Co-path full-waveform LiDAR for detection of multiple along-path objects

A co-path full-waveform light detection and ranging (LiDAR) system for detection of multiple objects along laser path is designed in this paper. The co-path full-waveform LiDAR system consists of optical and electrical units. The optical unit implements emission of laser pulses and reception of laser echoes, while the electrical unit controls the emission of laser pulses and acquires the waveforms of both emitted laser pulses and reflected echoes. Then, the acquired echoes are denoised through wavelet decomposition and fitted using Gaussian functions to obtain distances between the objects and the co-path full-waveform LiDAR system. To analyze the performance of the co-path full-waveform LiDAR system, a peak signal-to-noise ratio (PSNR) model of the received laser echoes is established and verified by using a diffuse reflectance reference target (DRRT) with 30% reflectivity at distances from 30 to 105 m. Meanwhile, the ranging uncertainty of the co-path full-waveform LiDAR system for the DRRT at distances from 30 to 105 m was analyzed. Experimental results show that the PSNRs calculated from the received laser echoes are 4 dB lower than the expected ones calculated by the established PSNR model, implying that the established PSNR model is of acceptable accuracy and the system is of better detection performance. The ranging uncertainties of the system for the DRRT at 30 and 105 m are 10 and 32 mm, respectively. In addition, experiments were carried out to verify the ranging performance of the co-path full-waveform LiDAR system for multiple along-path objects. Results show that (1) the system can decrease the influence of waveform overlap between the pulses reflected by two adjacent objects and improve the ranging accuracy; (2) the system can detect multiple along-path objects from the laser echoes when the distance between each two adjacent objects is larger than 1.5 times the full width at half maximum (FWHM) of each returned laser pulse; (3) the system can be applied to surveillance of the group of Unmanned Aerial Vehicles (UAVs).