The development of an automated PIV image processing software—SmartPIV

Since the popularity of digital particle image velocimetry technique (DPIV), many PIV image processing algorithms have been proposed. Amongst them, fast Fourier transform (FFT) Cross Correlation, Discrete Window Offset Cross Correlation, Iterative Multigrid Cross Correlation, Iterative Image Deformation Cross Correlation and cross correlation based particle tracking methods are widely used algorithms and have been extensively studied by researchers. All of these algorithms have their advantages and disadvantages in terms of computational load and measurement accuracy. To choose a suitable algorithm, researchers not only need to understand the complex principles of these algorithms, but also need to find out their applicable flow conditions. This could greatly increase work load for PIV users who focus more on flow structure itself instead of PIV algorithms. It is therefore necessary to develop a method which can choose PIV algorithms wisely according to the input PIV images. This paper firstly reviews the development of PIV algorithm with mainly focus on analysing advantages and disadvantages of six widely used algorithms. By using both synthetic and real PIV images, comparative studies are then carried out among these algorithms. The tests give a rate for the performance of the algorithms and provide a parameter to automatically separate pattern match and particle tracking algorithms. Based on qualitative and quantitative analysis, an automated PIV image processing method—SmartPIV is proposed and tested by both synthetic and real PIV images. For all the three test cases, the SmartPIV successfully picks the most suitable algorithm and gives very promising results.     

粒子图像测速（PIV）技术在烟丝流量检测中的研究

粒子图像测速技术（PIV）是一种全新的非接触式的,瞬时的,全场流速测量方法,广泛应用于流体力学中。本研究将PIV技术引入烟丝运动研究是一个尝试,旨在为烟丝流量的检测提供一个新的测量手段。通过分析烟丝在风送管道内的运动,利用PIV技术并结合PTV技术,采用图像处理得到烟丝的运动速度。粒子图像测速技术具有一定的优势,可以克服传统测量手段的不足。     

Digital image tiles: a method for the processing of large sections

Segmentation of large areas of light microscopic slides into N by N fields, and each of these fields into M digital image tiles, allows the scanning, storage and digital processing of large images. Any of the original N² fields or composites of M adjacent tiles can be recalled to the video display for analysis. Developed procedures for use on a microscope equipped with a precision scanning stage allow registration of the image coordinates (X-Y) for any original or composite field and the alignment of one of these fields along the depth (Z) axis by means of external, machined fiducial marks in serial sections. To facilitate work whenever unavoidable, we have incorporated methods for digital image panning and zooming (changes of magnification) and discuss their use and implications.     

Interactive image processing with an off-line minicomputer: organization,performance and applications

A recently established facility for interactive image processing is described, primarily from the point of view of the system's hardware organization and the special purpose software provided to support it. The performance of more general software (the ‘Semper’ system) in the new environment has been measured carefully, and found to be about 10 times its performance on our previous PDP 8/E computer; particular attention is given to the data management techniques crucial to the system's efficiency. Some current applications are illustrated, including high resolution image interpretation and image averaging of biological crystals.     

织物密度的数字图像检测方法

针对织物的纱线密度检测,提出一种对织物图像,信息进行检测的方法。通过数字相机获得织物图像,对织物图像进行最优二值化处理。利用像素黑白颜色区分织物上的纱线和间隙,通过扫描经线和纬线方向的像素颜色值获得纱线处像素颜色特性,从而计算出经线方向和纬线方向的纱线数目。根据各方向最大像素数得织物的大小,即可得知织物的密度。     

双图像传感器的球表面展开方法

钢球作为广泛应用的轴承组件,其表面质量直接影响轴承性能.在钢球表面缺陷自动检测中,钢球表面展开技术是核心,球表面能否充分展开直接决定了表面质量检测的准确性.目前发展的钢球表面展开技术仍存在机械结构复杂、展开不充分及随机性强的问题.基于计算机视觉技术研究了基于双图像传感器的球表面展开方法.首先,介绍基于双图像传感器的展开原理及装置.其次,建立数学分析模型,解算出完全展开整个球面所需要满足的参数条件;最后,设计实验完成全覆盖球表面的图像采集,验证理论模型结果.实验结果表明,在比例系数k为0.97,2个相机45.倾斜拍摄图像时至少需要拍摄4幅图像实现全覆盖展开,与理论模型分析结果一致.此方法在精确有效展开的同时,机械结构从复杂的二维运动简化为一维运动,提高了球表面展开的可靠性,具有广泛的应用前景.     

粗糙度关联的图像特征指标性能评价方法研究

当前基于机器视觉的粗糙度测量方法中,粗糙度关联的图像特征指标性能评价主要关注测量精度而忽略了指标的测量单调性、稳定性、效率以及灵敏度,而且大多数指标均是基于灰度图片而忽略了彩色图片多维性的优势。针对这样的问题提出采用视频质量专家课题组设计的视频质量预测模型评价体系来评价粗糙度关联的图像特征指标性能,设计了灵敏度与测量效率算法。根据红绿光源在不同粗糙度等级的样块表面产生的虚像混叠情况不同,提出了采用彩色图片能量差(ED)指标用于样块粗糙度测量。实验结果表明,采用的指标性能评价方法可以较为全面地表征指标的性能,所设计的ED指标较基于灰度图片的指标有较好的综合性能。     

Characterization of swirling-flow behavior in complex pipeline using bubble trajectory method with stereo particle tracking/image velocimetry

To understand the swirling-flow behavior in a complex pipeline geometry comprising an elbow and orifice, a quantitative flow visualization technique is introduced into the flow-field observation using a bubble trajectory method combined with stereo particle tracking/image velocimetry. For the chosen bubble sizes of approximately 2 mm un a pipe of 56 mm in diameter, their motion is correlated with the mean swirling flow, and when analyzed in a straight swirling flow, the bubbles cluster close to the point of maximum axial velocity for swirl intensities larger than 0.3. Subsequently, this experimental technique is applied to the characterization of a swirling flow in the Mihama pipeline model, for which the streamwise variation of the location of the maximum axial velocity and its magnitude are measured over the full range of the pipeline model. A spiral swirling flow is observed downstream of the elbow owing to the combined effect of the swirling and secondary flows in the elbow. The spiral swirling flow persists in the following straight pipe down to the orifice, where a highly accelerated flow with a high turbulence is generated towards the top wall of the pipe. This result agrees closely with the observation of pipe-wall thinning in the prototype Mihama pipeline.     

基于图像处理和改进A*算法的激光切割路径生成方法

为了提高纸类异形吸塑包装激光切割系统的自动化程度,实现加工路径智能生成功能,提出一种将图像处理与改进的A*算法相结合的激光切割路径自动生成方法。该方法以工业摄像机采集到的底板纸排料图像为基础,通过图像处理方法获得吸塑包装底板纸的轮廓轨迹路径,对各个轮廓轨迹进行排序,并获得各个轮廓加工的起始点,最后应用改进的A*算法生成各个轮廓间的辅助连接路径,实现激光头的自动避障,最终实现全部切割路径的自动生成,既进行了切割路径优化,又实现了加工路径的智能避障。详细介绍了该方法的原理及实现步骤,并进行了实际加工验证,效果良好。     

基于双光楔的像移补偿方法研究

车载扫描凝视系统在扫描成像时由于转台转动而引起的像移必然造成图像质量下降,进而导致虚警率升高,要消除像移必须进行像移补偿。基于像移产生原因以及双光楔对光束的导向模型,推解出因转台旋转而需补偿的光楔的初始位置及旋转速度,来补偿曝光阶段引起的像移。提出了基于双光楔的像移补偿的新方法。     

The three-dimensional point spread functions of a microscope objective in image and object space

The three-dimensional point spread function (3-D PSF) of an optical system in image space is distinguished from the 3-D PSF in object space and the relation between the two 3-D PSFs is derived. By using this relation one 3-D PSF can be easily obtained from the other. The 3-D PSFs are given in a single integral expression, which can be computed numerically. The results of this study can be used in 3-D image processing for microscopy and have been applied to the analysis of the diffusion of fluorescent molecules in a 3-D porous medium.     

基于机器视觉的平板式数粒机检测方法

以现代药品包装为应用背景,以新型平板式数粒机为研究平台,以机器视觉技术为研究重点,提出了一种基于机器视觉的平板式数粒机的检测方法。该检测方法可用于药品颗粒的缺陷检测和计数算法的研究。实验结果表明,基于机器视觉的平板式数粒机检测方法可达到用户的要求,实现高速度、高效率、高精度的在线检测计数。     

Measurement of the geometric features of a cutting tool edge with the aid of a digital image processing technique

For the further development of new machining systems such as flexible manufacturing systems (FMS), this paper reports on a new measuring system developed for the multi-purpose understanding of the geometric features of cutting tool edges having serious influences on the machining outputs. In this system, to detect three-dimensional (3D) features of the toolface and tool flank only from the two-dimensional (2D) microscopic observation of the toolface and to describe an overall 3D geometric feature of the tooledge as a digital 2D image as well as to enable inexpensive system development, two convenient measuring principles are used. These are the scanning optical section method for the toolface contour mapping and the cutting edge profile comparison method for the flank wear landwidth estimation. Based on these, experimental hardware was arranged and various processing softwares were developed. They were applied to an observation of the cutting edge wear development in some cylindrical turning experiments, to show that various effective cutting edge parameters could be easily extracted from the integrated toolface image recorded, and that sufficient accuracy and resolution for practical use could be obtained.     

The projection of a negatively-stained filamentous object down its central axis as revealed by image reconstruction from tilt series

Helical reconstructions of negatively stained biological objects contain distortions arising from filament flattening and the non-cylindrical profile of the stain envelope. Current methods of estimating flattening do not make full use of the information available in electron micrographs. We have applied the more rigorous approach of reconstructing the density profile from tilt series using digital image processing techniques. Tilt series were collected for tobacco mosaic viruses (TMV) and seven independent reconstructions were calculated using equatorial data out as far as ～1/9·3 nm^—1. They indicated that the filaments were flattened with an axial ratio of about 2·4:1, which was probably closer to 3:1 in the original specimen, because the limited resolution caused flattening to be underestimated. The stain envelope around TMV and some indication of the underlying carbon substrate were also observed. This information could enable correction factors for flattening to be developed, which could be useful when calculating helical reconstructions or indexing helical diffraction patterns. This method could also be extended to non-equatorial layer planes, which would provide three-dimensional information on a wide range of macromolecules that possess a one-dimensional repeat.     

A method to compensate for light attenuation with depth in three-dimensional DNA image cytometry using a confocal scanning laser microscope

A method to compensate for attenuation of detected light with increased depth of the collected optical section, and its application in three-dimensional (3-D) DNA image cytometry is described. The method is based on studying the stack of 2-D histograms that can be formed from each consecutive pair of sections in a stack of optical serial sections. An attenuation factor is calculated interactively and a new compensated section series is computed. Formalin-fixed paraffin-embedded rat tissue was stained with propidium iodide. Each cell nucleus is extracted by thresholding and its total intensity is calculated. The coefficient of variation (CV) of the total intensity of all cells in each stack is computed. For comparison the CV of the same cells is computed in the uncompensated stacks. This study shows a significantly lower CV for the compensated data, thus contributing to the accuracy of DNA quantification in 3-D DNA image cytometry.     

Photon event distribution sampling: an image formation technique for scanning microscopes that permits tracking of sub-diffraction particles with high spatial and temporal resolutions

In photon event distribution sampling, an image formation technique for scanning microscopes, the maximum likelihood position of origin of each detected photon is acquired as a data set rather than binning photons in pixels. Subsequently, an intensity-related probability density function describing the uncertainty associated with the photon position measurement is applied to each position and individual photon intensity distributions are summed to form an image. Compared to pixel-based images, photon event distribution sampling images exhibit increased signal-to-noise and comparable spatial resolution. Photon event distribution sampling is superior to pixel-based image formation in recognizing the presence of structured (non-random) photon distributions at low photon counts and permits use of non-raster scanning patterns. A photon event distribution sampling based method for localizing single particles derived from a multi-variate normal distribution is more precise than statistical (Gaussian) fitting to pixel-based images. Using the multi-variate normal distribution method, non-raster scanning and a typical confocal microscope, localizations with 8 nm precision were achieved at 10 ms sampling rates with acquisition of ~200 photons per frame. Single nanometre precision was obtained with a greater number of photons per frame. In summary, photon event distribution sampling provides an efficient way to form images when low numbers of photons are involved and permits particle tracking with confocal point-scanning microscopes with nanometre precision deep within specimens.     

Digital image processing as a tool to monitor biomass growth in Aspergillus niger 3T5B8 solid-state fermentation: preliminary results

The estimation of biomass is an essential parameter for controlling fermentation processes. However, monitoring biomass growth in filamentous fungi solid‐state fermentation is laborious. The aim of this study was to provide a better insight into the monitoring of biomass growth in Aspergillus niger 3T5B8 solid‐state fermentation using a digital image‐processing technique. The images were acquired with a stereomicroscope and a digital camera, and processed using KS400 software. Growth was evaluated every 24 h for 5 days, and quantified as the total area occupied by the hyphae. The correlation between the results of the proposed methodology and the polygalacturonase data was greater than 0.9, showing that a direct and linear relationship can be expected among these parameters. This work indicates that the digital processing technique can be used for indirect biomass estimation in a solid‐state fermentation process.     

Multiphoton fluorescent images with a spatially varying background signal: a ML deconvolution method

By means of multiphoton laser scanning microscopy, neuroscientists can look inside the brain deeper than has ever been possible before. Multiphoton fluorescent images, as all optical images, suffer from degradation caused by a variety of sources (e.g. light dispersion and absorption in the tissue, laser fluctuations, spurious photodetection and staining deficiency). From a modelling perspective, such degradations can be considered the sum of stochastic noise and a background signal. Among the methods proposed in the literature to perform image deconvolution in either confocal or multiphoton fluorescent microscopy, Vicidomini et al. (2009) were the first to incorporate models for noise (a Poisson process) and background signal (spatially constant) in the context of regularized inverse problems. Unfortunately, the so-called split-gradient deconvolution method (SGM) they used did not consider possible spatial variations in the background signal. In this paper, we extend the SGM by adding a maximum-likelihood estimation step for the determination of a spatially varying background signal. We demonstrate that the assumption of a constant background is not always valid in multiphoton laser microscopy and by using synthetic and actual multiphoton fluorescent images, we evaluate the face of validity of the proposed method, and compare its accuracy with the previously introduced SGM algorithm.