A High-Precision FMCW Laser Ranging Method Based on Pulse-Counting Technique

Frequency-modulation-continuous-wave (FMCW) laser ranging has emerged as a novel high-precision distance measurement technique with low laser power, high safety, and strong anti-interference ability. Traditional FMCW laser ranging methods highly rely on complex digital signal processing, particularly using analog-to-digital converters (ADCs) and fast Fourier transforms (FFTs) on field-programmable gate arrays (FPGAs). This approach can be costly and resource-intensive due to the high sampling rates and extensive logic resources required, especially as demand for higher speed and accuracy increases in applications like LiDAR and real-time metrology. In contrast, the proposed method uses a simpler, lower-cost pulse-counting technique instead of ADCs and FFTs. By converting the intermediate-frequency (IF) signal directly into pulses through comparators and tallying these pulses, this approach measures frequency more efficiently. Additional processing overcomes traditional pulse-counting limitations in handling continuously varying frequencies, achieving high accuracy with fewer resources. Experimental results show this method delivers precise measurements with a minimal setup, achieving an error margin within 10 cm at ranges from 0.5 to 10 m and a root mean square error (RMSE) below 0.71 cm. This innovation is well-suited for developing affordable, high-precision indoor FMCW laser ranging systems.