An image rectification scheme and its applications in RST invariant digital image watermarking

This paper presents an image rectification scheme that can be used by any image watermarking algorithm to provide robustness against rotation, scaling and translation (RST) transformations. Rotation and scaling transformations in the spatial domain result in cyclically translational shifts in the log-polar mapping (LPM) of the magnitude of the Fourier transform spectrum of an image. We cut a small block from the LPM domain as a matching template. A new filtering method is proposed to compute the cross-correlation between this template and the magnitude of the LPM of the image having undergone RST transformations to detect the rotation and scaling parameters. We employ the same strategy in the spatial domain to detect the translational parameters in the spatial domain. The scheme can also be used to detect image flipping. The cost of the templates is low and the templates can even be compressed. The detection accuracy for rotation, scaling and translation is also presented. We compare the matching results for the different filters and their performance by the three criteria: signal-to-noise ratio (SNR), peak-to-correlation energy (PCE), and Horner efficiency. We demonstrate that our phase-only filtering method is the only one that can be used in the LPM domain. We also introduce three applications for this rectification scheme and give their experimental results.

相位控制相控阵天线方向图

基于线阵,讨论成片零点的相位控制,提出和采用快速算法、部分单元控制方法和约束非线性离散变量优化算法。试验结果验证了数学模型和仿真结果的正确性。     

发射自适应波束形成技术研究

在天线阵发射波束时进行方向图零点控制是现代雷达采用的先进技术之一,该文分析了一种唯相位共轭梯度自适应于扰置零算法,并详细叙述了我们研制的基于TMS320C31的雷达自适应干扰对零阵列处理实验系统。理论分析和实验结果均表明系统能有效置零抑制干扰、是一种实用性强的系统。     

基于迭代二阶锥的唯相位波束形成

唯相位自适应波束形成技术对普通相控阵雷达自适应干扰抑制是非常重要的,在数字阵列雷达中,唯相位技术则可以充分利用各阵元发射模块微波功率从而提高雷达的威力。该文提出了一种新的唯相位波束形成方法,假定初始唯相位权重矢量有个较小的相位扰动,将唯相位模型的目标函数和约束函数在该相位扰动区域内分别用泰勒一阶展开式来近似,则可以将原来的非凸问题转化为凸优化问题,通过二阶锥规划方法(SOCP)求得使当前目标函数最小的扰动矢量,然后更新得到新的权重矢量并代替原来的权重矢量,重复上述迭代过程直到满足停止条件,可以得到满足要求的唯相位权重。计算机仿真结果验证了该方法的正确性和有效性。     

Multiplane full-color phase-only holograms generation based on iterative algorithm with a modified amplitude constraint

Depth-division multiplexing (DDM) is distinguished for generating full-color holograms. However, this method is confronted with such issues as poor quality and severe crosstalk when reconstructing multiplane color images. In this paper, we propose an improved iterative method based on Gerchberg-Saxton (GS) algorithm to generate multiplane full-color phase-only holograms (POHs), and the information of red (R), green (G), and blue (B) channels of images is recorded in three POHs, respectively. In the iterative process, we introduce an improved hologram plane constraint that consists of modified amplitudes given a static weighting factor, and display the reconstruction results for three-layer images, which ultimately improve the quality of the reconstructed images and effectively avoid the crosstalk among different color channels. And compared with GS algorithm, our method can effectively balance the reconstruction quality of three-color channels of each image. The feasibility of the method is verified by numerical simulations and optical experiments.     

动载体光电平台视轴稳定精度的检测

提出一种动载体光电平台视轴稳定精度的检测方法.介绍了光学测量原理,讨论了光电平台视轴稳定精度检测系统的实施路线,并对该系统使用的自准直光学成像系统、高速数字CMOS相机和光斑检测算法进行了研究.由安装在光电平台照准架上的平面反射镜反映光电平台视轴指向角度的变化,用高速数字CMOS相机采集图像,并通过计算图像之间归一化的...     

基于混合遗传算法的唯相位直接数据域算法

提出一种基于混合遗传算法的唯相位直接数据域最小二乘算法.通过采用标准遗传算法与Neider-Mead单纯形法相结合的混合遗传算法,提高了优化效率和运算速度.首先根据标准直接数据域算法推导得出目标函数,继而将目标函数作为适应度函数,将所有自适应权值的未知相位作为决策变量,通过混合遗传算法进行非线性优化,从而求得各个自适应权值的优化解.作为一种唯相位自适应算法,它在硬件实现上比传统算法更具简单性.同时,它只对单快拍数据进行处理,避免了样本协方差矩阵的构造以及矩阵求逆运算,更适合于实时处理.仿真结果表明,算法具有良好的信号恢复和干扰置零性能,比基于非线性其轭梯度法的唯相位直接数据域算法性能更优.     

A robust phase-only Direct Data Domain algorithm based on generalized rayleigh quotient optimization using hybrid Genetic Algorithm

A robust phase-only Direct Data Domain Least Squares （D3LS） algorithm based on generalized Rayleigh quotient optimization using hybrid Genetic Algorithm （GA） is presented in this letter. The optimization efficiency and computational speed are improved via the hybrid GA composed of standard GA and Nelder-Mead simplex algorithms. First, the objective function, with a form of generalized Rayleigh quotient, is derived via the standard D3LS algorithm. It is then taken as a fitness function and the unknown phases of all adaptive weights are taken as decision variables Then, the nonlinear optimization is performed via the hybrid GA to obtain the optimized solution of phase-only adaptive weights. As a phase-only adaptive algorithm, the proposed algorithm is simpler than conventional algorithms when it comes to hardware implementation. Moreover, it proc- esses only a single snapshot data as opposed to forming sample covariance matrix and operating matrix inversion. Simulation results show that the proposed algorithm has a good signal recovery and interferences nulling performance, which are superior to that of the phase-only D3LS algorithm based on standard GA.