Theoretical model and correction method of range walk error for single-photon laser ranging

摘要

Single-photon laser ranging is a new generation of lidar which represents the future lidar development trend. It uses the single photon detector as the receiving device. Due to the fact that single-photon detector possesses the ultra-high sensitivity, the single-photon laser ranging is much easier to achieve the high density as well as the high coverage target sampling. However, the existence of the range work error in single-photon laser ranging, resulting from the fluctuation in the number of signal photoelectrons restricts the improvement of the ranging accuracy. In this paper, the range walk error model based on the lidar equation and the statistical property of single-photon detector is established. Then the relation between the range walk error and the number of signal photoelectrons is also derived. The range walk error of single-photon laser ranging is predicted and the corresponding compensation for the original result is obtained, with the derived function and the detection probability model of single-photon laser ranging. The experiment for its proof is also carried out. In the experiment, the number of signal photoelectrons is changed by the different attenuators for the same target and at the same distance. When the attenuator is changed, the pulse width of echo signal changes very little (about 3.2 ns). However, the average number of signal photoelectrons varies between 0.03 counts and 4.3 counts. So the range walk error, resulting from the fluctuation in the number of signal photoelectrons cannot be ignored. For example, when using an attenuation of 1/10 pass rate, the average number of signal photoelectrons is about 4.3 counts and the range walk error is almost 46 cm, which is the main factor of the range error. The reduction of the range walk error is achieved by applying the correction of the range walk error in this paper. After correction, the standard deviation of the range walk error decreases significantly from 15.17 cm to 1.16 cm. The mean absolute error is also reduced from 11.56 cm to 0.99 cm. Generally, the range walk error has an unnegligible influence on the ranging accuracy. The experimental result confirms that the theoretical model is accurate. It also shows that the bigger the number of the received signal photoelectrons, the greater the range walk error is, and the accuracy of single-photon laser ranging is improved by applying the technique proposed in this paper. Briefly, this paper presents the technical method of optimizing the design and evaluating the performance of single-photon laser ranging.