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Implementation of a Reference Interferometer for Nanodetection
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Phase Unwrapping and Frequency Points Subdivision of the Frequency Sweeping Interferometry Based Absolute Ranging
Luming Song1, Guang Shi2, Hong Liu1
1School of Optoelectronic and Communication Engineering, Xiamen University of Technology, Xiamen 361024, China.
Sensors (Basel, Switzerland)
|April 23, 2022
Summary
Frequency sweeping interferometry (FSI) achieves precise absolute distance ranging. A new Hilbert Transform (HT) and Chirp-z Transform (CZT) method improves accuracy by addressing nonlinear frequency modulation, enhancing ranging resolution.
Area of Science:
- Optics and Photonics
- Metrology and Measurement Science
Background:
- Frequency sweeping interferometry (FSI) offers high-precision absolute distance ranging without blind areas, suitable for large-scale and non-cooperative targets.
- Nonlinear frequency modulation in lasers significantly degrades ranging accuracy in FSI systems.
Purpose of the Study:
- To develop an advanced measurement method for enhancing the accuracy of FSI-based absolute distance ranging.
- To mitigate the impact of nonlinear frequency modulation on ranging precision.
Main Methods:
- A novel measurement approach integrating Hilbert Transform (HT) and Chirp-z Transform (CZT) was developed.
- The method facilitates phase unwrapping of the beat signal and reduces the effective length of the auxiliary optical path's delay fiber.
- Optimization of narrow-band frequency selection for HT application was investigated.
Main Results:
- The proposed HT and CZT assisted method successfully addressed phase unwrapping and improved frequency resolution.
- Experimental validation demonstrated a ranging resolution of 70 μm and a standard deviation of 12.6 μm over a distance of 4005 mm.
Conclusions:
- The developed HT and CZT assisted FSI method significantly enhances ranging accuracy, overcoming limitations of nonlinear frequency modulation.
- This technique provides a robust solution for precise large-scale and non-cooperative target distance measurements.
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