Theory And Realization Of Simulation To Laser Active Illumination System

Laser active illumination is a technology of illuminating long range dim target and making beacon for wavefront sensing with near-infrared multi-beam laser. Since laser beam possess qualities in its well orientation and high luminance, the laser illumination is widely applied in laser radar, laser weapon, beacon for adaptive optics system, etc. The laser beam propagated through atmosphere will be affected by the atmospheric turbulence. It is unrepeatable for doing experiments in exactly the same atmospheric situation, due to the randomness of turbulence. That makes numerical simulation become an important method to study laser illumination via atmosphere. This article beginning with the theory of beam propagation in atmosphere, studied the models in simulate the physical procedure of laser illumination simulation. Several common algorithms of simulation are analyzed in this article. A simulation program is designed, and the results of simulation are compared to those of an experiment that has been done. The main work in this article is shown below:1. In the numerical simulation of laser beam propagation in atmosphere, dated from the theory of turbulence screen, three kinds of algorithms of generating phase screen are analyzed. The study shows that to generate static phase screen without time evolution, the fractal method shows best quality correspond to the Kolmogorov model, and it is the fastest algorithm. Considering the time variance, the phase screen should shift by the wind. In this situation, the FS method delivered better result and shorter operating time. To the phase-wrapped problem in solving the wavefront of laser beam propagation through turbulence, a new algorithm, AOV-network method a figured out, which has better result compared by other common unwrap algorithms when solve high resolution phase screen. The error rate of AOV method is less than 1%.2. A simulation procedure of the laser active illumination system is programmed. The results of simulation are compared to the data of the experiment. the uniformity and scintillation characterization of the spot on target are analyzed, which show that the simulation is able to predicted the experiment result. The RMS in space distribution in simulation is 0.2514, and the RMS in time distribution in simulation is 0.4292, witch are similar to the experiment result 0.2746 and 0.4521.3. The simulation of beam propagation in atmosphere is a computation-intense task. To make the simulation speed faster, 2 calculation acceleration plans are presented: using GPU calculation, or the distributed calculation. A simple try of acceleration the FFT function was done. Shows that the GPU calculation can make the simulation time-spent decrease to 19.6% than before, and the distributed calculation via 4 PCs in LAN can make the time usage decrease to 43%.