周期信号高精度测量中高斯窗的优化配置研究

周期信号的高精度测量中,附加高斯窗能够有效地改善由于采样周期与信号周期不同步而造成的幅值测量精度降低问题.如何利用已获取的被测信号的相关信息进行参数设定尚无严格的理论依据,因而通常采用缺省配置.这在一定程度上限制了高斯窗最佳效能的发挥.本文从高斯窗的逼近入手,提出了一种既能降低远程频谱泄漏又能避免频谱混叠的参数设置方法,并进行了仿真实验.实验结果表明,该参数设置方法能有效地提高周期信号的幅值测量精度.     

高斯型点扩展函数估计的最近邻算法

本文针对计算光学切片中的最近邻算法提出了一种改进算法.通过小波变换计算出高斯点扩展函数的方差值,再根据相邻图像成像及高斯函数特性,得出所需的高斯型层间点扩展函数.同时,文章还给出了两种高斯型层间点扩展函数方差的获得方式及获得过程,对最近邻算法中的加权因子的取值范围做出了讨论,对传统的最近邻算法做出了改进.实验表明,本算法能够更有效地复原符合最近邻要求的切片图像.在点扩展函数未知的情况下,复原效果要优于传统方法.     

基于APEX算法改进的图像复原算法

在高斯类点扩函数退化图像复原的研究中,提出了一种基于降晰图像频谱特征改进的APEX图像复原算法.该算法采用APEX算法的基本原理,根据图像频谱信息特征,对点扩散函数(PSF)估计过程进行了改进,采用加权最小二乘算法拟合出降晰图像频谱主方向,采用图像频谱主方向上的数据进行PSF估计,以利用更多的有效数据,从而减少PSF的估计误差.针对模拟和实际采集的降晰图像进行实验,采用主观视觉和峰值信噪比进行评价.实验结果表明,改进的算法较使用非主频谱方向上的频谱数据的复原算法在复原效果上有一定的提高.     

基于JTC和扩频技术的多二值图像光学加密技术

为了提高光学加密系统的传输效率和安全性,提出了一种多二值图像光学加密技术。该方法加密时采用数字方法和光学方法联合实现,解密过程可采用纯光学方法实现。加密时,首先将待加密图像乘以不同密钥进行频谱扩展,再进行算术叠加生成复合图像。然后将复合图像置于联合变换相关器的输入面上进行光学加密。解密时,需要在频率域利用光阑从复合图像中提取出每一幅原始图像。理论分析和计算机仿真表明,该多二值图像光学加密技术系统结构简单,图像复用容量巨大,具有较高的安全性。     

基于LabVIEW的相位差测量仿真平台设计

本文设计实现了一个基于LabVIEW的相位差测试平台,采用频谱分析法、过零点法和相关分析法3种方法实现信号的相位差测量,设计产生信号噪声源模拟真实测量环境,实验验证3种测量方法的测量准确度,分析它们各自的适用范围。一、相位差测量原理1.频谱分析法频谱分析法是通过对被检测信号进行频谱分析,获得信号的相频特性,然后计算两信号在主频率处对     

载频条纹相位分析自适应滤波器的设计

提出了一种基于统一准则的自适应滤波器的设计算法,并结合空间滤波处理技术及数字图像处理分析技术,根据每一幅光学条纹图像的频谱分布状况,自动提取+1级频谱信息,实现对载频条纹图像的自适应滤波,最终达到自动化数值分析的目标。文中以三维形貌测量为例,首先通过计算机数值模拟,指出分析位相质量与滤波窗口的选择是紧密相关的。而光学条纹图像的频谱分布则因待测物体而异,因此在空间滤波过程中,要针对不同的待测物体对滤波窗口的形状以及大小进行精确选取。文章给出了自适应滤波器精确选取的法则与步骤。最后以三维石膏像为测量物体,给出实验验证,证明该方法的可行性与有效性。     

国内首条光学低通滤波器生产线量产

国内首条光学低通滤波器(简称OLPF)专业生产线,目前在星星集团浙江水晶光电科技有限公司启动运行。 光学低通滤波器是一种新型的空间频率滤波器件,与数码相机的CCD或CMOS成像传感器匹配,采用前置滤波方式利用石英的光学特性,使入射光经过OLPF后所形成点列阵与CCD或CMOS的像素周期相匹配,降低图像在光敏面上的频谱宽度,以达到有效抑制高于CCD或CMOS所能分辨的最高频率成份,消除频谱混叠现象,使数码相机获得高清晰的图像。     

通过复数几何光学对一种天线面型诊断方法的改进

通过天线所辐射的电场幅值来求解天线面形变是一种新的天线面型诊断方法,但是由于该方法基于实数几何光学(RGO),忽略了高斯馈源的影响,从而导致了一定的误差。本文通过复数几何光学(CGO)对高斯馈源所发射的电磁波的复数相位进行了研究,推导得出了较准确的天线面形变和天线辐射场幅值之间的关系表达式。在此基础上,提出了一种迭代算法来求解天线面形变,仿真结果表明该方法可以有效提高天线面形变的求解精度。     

相关熵和双谱分析齿轮故障诊断研究

相关熵为高斯、非高斯噪声处理的一种有效方法,针对强高斯噪声和非高斯噪声干扰下齿轮故障诊断问题,提出了一种基于相关熵和双谱的齿轮故障诊断方法。该方法综合利用高斯核函数和不完全 Cholesky 分解算法计算信号的相关熵,然后再计算相关熵的双谱,根据相关熵的双谱特征识别齿轮故障。通过不完全 Cholesky 分解算法计算信号的相关熵,不仅大大压缩了数据量,突出了齿轮故障特征,而且提高了计算效率。通过仿真和齿轮磨损故障振动信号分析结果表明：强背景噪声会造成传统双谱故障诊断方法失效,而基于相关熵和双谱分析的齿轮故障诊断方法,能在强噪声干扰背景中提取齿轮的故障特征准确识别齿轮故障,其性能优于传统双谱和小波变换域双谱,为一种有效的齿轮故障诊断方法。     

利用液晶光阀实现的Joint变换

本文叙述了Joint变换的基本原理,并利用液晶光阀的偏振调制特性实现了Joint变换,液晶光阀作为实时记录器件,可以对物体的频谱进行改善,从而得到了较好的相关输出,实验结果与理论分析相符,提供了实时光学相关的一种新方法。     

Fourier-plane windowing in the binary joint transform correlator for multiple target detection

With recent advances in state-of-the-art spatial light modulators, the optical joint transform correlator (JTC) and the binary joint transform correlator (BJTC) are becoming practical signal-processing tools. The performance of these devices is limited by the difficulty of separating the cross correlation between the reference and the targets in the scene from signals resulting from cross correlations between objects in the target scene. One technique that reduces this problem is to use a sliding window in the Fourier plane as a convolution mask filter to set an adaptive binarization threshold. This suppresses the autocorrelation response and reduces the dynamic range of the Fourier-plane signal. This results in correlation performance improvement by a factor of 2 to 4. A mathematical model is developed to describe the windowing process for both the JTC and BJTC for the case in which the scene contains multiple targets and background clutter. The derivation of the windowing process is general and includes any spatial high-pass or bandpass filtering in the Fourier plane. The results are supported with experimental data.     

基于液晶光阀微分处理的实时联合变换相关器

提出了一种用液晶光阀实现对输入图像的微分预处理和对功率谱微分处理的实时联合变换相关器。两个液晶光阀均处于非线性变换态,分别在输入面和频谱面上实现对输入图像和联合功率谱的微分处理。微分功率谱经傅里叶透镜变换后得到相关输出。实验表明,该相关器采用全光方式不仅保证了实时性,而且锐化了相关峰;经该相关器微分后的图像,其相关性能明显优于常规联合变换相关器输出的结果。     

Color image security system using double random-structured phase encoding in gyrator transform domain

A novel method for encoding color information based on a double random phase mask and a double structured phase mask in a gyrator transform domain is proposed. The amplitude transmittance of the Fresnel zone plate is used as structured phase-mask encoding. A color image is first segregated into red, green, and blue component images. Each of these component images are then independently encrypted using first a random phase mask placed at the image plane and transmitted through the first structured phase mask. They are then encoded by the first gyrator transform. The resulting information is again encrypted by a second random phase mask placed at the gyrator transform plane and transmitted through the second structured phase mask, and then encoded by the second gyrator transform. The system parameters of the structured phase mask and gyrator transform in each channel serve as additional encryption keys and enlarge the key space. The encryption process can be realized with an electro-optical hybrid system. The proposed system avoids problems arising from misalignment and benefits of a higher space-bandwidth product. Numerical simulations are presented to confirm the security, validity, and possibility of the proposed idea.     

刮板细度计非接触测量数据处理研究

对基于光谱共焦技术搭建的刮板细度计斜槽面深度测量装置的非接触测量数据进行处理算法研究.引入高斯滤波对整段测量数据进行滤波分析,再分左上平面、右上平面、斜槽底面三段进行高斯滤波,分离三个测量面的表面粗糙度信号及波纹度信号,解算出粗糙度值.对于高斯滤波中线,利用最小二乘法进行拟合,结果表明左右上平面的直线倾斜度一致,可拟合...     

Reference phase-encoded fringe-adjusted joint transform correlation

A novel reference phase-encoded joint transform correlation technique is proposed for efficient multiple-target detection. The proposed method employs phase encoding for the reference image and nonlinear Fourier plane apodization to optimize the detection performance. Existing joint transform correlators (JTC's) require multistep on-line processing to eliminate the false alarms. The proposed reference phase-encoded JTC overcomes false-target detection by eliminating the false correlation peaks while alleviating the effects of noise and other artifacts in just one step, thus ensuring higher processing speed. This technique yields only one peak per target instead of a pair of peaks produced by alternate JTC's. An all-optical implementation for the reference phase-encoded JTC technique is proposed, and computer simulation results are presented.     

Modified fringe-adjusted joint transform correlation to accommodate noise in the input scene

A modified fringe-adjusted joint transform correlator is proposed that is able to accommodate noise in the input scene. The effect of noise in the input scene on the performance of the joint transform correlator is analyzed and quantified. When the target is embeddedin aseverely noise-corrupted input scene, it is shown that the proposed modified fringe-adjusted filter joint transform correlator delivers a better correlation performance and the capacity to accommodate this noise than does the fringe-adjusted filter-based correlator. When the power spectra of the input image and the reference image are subtracted from the power spectrum of the joint-input image, it is found that the noise effect on the output plane is independent of the objects in the input scene and originates from the convolution of the reference image and noise in the input scene.     

Optimization of the rolling-circle filter for Raman background subtraction

A procedure is proposed to optimize a high-pass filter enabling one to subtract the broadband background signals inherent in Raman spectra. A spectral approach is used to analyze the characteristics of the filter and the distortions in the processed spectra. Examples of the processing of real spectra are presented.     

圆度测量中高斯滤波的逼近实现方法

以B样条函数为基础,将约束条件引入变分原则,并结合小尺度参数高斯滤波器卷积特性,建立高斯滤波器的逼近滤波器。该滤波器与理论滤波器的幅度最大偏差小于1%,并具有零相移特性。在数字滤波算法中,包含两次零相移滤波和加权滤波循环计算,整个算法具有结构形式简单和计算效率较高的特点。根据圆度信号的周期封闭性,采用周期延拓法,消除数字滤波算法存在的边界效应问题。为圆度测量中高斯滤波器的实现提供了一种高精度、高效率的实现方法。     

Noninvasive OCT imaging of the retinal morphology and microvasculature based on the combination of the phase and amplitude method

To implement the optical coherence tomography (OCT) angiography on the low scanning speed OCT system, we developed a joint phase and amplitude method to generate 3-D angiograms by analysing the frequency distribution of signals from non-moving and moving scatterers and separating the signals from the tissue and blood flow with high-pass filter dynamically. This approach firstly compensates the sample motion between adjacent A-lines. Then according to the corrected phase information, we used a histogram method to determine the bulk non-moving tissue phases dynamically, which is regarded as the cut-off frequency of a high-pass filter, and separated the moving and non-moving scatters using the mentioned high-pass filter. The reconstructed image can visualize the components of moving scatters flowing, and enables volumetric flow mapping combined with the corrected phase information. Furthermore, retinal and choroidal blood vessels can be simultaneously obtained by separating the B-scan into retinal part and choroidal parts using a simple segmentation algorithm along the RPE. After the compensation of axial displacements between neighbouring images, three-dimensional vasculature of ocular vessels has been visualized. Experiments were performed to demonstrate the effectiveness of the proposed method for 3-D vasculature imaging of human retina and choroid. The results revealed depth-resolved vasculatures in retina and choroid, suggesting that our approach can be used for noninvasive and three-dimensional angiography with a low-speed clinical OCT, and it has a great potential for clinic application.     

Image rotation and translation measurement based on double phase-encoded joint transform correlator

An image rotation and translation measurement technology based on a double phase-encoded joint transform correlator (DPEJTC) is proposed. The reference and the target images are Fourier transformed. Then the magnitude of the Fourier-transformed reference (MFR) and target (MFT) images are multiplied with a high-pass emphasis filter and transformed from Cartesian space into polar space. Rotation between the reference and the target image is obtained by measuring the emphasized MFR and MFT in polar coordinates by the DPEJTC. The target image is rotated by the rotation angle in the inverse orientation to get the rotation-correction target image. Finally, translation between the reference and the target image is obtained through measuring the reference and the rotation-correction target image by the DPEJTC. Results based on digital computation are given to verify our proposal. A possible optical setup is suggested.