Poisson distribution model is the basis of data analysis for GM-APD lidar, but it is only applicable to the mirror reflected target under ideal conditions, and cannot accurately describe the photon triggering process of actual GM-APD lidar detection. For the actual target with rough surface, the negative binomial distribution with M as the parameter can describe the photon distribution model more accurately. In order to solve this problem, this paper compares and analyzes Poisson distribution triggering model and the negative binomial distribution triggering model that conforms to the triggering situation of the echo signal of the target with rough surface, considering the differences in the triggering probability under different noise and signal levels. The results show that the trigger probability curve corresponding to the trigger model based on negative binomial distribution is lower in peak value, wider in bottom value and fatter overall than that of the trigger model based on Poisson distribution, and the difference between the two is more prominent under the conditions of low noise level and high signal level. This study has guiding significance for the signal extraction research based on different surface echoes.
KEYWORDS: Photons, Light scattering, Electric fields, Monte Carlo methods, Polarization, Mie scattering, Particles, Laser scattering, Scattering, Electromagnetic scattering theory
Traditional Monte Carlo method lacks the capability to trace and record polarization and phase information when simulating the transmission of photons. In this paper, based on Mie scattering theory and Electric Field Monte Carlo(EMC) method, we simulates the multiple scattering between photons and smoke particles and obtains the intensity and electric field information of backscattered photons, by calculating the rotation rules of local coordinate system and amplitude scattering matrix of photon. Simulations reveal that with an idealized point light source, backscattered photons concentrate into a speckle on the receiving surface, which expands as the scattering media thickens. The number of backscattered photons rapidly decreases over time, while their degree of polarization stabilizes within a specific range, forming a cross pattern that rotates based on the light's initial polarization. These findings offer valuable insights for developing anti-smoke interference imaging techniques.
In recent years, the array Geiger-mode avalanche photodiode (Gm-APD) has become a research hotspot in the world due to its advantages of detection sensitivity, spatial resolution and range resolution. A set of 1064 nm laser active imaging experiment platform is built with the core device of 256×128 pixel domestic self-developed InGaAs material Gm-APD. The data of 500m and 350m targets in external field are obtained, and the three-dimensional distance image, intensity image and photon counting image are reconstructed by using single photon echo signal detection method. Through the experiment, the range resolution of the detector is 0.3m, and the contrast of the photon count intensity image are larger than the intensity image. It is proved that the self-develop array Gm-APD detector with 1064nm lase has good performance, and it can demonstrate the field laser active imaging function, which lays a good research foundation for future practical application.
In the military and civil fields, detecting small aircraft is of great significance. In recent years, the rapid development of LiDAR technology has made it possible to detect small aircraft at long distances. However, the scale change and attitude change make the detection difficult. Therefore, a detection network of multi-attitude small aircraft based on LiDAR anchorfree is proposed in this paper. The network structure is improved on the basis of the CenterNet network; using the encoder-decoder network structure, the extended convolutional module is designed to improve the receptive field and obtain the multi-scale information of the object. The IOU sensing branch is added to the detection header of the network to improve the localization accuracy of the object. The experimental results show that the detection accuracy of the improved network on the self-built simulation data set is 2.12% higher than that before the improvement and finally reaches 92.45%. Therefore, using this method can effectively improve the detection accuracy of the object.
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