Stitched sinusoidal frequency-modulated coherent LiDAR for high-precision ranging sensing

Frequency-modulated continuous wave (FMCW) laser ranging technology has a wide range of applications in both science and industry. Traditional FMCW laser ranging mostly uses a strictly linear frequency-modulated tunable laser to achieve high-precision measurement. However, it is highly challenging to achieve that a tunable laser maintains a linear sweep with a large bandwidth for a long time. To address this challenge, this paper proposes an innovative stitched sinusoidal FMCW laser ranging system for high-precision ranging. The proposed system uses a sinusoidal signal that can easily maintain the waveform characteristics for stable frequency modulation and realizes high-precision range demodulation by a post-processing technique and coherent stitching by an in-phase quadrature (I/Q) modulation method. The results of the proof-of-concept experiments show that after coherently stitching the measurement signals with three-band sinusoidal modulation, the ranging precision and relative accuracy in a range of 4 m can be improved by 85 μm and 13 × 10^-6, respectively, compared to a reference interferometer. The proposed system has the potential to significantly benefit real-time, high-precision three-dimensional imaging applications.