors when target velocity is non-constant as is the case in dynamic calibrations. This paper presents a phase delay compensation method by measuring instantaneous detection frequency and solving for the corresponding phase delay in a field-programmable gate array (FPGA) in real time. The FPGA hardware-in-the-loop simulation shows that this method can significantly decrease the displacement error from ±100's nm to ±3 nm in dynamic cases and it will still keep subnanometer resolution for quasi-static calibrations.