Improved algorithm for image encryption based on stochastic geometric moiré and its application

A technique based on optical operations on moiré patterns for image encryption and decryption is developed. In this method, an image is encrypted by a stochastic geometric moiré pattern deformed according to the image reflectance map. The decryption is performed using pixel correlation algorithm in the encrypted image and the stochastic geometrical moiré pattern. The proposed technique has a number of advantages over existing encryption techniques based on moiré gratings. No original moiré grating can be reconstructed only from the encrypted image. Stochastic moiré grating can be deformed in any direction what is an important factor of encryption security. Finally, the quality of the decrypted image is much better compared to decryption methods based on the superposition of the regular and deformed moiré gratings. The proposed technique has a great potential, because the process is performed using computational algorithms based on optical operations and optical components are avoided.     

Image hiding based on time-averaging moiré

Image hiding based on optical time-averaging moiré technique is presented in this paper. It is a new visual decoding scheme when the secret image is embedded into a moiré grating and can be interpreted by a naked eye only when the image is harmonically oscillated in a predefined direction. The secret image is visualized at strictly defined amplitude of oscillation. Computational and experimental examples are used to demonstrate the functionality of the method.     

基于Talbot-Moiré法测量透镜焦距的莫尔条纹的图像处理

利用Ronchi光栅的Talbot效应和Moiré条纹测量了长焦透镜焦距,并根据焦距与莫尔条纹斜率之间的定量关系可求得透镜焦距.为获得条纹斜率,用CCD采集莫尔条纹图像后,利用数学形态学滤波方法进行图像滤波平滑等预处理,有效地增强了图像的对比度.通过二值化、细化获得单像素宽连通的条纹,通过对条纹进行标记,为条纹斜率的直线拟合计算提供了可靠的数据,采用这些数据计算的焦距的误差为0.10%.     

A novel fringe adaptation method for digital projector

Aimed to obtain high-quality sinusoidal fringe projection, a new method to correct the output fringe of digital projector is presented. The method is based on the proposed fringe transform model, which describes the relationship of the input and output fringe pattern. Firstly, a series of fringe patterns are projected and from the fringe images, the transform function is calculated by the pattern shifting method. At last, by modifying the input fringe pattern, a standard sinusoidal output fringe can be achieved. Different from the previous methods, the waveform nonlinearity is estimated by varying the intensity of the projected fringe pixel by pixel; thus the waveform nonlinearity can be estimated precisely and the time cost is considerably reduced. Experimental results show that by modification of the input projection patterns the projector can project fringe with high-quality sinusoidal waveform leading to high performance of the projection system.     

压印光刻中的两步对正技术

压印光刻中套刻需要粗、精两级对正.实验采用一对斜纹结构光栅作为对正标记.利用物镜组观察光栅标记图像的边界特征进行粗对正,其准确度在精对正信号的捕捉范围内;利用光电接收器件阵列组合接收光栅莫尔信号,在莫尔信号的线区进行精对正.由于线性区的斜率大, 精对正过程中得到相应x,y方向的对正误差信号灵敏度高,利用高灵敏度对正误差信号作为控制系统的驱动信号,对承片台进行驱动定位,实现精对正.最终使X,Y方向上的重复对正准确度分别达到了± 21 nm(± 3σ)和±24 nm(± 3σ).     

A study on the 3-D measurement by using digital projection moiré method

Moiré topography method is a well-known non-contacting 3-D measurement method. Recently, the automatic 3-D measurement technique by moiré topography has been developed in order to apply to the engineering and medical fields. The projection moiré topography is very attractive because of its high measuring speed and high sensitivity. In this paper, using the two-wavelength methods of projection moiré topography was investigated to measure the 3-D shape of an object with 2π-ambiguity problems. Rapid measurement can be accomplished by the synchronization between CCD camera and projector. The experimental results prove that the proposed scheme is capable of finding absolute fringe orders, so that the 2π-ambiguity problems can be effectively overcome so as to treat large step discontinuities in measured objects.     

Scanning moiré and spatial-offset phase-stepping for surface inspection of structures

In order to develop a high-speed and accurate surface inspection system of structures such as tunnels, a new surface profile measurement method using linear array sensors is studied. The sinusoidal grating is projected on a structure surface. Then, the deformed grating is scanned by linear array sensors that move together with the grating projector. The phase of the grating is analyzed by a spatial offset phase-stepping method to perform accurate measurement. The surface profile measurements of the wall with bricks and the concrete surface of a structure are demonstrated using the proposed method. The change of geometry or fabric of structures and the defects on structure surfaces can be detected by the proposed method. It is expected that the surface profile inspection system of tunnels measuring from a running train can be constructed based on the proposed method.     

基于多激光传感器装配的自由曲面法线找正方法研究

在国产化、技术自主化的大型飞机项目上,对孔位精度的标准正逐步升高,钻头的垂直度又是这一标准中最受关注的条件。机器人自动钻铆系统工作时,所产生的装配误差、磕碰、偏移等状况,不仅降低了制造及检测的准确度,还影响了整个结构件的疲劳性能。针对这一问题,提出了基于多激光传感器装配的自适应自由曲面法线检测技术,搭建了以该方法进行姿态找正的数学模型,并研究了检测装置的标定方法及流程。同时,着重讨论了在自适应方法检测时,利用电子经纬仪等装置进行误差补偿的相关技术。该方法的验证实验结果显示,多组实验数据均达到了法向精度<±0.5°的关键技术指标要求,找正后的法线平均偏差值为0.0667°。该方法能有效补偿在制孔工作中所产生的相关误差,进一步提高机器人的定位精度及法线方向检测精度。     

A general method for automated analysis of caustics

In most published work on the optical method of caustics, experimental results were obtained by manually measuring some characteristic dimensions of the shadow pattern and, therefore, used only a limited amount of data from the caustic. However, some previous work has been done using digital image processing and light intensity plots combined with least-squares techniques to analyse the shape of a caustic obtained from a particular problem. All of these methods have been developed to solve only one specific problem. This paper highlights the essential guidelines of an automated method, which has the novelty of generalising the whole analysis, such that only the parametric equations of a particular problem are required to solve it. In the proposed method the image is digitised, the central line of the caustic pattern is identified, and the parameters in the mapping equation of the caustic are determined. The method has been validated, and the aim of this paper is to describe the key features of the method, i.e. the optical arrangement, digital image processing, and numerical analysis.     

基于影像实时处理的加油对接段辅助对准技术北大核心CSCD

针对空中加油试飞中加油对接困难的问题,设计了一种基于影像实时处理的加油对接段辅助对准系统,通过影像测量技术计算受油头与加油锥套中心的精确相对位置,实现位置参数与视频画面实时同步显示,用于空中加受油对接辅助对准。并对复杂光学条件下锥套跟踪技术、基于约束的像机标定技术和加受油组件相对位置实时测量等关键技术进行研究。实验结果表明,该算法可实现空中复杂环境下锥套图像快速、稳定识别与跟踪;采用双目视觉前方交会测量实时计算加油锥套与受油头相对位置,与事后处理结果对比分析,精度优于0.1 m,可辅助飞行员进行空中加油对接操作,提高加受油对接成功率。     

一种基于参数标定的投影条纹周期简易校正方法

基于三角测量原理的条纹投影轮廓测量系统中,倾斜投影到参考平面上的条纹将产生周期展宽现象,引起相位失真甚至影响测量精度.论文以条纹位置为控制变量推导出条纹周期校正的线性数学模型,通过简便的标定获得模型参数,由此反算出新的待投影条纹,并在参考平面上获得周期分布的投影条纹.实验结果表明校正后的条纹周期变化范围在±0.1像素内...     

A simple method of contrast enhancement and extremum extraction for interference fringes

A method of interference fringe processing by finding the average and the extremum gray levels of image points within a fixed or varying window and then computing the modified image intensity with a simple algorithm is proposed. This method can yield a uniform brightness and high (1 or near to 1) contrast at the same time over the whole image area for an input pattern with low contrast and considerable luminance variation, when a relatively large window is used. It can also perform extremum extraction if a small window is employed. This technique is simple, effective and convenient for use, as has been verified by a series of examples of simulated and experimental fringe processing.     

基于合肥先进光源的准直参考网络机械系统设计及其仿真分析

新一代粒子加速器中磁铁位置与姿态的准确测量和安装依赖于各项技术的综合运用。实现磁铁在全局坐标系中准确定位,并且快速精密安装测量,为了建造高亮度、低发射度的第四代同步辐射光源,国家同步辐射实验室开展了“合肥先进光源（HALF）”的预研工作。作为准直测量系统的重要研究内容,创新性地提出了准直参考网络方法。为了保证准直测量精度,对准直参考网络的机械系统本身的形变要求很高,通过ANSYS软件对机械系统整机进行了静力学仿真,根据分析结果对准直基准板进行了优化设计,使其满足工作条件要求。     

基于图像挖掘技术的车辆目标识别方法

在目前的图像处理技术发展现状中,图像挖掘技术是其中一项较为突出和新颖的技术分支。而随着日益庞大的图像数据信息处理量的要求增加,却没有一个有效的分析和处理技术,为此,如何解决大量数据的解析和处理问题是目前图像挖掘技术的主要方向。本文将着重研究图像挖掘技术的原理和其在目前社会中的应用情况。利用简析图像挖掘技术的基本原理分析其数据模型,探讨其所具备的基本功能以及在车辆目标识别上的应用和方法。总结出图像挖掘技术对图像中所存在信息的完全解读,挖掘图像中存在的隐形关联,而且随着图像挖掘技术的不断改进,其目标识别的功能可以应用到车辆管理模式当中。通过实验表明,此方法可以对目标图像中车辆数量和种类的辨识度达到80%以上。     

光电编码器单莫尔条纹测速方法

为了提高编码器的测速精度,研究了基于希尔伯特-黄变换的光电编码器单莫尔条纹测速方法。首先,利用AD采集编码器的单路莫尔条纹光电信号,并将信号序列通过EMD变换,滤除直流分量;然后,利用希尔伯特变换求出信号的相位变化,并通过差分运算求取信号的瞬时频率;最后,结合编码器的具体参数求取编码器的转速。实验结果表明:对某21位编码器进行测速实验,测速误差均方差由0.022 4 rad/s降低到0.013 4 rad/s。此方法测速稳定性高,抗干扰能力强,可用于速度精度要求较高的测速场合。     

基于条纹等值线相关的散斑条纹图处理新方法

在数字散斑干涉术中,通常由物体变形前后得到的两幅原始散斑场用相减方法来得到条纹图,并由相移后的多幅(三幅以上)条纹图来求取相位场。介绍了一种基于条纹等值线相关的条纹图生成新方法,并在此基础上提出了基于单幅干涉条纹图的相位场提取新方法和基于条纹等值线相关的单步相移新方法。实验结果表明,该方法具有良好的结果和发展前景。     

A novel method for identification of cotton contaminants based on machine vision

Foreign matter is easily mixed into cotton during picking, storing, drying, transporting, purchasing, and processing. These contaminants are difficult to remove in the spinning process and can cause yarn breakage, thus reducing efficiency of working. This paper proposed the new method based on machine vision to measure the contaminants in raw cottons. The color images of cottons with contaminants are acquired and divided three channels images. Intensity of illumination of cottons often is unstable because of the driving voltage of light source unsteady. The intensity of illumination of images should be corrected for measuring correction and precision. The Gamma adjustment function was adopted to correct non-uniform illumination for images. Through the experimental contrast, Gamma correction parameter is set as 0.8. The Otsu method is used to segment the image. After images of three channels’ information fusing, the contaminants of cotton samples can be correctly detected and cotton seeds also can be effectively inspected. The false detection ratio of the measuring system is less than 5%. The experimental results show the measuring system can meet with the requirement of the cotton's industry application.     

Study of mutual information multimodality medical image registration based on modified simplex optimization method

Because of a different imaging mechanism and highly complexity of body tissues and structures. Different modality medical images provide non-overlay complementary information. This has very important significance for multimodal medical image registration. Image registration is the first and key part of problem to be solved in the integrations. When the spatial position of two medical images is same, the registration could be achieved. For two CT and PET images, the principal axis method is adopted to achieve the rough registration. The modified simplex algorithm is employed to implement global search using the mutual information as similarity measure. The initial registration parameters are achieved through principal axis Based on the results of test, improved simplex method can adjust reflecting distance. Stepped-up optimization algorithm on the new experimental points through the methods of “reflection”, “enlargement”, “shrinkage” or “global systolic”. A mutual information registration based on modified simplex optimization method is presented in this paper to improve the speed of medical image registration.Results indicate that the proposed registration method prevents the optimizing process from falling into local extremum and improves the convergence speed while keeping the precision. The accurate registration of multimodal image with different resolutions is achieved.     

A fusion method for visible and infrared images based on contrast pyramid with teaching learning based optimization

This paper proposes a novel image fusion scheme based on contrast pyramid (CP) with teaching learning based optimization (TLBO) for visible and infrared images under different spectrum of complicated scene. Firstly, CP decomposition is employed into every level of each original image. Then, we introduce TLBO to optimizing fusion coefficients, which will be changed under teaching phase and learner phase of TLBO, so that the weighted coefficients can be automatically adjusted according to fitness function, namely the evaluation standards of image quality. At last, obtain fusion results by the inverse transformation of CP. Compared with existing methods, experimental results show that our method is effective and the fused images are more suitable for further human visual or machine perception.     

A novel denoising method based on Radon transform and filtered back-projection reconstruction algorithm

A novel denoising method based on Radon transform and filtered back-projection (FBP) image reconstruction algorithm was proposed. This method can be considered as a special mean filter on projection line, which is different from most of the traditional filters operated on adjacent templates that could bring serious blurs to images. The details of images processed by the proposed method can be preserved relatively complete and the denoising effect is satisfactory. To verify the denoising effect of the proposed method, the simulation was designed and carried out, and the image evaluation parameters were applied to analyze the denoising effect and the detail-preserving ability quantitatively. For further understanding of the proposed method, the basic denoising principle of this method was analyzed. Noise points and information points can be distinguished: the attenuation velocity of gray scale of noise points is faster than that of information points, which was verified by the experiment. The results of different parameters in the proposed method were compared and analyzed. Several kinds of traditional filters were compared with the proposed method, and the result shows that the proposed method is better than the traditional filters in the aspects of both denoising effect and detail-preserving ability. Apart from this, the proposed method is not particular about the kind of noise; therefore, it is a powerful method to deal with atypical noise, uncertain noise, and mixed noises.