The photon counting lidar uses a single-photon detector with extremely high sensitivity, which can increase the sensitivity of the lidar system by 2-3 orders of magnitude. However, the use of a single photon detector makes the noise amplitude the same as the signal amplitude. It cannot be filtered by the threshold comparison method on the circuit. The output is a 0/1 digitized signal, and the trigger will output an indistinguishable saturation avalanche pulse. So it is impossible to distinguish whether it is a signal or a noise trigger. In clear daylight, the background noise of the sun is unavoidable. In this environment, the false alarm probability of photon lidar is very high. Therefore, the false alarm probability is the research focus of pulsed photon lidar. We use the Monte Carlo method to simulate the detection process according to the statistical characteristics of the signal and noise. We know that multi-pulse accumulation can effectively reduce the probability of false alarms. In this article, we propose an improved Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm to classify signals and noise, which can further reduce noise on the basis of multi-pulse and achieve a lower false alarm probability.
The study of the influence of the changes of laser parameters on the temperature field distribution of PbS detector irradiated under 2.79μm mid-infrared laser has important reference value. In this paper, the theoretical simulation of a typical PbS detector irradiated by a 2.79μm mid-infrared laser is carried out by using the Finite Element Analysis method (FEA). The maximum temperature of PbS detector irradiated by 2.79μm mid-infrared laser with different laser parameters is investigated. The maximum temperature on the photosensitive surface of the PbS detector under different conditions is obtained by adjusting the spot radius, pulse width, and repetition frequency of the simulated pulsed laser. The effects of the changes of spot size, repetition frequency and pulse width on the maximum temperature of the photosensitive surface are investigated. The simulation results show that under the same energy density irradiation condition, the maximum temperature of the photosensitive surface decreases with the increase of the spot radius and pulse width. Under the condition of the same spot radius and pulse width, the higher repetition frequency can make the maximum temperature of photosensitive surface reach a higher temperature. This work gives the law of the temperature changes of the photosensitive surface caused by changing the laser parameters, which is helpful to improve the damage resistance of PbS detector to high power 2.79μm mid-infrared laser step by step.
The damage of a nanosecond pulse laser on ultraviolet(UV) image intensifier was studied. A laser pulsed with a wavelength of 266nm and pulse width of 25ns was used to radiate an UV imager intensifier. The laser induced damage threshold(LIDT) of the internal components of the UV imager intensifier was measured, and the LIDTs of the optical windows, the microchannel plate and the ultraviolet photocathodes are 1.8mJ / cm2 , 3.3mJ / cm2 and 17.6 mJ / cm2, respectively. It is shown that as the incident laser energy increases, the order of damage of the components inside the image intensifier is: photocathode, microchannel plate and optical window.
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