激光投影显示中二次散射散斑抑制方法

在光学投影系统中,激光经各种元件散射后在投影屏上形成一次散射散斑,投影屏对激光的再次散射,经人眼成像后在视网膜上形成二次散射散斑.在激光投影系统的照明系统中,引入位相调制器调制照明光束,可抑制在投影屏平面上的一次散射散斑,和投影屏二次散射后在人眼视网膜上的二次散射散斑.通过简化的投影系统,对二次散射散斑形成和抑制进行了理论分析,获得了二次散射散斑抑制的条件和抑制后散斑衬度的规律,并进行了仿真和实验验证.理论结果表明,在一定条件下,一次散射散斑与二次散射散斑的衬度变化规律相同.对简化模型进行了仿真计算,得到在投影屏上的像面散斑衬度为0.0096,在探测器平面上的二次散射散斑的衬度为0.019,表明位相板调制投影系统照明光束能抑制一次散射散斑和二次散射散斑.对理论和仿真结果进行了实验验证.     

积分球内壁漫射照度分布的近似矩阵计算法

本文推导了位于积分球中心处的光源在球内壁及挡屏表面的漫射照度分布的近似矩阵计算方法。此计算可归结为根据积分球的基本参数确定“光通量交换系数矩阵”的矩阵元问题。 对几种不同光强空间分布的光源在积分球内壁产生的漫射照度分布进行了计算,并将对两个光源的计算结果与用R.Brown的数值法的结果作了比较,符合较好。     

散斑干涉条纹图的总变分去噪方法

去除散斑条纹图中的噪声是电子散斑干涉测量技术的关键问题.提出将总变分图像去噪方法应用于电子散斑干涉条纹图滤波过程中,并对保真系数进行了改进.用总变分模型定义图像的能量函数,利用变分法求得满足能量函数的最优解,将图像去噪过程转化为求解偏微分方程的过程.分别对计算机模拟的条纹图和实验获得的条纹图进行了测试,定性和定量分析的结果表明该技术能够在显著滤波的同时保持条纹的对比度.     

基于积分球反射法的面辐射源发射率分布测量研究

发射率分布测量是评价大口径辐射源辐射均匀性的重要基础，但目前针对相关参数的研究较为匮乏。基于全半球激光积分反射方案，设计搭建了基于积分球反射法的红外辐射源发射率分布特征测量系统；开展了测量系统的性能研究，评价了激光光源子系统的稳定性，并在3 W的激光器功率下开展了面辐射源发射率分布特征测量实验。结果表明：建立的测量系统的稳定性良好，以标准金板表面为研究对象，多次测量结果的重复性为0.30%;开展了碳基面辐射源发射率分布实验测量，获得面辐射源发射率的分布云图，发射率的均匀性为98.1%。     

基于光泽分析的分光测色仪SCI误差修正模型

在对相同材质,不同光泽的物体表面进行颜色测量时,为了去除表面光泽对颜色测量产生的影响,多选择漫射照明、8?观察角、包含镜面反射光的照明观测条件。在理想情况下,由于积分球对照明光线的匀化,测量结果不会受到材料表面光泽的影响。但是在实际仪器结构设计中,由于测量结构设计的限制导致相同光谱反射率,不同表面光泽的测试样品颜色测量结果不同。文章从理论上分析了漫射照明、8?观察角、包含镜面反射光的照明观测条件下不同光泽材料表面测量产生误差的原因,设计了一种可以同时测量颜色数据和光泽数据的测量结构,提出了一种根据被测材料表面光泽数据对SCI测量数据进行修正的矫正模型,并设计相关实验进行验证。实验结果证明,应用该矫正模型对测量结构进行修正可以显著减小该测量误差。     

探测器响应度不均匀性对测量LED平均发光强度的影响

使用响应度分布不均匀的探测器来测量光分布不均匀LED的平均发光强度时,其测量结果可能会引入显著的测量误差。设计实验装置对3种不同类型的探测器的响应度分布进行测量,结果表明带光漫射器的光度探测器响应度均匀性很差,这样的光度探测器用于测量一种白光LED平均发光强度时,响应度不均匀引起的测量误差可达2.0%。类似于光谱失配修正方法,给出了对探测器响应度不均匀性评价的方法以及响应度不均匀性评价因子c的表达式,并建议在进行LED平均发光强度测量时,应避免使用带光漫射器的光度探测器。     

电子错位散斑干涉系统中错位量的研究

电子错位散斑检测系统中,错位量对测量精度、灵敏度以及条纹对比度有很大影响。本文介绍了电子错位散斑干涉原理,研究了错位量与测量精度、灵敏度和条纹对比度之间的对应关系,并利用MATLAB模拟出不同错位量下干涉条纹图,将错位散斑模拟条纹图与理论分析有效结合,总结出选取错位量的方法,并将其应用于轮胎变形检测实验,取得了良好的实验效果。本文研究工作对无损检测中错位量定量选取具有实际指导意义。     

旋转柱面产生动态散斑的统计特性分析

高斯光束照射到以角速度ω 旋转的圆柱体表面时,反射空间将出现的动态散斑随着被测表面的运动连续变化,这是一个随机过程。研究了当旋转圆柱体表面满足弱散射体条件时,在菲涅尔衍射场形成的动态散斑的统计特性;给出了几种特定情况下描述动态散斑时间-空间相关性质的参数——动态散斑的空间相关长度,动态散斑的相关时间,动态散斑的平移距离和相关距离。这些参数表明动态散斑的统计特性与圆柱体曲率半径、入射光束、表面微观形貌、物体旋转角速度、光学几何结构因素有关;依据参数分析了动态散斑运动形式,动态散斑纯沸腾运动取决于观察面到散射屏出射平面的距离,投射到散射屏出射平面上的照明光波波面的曲率半径和散射体的曲率半径。     

圆周式脉冲喷吹对滤筒清灰均匀性的影响

为了探究圆周式脉冲喷吹对滤筒清灰均匀性的影响，改变喷吹压力，研究最优喷吹距离下的喷嘴与内置旋转器2种不同的脉冲喷吹方式下，侧壁压力沿滤筒轴向和水平圆周方向上的分布特性。结果表明：在使用普通喷嘴时，沿滤筒轴向方向至上向下的侧壁压力逐渐增大，下部压力大于中、上部；在使用内置旋转器时，滤筒侧壁压力分布为上部压力小，中部和下部压力相差不大。在滤筒水平圆周方向上，侧壁压力峰值并不是完全对称，相较与普通喷嘴，内置旋转器在水平圆周方向的侧壁压力峰值差均不超过100 Pa,且各测点压力标准偏差较普通喷嘴显著降低48.14%～95.38%,说明圆周式脉冲喷吹均匀性更优。圆周式脉冲喷吹能明显提升滤筒中部清灰强度和在滤筒轴向和水平圆周方向上的清灰均匀性，同时减小脉冲气流对底部的冲击，改善滤筒下部滤料破损的问题。     

球冠型入射光学系统中等效辐射平面位置的计算

为了满足包括太阳直射和天空散射在内的2π球面度立体角范围的入射光线的测量需求,要求太阳紫外光谱辐射测量装置的入射光学系统必须具备较好的余弦响应特性。研制的入射光学系统由聚四氟乙烯积分球、磨砂石英球冠型余弦漫射器和修正环组成,积分余弦误差〈f2〉=0．94％。引入等效辐射平面接收器的概念,根据漫射器的几何形状和上面的光谱辐射照度分布以及接收系统的角度响应特性,采用数学分析方法对漫射器和积分球组合入射光学系统的等效辐射平面位置进行了精确计算,分析了影响等效辐射平面位置的因素,并采用实验统计方法进行了验证。     

基于神经网络的红外图像实时去斑方法

在分析红外图像斑纹产生机理基础上,提出利用人眼视网膜自适应调节原理的去斑方法。去斑时,根据距离不同作用不同原则,对中心及其周围像素分别予以不同权重;将斑纹信息加入求解过程,能有效快速去斑;去斑后,采用基于阈值的直方图规定化方法,以弥补对比度可能降低情况。研制出的DSP去斑系统实现了实时去斑功能。     

利用积分球对CCD线性和面均匀性的标定

积分球对CCD(Charge-coupled Device)的标定,主要是利用积分球光源具有较好的均匀性、稳定性以及精度高的特点,通过CCD采集积分球光源的图片,将积分球光源亮度转换为CCD拍摄图像的灰度,通过对采集图片灰度信息的提取,得出了CCD标定的各项参数。CCD线性标定试验的结果表明:在CCD快门值固定时,光源亮度的变化和图像灰度呈线性关系,并且在转换后的不同灰度值区段,线性度有一定的差别:在中值区,线性度最好,低值区次之,高值区最差;在光强一定的情况下,CCD快门值的改变和采集图像的灰度也呈线性关系。均匀性标定的试验结果表明:CCD的光电响应的非均匀性是随着快门值和灰度的增加而减小的,但最终趋于一个较稳定的值。     

Speckle reduction using orthogonal arrays in laser projectors

We propose using a two-level (-1 and +1 as variables) orthogonal array (OA) to generate a binary phase diffuser for speckle reduction in laser projection displays. Compared with the Hadamard matrix, the diffuser generated from OA is more flexible. The speckle contrast ratio (CR) when introducing the binary phase diffuser at an intermediate image plane within the projector is calculated, and the minimum speckle CR can be achieved by finite step change of the diffuser patterns. With Kronecker algebra, the two-dimensional diffuser can also be replaced by two one-dimensional diffusers with the same function, and it can be implemented into the laser projector electronically and easily.     

Proposed Framework for Detection of Breast Tumors

Computer vision is one of the significant trends in computer science. It plays as a vital role in many applications, especially in the medical field. Early detection and segmentation of different tumors is a big challenge in the medical world. The proposed framework uses ultrasound images from Kaggle, applying five diverse models to denoise the images, using the best possible noise-free image as input to the U-Net model for segmentation of the tumor, and then using the Convolution Neural Network (CNN) model to classify whether the tumor is benign, malignant, or normal. The main challenge faced by the framework in the segmentation is the speckle noise. It’s is a multiplicative and negative issue in breast ultrasound imaging, because of this noise, the image resolution and contrast become reduced, which affects the diagnostic value of this imaging modality. As result, speckle noise reduction is very vital for the segmentation process. The framework uses five models such as Generative Adversarial Denoising Network (DGAN-Net), Denoising U-Shaped Net (D-U-NET), Batch Renormalization U-Net (Br-U-NET), Generative Adversarial Network (GAN), and Nonlocal Neutrosophic of Wiener Filtering (NLNWF) for reducing the speckle noise from the breast ultrasound images then choose the best image according to peak signal to noise ratio (PSNR) for each level of speckle-noise. The five used methods have been compared with classical filters such as Bilateral, Frost, Kuan, and Lee and they proved their efficiency according to PSNR in different levels of noise. The five diverse models are achieved PSNR results for speckle noise at level (0.1, 0.25, 0.5, 0.75), (33.354, 29.415, 27.218, 24.115), (31.424, 28.353, 27.246, 24.244), (32.243, 28.42, 27.744, 24.893), (31.234, 28.212, 26.983, 23.234) and (33.013, 29.491, 28.556, 25.011) for DGAN, Br-U-NET, D-U-NET, GAN and NLNWF respectively. According to the value of PSNR and level of speckle noise, the best image passed for segmentation using U-Net and classification using CNN to detect tumor type. The experiments proved the quality of U-Net and CNN in segmentation and classification respectively, since they achieved 95.11 and 95.13 in segmentation and 95.55 and 95.67 in classification as dice score and accuracy respectively.     

Detection of the Object Velocity Using Doubly-scattered Dynamic Speckles Under Gaussian Beam Illumination

Abstract

The dynamic properties of doubly-scattered speckles produced at the image plane have been investigated using a scattering model that consists of a coherent Gaussian beam, a cascade of two moving diffusers and a single imaging lens. Dependence of the fluctuation speed of time-varying image speckles on the velocities of the diffusers is found to change with the size of illuminating speckles and the width of the point-spread function of the imaging lens. When the point-spread function and the focal position satisfy certain conditions, three kinds of velocity information—the velocity of each diffuser, the average velocity of the diffusers and the velocity difference between the diffusers—can be obtained by measuring a temporal correlation length of the time-varying speckle intensity. Experimental results confirm the theoretical predictions.     

数字散斑相关技术在高分子材料蠕变测试中的应用

将数字散斑相关计算与压痕硬度测试相结合,探讨在洛氏硬度计上测试高分子材料的蠕变性。首先使用CCD连续采集压头移动图像,然后进行散斑计算,根据计算结果绘制出压头位移-时间曲线,据此建立压入深度与时间、材料的蠕变与时间以及应力与时间之间的关系式,最后通过线性拟合得到被测材料的蠕变指数。通过对高密度尼龙、有机玻璃及环氧树脂的试验证实,该方法是可行的,试验得到三种材料的蠕变指数分别为0.12、0.012、0.07。试验中还发现,根据深度计算的硬度值与通过表盘读出的硬度值是不同的,在比较不同高分子材料的硬度时,前者比后者更合理。     

High resolution speckle interferometry using virtual speckle pattern produced by information of deformation process

A high resolution new fringe analysis method for ESPI with only one camera is proposed by using features of speckle interferometry in a deformation process of a measured object. The profile of intensity of each speckle of the speckle patterns in the deformation process is analyzed by the Hilbert transform. A virtual speckle pattern for creating a carrier fringe image is produced artificially by using the information of profiles of intensities of speckles. The deformation map of the measured object can be detected by the virtual speckle pattern in an operation based on the spatial fringe analysis method. Experimental results show that the difference between the results by the new and the ordinary methods is 0.1 rad as standard deviation. From the results, it is confirmed that the high resolution measurement can be performed by this method the same as compared to the ordinary measurement method which needs to employ three speckle patterns.     

Optical characterization of ophthalmic lenses by means of modulation transfer function determination from a laser speckle pattern

A method is presented for measuring the modulation transfer function of ophthalmic lenses by use of the generation of laser speckle with an integrating sphere. The measurements are performed with a rectangular double-slit aperture positioned at the output port of the integrating sphere. The distance between the lens and the detector determines the spatial frequency being tested; therefore high frequencies are tested close to the lens and low frequencies are tested far away from the lens. We can conclude that the double-slit method can be a versatile technique for comparing the optical quality of ophthalmic lenses from different makers.     

Ultrasound Speckle Reduction Based on Histogram Curve Matching and Region Growing

The quality of ultrasound scanning images is usually damaged by speckle noise. This paper proposes a method based on local statistics extracted from a histogram to reduce ultrasound speckle through a region growing algorithm. Unlike single statistical moment-based speckle reduction algorithms, this method adaptively smooths the speckle regions while preserving the margin and tissue structure to achieve high detectability. The criterion of a speckle region is defined by the similarity value obtained by matching the histogram of the current processing window and the reference window derived from the speckle region in advance. Then, according to the similarity value and tissue characteristics, the entire image is divided into several levels of speckle-content regions, and adaptive smoothing is performed based on these classification characteristics and the corresponding window size determined by the proposed region growing technique. Tests conducted from phantoms and in vivo images have shown very promising results after a quantitative and qualitative comparison with existing work.     

Speckle reduction in optical coherence tomography by adaptive total variation method

An adaptive total variation method based on the combination of speckle statistics and total variation restoration is proposed and developed for reducing speckle noise in optical coherence tomography (OCT) images. The statistical distribution of the speckle noise in OCT image is investigated and measured. With the measured parameters such as the mean value and variance of the speckle noise, the OCT image is restored by the adaptive total variation restoration method. The adaptive total variation restoration algorithm was applied to the OCT images of a volunteer’s hand skin, which showed effective speckle noise reduction and image quality improvement. For image quality comparison, the commonly used median filtering method was also applied to the same images to reduce the speckle noise. The measured results demonstrate the superior performance of the adaptive total variation restoration method in terms of image signal-to-noise ratio, equivalent number of looks, contrast-to-noise ratio, and mean square error.