Single-photon lidar is one of the important development directions of long-range lidar in the future. Since the detection mechanism of single-photon lidar is quite different from the traditional lidar detection system, it is necessary to measure the range walk error caused by its measurement. We analyzed the detection mechanism of single-photon lidar, established a mathematical model of laser echo signal and detector’s timing jitter, and deduced the relationship between the range walk error and timing jitter. Besides simulation, we set up a coaxial lidar and utilized three kinds of Geiger mode avalanche diode(GM-APD) detectors with different timing jitter to verify the simulation results. The results show that with the increase of the detector’s timing jitter, the range walk error of the system also increase, and the two are positively correlated. When the standard deviations of the detector timing jitter are 15ps, 350ps, and 1152ps, the range walk error are 0.88cm, 2.55cm, and 12.56cm, respectively. Finally, an evaluation model of ranging accuracy is established by using appropriate data fitting method, which provides an evaluation model for the ranging accuracy of single-photon radar and it has potential application value.
A first signal photon unit method (FSPU) was proposed in this paper which is suitable for photon-counting imaging application with low signal level and severe noise. The method exploits the different statistics of signal detections and noise detections that signal detections would cluster while noise detections tend to be equally distributed to distinguish signal from noise. For each spatial pixel, laser illumination would not stop until the first signal photon unit or the first n detections that cluster within ε range is discovered where n and ε is a preset parameter to describe what kind of cluster we wish to identify. The number of pulses to obtain this first signal photon unit is a random variable and it contains the intensity information. Depth and intensity images are reconstructed through the mean time of FSPU and maximum likelihood estimation from the number of emitted pulses respectively. Simulation verifies its feasibility even when signal to noise ratio is well below 0dB.
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