Search

Experiments, including our own (Gould et al., 1984; 1986), have shown that people read more slowly from CRT displays than from paper. A series of experiments shows that the explanation centers on the image quality of the characters. Reading speeds, equivalent to those on paper, have been found for CRT displays containing character fonts that resemble those on paper (rather than dot matrix fonts, for example), that have a polarity of dark characters on a light background, that are anti-aliased (i.e., contain grey level), and that are shown on displays with relatively high resolution (e.g., 1000 × 800).

A fast optically addressed spatial light modulator (OASLM) is demonstrated using a p-i-n photodiode of hydrogenated amorphous silicon (a-Si:H) and the electroclinic effect in chiral smectic A liquid crystals. The response time depends on the material and the temperature. We used a material with a response time of 40 μs at 29°C and 4 μs at 51°C. This work shows that there is an excellent match between a-Si:H photodiodes as photosensors and high speed liquid crystals as electrooptic modulators. The optical response varies with the field and write-light intensity, allowing for grey level applications.

Any model-based image interpretation system must be capable of describing objects, whose appearance in real images can vary widely, in sufficient detail to ensure that robust location of objects is possible. The system must cope with circumstances where data is incomplete, for example when touching and occlusion occur. It is argued that to achieve this it is necessary to describe grey-level properties as well as geometric ones, and their expected variations. This paper proposes an object description which combines an explicit shape model with models of expected grey-level boundary appearance together with a mechanism for evaluating image data for correspondences to the model. The results of applying the method to locating the boundaries of overlapping and touching objects in microscope images of metaphase chromosomes and manmade mineral fibres are presented.

Already a certain number of systems have been studied and realized in France and abroad for biomedical picture sequences processing.Specialized work has been done on the cineangiocardiography which is concerned principally by the volume rebuilding of the left ventricle and its variations. Extension of this work has been done on the gastric X-ray pictures for the pattern recognition of the stomach and for the reconstitutions of the biomechanical characteristics of the stomach, especially its contractility

This chapter discusses the application of the Quantimet image analyzer to agricultural aviation problems. The Quantimet is an instrument that can determine size distributions of droplet pictures, and can transmit the data to an online computer, which then calculates droplet density, VMD, NMD, and possibly other parameters, and plots droplet spectra and sum curves on an XY-plotter in real time. The spray pattern is observed through a microscope on a vidicon camera, and appears on the screen of the Quantimet, where it is divided into 625 × 800 picture elements. For each picture element, it is decided whether the intensity exceeds a preset grey level, and so a digital picture of the spray pattern is obtained.

The authors report their continuing research aimed at computer aided echography by processing B-scan videofrequency images with SGLD method. They find a reduction of subjectivity of diagnosis of pathology.

An experimental setup of a semiconductor laser scanner for 3D-mapping is described. First measurement results are presented. The experimental results are discussed and estimations for a future remote sensing system are given. Finally the main possibilities for applications of a semiconductor laser mapper are identified.

Computer vision will revolutionise manufacturing in two important areas: inspection and adaptive control of robots. Already both these uses of computer vision are beginning to change manufacturing, with many systems now in production. The two specific industrial vision systems to be described in this paper, KEYSIGHT and CONSIGHT, will give a general indication of the state of the technology.

The problem of extracting an edge in real images is briefly described. A number of methods grouped as local, regional, global, sequential, heuristic, dynamic and using relaxation are schematically illustrated with an attempt to give some insight to the ideas which originated each approac-. Evaluation of results and critical aspects of some methods, according to certain authors are also included, as well as some hints on the latest research trends in this area.

We begin our study of the automatic generation of set recognition algorithms by giving a brief review of the essential elements of mathematical morphology. Though we cannot hope to cover all of it in such a short space, I will describe the main principles of the theory and give a general overview of the major classes of operations, while concentrating on those which made up the focus of this project. The purpose of this review is to provide the mathematical underpinnings for what is to follow. Some of the material in this chapter, particularly that in Sections 2.3, 2.5, 2.7, 2.10 and 2.11, is treated in greater depth in Serra [1982].

The two main prerequisites of accurate and reliable automatic image analysis and interpretation are low noise and distortion free performance of the image forming device and accurate image segmentation.

A class of transformations on grey level images which replace each pixel (in parallel) by some function of its neighbouring pixels

Two image processing projects are presented for introductory students that require only minimal computer facilities. The first produces a binary (black or white pixel) image and introduces signal processing concepts. The second project extends these ideas to the production of a grey level image.

The display of computerized tomographic (CT) data requires data compression because of the limited shades of grey which the eye can differentiate. This may lead to information loss which can be minimized by a more efficient utilization of the available levels of grey than that afforded by conventional linear windows. Automated histogram equalization for grey level assignment has not been satisfactory because of the underlying assumption that the information content at any given CT level is proportional to the number of pixels at that level. For four different anatomic regions; the lumber spine, abdomen, brain and chest, an empiric graph of the clinical information content vs CT levels was integrated to yield the shape of a graph assigning shades of grey vs CT level i.e. a non-linear window. This non-linear window curve was utilized in the same manner as the linear window, namely the window center and width were under the direct control of the observer through the window center and width knobs. Each non-linear window was implemented on images of its anatomic region and interactively optimized on the screen till a maximal display of information was obtained. These optimal non-linear windows compared favorably with linear windows in most cases. This method provides the means to display more information on a CT image with no extra processing time, additional equipment or special training.

Until now different uses of computers are known in nematology, e.g. Boag (1981) described an electronic system for measuring nematodes and Fortuner (1983) designed a computer program (NEMAID) for identifying Helicotylenchus species, including a database with measurements.

The most common tasks of low level image processing are considered in order to define a set of primitives to be implemented in parallel image processing systems. In particular arithmetic primitives, global features (as grey level statistics), linear transforms and local computations are discussed taking care of the effectiveness of the implementations on array and pyramidal systems. The propagation capability supplied by flat arrays and pyramids is then presented in some extent with the purpose to highlight the performances of this kind of machines in well known low level tasks.

The aim of this paper is three fold. In a first part, the basics of electron beam testing are reviewed. Next, a second part details experiences in using electron-beam testing for failure analysis of memories and microprocessors. The third part gives results on the use of an electron beam tester in a more structured methodology for failure analysis and debug of ICs.

The raw material for the paper industry is wood. To have an exact account of the stock of piled sawn tree trunks every truck load entering the plant's stockyard must be measured as to the amount of wood being brought in. Weighting down the trucks has its own problems, mainly, due to the high capacity of the tree trunks to absorb water. This problem is further enhanced when calculations must be made to arrive at the mass of sawn tree trunks which must go into the process of producing a certain quantity of paper pulp. The method presented here is based on two fixed cameras which take the image of the truck load. One takes a view of the trunks in order to get information on the average length of the tree trunks. The other obtains a side view which is digitised and by just discriminating against a grey level the area covered by the tree trunk cross section is measured. A simple arithmetic operation gives the volume of wood in the trunk. The same computer, a PC, will register the trucks particulars is almost independent of weather the wood is wet or dry and it serves trucks of any size.

A computerized method for detecting microaneurysms is described, based upon the concepts introduced by the Mathematical Morphology. On the grey level image of a fluoroangiogram, magnified by a microscope, a first transformation, searching the regional minima, gives a binary image where appear vessels and microaneurysms. Then the microaneurysms are extracted using a shape criterion which selects almost circular particles among stretched particles in one direction. The most complex part is to discriminate diffusing microaneurysm (leakage of fluorescein) from vessel. The algorithm is tested on 25 angiograms. We obtain a good correlation between the automatic counting and the manual counting performed by three reading-technicians.

Summary. Fourteen allocortical areas of Tupaia belangeri are described after measuring the grey level index (Zilles et al., 1978b) with a new, automatic, high resolution measuring procedure. The laminar pattern of the cortical areas is quantitatively described after vertical changes in this index occurred from the pial surface to the white matter. The registered profiles show characteristic features for the different allocortical brain regions. The results are compared with lamination systems gained by comparative cytoarchitectonic studies using purely qualitative criteria.

Video Pulse radar systems are used to detect underground features at the Curtis School yard in Trumbull County, Ohio. Measured results and their interpretation are given. The results are correlated with a map based on drill hole data and local history. Keywords include: Video pulse radar, Tunnel scattering, Radar measurements, Grey level plots, and Underground void.

Several algorithms are tested to characterize order and disorder in digitised images of spatial patterns. As source of images, the BelousovZhabotinskii reaction coupled to convective motion in a thin liquid layer is used.

New structural applications of polymer matrix composites require the use of thick sections. The fabrication and use of such thick sections create new needs for flaw detection and characterization which cannot be met adequately by conventional nondestructive evaluation (NDE). These composites are susceptible to manufacturing defects due to thermal gradients and nonuniform resin bleeding during curing.

Automatic inspection of composite materials is an important task, due to their increasing diffusion in several application fields.

An algorithm to compress and decompress grey level images is described, in which we combined a classical method like D.P.C.M. with an entropy code based on a new statistical approach. The reconstructed image quality is improved by subsequent image postprocessing. The method is low-time consuming and very simple in order to implement it on P.C. machine.

A method has been developed that substantially increases quantitative tissue discrimination of pathology in in-vivo magnetic resonance (MR) imaging. Results from a study of carcinoma and benign hypertrophy of the prostate show the potential for classification of tissues from individual patients and demonstrate increased class separation. This appears to be the firstapplication of pattern recognition techniques to relaxation-time data from in-vivo MR images. Multiple-point relaxation-time maps were classified using both statistical measures and texture descriptors derived from spatial grey level dependency matrices. These parameters were combined in a new pattern-recognition method based upon the Karhunen- Loeve expansion.

The progress of digital processing of satellite earth resources data is charted over the past four years. From the general trends, probable patterns for future processing are inferred. These lead to suggestions for a new approach to the provision of earth resources services involving satellite data. Mechanisms are proposed and discussed for implementing this approach, and basic questions that must be answered are set forth.

Human renal histological sections have been photographed on a black and white transparency and digitized. The digitizing camera, an image dissector, converts a 2 cm 2 picture into 400 × 400 numbers each representing the grey level value of the sampled point. The grey levels are represented in the computer by numbers ranging between 0–255. In this scale ‘0' stands for black and 255, for white. The program provides 2 grey level thresholds, which outline a window through which the picture is scanned. Only structures, whose grey level value lies in the window range, are taken into consideration. The thresholds are set during digitization from the console switches. Image analysis is performed on-line in real time.

An accurate single-cell classifier is an essential part of any system that uses image-processing and pattern-recognition techniques for prescreening cervical smears. The cell classifier, however, is heavily dependent on the feature extraction, which must be done automatically. This paper describes an attempt to use the grey-level histogram from a cell as a feature vector, in order to simplify part of the automatic feature-extraction process.

SUMMARY A new semi-automatic method is introduced which makes possible the quantitative examination of cresyl-fast-violet stained sections of the cerebral cortex. These sections are divided into measuring fields of 20 × 20 μm in a well-defined area. A scanning procedure then automatically determines the grey level index of every single field. The image of the histological section can be compared with the grey level index data matrix by means of a plotted image, the density of the plotted points of which is proportional to the measured grey level index. By overlaying this plotted image with the original section, the boundaries of the laminae can be fixed in the data matrix. The grey level index profiles—the grey level data plot as a function of the cortical depth—after smoothing and standardization are typical of special cortical areas. The mean thickness and the mean portion of the grey level index profile of the different laminae of the striate area are compared with data from other publications.

A survey of some digital image processing techniques which are useful in the analysis of remotely sensed imagery, particularly Landsat, is presented. An overview of the various steps involved in computer automated processing of Landsat imagery is first given. A number of specific tasks, which employ digital image processing methods are then discussed: on-board processing, radiometric corrections, geometric transformation, image enhancement and multitemporal analysis.

The grey level index (= GLI) and the fresh volume were determined with the image analyser Micro-Videomat for the nucl. n. facialis after axotomy of the left n. facialis. The experiments were performed on 10 rats in different stages of ontogenesis. The GLI is a quantitative parameter which could be quickly obtained and which demonstrated quantitative changes during retrograde reaction in the respective centres. A decrease in the fresh volumes of the affected nucl. n. facialis could also be demonstrated. The meaning of GLI is discussed.

A system for face recognition using range images as input data is described. The range data acquisition procedure is based on the coded light approach, merging range images that are recorded by two separate sensors. Two approaches, which are known from face recognition based on grey level images have been extended to dealing with range images. These approaches are based on eigenfaces and hidden Markov models, respectively. Experimental results on a database with various range images from 24 persons show very promising results for both recognition methods.

Automated grading of lumber is attractive for the sawmill industry. Achieving better accuracy of quality grading and control of quality variation in volume production easily improves the profit obtained from it. We describe a color vision based framework to grading softwood lumber. The proposed inspection principle is to recognize the sound wood regions early, as this reduces the computational requirements at later defect recognition stages. The recognition stages are ordered based on their estimated costs and implementational complexity. This is important because color increases the data volumes significantly over grey scale images. Finally, the description of the board and its defects is passed to the quality grader which assigns the class giving the best price for each board. In comparative tests, the computational solutions have turned out to be simpler than with grey level images, compensating for the higher cost of the color imaging system. The effects of changes in the spectrum of illumination have also been evaluated to identify robust color features and to produce the requirements for color calibration.

The normal human adult kidney contains between 300,000 and 1 million nephrons (the functional units of the kidney). Nephrons develop at the tips of the branching ureteric duct, and therefore ureteric duct branching morphogenesis is critical for normal kidney development. Current methods for analysing ureteric branching are mostly qualitative and those quantitative methods that do exist do not account for the 3- dimensional (3D) shape of the ureteric "tree". We have developed a method for measuring the total length of the ureteric tree in 3D. This method is described and preliminary data are presented. The algorithm allows for performing a semi-automatic segmentation of a set of grey level confocal images and an automatic skeletonisation of the resulting binary object. Measurements of length are automatically obtained, and numbers of branch points are manually counted. The final representation can be reconstructed by means of 3D volume rendering software, providing a fully rotating 3D perspective of the skeletonised tree, making it possible to identify and accurately measure branch lengths. Preliminary data shows the total length estimates obtained with the technique to be highly reproducible. Repeat estimates of total tree length vary by just 1-2%. We will now use this technique to further define the growth of the ureteric tree in vitro, under both normal culture conditions, and in the presence of various levels of specific molecules suspected of regulating ureteric growth. The data obtained will provide fundamental information on the development of renal architecture, as well as the regulation of nephron number.

An image analysis based method for the automatic measurement of the degree of recrystallization in alloys is presented. Recrystallized and non-recrystallized areas are visualised using back scattered channelling contrast in the scanning electron microscope. Non-recrystallized areas are identified by grey level gradient detection operations and subsequent mathematical morphology based image operations. The approach is applied to ultra low carbon steel and high purity copper. Automatically derived fractions are compared with manual measurements. Detected non-recrystallized areas are more irregular and fragmented than found in real structures. Excellent correlations between manually and automatically measured fractions are achieved in spite of the mismatch between detected and real structure. The presented method is implemented on a GOP image analyser. Simplified versions of the algorithm should be possible to use on most image analysis systems.

An experimental analysis of the effectiveness of gray-level co-occurrence (GLC) statistics to characterize texture of SAR images for classification purposes is reported. The analysis was carried out on simulated SAR images.

Afortran iv computer program for grey-level mapping of spatial data using a CDC 6600 is described. The program produces maps for irregularly distributed data in as many as 10 intensity levels which are displayed in grey tones by a lineprinter. Unlimited map size and unrestricted data input provide for as many as 5000 data points per 13-in.-wide strip of map. The program is easily modified for other installations. Examples are given of geochemical analyses of stream sediments in Northern Ireland.

Experimental and clinical studies have shown that a preserved cyclic (diastolic-to-systolic) echoreflectivity variation, assessed by radiofrequency sampling of backscatter signal with non commercially available prototypes, identifies viability in a myocardial segment with a resting dyssynergy. Aim of this study was to assess whether a videodensitometric analysis of myocardial gray level variation during cardiac cycle might identify viable but dyssynergic myocardium in a clinical setting. Thirty-four patients with a resting dyssynergy (akinesis in 26, marked hypokinesis in 8 patients) in the septum and/or infero-posterior wall were evaluated by videodensitometry. All echo studies were performed with commercially available instruments in the long axis parasternal view, with quantitative analysis of gray levels performed off-line on digitized images. Segmental wall motion was assessed with a 16 segment model of the left ventricle, each scored from 1, normal, to 4, dyskinetic. A follow-up echo study was obtained in all patients g4 weeks after successful revascularization (achieved with angioplasty in 22, with bypass surgery in 12). Two groups of segments were identified: 18 “viable” segments (contractile improvement of 1 grade or more in resting function after revascularization); 16 “necrotic” segments (no contractile improvement in resting function after revascularization). The % cyclic variation was higher in “viable” vs “necrotic” segments (26 ± 16 vs 1 ± 13%, p l 0.01), in spite of similar % systolic thickening (5 ± 5 vs 4 ± 6%, p = ns) and end-diastolic thickness (10 ± 2 vs 10 ± 2 mm, p = ns). When individual patient analysis was performed, % cyclic variation was below the 95% confidence limits obtained from normal control regions (n = 34; % cyclic variation = 38 ± 14) in 2 out of 18 viable and in 14 out of 16 necrotic segments. A cut-off ≥ 9.4% cyclic variation in a dyssynergic segment yielded a 89% sensitivity and a 88% specificity for predicting functional recovery following successful revascularization. In conclusion, viable dyssynergic myocardial segments show a cyclic gray level variation at rest, which can be detected by simple videodensitometric analysis, much less technologically demanding than radiofrequency backscatter evaluation.

Two methods for detecting and classifying watercore in 'Red Delicious' apples using computer vision techniques were examined. The first method used was to average radii perpendicular and parallel to the stem-calyx axis for each apple and use these radii to compute an approximate apple volume which, in conjunction with measured weight of fruit, was used to calculate weight density. A correlation of 0.98 was found between the computed volume and measured volume. Weight density correctly separated 86.7% of a 60-apple test sample with 5.0% misclassified as having watercore and 8.3% misclassified as watercore free. The second method used was to measure light transmission through apples, viewed from the stem-end, as an indicator of watercore. The mean grey level of a 130 pixel X 100 pixel window located around the fruit center indicated the presence of watercore, but was not a good feature for accurately measuring the degree of watercore. All of the 60-apple test samples were correctly classified for the presence or absence of watercore. Application of computer vision techniques to measure transmissibility of visible radiation through apples by finding the mean grey level is a feasible method for detecting watercore presence, but cannot determine how severe the watercore damage is. This noncontact method for separating and marketing of watercore fruit could reduce the storage losses due to core browning and decay..

Two-dimensional noise-reduction techniques are used on synthetic images and compared. A new edge-preserving smoothing method is presented which is a simpler alternative to some selective-neighbourhood smoothing approaches already in use. Quantitative methods to measure noise reduction in images are used to evaluate and compare the performances of these techniques.

A RECENT Admiralty "Notice to Mariners," No. 1720 of 1930, has announced the discovery of a hole in the floor of the North Sea 80 fathoms deeper than anything shown on the charts in its neighbourhood. The Notice warns trawlers of the liability to accidents to their nets owing to the abruptness of the edges of this deep. It has already acquired the name of the "Devil's Hole," apparently through some trawls having been lost on its steep sides. The existence of a depth of 130 fathoms in the North Sea is surprising, especially as it occurs in an area represented on the Admiralty Chart No. 2182 B as a gently undulating plain varying in depth from 38 to 50 fathoms. It is also one of an extensive series of depressions, which occur in two groups. The southern group is beside 550 50' N. and on the meridian of Greenwich, about 65 miles east of Berwick-on-Tweed. This group consists of two "trenches"?to use the term recommended by the International Geographical Congress (cf. Geogr. Journ., 22,1903, pp. 191-4), each trending approximately north and south. The south-western trench is about 6 miles long and 1 mile broad, and its depth below sea surface is 53 fathoms. The north-eastern trench is 8 miles long by about 1 \ miles wide. Its greatest depth is 87 fathoms between previously known soundings of 43 and 53 fathoms. The second group, about 60 miles to the north-north-east, and about 100 miles east of Montrose, includes, as shown by the recharting of the area by H.M. Survey Ship Fitzroy, a line of three trenches, trending a little to the west of north. This line is about 30 miles long and ranges 51 to 100 fathoms deep. The greatest previously known depths were 50 fathoms east of the 100-fathom sounding and elsewhere between 42 and 47 fathoms. A little east of this line and on an approximately parallel course are five depressions, each more than 50 fathoms deep. The southernmost of these is the DeviPs Hole, which is about 4 miles long and plunges steeply to the depth of 130 fathoms from a level plain from 44 to 48 fathoms deep. The Devil's Hole is a trench with steep sides. The average slope for a mile in a cross section is 1 in 11, but part ofthe slope is probably much steeper than the rest. The western depressions of this northern group are four smaller patches below the 50-fathom contour. The discovery of the Devil's Hole and the neighbouring trenches has many features of geographical interest. It is a useful warning of the inadequacy of our knowledge of the form of the sea-floor; for if such deep depressions exist hitherto unsuspected in a sea so well known and so relatively shallow as the North Sea, the ocean floors may be far less regular than our usual conception of them as "great grey level plains of ooze." The soundings however strikingly confirm the accuracy of those on the former Admiralty Charts. Where the new depths coincide or are close to depths marked on the charts the figures are concordant. The failure to discover these hollows was due to the soundings having been so far apart that they happened to miss these narrow deeps. Thus on the line east and west through the Devil's Hole the Admiralty Chart recorded 48 fathoms to the east; then 46 fathoms between new soundings of 48 and 49 fathoms, just east of the line of trenches; and the next soundings were of 33 and 50 fathoms west ofthe area.