基于ARM7处理器的快速聚焦方法

快速、准确地自动聚焦是获取高质量图像信息的前提。现对基于ARM7处理器和CCD图像传感器的自动聚焦系统进行研究,对模拟视频信号滤波提取高频分量作为判据的方法进行探讨,根据实际需要进行滤波选频和带宽选择,对系统实现中的关键技术进行了详尽的分析讨论。同时,针对系统在自动聚焦过程中实际出现的问题,对聚焦评价函数和搜索策略进行了优化,使系统的聚焦更加准确,并给出相应的实验结果。实验表明,该方法提高了聚焦的精度和速度,并且已成功应用于显微镜自动调焦系统中。     

一种全自动显微镜快速聚焦方法

自动聚焦技术是全自动控制显微镜系统的核心部分,主要解决的问题是如何提高聚焦的精度和速度,其中聚焦评价函数用来衡量图像是否聚焦。通过对几种聚焦评价函数的仿真实验对比分析,以及结合实际工程应用,提出一种直接截取图像的视频信号进行实时处理的聚焦方法,并对其中的关键技术分析、实验。实验表明:该方法提高了聚焦的精度和速度,并且它已成功应用于显微镜自动调焦系统中。     

基于CPLD的高分辨力视频展台快速自动聚焦方法及实现

文中设计了一种基于复杂可编程逻辑器件(CPLD)和专用视频处理芯片的高分辨力快速自动聚焦视频展台。把显微镜的快速自动聚焦算法应用在教学视频展台上,具有实现简单、精度高、聚焦快等特点,利用CPLD编程的灵活性的特点进行设计,加快了数据处理的速度,节约了硬件上的成本。实验表明,该系统聚焦速度快、精度高、图像效果较好。     

自动化便携式铁谱仪的设计与实验研究

设备油液中的磨粒携带的各种特征信息是设备进行故障诊断与维护的重要依据，铁谱仪是分析研究机械设备磨损状态的专用设备。为满足铁谱仪自动化以及制谱分析过程快捷方便的要求，设计了一套便携式铁谱仪系统。该铁谱仪采用单片机控制，运用PID速度环控制方法，实现了从制谱到清洗的全自动过程，成功制得沉积效果良好的谱片。结合自动扫描显微镜观测部分，以图像灰度方差函数为目标函数，采用变步长遍历搜索法，实现了图像的自动聚焦与采集，验证了自动化便携式铁谱仪的制谱效果。     

自动聚焦技术在刀具测量仪器中的应用

在光学测量仪器中,如何提高聚焦精度是非常重要的。本文针对刀具几何参数测量仪,设计了自动聚焦系统。提出了以步进电机驱动显微镜移动,结合图像处理技术来实现自动聚焦的方法。通过对比实验,选择了图像的灰度梯度向量模方和算子作为图像是否聚焦的评价函数,以及给出了登山式自动聚焦策略。最后对该系统做了重复性聚焦实验,证明上述方法可以提高系统的聚焦精度。     

结核杆菌涂片显微视觉检测系统的自动聚焦

结核杆菌医学涂片大多具有观察区内容稀疏不均匀、杂质较多的特点,使用自动显微镜检方法进行图像采集时,会出现清晰度区分困难、效率低下、甚至聚焦评价失效的问题,为提高自动镜检的效率和准确度,本文自主搭建了显微视觉计算机自动检测系统,对结核杆菌涂片的自动聚焦技术进行系统的研究。首先,对比研究11种常用聚焦函数对结核杆菌镜检玻片图像聚焦评价的优劣,并分析了聚焦成功和失效的原因。在综合分析各聚焦函数对结核杆菌涂片的聚焦效果基础上,提出了一种基于Tenengrad的改进型聚焦评价函数,通过改进内容像素的聚焦权重提高聚焦准确度,优化图像处理算法来提高图像采集效率。实验结果表明:改进型Tenengrad聚焦函数FTen-Q在结核杆菌涂片的各类视野图像评价方面具有高灵敏度和准确度,其聚焦成功率和运算效率分别提高了13.884%和17.616%,可以满足结核杆菌涂片类非均匀涂片的显微视觉自动检测应用要求。     

基于加权邻域相关性的显微镜自动聚焦函数

目的：提出了一种基于加权邻域相关性的显微镜自动聚焦函数,并在研究显微镜聚焦原理及成像过程的基础上,分析了显微镜图像中像素邻域灰度相关性及像散现象对聚焦评价的影响。方法：首先,分别计算每幅显微镜序列图像中各像素与其四邻域像素的灰度相关性。然后,计算基于此相关性加权平均值的二次多项式聚焦函数,其中权值根据对应像素与显微镜视场中心的距离来确定。最后,选取该函数值最大的图像为聚焦图像。结果：实验结果表明,与经典的聚焦函数如方差函数、绝对梯度函数、Roberts梯度函数及Tenengrad函数相比,本文方法的聚焦灵敏度因子提高了0.3185~0.3268,噪声环境下聚焦的平均正确率提高了0~40%。结论：该方法能够准确地评价图像聚焦的程度,并具有较高的灵敏度和较强的抗噪性。     

基于数字图像处理的自控显微镜聚焦算法研究

自动聚焦的评价函数是基于数字图像处理的自动聚焦算法的关键问题.从空域和频域详细分析了离焦图像的成像原理,利用带步长的拉普{记斯算子比较了一系列模糊l冬I像的清晰度.改进的拉普拉斯算子结合爬山法能够实现自控显微镜的高效率精确聚焦,是一种简洁实用的聚焦策略.改进后的聚焦评价函数具有灵敏度高、单峰值、无偏离、计算量小和较高的信噪比等特点.实验表明,与传统的梯度算子聚焦算法相比较,改进的自动聚焦算法效率更高,聚焦位置更精确.     

显微视觉系统的自动聚焦及控制

对自动显微镜的自动聚焦评价函数及聚焦控制策略进行了研究.首先,介绍了频域聚焦函数提升小波变换及时域聚焦函数Sobel-Tenengrad算子,通过将提升小波变换和Sobel-Tenengrad算子有机组合提出了一种新型聚焦评价函数.然后,利用离焦、正焦样本图像对自组织算法进行无监督训练,使用粒子群优化算法加速训练过程,并以经过学习的自组织映射算法作为聚焦控制器.最后,进行了显微视觉自动聚焦实验.实验结果表明:新型组合算子具有单峰性,峰值处变化陡峭,对不同样本、不同倍数物镜均可在正焦位置达到最大值,鲁棒性强;经过学习控制器后平均仅用7.6步即可完成自动聚焦,与爬山法相比,该聚焦算法不仅大大提高了聚焦速度且性能稳定,对每幅输入图像处理、识别时间约为120ms;满足了显微视觉自动聚焦要求,获得了良好聚焦效果.     

显微镜自动聚焦算法的研究

自动聚焦技术是全自动控制显微镜系统中的核心部分。自动聚焦算法综合了快速灰度差分法和高精度拉普拉斯函数法的优点,根据聚焦过程中各阶段聚焦评价函数的梯度选择合适的焦距评价函数和步长,并通过改变步长实现了从快速粗调到精确细调的过渡。实验表明,与传统的单一聚焦评价函数和单一步长的聚焦算法相比较,该算法在保证聚焦速度的情况下显著地提高了聚焦位置的精度。     

基于Internet的嵌入式数字图像自动对焦系统

提出了一种利用网络技术实现嵌入式数字图像自动对焦系统远程监控的方法,建立了基于DM642的数字显微镜自动调焦系统,设计了系统的网络传输应用程序。最后通过实验证明了该方法的可行性。     

Bilateral prediction and intersection calculation autofocus method for automated microscopy

In this paper, a bilateral prediction and intersection calculation autofocus method for automated microscopy, which obtains the in‐focus position by calculating the intersection of the predicted left and right focus measure curves located respectively in the left and right sides of the peak position of the focus measure curve, is proposed and performed. According to the autofocus method, the area including the peak position of the focus measure curve and its left and right neighbourhoods should be determined firstly, and the left and right neighbourhoods are considered as the left and right sampling areas. The left and right focus measure curves are predicted by appropriate predicting models according to the two sample sequences, which comprise the focus values by evaluating the sampled images in the left sampling area and right sampling area, respectively and their corresponding sampling positions. The intersection of the predicted left and right focus measure curves is calculated and can be considered as the in‐focus position. The autofocus can be realized by moving the focus plane of the microscope to the intersection of the predicted left and right focus measure curves. The proposed bilateral prediction and intersection calculation autofocus method is experimentally verified in an automated light microscopy for implementing microassembly and micromanipulation. The theoretical analyses have shown that the proposed bilateral prediction and intersection calculation autofocus method can not only effectively avoid the principle error caused by assuming the symmetrical focus measure curve in the autofocus methods based on curve fitting, but also eliminate the possible waver search near the peak position in the modified fast climbing servo method. The experimental results have shown that the proposed bilateral prediction and intersection calculation autofocus method possesses the merits as follows: (1) the focusing accuracy is high and slightly affected by the sampling step size and (2) the focusing speed is higher than those of the 7‐point hill‐climbing search method and the quadratic curve fitting method with a determinate focusing accuracy.     

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.     

Evaluating sharpness functions for automated scanning electron microscopy

Fast and reliable autofocus techniques are an important topic for automated scanning electron microscopy. In this paper, different autofocus techniques are discussed and applied to a variety of experimental through-focus series of scanning electron microscopy images with different geometries. The procedure of quality evaluation is described, and for a variety of scanning electron microscope samples it is demonstrated that techniques based on image derivatives and Fourier transforms are in general better than statistical, intensity and histogram-based techniques. Further, it is shown that varying of an extra parameter can dramatically increase quality of an autofocus technique.     

Region sampling for robust and rapid autofocus in microscope

This paper proposes a region sampling based autofocus method for rapid and robust autofocus in microscope. Image content and region size are considered in region sampling criteria. An intelligent search algorithm which employs quartering hill climbing search and golden section search is developed, in which rule‐based evaluation of sampled focusing regions is applied. Experimental results demonstrate that the proposed method can significantly improve the performance of image‐based autofocus. Microsc. Res. Tech. 78:382–390, 2015. © 2015 Wiley Periodicals, Inc.     

Fast,high-precision autofocus on a motorised microscope: Automating blood sample imaging on the OpenFlexure Microscope

The OpenFlexure Microscope is a 3D-printed, low-cost microscope capable of automated image acquisition through the use of a motorised translation stage and a Raspberry Pi imaging system. This automation has applications in research and healthcare, including in supporting the diagnosis of malaria in low-resource settings. The plasmodium parasites that cause malaria require high magnification imaging, which has a shallow depth of field, necessitating the development of an accurate and precise autofocus procedure. We present methods of identifying the focal plane of the microscope, and procedures for reliably acquiring a stack of focused images on a system affected by backlash and drift. We also present and assess a method to verify the success of autofocus during the scan. The speed, reliability and precision of each method are evaluated, and the limitations discussed in terms of the end users' requirements.     

The influence of the scene parameters and of noise on the behaviour of automatic focusing algorithms

A systematic study is presented of the properties of autofocus criteria. Special importance is attributed to their behaviour with respect to noise, working range and image sharpness, whose reproducibility has been investigated. It can be demonstrated that autofocus algorithms have either a large working range and do not focus in an unambiguous way or vice versa. From considerations of the properties of autofocus algorithms two novel algorithms have been developed which are insensitive to noise. One of these algorithms is characterized by a particularly large working range, whereas the other is capable of achieving maximum sharpness in a reproducible manner.     

一种基于DFD的自动对焦算法

引入了一种基于DFD的自动对焦算法。通过这种算法,只要给定了两幅不同离焦位置的图像,就可由算法推导出目标物体的正确对焦位置,从而控制镜头完成自动对焦。实验表明,这种算法精度比较高,速度比较快,鲁棒性良好。     

Scanning Optical Microscopy via a Scanning Electron Microscope

We have described in detail the principles of operation of a commercially available SEM-based scanning optical microscope. The stage consists of a cathodoluminescent material which converts the scanning electron beam into a scanning optical beam and an optical system to focus the light beam onto the specimen. The resolution attainable with such a stage is discussed as well as the efficiency of electron-to-photon conversion. Simplified formulae are given and a set of curves plotted which can be used to determine the appropriate tradeoff between resolution and optical power. Examples of the imaging ability in the optical beam induced current mode from various semiconductor devices are presented.     

A two-channel four-dimensional image recording and viewing system with automatic drift correction

Four-dimensional image acquisition systems have been described to analyse various developmental processes, for example, the Caenorhabditis elegans cell lineage. A practical problem that is often encountered during recordings is mechanical slippage of the microscope stage, causing the sample to drift out of focus. Furthermore, with the advent of green fluorescent protein (GFP) as an in vivo marker, affordable two-channel imaging systems are needed to correlate gene expression with changes through development. To overcome the mechanical drift a device-independent, software-only solution for the MacOS was devised that can compensate for Z -axis drifts in sample position. The software also allows recording of 4D stacks in two channels. To correct for drift, a small reference object beside the main object to be recorded is kept in focus using a simple autofocus principle, and this automatic drift correction allows for effective 4D recordings. In addition to the Z -axis drives and the shutters of the microscope, a video camera can be computer controlled to switch between two light levels. Second channel live GFP recordings are presently limited by the fact that the high intensity of the blue light heats and kills C. elegans embyros quickly. To view and annotate the stacks a MacOS viewing application was developed.