Real-Time in Situ Laser Ranging Based on Online Echo Waveform Fitting

In this paper, an online echo waveform fitting-based method is proposed for the real-time in situ laser ranging. In the method, an embedded FPGA is employed to realize the fast single-pulse fitting, and the parameters of the echo waveform of an object under detection are, thus, extracted in an online manner. The parameters of the echo waveform are utilized to estimate the time interval between the emitted pulse and the echo. The distance of the object is then calculated from the time interval. The simulations were first done to analyze and obtain the computational resource consumption and the time cost of a single measurement. Then, an FPGA- and ADC-based ranging system was designed, and an experiment was carried out to verify the proposed method. The results show that a single measurement of the distance can be done within 8.7 μ s, which is fast enough for online ranging. At a distance of 70 m with an SNR of 18.4 dB, the mean range error and the range standard deviation are 4.9 and 10.7 cm, respectively. In addition, the proposed method was also compared with the TDC-based in situ method and the Gauss-Newton algorithm-based off-line method.