Fast Calculation Method Of GPU For Measuring Laser Wavefront By Phase Diversity

Laser wavefront is an important criterion to evaluate the performance of laser.It is closely related to the characteristics of laser transmission and focusing.How to accurately and quickly measure laser wavefront is a very important research direction in laser technology.Among the many methods for measuring laser wavefront,Phase Diversity(PD method)has the advantages of simple system structure,easy implementation,low cost,and no need to refer to the target image processing afterwards,but the disadvantage is severely time consuming.In this thesis,GPU acceleration is applied to the calculation of laser wavefront by Phase Diversity.The advantage of GPU parallel computing is used to accelerate the laser wavefront measurement by Phase Diversity.In this thesis,the principle of laser wavefront measurement by Phase Diversity is analyzed.The objective function,gradient function and L-BFGS optimization algorithm constructed by Phase Diversity in laser wavefront process are parallelized and modified,so that Phase Diversity can be used in GPU.Parallel processing;analyze Phase Diversity to measure the whole time-consuming situation of laser wavefront,find out the most time-consuming Fourier transform,summation,matrix multiplication in the process,and have targeted GPU acceleration calculation for these links.Combining the optical principle,the redundant calculation of the point spread function in the Phase Diversity is eliminated,and the computational efficiency of the algorithm is improved.Finally,the PD method is used to measure the GPU acceleration experiment of laser wavefront,and the hardware system and software system are constructed.The laser wavefront under different spot image sizes is calculated by CPU and CPU+GPU respectively,and measured with BeamWave 500 wavefront measuring instrument.The data is compared and the acceleration effect is compared under the premise that the measurement results are valid.The experimental results show that the GPU-accelerated Phase Diversity measures the laser wavefront in terms of measurement results and the reference value is close to meet the validity requirements of the measurement results;the 256×256 pixel image is calculated by GPU acceleration method,and the measurement time is measured.Keep it within 6 seconds,compared with the speed measured by the CPU,the acceleration ratio reaches 53.7,the acceleration effect is obvious,which can greatly improve the operating efficiency of the algorithm.The GPU fast calculation method for measuring laser wavefront by Phase Diversity is of great significance for the fast and accurate measurement of laser wavefront.