相位调制无关的测量设备无关量子密钥分配协议

提出一种相位调制无关的改进测量设备无关量子密钥分配协议,在实际系统中通信双方 参考系随时间相对缓慢移动的条件下,该协议不需要添加辅助校准系统来补偿相位漂移,降 低了系统的复杂性。文章分析了相位调制无关的测量设备无关量子密钥分配协议在弱相干光 源及参量下转换光源下的安全密钥生成率和最大安全传输距离,并进一步探究了有限密钥长 度引起的统计波动问题对安全密钥率的影响。仿真结果表明,该协议的最大安全传输距离接 近经典协议的最大安全传输距离。同时,考虑统计波动的影响,当达到相近的最大传输距离 时,本文协议所需的脉冲数比传统协议低约5个数量级,进一步提高了系统效率。     

海洋声场计算的相位重构方法

海洋声场计算是海洋声学的重要研究课题,本文利用傅立叶变换推导了声场的平面波表示,平面波的传播可由相位进行表征,利用相位重构方法得到了声波在海洋中的传播情况并进行声场预报。利用典型深海声速分布模型检验该方法的有效性。     

路径导引的四波横向剪切干涉波前重构方法

为了解决区域法在四波横向剪切干涉波前重构过程中噪声误差沿积分路径累积影响波前重构精度的问题,本文提出了一种路径导引的四波横向剪切干涉波前重构方法。首先分析了噪声环境下无积分路径导引的区域法波前重构存在噪声误差累积的缺陷,然后在此基础上建立了基于差分相位导数偏差的积分路径评价图模型,并给出了基于积分路径导引的波前重构算法流程。为了验证所提方法的有效性,本文进行了理论仿真研究,结果表明在不同信噪比噪声下所提方法能有效地阻止噪声误差的传播和累积。搭建了基于纯相位型液晶空间光调制器的实验验证装置,实验结果表明：所提方法重构波前与理论波前残差的RMS相比无积分路径导引区域法重构波前与理论波前残差的RMS降低了39.7%,且所提方法重构波前PV值与理论波前PV值的偏差相对无积分路径导引区域法重构波前PV值与理论波前PV值的偏差减小了1.6943λ。所提方法可为提高噪声环境下四波横向剪切干涉波前重构精度提供一种有效方法。     

用改进的光谱相位相干直接电场重构法装置测量飞秒激光脉冲的相位

在对光谱相位相干直接电场重构法(SPIDER)硬件和软件进行深入研究的基础上,建立了光谱相位相干直接电场重构法测量系统。测量装置中,利用厚度为50μm的非线性晶体(BBO)来保证测量装置的带宽,并对分束镜进行改进,使之引入色散减小。自行开发了一套基于Labveiw软件的光谱相位相干直接电场重构法测量系统,并能够用于实时测量。其中在还原算法中以脉冲对倍频干涉条纹中的ωτ作为线性快变项,并只对具有干涉条纹部分的频率范围进行还原相位,大大提高了光谱相位相干直接电场重构法测量的精度。用此系统测量了钛宝石激光振荡器的输出脉冲特性,并与干涉自相关比较,证实了测量的准确性。     

相位图去包裹的一种新的综合方法

提出了相位图去包裹的一种新的综合方法。首先建立了一个消除局部不连续点的模型，利用此模型可有效地消除包裹相位图中的不连续点，同时不会影响到其他正常点；在此基础上进行多方向去包裹运算，然后求其平均值，从而达到与路径无关的目的。给出了具体算法，并通过数值模拟和实验验证了该方法的有效性和可行性。结果表明，这种方法既具有很强的抗噪声能力，又能很好地处理较大面积的欠采样区域，并且具有较高的稳定性和处理效率。     

用全相位傅氏法重构间断信号

为利用有限的信息为最小误差重构间断信号,将全相位处理的思想与传统傅氏逼近相结合,利用对信号离散采样后得到的DFT系数,并充分利用高次谐波信息,形成了全相位傅氏重构法。理论和实验表明:用全相位傅氏法对间断信号进行重构的波形,相比于传统的连续傅氏积分逼近和离散傅氏重构的波形,具有更小的误差。     

基于Kolmogoroff方法重构光纤光栅相位响应

借用信号处理的kolmogoroff方法,在最小相移的前提下,由光纤光栅的强度响应谱重构相位响应及冲激脉冲响应,由此确定时延、色散以及光纤光栅的某些结构特征。以均匀光纤光栅为例,证明该方法是行之有效的。     

用光谱位相相干电场重构法还原飞秒脉冲相位

基于光谱相位相干直接电场重建法(SPIDER)测量飞秒激光脉冲的基本原理和重构相位的反演算法,数值模拟了SPIDER技术重构飞秒脉冲相位的过程,分析了非线性晶体、时间延迟τ、光谱剪切量Ω的选取原则。以高斯型线性啁啾脉冲为例,还原出了脉冲的位相,得到不同的待测脉冲重构出的最佳位相曲线具有不同的最佳延迟时间和光谱剪切量。     

唯相位方法实现方向图可重构阵列天线

使用唯相位方法设计方向图可重构天线,对阵列的激励电流幅度和相位同时进行优化,得到一组电流幅度值,使它适用于多种形状的方向图,同时得到与每种方向图对应的相位值。优化算法选用实数编码的遗传算法。为了把设计结果应用于实践,文中还对电流幅度的分布进行了一定的限制,设计出了具有2种工作状态的方向图可重构天线,最后给出了仿真结果,结果表明,文中讨论的方法在设计方向图可重构天线方面是有效的。     

光谱相位相干直接电场重构法测量飞秒脉冲的适用性问题

分析了现有光谱相位相干直接电场重构法(SPIDER)系统的一个缺点,即需预先估计待测脉冲的特性,来设定合适的系统参数.因而其适用范围受到一定限制,特别是在测量啁啾脉冲时容易出现偏差.实验用SPIDER系统分别测量了钛宝石飞秒激光器输出的脉冲及其经BK7玻璃块展宽得到的啁啾脉冲,测得啁啾脉冲的宽度为295 fs,作剪切量修正后测得脉宽为322 fs,后者更接近理论预期的313 fs.这表明SPIDER系统测量啁啾脉冲时,如果色散器提供的色散量不够大,会出现一定程度的偏差.通过补充记录两个和频脉冲的光谱,修正实际的剪切量,可有效减小误差,但问题仍未完全解决.     

Two-dimensional phase unwrapping using a block least-squares method

We present a block least-squares (BLS) method for two-dimensional (2-D) phase unwrapping. The method works by tessellating the input image into small square blocks with only one phase wrap. These blocks are unwrapped using a simple procedure, and the unwrapped blocks are merged together using one of two proposed block merging algorithms. By specifying a suitable mask, the method can easily handle objects of any shape. This approach is compared with the Ghiglia-Romero (1994) method and the Marroquin-Rivera (1995) method. On synthetic images with different noise levels, the BLS method is shown to be superior, both with respect to the resulting gray values in the unwrapped image as well as visual inspection. The method is also shown to successfully unwrap synthetic and real images with shears, fiber-optic interferometry images, and medical magnetic resonance images. We believe the new method has the potential to improve the present quality of phase unwrapped images of several different image modalities.     

A model-based method for phase unwrapping

Presents a model-based phase unwrapping method which represents the unwrapped phase function by a truncated Taylor series and a residual function. An efficient, noniterative computational algorithm is also proposed for calculating the model parameters from the phase derivatives. Sample experimental results are shown to demonstrate the effectiveness of the algorithm for extracting unwrapped phase images from two-dimensional (2-D) magnetic resonance imaging (MRI) data.     

Two-dimensional phase unwrapping using wavelet transform

A method for solving the least squares two-dimensional phase unwrapping problem is presented. This technique is based on the multiresolution representation of a linear system using the discrete wavelet transform. By applying the wavelet transform to the original system, a better convergence condition of an equivalent new system can be achieved     

Least-squares two-dimensional phase unwrapping using FFT's

A solution of the least-squares two-dimensional phase-unwrapping problem is presented that is simpler to understand and implement than previously published solutions. It extends the phase function to a periodic function using a mirror reflection, and the resulting equation is solved using the Fourier transform     

Interferometric SAR phase unwrapping using Green's formulation

Any method that permits retrieving full range (unwrapped) phase values starting from their (-π,π) determination (wrapped phase) can be defined as a phase unwrapping technique. This paper addresses a new procedure for phase unwrapping especially designed for interferometric synthetic aperture radar applications. The proposed algorithm is based on use of Green's first identity. Results on simulated as well as on real data are presented. They both confirm the excellent performance of the procedure     

改进的阶梯相位去包裹算法研究

为减少投影条纹数量,提高测量速度,提出了一种 改进的阶梯相位去包裹算法。算法 采用彩色条纹投影测量物体三维形貌,将正弦和阶梯相位条纹分别输入彩色图像的红 色和蓝色通道构成彩色条纹,由DLP投影仪将四步相移彩色条纹投影到待测物体上,由彩色 CCD相机采集。利用颜色分离技术得到2组四步相移条纹图,其中一组为4幅正弦条纹,由四 步相移法求得正弦条纹包裹相位,另一组4幅阶梯相位编码条纹图,由与正弦条纹周期一致 的阶梯相位构成,经阶梯相位解码确定条纹级次,利用自校正算法去除条纹级次噪点后,实 现相位去包裹。进行了实际测量,结果表明,本方法 测量精度与采用四步相移法相当,但只需4幅条纹图,有效减少了投影和采集的条纹数量, 提高了测量速度。     

三基线毫米波InSAR的相位解缠及高程反演

场景内高程突变超过干涉雷达不模糊高程的一半时, 会导致常规相位解缠绕方法失效, 在毫米波段该问题尤为突出.研究了基于聚类分析的三基线毫米波InSAR相位解缠绕方法, 改进了聚类分析中直方图包络波峰选取策略.对场景中高程突变引起的阴影区域相位噪声较大的问题, 使用掩膜门限处理, 改善了聚类分析结果.计算机仿真结果和机载毫米波三基线InSAR实际数据处理结果验证了上述方法的有效性.     

A complementary binary code based phase unwrapping method

Phase unwrapping is used to establish the mapping relationship between camera and projector, which is one of the key technologies in fringe projection profilometry(FPP) based three-dimensional(3D) measurement. Although complementary Gray code assisted phase unwrapping technology can get a good result on the periodic boundary, it needs more coded images to obtain a high frequency fringe. Aiming at this problem, a complementary binary code assisted phase unwrapping method is proposed in this paper...     

Two-dimensional phase unwrapping using a minimum spanning treealgorithm

Phase unwrapping refers to the determination of phase from modulo 2pi data, some of which may not be reliable. In 2D, this is equivalent to confining the support of the phase function to one or more arbitrarily shaped regions. A phase unwrapping algorithm is presented which works for 2D data known only within a set of nonconnected regions with possibly nonconvex boundaries. The algorithm includes the following steps: segmentation to identify connectivity, phase unwrapping within each segment using a Taylor series expansion, phase unwrapping between disconnected segments along an optimum path, and filling of phase information voids. The optimum path for intersegment unwrapping is determined by a minimum spanning tree algorithm. Although the algorithm is applicable to any 2D data, the main application addressed is magnetic resonance imaging (MRI) where phase maps are useful.     

基于FPGA的数字相位展开技术研究

针对相位展开软件算法运算复杂的缺点,通过分析相位展开原理,提出基于FPGA的相位展开技术的硬件实现。采用加/减模块、乘法器以及除法器构成截断相位处理模块,将软件算法查找链表的思路转换成RAM存储器读写操作,利用状态机完成对存储器和截断相位处理模块的控制。采用ALTERA 系列EP4CE115F29C7芯片,针对256*256和512*512的图像实现设计,最高工作频率分别达到80.22MHZ,80.45MHZ;资源消耗分别为792和1436个LE。采用SignalTap II Logic Analyzer工具实时验证了相位展开设计模块的正确性。