# Adaptive Suppression Method of LiDAR Background Noise Based on Threshold Detection
###### Abstract  
Background radiation in the LiDAR detection field of view is complex and variable, and the background noise generated can easily cause false alarms in the receiver, which affects the effective detection of the system. Through the analysis of the influence of background radiation noise of LiDAR on the detection performance, an adaptive suppression method of LiDAR background noise is proposed. This method realizes the rapid suppression of background noise in the instantaneous field of view through an adaptive threshold adjustment of current steering architecture with a back-end digital-to-analog converter (DAC) correction based on the principle of constant false alarm rate (CFAR) control. Aiming at the problem of accurate noise detection and quantification in a very short time, a dynamic comparator is used to replace the traditional continuous comparator. While detecting the number of noise pulses, the measurement of the pulse duration of noise is realized, which improves the accuracy of short-time noise detection. In order to verify the actual effect of the adaptive method, experiments were carried out based on the team's self-developed LiDAR. The experimental results show that the measured noise ratio of the adaptive mode by using this method is the lowest. Even at 12 a.m., the noise ratio of the point cloud obtained by the adaptive mode is 0.012%, compared with 0.08% obtained by the traditional mode, which proves that this method has a good ability to suppress background noise. The proportion of noise reduction of the adaptive mode is more than 80% compared with the traditional mode. It achieves noise suppression through hardware at each detection, and each adjustment can be completed within a single period of pulse detection. Therefore, it has great advantages in real-time detection compared with the back-end software noise reduction processing method, and it is suitable for the application of LiDAR in the complex background environment. LiDAR; background radiation; noise detection; constant false alarm rate (CFAR) +
Footnote †: journal: Applied Sciences  
suppress the noise and thus improve LIDAR interference immunity and environmental adaptability. Common methods to suppress background radiation noise include the field-of-view method [10], spectrum filtering method [11], video bandwidth method [12], time discrimination method [13], time program gain method [14], polarization identification method [15], CFAR control method [16] and logic resolution method [17]. Among them, the method of adjusting the circuit performance parameters in LiDAR to suppress the background radiation noise is relatively simple, particularly the CFAR control method, which is used to control the FAR of the system by adjusting the receiver circuit parameters according to the noise detection in the receiver, and which can effectively suppress the false alarm interference caused by the background radiation. In the published reports and literature, there has been much research on the influence of background radiation noise on the detection performance of LiDAR and the adjustment and suppression methods [18; 19]. Based on the characteristics of the avalanche photodiode (APD) optoelectronic receiver system, the FAR Gaussian model was modified to improve the model accuracy at higher temperatures and avalanche gain effectively [20]. The relationship between background radiation and multiplication factors of APD was modeled by studying the effect of background radiation on APD detection performance, combined with the principle of CFAR compensation [21]. Aiming at the background radiation noise and multiplication characteristics of APD, the study of an adaptive bias control method was carried out [22]. According to the different background radiation levels, a CFAR control technique is proposed based on FPGA in LiDAR [23].