Measurement of electron probe beam diameter by digital image processing

The present report illustrates a computerized method for precise measurement of the diameter of an electron beam. The value of this measurement extends beyond simply providing an accurate estimate of resolution. Other salient areas which will benefit include quantitative X-ray microanalysis, energy loss spectroscopy, diffraction studies, and electron beam lithography. The biological sciences as well as the material sciences will gain enormously from improved accuracy in measurement (control) of beam diameter. It is anticipated that most or all of the mathematical manipulations outlined in this paper will be incorporated into digital electronic packages which will perform the functions automatically for setting the electron beam diameter to the scientist's choice. The purpose of the present report is to indicate some of the principles involved so that as electron microscopy becomes more computerized and automated, the user will have some understanding of what the electronics are doing rather than simply depressing a button or two and ignoring the power of what resides within the walls of the instrument. The performance of a scanning electron microscope (SEM) and a scanning transmission electron microscope (STEM) is roughly determined by the incident electron probe beam size (diameter) involving a sufficient electron current. In the present paper, the diameter of an ultrafine electron beam is measured indirectly from the information given by the blurring of an edge in a STEM or a SEM image of a crystalline specimen with fine, sharp edges. The obtained data were processed by digital image processing methods which give an accurate value of the beam diameter. For confirming the validity of this method, a suitable simulation based on the convolution theorem was performed. By using this measurement, we could measure the diameter of an ultrafine electron beam down to 2 nm, which could not be measured easily by previous techniques.     

A method using an on-line digital computer for the improvement of resolution of backscattered electron images

In principle, the resolution of backscattered electron (BSE) images can be little improved, even though an infinitely small beam size is achieved by various improvements in the intrinsic instrument. In order to circumvent this problem, a method is proposed which utilizes an on-line digital computer for the image recording and processing. The major image-processing tools are reduction, expansion, super-imposition with matching of the images, and high-emphasis filtering in the Fourier domain. By using various combinations of these techniques, the resolution of BSE images has been significantly improved. The validity of these improved images has been confirmed. In the case of a BSE image with too wide a dynamic range, both the present method and digital homomorphic filtering provide successful results.     

A computer system for on-line image capture and analysis

A computer control system for electron microscopy is proposed; it consists of functionally distinct microprocessors communicating via a central microprocessor (the supervisor) by direct memory access or a common data bus. The control functions such as digital beam scan, accelerating voltage, focusing, etc., are controlled by distributed microprocessors under the direction of the supervisory microprocessor. The system includes a framestore for image storage and a special high speed processor that contains a microcode library of functions. The system is used for interactive real-time image analysis by comparison of calculated images and processed experimental images.     

An electron beam lithography and digital image acquisition system for scanning electron microscopes

A low‐cost microcontroller based control and data acquisition unit for digital image recording of scanning electron microscope (SEM) images and scanning electron microscope based electron beam lithography (EBL) is described. The developed microcontroller low‐level embedded software incorporates major time critical functions for image acquisition and electron beam lithography and makes the unit an intelligent module which communicates via USB with the main computer. The system allows recording of images with up to 4096 × 4096 pixel size, different scan modes, controllable dwell time, synchronization with main power frequency, and other user controllable functions. The electron beam can be arbitrary positioned with 12‐bit precision in both dimensions and this is used to extend the scanning electron microscope capabilities for electron beam lithography. Hardware and software details of the system are given to allow its easy duplication. Performance of the system is discussed and exemplary results are presented.     

Efficient work measurement system of manufacturing cells using speech recognition and digital image processing technology

Work measurement methods previously proposed require considerable time and effort by time study analysts because they have to measure the required time through direct observations. In this study, however, we propose a method which efficiently measures the standard times without involving human analysts by using speech recognition and digital image processing techniques. First, we implement a prototype system which can acquire the status of manufacturing cells through a speech recognition system. Second, using image processing, we suggest a method which consists of two main steps: motion representation and cycle segmentation. In the motion representation step, we first detect the motion of any object distinct from its background by differencing two consecutive images separated by a constant time interval. The images thus obtained then pass through an edge detector filter. Finally, the mean values of coordinates of significant pixels of the edge image are obtained. Through these processes, the motions of the observed worker are represented by two time series of data of worker location in horizontal and vertical axes. In the cycle segmentation step, we extract the frames which have maximum or minimum coordinates in one cycle, store them in a stack, and calculate each cycle time using these frames. In this step we also consider methods for detecting work delays due to unexpected events such as an operator’s movement out of the work area, or interruptions. To conclude, the experimental results show that the proposed method is very cost-effective and useful for measuring time standards for various work environments.     

Charging control using pulsed scanning electron microscopy

This paper describes a novel method to observe highly charging specimens at high-beam voltages without specimen preparation. It is found that the technique greatly reduces charging artifacts such as image shift, astigmatism, and defocussing without sacrificing image quality. Images obtained of uncoated specimens are found to be comparable to gold-coated specimens and without exhibiting charging effects. The technique also allows the study of charge distribution effects in specimen charging of which very little understanding exists, particularly as far as the spatial and time-dependent properties of charging are concerned.     

The conversion of a field-emission scanning electron microscope to a high-resolution,high-performance scanning transmission electron microscope,while maintaining original functions

Recently, the reliability of field-emission electron guns has increased. In addition, the cost of computer systems for on-line processing has dropped. Hence, we should now consider the use of scanning transmission electron microscopy (STEM) for routine work, especially, in the field of biology where one may expect to utilize digital image processing techniques. An STEM has been constructed, without disturbing the original functions, by converting a commercial scanning electron microscope equipped with a fieldemission gun. The STEM is generally operated at accelerating voltage 30 kV, focal length 7.5 mm, and beam current 1?2 × 10^?10 A. Several improvements have been incorporated for removing the effects of vibration, contamination, and stray magnetic fields. Also, an adjustable detector aperture was utilized. The modified instrument was connected to an on-line digital image processing system for utilizing the information obtained from STEM images. The advantages of the modified system were studied from various viewpoints.     

Proper acquisition and handling of scanning electron microscopy images using a high-performance personal computer

The modern high-performance personal computer (PC) has very recently expanded the range of utilization of digital scanning electron microscopy (SEM) images, and the PC will be used increasingly with SEMs. However, the image quality of digital SEM images may be considerably influenced by scanning and digitization conditions. In particular, the effects of the aliasing error peculiar to digital data are often serious in the low-magnification acquisition (undersampling) of SEM images, and moreover even a high-magnification image (oversampling) is disturbed by the undersampled noise (a sort of aliasing error). Furthermore, the signal-to-noise ratio of a digitized SEM image is closely related to the performance of the analog-to-digital converter. To prevent a flood of low-quality digital images with artifacts by the aliasing and additional noise, we propose a method using very high-density sampling (scanning). In addition, we will discuss how to handle digital SEM images from the point of view of the sampling and quantization.     

Personal-computer-based system for electron beam X-ray microanalysis of biological samples

A system based on a personal computer has been developed which provides a relatively inexpensive way to equip an electron microscopy laboratory for quantitative elemental analyses of cryosectioned biological samples. This system demonstrates the feasibility of making an X-ray analyser from a personal computer, together with commercially available hardware and software components. Hardware and software have been assembled to drive the beam in a scanning electron microscope, collect and analyse X-ray spectra, and save, retrieve, and analyse data. Our software provides a menu-controlled user interface to direct spectra acquisition and analysis. Spot analyses, video images, and quantitative elemental images may be obtained and results transferred in ASCII format to other computers. Wet weight, as well as dry weight, concentrations are calculated, if measurements were made of areas of the hydrated sample before it was freeze-dried. Grey-level copies of video and quantitative elemental images may be made on a laser printer.     

热轧圆钢截面轮廓及直径结构光在线检测系统

基于激光视觉三维测量原理,采用四个结构光传感器设计了一套热轧圆钢截面轮廓及直径结构光在线检测系统.提出了一种现场快速统一标定方法,并设计了相应的新型立体标定靶标.提出了一种对截面轮廓三维数据进行筛选和融合的数据处理方法,得到圆钢截面较理想三维坐标,从不同方位采用平行线相夹法测量圆钢截面直径.进行了系统标定实验和测量实验,实验结果证明系统在一定测量范围内能实时获取圆钢截面轮廓,直径测量精度在0.2mm以上.     

Scatter diagrams in energy analysed digital imaging: application to scanning Auger microscopy

In order to improve methods for the systematic characterization of inhomogeneous materials the procedures of multi-spectral imaging and scatter diagram construction have been deployed. Although the techniques described are relevant to all instruments which detect signals on several different information channels (e.g. wavelength or energy analysed optical, X-ray or electron imaging), they are illustrated with scanning Auger microscopy (SAM). The construction and use of bivariate correlation diagrams is described by reference to simple samples consisting of patterns of Al film upon Si substrates. The method is then applied to LaNi₅ and GaInAs samples each with different signal/noise ratios and chemical characteristics. The software windowing of scatter diagrams by computer combined with presentation of false colour images is demonstrated. The multi-spectral Auger mapping (MUSLAM) procedure thus evolved is demonstrated to be a powerful, general analytical technique for characterizing the number, abundance and chemistry of each type of region in the surface of an inhomogeneous solid.     

基于图像熵的直线电机动子位置精密测量方法

采用图像熵对栅栏条纹进行筛选,改进了图像相关测量方法,实现了对直线电机动子位置的精确实时测量。首先,分析了栅栏图像的Pnatt熵与像素相关性之间的关系,提出了采用图像熵表征栅栏图像筛选的特征值,从而筛选出非周期性更好的栅栏图像;其次,通过子区大小智能选择获得相邻两幅图像的计算区域,再采用粒子群优化算法对两计算区域的归一化互相关系数矩阵进行搜索,从而得到图像平移值,最后根据系统标定系数得到直线电机动子在拍摄间隔内的位移量。实验结果表明,基于图像熵筛选的栅栏图像在直线电机动子位置测量中具有更强的抗干扰性,测量精度达0.01像素。     

Differentiation of human hair by colour and diameter using light microscopy,digital imaging and statistical analysis

This research introduces and evaluates a novel method that offers the potential of providing objective criteria to forensic microscopical hair comparisons. The method combines hair diameter with numeric characterisations of red, green, and blue colour content as determined with the use of digital imaging at defined locations of the hair. Thirty hairs were collected from each of twenty participants, all with naturally coloured brown hair. The hairs were examined with an Olympus BX53® polarising light microscope and digital images were viewed with an Olympus DP72® camera under 400× magnification. Using Olympus cellSens^? Entry software, hair diameter was measured at 1000, 1500 and 2000 m from the base of the root. The Olympus cellSens^? Entry software uses a red, green and blue (RGB) colour model to quantitatively define the colour of each pixel on an image based on its composition of these three principal colour components. This software was used to collect numerical characterisations of hair colour at each distance interval. The diameter and colour values for each hair were compared using discriminant analysis (DA) and principal component analysis. Although a large amount of intrapersonal variation was observed, the degree of interpersonal variation was greater and enabled the statistical model to differentiate between the hair samples from each participant. The DA model achieved sample reclassification with an error rate of 7.33%. A validation study was conducted on a subset of hair samples from which 18 of the 20 were correctly assigned to the participant from whom they originated. These results support the potential of this method to provide an objective addition to current microscopical hair comparison practices.     

Correction for piezoelectric creep in scanning probe microscopy images using polynomial mapping

We describe a method for using polynomial mapping to correct scanning probe microscope images for distortion due to piezoelectric creep. Because such distortion varies from image to image, this method can be used when the actual locations of some features within an image are known absolutely, or in a series of images in which the actual locations of some features are known not to vary. While the general case of polynomial mapping of degree N requires the determination of 2(N+ 1)2 matrix elements by regression, we find that by understanding the mechanism by which piezoelectric creep distorts scanning probe microscope images, we can fix most of these coefficients at 0 or 1 a priori, leaving only 2(N+ 1) coefficients to be determined by regression. We describe our implementation of this strategy using the Interactive Data Language (IDL) programming language, and demonstrate our technique on a series of atomic force microscopy (AFM) images of diblock copolymer microdomains. Using our simplified scheme, we are able to reduce the effects of distortion in an AFM image from 5% of the scan width to a single pixel, using only five reference points.     

Mechanical scanning of the specimen in the scanning electron microscope

A scanning electron microscope (SEM) system equipped with a motor drive specimen stage fully controlled with a personal computer (PC) has been utilized for obtaining ultralow magnification SEM images. This modem motor drive stage works as a mechanical scanning device. To produce ultra-low magnification SEM images, we use a successful combination of the mechanical scanning, electronic scanning, and digital image processing techniques. This new method is extremely labor and time saving for ultra-low magnification and wide-area observation. The option of ultra-low magnification observation (while maintaining the original SEM functions and performance) is important during a scanning electron microscopy session.     

A novelty digital algorithm for online measurement of dielectric loss factor of electronic transformers

There are many inherent performance limitations using traditional algorithms for online measurement of dielectric loss factor including synchronous sampling, no interharmonics and power system frequency must be invariable. In a non-stationary signal environment where power frequency fluctuation and interharmonic components exist, there is no guarantee of measurement accuracy by using traditional methods. The paper proposed a high-accuracy digital algorithm for online measurement of dielectric loss factor of electronic transformers. Theoretical basis of the new algorithm is based on a new data processing procedure including data truncation and data addition which compensates phase distortion as a result of the spectrum of addition data contains offsets. The algorithm can accurately extract the fundamental signal and calculate dielectric loss factor. Measured results from simulations and practical engineering projects show that the new algorithm has good application feasibility without being affected by the limitations rendered above.     

New generation scanning electron microscopy technology based on the concept of active image processing

A new generation of scanning electron microscopy (SEM) technology is proposed based on the concept of “active image processing.” In order to collect sufficient data for a purpose which is defined in the utilization of active image processing, we may need more devices from among a variety of useful hardware, for example, a digital scan generator with meaningful parameters and an analog-to-digital converter for ultrahigh density recording. After the data acquisition, the application of some digital image processing techniques is certainly effective, because the method in question is specially designed so that the property of obtained data will be suitable for the application of these techniques. The present technology should produce a variety of attractive options in the field of SEM.     

Reduction in acquisition time of scanning electron microscopy image using complex hysteresis smoothing

Complex hysteresis smoothing (CHS), which was developed for noise removal of scanning electron microscopy (SEM) images some years ago, is utilized in acquisition of an SEM image. When using CHS together, recording time can be reduced without problems by about one-third under the condition of SEM signal with a comparatively high signal-to-noise ratio (SNR). We do not recognize artificiality in a CHS-filtered image, because it has some advantages, that is, no degradation of resolution, only one easily chosen processing parameter (this parameter can be fixed and used in this study), and no processing artifacts. This originates in the fact that its criterion for distinguishing noise depends simply on the amplitude of the SEM signal. The automation of reduction in acquisition time is not difficult, because CHS successfully works for almost all varieties of SEM images with a fairly high SNR.     

Deconvolution of scanning electron microscopy images

This paper describes a method of removing blurs in scanning electron microscopy (SEM) images caused by the existence of a finite beam size. Although the resolution of electron microscopy images has been dramatically improved by the use of high-brightness electron guns and low-aberration electron lenses, it is still limited by lens aberration and electron diffraction. Both are inevitable in practical electron optics. Therefore, a further reduction in resolution by improving SEM hardware seems difficult. In order to overcome this difficulty, computer deconvolution has been proposed for SEM images. In the present work, the SEM image is deconvoluted using the electron beam profile estimated from beam optics calculation. The results show that the resolution of the deconvoluted image is improved to one half of the resolution of the original SEM image.