Nonlinear correction of FMCW LIDAR based on the superlets transform algorithm.

Area of Science:

• Optics and Photonics
• Metrology
• Signal Processing

Background:

• Nonlinearity in laser frequency modulation in FMCW LIDAR degrades ranging precision.
• The full width at half maximum (FWHM) of the beat signal increases due to modulation nonlinearity.
• Existing methods struggle to adequately address this precision-limiting factor.

Purpose of the Study:

• To propose and validate a novel nonlinear correction method for FMCW LIDAR.
• To enhance the ranging precision and velocity measurement accuracy of FMCW LIDAR systems.
• To mitigate the impact of laser frequency modulation nonlinearity.

Main Methods:

• A nonlinear correction method based on superlets transform (SLT) was developed.
• An auxiliary interferometer was integrated into the FMCW LIDAR system.
• Time-frequency relations from the SLT of the auxiliary beat signal were used for resampling the measurement beat signal.

Main Results:

• The nonlinearity after resampling was reduced to 2.60 × 10^-10.
• The system maintained clear spectral peaks even with a 13-fold extended fiber length.
• Average ranging standard deviation (SD) was 2.35 mm and resolution was 4.8 cm within 2.5 m.
• Average velocity measurement SD was 7.7 mm/s within 6 cm/s.

Conclusions:

• The proposed SLT-based nonlinear correction method effectively improves FMCW LIDAR linearity.
• The method significantly enhances ranging precision and velocity measurement accuracy.
• This technique offers a robust solution for high-precision FMCW LIDAR applications.