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。

Abstract

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.

参考文献

[1] ROGGEMANN M C, WELSH B M. Imaging Through Turbulence ［M］. Washington: CRC Press, 1996.

[2] 吴元昊，王斌，赵金宇，等.利用相位差异技术恢复宽带白光图像［J］. 光学精密工程，2010, 18(8): 1849-1854.

WU Y H, WANG B, ZHAO J Y, et al.. Restoration of broadband white light image using phase diversity technique ［J］. Opt. Precision Eng., 2010,18(8): 1849-1854.(in Chinese)

[3] 王建立，汪宗洋，王斌，等.相位差异散斑法图像复原技术［J］. 光学精密工程,2011,19(5): 1165-1170.

WANG J L, WANG Z Y, WANG B, et al.. Image restoration by Phase-diversity Speckle ［J］. Opt. Precision Eng.,2011,19(5): 1165-1170.(in Chinese)

[4] SELDIN J H, PAXMAN R G. Phase-diverse speckle reconstruction of solar data［C］.Image Reconstruction and Restoration, Proc. SPIE, 1994, 2302: 268-280.

[5] PAXMAN R G, SCHULZ T J, FIENUP J R. Joint estimation of object and aberrations by using phase diversity ［J］. Opt.Soc.Am., 1992, A9: 1072-1085.

[6] PAXMAN R G, SELDIN J H, LFDAHL M G, et al.. Evaluation of phase-diversity techniques for solar-image restoration［J］. The Astrophysical Journal. 1996, 466: 1087-1099.

[7] THELEN B J, PAXMAN R G, CARRARA D A, et al.. Maximum a posteriori estimation of fixed aberrations, dynamic aberrations, and the object from phase-diverse speckle data［J］. J.Opt.Soc.Am., 1999, A16: 1759-1768.

[8] VOGEL C R. Computational Methods for Inverse Problems ［M］. Philadelphia: SIAM Press, 2002.

[9] VOGEL C R, CHAN T, PLEMMONS R. Fast algorithms for Phase Diversity-Based Blind Deconvolution［C］. Adaptive Optical System Technologies, Kona, Hawaii, USA, SPIE, 1998, 3353: 994-1005.

[10] LFDAHL M G, BERGER T E, SHINE R S, et al.. Preparation of a dual wavelength sequence of high-resolution solar photospheric images using Phase Diversity ［J］. The Astrophysical Journal, 1998,495: 965-972.

[11] LFDAHL M G, SCHARMER G B. Wave-front sensing and image restoration from focused and defocused solar images［J］. Astron.Astrophys,1994, 107: 243-264.

[12] 王斌，汪宗洋，等. 双相机相位差异散斑成像技术［J］. 光学精密工程,2011,19(6): 1384-1390.

WANG B, WANG Z Y, et al.. Phase-diverse Speckle with two cameras ［J］. Opt. Precision Eng.,2011,19(6): 1384-1390.(in Chinese)

[13] BYRD R H, LU P, NOCEDAL J, et al.. A limited memory algorithm for bound constrained optimization［R］. Report NAM-08, EECS Department, Northwestern University, 1994.

[14] ZHU C, BYRD R H, LU P, et al.. LBFGS-B: Fortran subroutines for large-scale bound constrained optimization［R］. Report NAM-11, EECS Department, Northwestern University, 1994.

[15] PARKER J A, KENYON R V, TROXEL D E. Compare of interpolation methods of image resampling［J］. IEEE Trans. Med. Imaging,1983,MI 22: 31-39.

赵金宇, 陈占芳, 王斌, 汪宗洋, 张楠, 王建立, 吴元昊, 张世学. 相位差异法目标函数的并行化改造[J]. 光学精密工程, 2012, 20(2): 431. ZHAO Jin-yu, CHEN Zhan-fang, WANG Bin, WANG Zong-Yang, ZHANG Nan, WANG Jian-li, WU Yuan-hao, ZHANG Shi-xue. Parallelity improvement of object function for phase diversity[J]. Optics and Precision Engineering, 2012, 20(2): 431.

相位差异法目标函数的并行化改造

关于本站 Cookie 的使用提示

全站搜索

相位差异法目标函数的并行化改造

相关论文

相关资讯

关于本站 Cookie 的使用提示

全站搜索