光学显微镜自动聚焦的技术研究

在对普通光学显微镜进行一定改装的基础之上 ,设计了一套显微镜自动聚焦系统 ,并且给出了图像的灰度差分绝对值之和算子 ,解决了自动聚焦过程中是否正确聚焦的判断问题。最后还给出了一套基于启发式搜索算法的聚焦搜索策略 ,以加快焦平面的搜索。     

基于液体透镜的自动变焦扫描镜头的设计与验证

由于定焦镜头自身的景深问题使传统的扫码器不具备大的工作距离。为了满足工作人员在不更换扫描器的情况下既能实现近距离的信息读取又能实现十几米外的信息读取,研发了一款基于电润湿（electrowetting on dielectric,EWOD）液体透镜的自动变焦扫描镜头。通过调整液体镜片形状来实现镜头参数特别是焦距的变化,使得从近到远的所有对象都能成像在焦面上,从而达到自动变焦的效果。通过Zemax软件设计出一款成像范围为80 mm至无穷远的自动变焦扫描镜头,并完成了成像质量的验证。     

光学显微成像系统图像清晰度评价函数的对比

图像清晰度评价函数是评价各类成像系统成像质量的一个关键函数,为找到合适的图像清晰度评价算法,采用MATLAB软件对16种适用于光学显微成像系统的清晰度评价函数进行仿真,定量分析了不同算法的灵敏度、单峰性、无偏性以及运算速度。实验表明:Laplacian函数具有较高的单峰性、无偏性和灵敏度;存在高斯噪声时,Brenner函数、Tenengrad函数和基于Prewitt算子的函数以及中值滤波-离散余弦函数稳定性好;而存在椒盐噪声时,Roberts函数综合性能最优。     

A novel autofocusing method using the angle of hilbert space for microscopy

Autofocusing technology is indispensable for routine use of microscopes on a large scale in biological field. The autofocusing method using the angle of Hilbert space is brought forward to measure whether the image is focused or not. The angle of Hillbert space can be used to evaluate accurately the similarity degree of two images. The experiment results show that the autofocusing method can decrease the computational cost and get accuracy for real‐time biological and biomedical images with noise robustness. The focus curves are smooth and possess the unimodality, the monotonicity and the symmetry. Compared with other classic and optimum focus method, the Hilbert method demonstrates its robustness to noise and can improve the focus speed. The experiments showed that the proposed method can increase the overall performance of an autofocus system and has strong applicability in various autofocusing algorithms. Microsc. Res. Tech. 77:289–295, 2014. © 2014 Wiley Periodicals, Inc.     

Application of the "imaging plate" to TEM image recording

The "imaging plate" is a highly sensitive image recording plate for X-ray radiography, which is coated with photo-stimulable phosphor. The imaging plate is exposed to electrons in a transmission electron microscope. Its fundamental properties (sensitivity, dynamic range and sharpness) have been estimated in detail. Also, the image quality of the imaging plate for some specimens in a transmission electron microscope has been estimated. As a result, it has been ascertained that the imaging plate has superior properties and high practicability as an image recording material in a transmission electron microscope.     

手机模组生产线被动自动对焦技术研究

自动对焦系统在手机中得到越来越广泛的应用。根据手机镜头焦距短,可调范围窄等特点,全面分析了噪声,视场,清晰度评价函数,窗口选取等各种因数的影响。构建了适于生产线检测的自动对焦系统,并成功地实现快速调焦。     

A simple and stable autofocusing protocol for long multidimensional live cell microscopy

Focus maintenance is a challenging problem in multidimensional wide‐field microscopy. Most automated microscopes use software algorithms, which are applied to z‐sections of the object, to select for the plane with the best signal to noise ratio. When applied automatically in multidimensional imaging applications, autofocus routines significantly increase light exposure and can become cytotoxic if applied too frequently. In addition, automated focusing procedures can readily focus on unwanted high contrast objects. By labelling a defined position with a fluorescent marker, we were able to separate the focusing procedure from the actual image acquisition positions and therefore overcome some of the major drawbacks of routine autofocus procedures. To implement this method in a multidimensional acquisition experiment, we created a visual basic‐based program, which is run prior to each image acquisition. This technique allows tight control of focus whilst keeping light toxicity in live cell imaging experiments to a minimum.     

基于图像清晰度评价的跟踪望远镜自动调焦算法研究

为了减小跟踪望远镜调焦时间,分析了自动调焦的光学原理及数字图像处理相关技术,提出一种适合跟踪望远镜的实时自动调焦算法。该算法基于对图像清晰度的评价,通过步进电机驱动次镜移动来搜索最佳成像位置,并且综合了全局搜索法与传统爬山法的优点。在实验中,完成了对远处静态目标自动对焦,有效地避免了局部峰值导致的对焦失败,在保证系统调焦精度的前提下使对焦速度小于3s。     

A robust focusing and astigmatism correction method for the scanning electron microscope—Part II: Autocorrelation-based coarse focusing method

This paper describes the development of a new coarse focusing algorithm for the scanning electron microscope (SEM). The algorithm is based on a new focus parameter that has been developed for quantifying the sharpness of an image. This parameter is found to be more robust to noise compared with other conventional focus parameters. A peak detection technique is also incorporated to shorten the number of iterations needed for the coarse focusing. Results show that the coarse focusing algorithm is able to bring a defocused and astigmatic image to either the best focus, the upper line focus, or the lower line focus in fewer iterations compared with the conventional approach in which the full focus range is searched.     

Influence of Non-Gaussian-Distributed Surface Roughness on the Static Performance of Slider Bearings

An investigation on full fluid film lubrication assuming non-Gaussian-distributed surface roughness has been conducted. A typical slider bearing is chosen as the research object. Edgeworth expansion containing skewness and kurtosis is introduced to approximate the roughness density function. Using Christensen's stochastic roughness model, effects of roughness direction and non-Gaussian distribution properties on the working performance of slider bearings have been quantitatively analyzed. The results show that the variation range of working performance caused by skewness and kurtosis is up to 9.82%. Effects of skewness and kurtosis on the performance are nontrivial and should not be neglected. Compared to the Gaussian distribution, Edgeworth series can represent physical rough surfaces more accurately. Though the effects of skewness and kurtosis on the working performance are complicated, some laws can still be found. For example, large skewness decreases the load capacity, whereas large kurtosis reduces friction force. According to the results, we can choose certain machining processes that can produce the desired surface roughness.     

Frequency discriminators for the characterization of narrow-spectrum heterodyne beat signals: application to the measurement of a sub-hertz carrier-envelope-offset beat in an optical frequency comb

We describe a radio-frequency (RF) discriminator, or frequency-to-voltage converter, based on a voltage-controlled oscillator phase-locked to the signal under test, which has been developed to analyze the frequency noise properties of an RF signal, e.g., a heterodyne optical beat signal between two lasers or between a laser and an optical frequency comb. We present a detailed characterization of the properties of this discriminator and we compare it to three other commercially available discriminators. Owing to its large linear frequency range of 7 MHz, its bandwidth of 200 kHz and its noise floor below 0.01 Hz(2)/Hz in a significant part of the spectrum, our frequency discriminator is able to fully characterize the frequency noise of a beat signal with a linewidth ranging from a couple of megahertz down to a few hertz. As an example of application, we present measurements of the frequency noise of the carrier envelope offset beat in a low-noise optical frequency comb.     

磨机负荷的磨音多频带检测研究与开发

对磨音的频谱分析。发现与磨机负荷相关的磨音频带范围比较大,从500Hz到4kHz左右。在此基础上本文设计多组带通滤波器将磨音信号的频域划分多个频带。对磨机的各个状态（空磨、正常、饱磨）在不同的频带内检测,经相关软件分析处理,确定磨机的工作状态以及磨机的负荷量。     

The influence of the regularization parameter and the first estimate on the performance of Tikhonov regularized non-linear image restoration algorithms

This paper reports studies on the influence of the regularization parameter and the first estimate on the performance of iterative image restoration algorithms. We discuss regularization parameter estimation methods that have been developed for the linear Tikhonov–Miller filter to restore images distorted by additive Gaussian noise. We have performed experiments on synthetic data to show that these methods can be used to determine the regularization parameter of non-linear iterative image restoration algorithms, which we use to restore images contaminated by Poisson noise. We conclude that the generalized cross-validation method is an efficient method to determine a value of the regularization parameter close to the optimal value. We have also derived a method to estimate the regularization parameter of a Tikhonov regularized version of the Richardson–Lucy algorithm.   These iterative image restoration algorithms need a first estimate to start their iteration. An obvious and frequently used choice for the first estimate is the acquired image. However, the restoration algorithm could be sensitive to the noise present in this image, which may hamper the convergence of the algorithm. We have therefore compared various choices of first estimates and tested the convergence of various iterative restoration algorithms. We found that most algorithms converged for most choices, but that smoothed first estimates resulted in a faster convergence.     

自动影像测量系统关键算法

为了实现对工件的自动影像测量,建立了自动影像测量系统。对该系统所采用的图元识别、图元测量、基于自动聚焦原理的高度测量等算法进行研究。根据圆形和矩形图元的面积和真圆度等特征参数介绍了图元识别算法。以直线和圆形图元为例分析了典型图元的测量算法,即在提取图元边缘点的基础上进行图元拟合。在分析比较能量谱等聚焦评价方法的性能的基础上,说明了采用自动聚焦原理进行高度测量的算法。最后,介绍了系统比例尺的设定方法以及光栅尺读数的误差补偿方法。实验结果表明:比例尺的标定精度为0.5 μm;图元的测量精度在微米级;高度测量精度为0.035 mm,基本满足自动影像测量的稳定可靠、精度高、抗干扰能力强等要求。     

Optical microscopy with flexible axial capabilities using a vari‐focus liquid lens

The axial imaging range of optical microscopy is restricted by its fixed working plane and limited depth of field. In this paper, the axial capabilities of an off‐the‐shelf microscope is improved by inserting a liquid lens, which can be controlled by a driving electrical voltage, into the optical path of the microscope. First, the numerical formulas of the working distance and the magnification with the variation of the focus of the liquid lens are inferred using a ray tracing method and conclusion is obtained that the best position for inserting a liquid lens with consistent magnification is the aperture plane and the rear focal plane of the objective lens. Second, with the liquid lens embedded in the microscope, the numerical relationship between the magnification and the working distance of the proposed flexible‐axial‐capability microscope and the liquid lens driving voltage is calibrated and fitted using the inferred numerical formulas. Third, techniques including autofocus, extending depth of field and three‐dimensional imaging are researched and applied, improving the designed microscope to not only flexibly control its working distance, but also to extend the depth of field near the variable working plane. Experiments show that the presented flexible‐axial‐capability microscope has a long working distance range of 8 mm, and by calibrating the magnification curve within the working distance range, samples can be observed and measured precisely. The depth of field can be extended to 400 μm from the variable working plane and is 20 times that of the off‐the‐shelf microscope.     

V-shaped metal-oxide-semiconductor transistor probe with nano tip for surface electric properties

We design and fabricate a V-shaped metal-oxide-semiconductor (MOS) transistor probe with the focused-ion-beam (FIB) nano tip to measure surface electric properties. The V-shaped structure is selected for its better lateral stiffness, and the specific dimensions are determined using the parallel beam approximation (PBA). The deposition conditions for the nano tip are also investigated for better tip sharpness. The high working frequency of the MOS transistor improves the scanning speed and the high sensitivity reduces the additional equipment required. The detection properties of the device are investigated with PZT poling patterns. The measured results show well-defined patterns, promising that the device can detect surface electric properties with high sensitivity and high working frequency.     

基于导向滤波Retinex和自适应Canny的图像边缘检测

机器视觉识别常用金属制品边缘时,表面亮度不均易导致边缘误识别,且传统的边缘检测算法去噪的同时也抑制了大量边缘信息,降低了边缘检测质量。本文提出一种基于导向滤波Retinex和自适应Canny的图像边缘检测算法。该算法采用基于导向滤波的Retinex法得到金属制品图像的反射分量,通过加权分布的自适应伽马校正提升反射分量图像对比度;然后,采用自适应各向异性扩散滤波对增强后图像进行去噪处理,抑制增强后图像的噪声及低对比度纹理,再采用改进四方向Sobel梯度模板提取图像边缘;最后沿用传统Canny算法的非极大值抑制及双阈值分割进一步细化边缘。实验结果表明,新算法检测典型金属小零件时,图像锐度指标由原图的47.11提升至68.39,金属表面的亮度标准差从原图的44.76下降至20.16;噪声指标从原图的1.1下降到0.15左右,并且在去噪的同时较好地保留了图像边缘锐度。新方法有效改善了金属表面图像因亮度不均导致的边缘误识别问题,并且提取的边缘连接性较好。     

Analysis of quantities influencing the performance of time synchronization based on linear regression in low cost WSNs

Time synchronization is a key feature of Wireless Sensor Networks (WSNs). In low cost WSNs this is a very challenging issue since the general employment of a large number of nodes, characterized by low power and limited energy resources. Therefore, in such contexts, the adoption of synchronization algorithms is preferable to the adoption of GPS-based solution because of its high energy consumption, high cost and poor performance in indoor environment. An even increasing number of papers dealing with the design and the implementation of protocol-based techniques for synchronization can be found in literature.These synchronization algorithms can be divided into three main categories: one way messaging, two ways messaging and consensus based synchronization. Among the others, those based on the one way messaging and, in particular, on the adoption of regressive algorithms are widely used in many application contexts. Focusing the attention on this class of synchronization algorithms, this paper proposes a deep performance analysis aimed at highlighting the sensitivity of the regression-based algorithms to some factors that influence the accuracy in typical low cost applications, such as the finite resolution of the local timing clock, the presence of clock drift, clock high frequency noise and low frequency noise, the presence of latencies due to the radio devices, the presence of latencies due to the microcontroller device. The main goal is to evaluate the effect of each one of these factors of influence on the overall synchronization performance. To these aims, suitable analyses both in simulation environment and on real nodes have been carried out.     

基于窗口模式的自动聚焦算法

随着数字智能化技术的不断成熟与提高,自动聚焦技术也日益完善并广泛应用。简单介绍了目前一些经典的图像清晰度评价函数,并提出一种改进的拉普拉斯算子的图像清晰度评价函数。该算法把整幅图像分成不同的窗口,提出一个新的概念——兴趣参数,并引入至不同窗口。经过与其它一些经典算法进行大量的实验研究对比,证明该算法在聚焦的适时性、灵敏性和准确性上都具有一定的优越性。     

Sound quality change of the automotive engine noise by variation of engine oil condition

Sometimes, engine oil is referred to as a factor that affects engine sound and driving feeling. To investigate the difference of engine noise according to the engine oil conditions in the viewpoint of sound quality, the interior and exterior sound of middle-class sedan with gasoline engine was compared under the different oil conditions. Objective analysis was conducted to find the existence of any appreciable change in psychoacoustic attributes. Loudness, sharpness, and roughness are observed as the important sound quality metrics. It was observed that the noise differences were induced by the oil property, temperature and used time. Basically, the dramatic difference is rarely observed with the difference of initial property of oil. According to change of temperature, lower loudness is observed at the high temperature condition. Comparing new and used oils, the relatively high loudness was observed at idle condition after replacing oil, especially in the low frequency range.