相位差异法目标函数的并行化改造

考虑自适应光学波前探测技术利用相位差异法来估算波前相位畸变和恢复图像时运算量较大,难以用软件在PC平台上实现,而使用数字信号处理(DSP)和现场可编程门阵列(FPGA)搭建计算平台虽然可使运算并行化从而缩短运算时间,但其目标函数结构复杂,因此,本文利用泽尼克多项式的性质,提出了一种相位差异目标函数的改造方法.给出了改造后的目标函数计算公式和梯度计算公式,使相位差异法在每次计算目标函数时只进行多项式运算,从而不仅方便了用DSP和FPGA的硬件实现,也充分利用了硬件处理的并行性.设计了仿真实验和室内实际光路实验,分别以分辨率板和光纤光束为例对模拟图像和实际采集图像进行了恢复.实验结果表明,改造后的相位差异法仍具备较好的图像恢复能力,光纤光束成像分辨率显著提高,颗粒间轮廓清晰可见.

Parallelity improvement of object function for phase diversity

The Phase Diversity(PD) method in adaptive optical waveforn detection shows great computations when it is used to estimate the wave-front phase aberration and to restore the degraded images,and it is difficult to increase the speed of PD to achieve its real time application on a PC platform.The computational-hardware such as Digital Signal Processor(DSP) and Field Programming Gate Array(FPGA) is a proper way to improve its performance,however,the complex structure of the PD object function and plenty of Fourier transformations in each computation loop influence on its hardware implementation.According to the theory of Zernike polynomial,a method which utilizes polynomial operation instead of Fourier transformations is proposed to modify the PD object function.The modified computing formula and gradient formula are given,by which the computation of the PD object function only depends on the polynomials and the hardware implementation of DSP,FPGA and the parallelism of hardware processing are more easily.A test and an experimental platform are designed,and simulative images and grabbed images for a resolution plate and an optical fiber bundle are restored respectively.Experiment results indicate that the modified PD is still a good means to restore the degraded images,the optical fiber bundle has a higher resolution and its particle profile can be distinguished.