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Updated: Sep 11, 2025
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Nonlinear real-time correction in homodyne interferometers by multi-area spatial sampling and dimensionality-reduced
Applied Optics
|August 12, 2025
Summary
This study introduces a real-time, FPGA-based method to correct nonlinear errors in homodyne interferometers, significantly improving displacement measurement accuracy by reducing residual error and computational load.
Area of Science:
- Metrology
- Optical Engineering
- Signal Processing
Background:
- Homodyne interferometers are prone to signal instabilities (amplitude, phase, DC bias).
- These instabilities cause dynamic nonlinear errors, compromising full-range displacement measurement accuracy.
- Real-time correction is essential for accurate measurements.
Purpose of the Study:
- To develop a real-time, non-iterative nonlinear correction method for homodyne interferometers.
- To balance high accuracy with computational efficiency using FPGA implementation.
- To address signal instability issues affecting measurement precision.
Main Methods:
- Implemented a Field-Programmable Gate Array (FPGA)-based approach for real-time processing.
- Utilized peak detection to simplify the elliptical fitting matrix.
- Employed feature-based segmented sampling for reduced-order correction.
Main Results:
- Reduced residual error from 1.14 nm to 0.12 nm under unstable elliptical signal conditions.
- Maintained nonlinear error deviation within the sub-nanometer range during a 25 µm displacement test.
- Decreased computational load by two orders of magnitude compared to traditional methods.
Conclusions:
- The proposed FPGA-based method effectively compensates for dynamic nonlinear errors in homodyne interferometers.
- Achieved a significant balance between high correction accuracy and computational efficiency.
- Enables more reliable and precise full-range displacement measurements despite signal instabilities.
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