Digital Image Processing System Research Articles

Tracing boundary contours in a binary image

Abstract This paper presents a new contour tracing algorithm for tracing boundary contours in a 2D binary image, which plays a very important role in digital image processing, pattern recognition and machine vision system. The new algorithm has three main advantages compared to existing algorithms. First, it never loses inner boundaries of arbitrary complicated regions. Second, it preserves space connectivity. Third, the algorithm is faster on implementation. These advantages are proved in theory and experiments.

Applying an On-line Crack Detection Technique For Laser Cutting by Controlled Fracture

A new laser cutting system, which uses a laser to induce controlled fracture and combines an image processing technique for crack detection and compensation of the laser path to control crack direction, is proposed in this study. The laser cutting is based on the controlled fracture technique, the laser beam strikes the surface of a thin brittle plate which results in a stable fracture. The cutting of the material results from crack propagation along the cutting path. Because the crack propagation at the crack tip is slower than the moving laser beam, the actual fracture trajectory will deviate from the desired trajectory, for example, when cutting a curve or a right angle, especially at high cutting speed. In order to eliminate the deviation, the actual position of the crack tip must be detected on-line and the path of the laser beam must be modified. The compensation is based on the lagging distance between the crack tip and the laser spot. The laser cutting system comprises a CO 2 laser, a digital image-processing system, and an XYZ positioning table. The cutting of right angles for silicon wafers and the cutting of circular arcs for alumina ceramics are carried out to validate the system. The image processing speed of the crack detection system is 0.1 s S per detection, which is fast enough for continuous on-line crack detection, so that the method can be applied for any complicated curve cutting.

A novel digital image processing system for the transient liquid crystal technique applied for heat transfer and film cooling measurements.

This paper is dedicated to the transient liquid crystal technique measurements for multiple view access by using a novel digital recording and image processing system. The transient liquid crystal technique is widely used for heat transfer investigations in turbomachinery. It has been applied in our laboratory in several test facilities such as a linear cascade for external film cooling measurements or on a ribbed squared duct for internal cooling measurements. The data analysis as well as the measurement equipment is described, with a special focus on the newly developed computerized image processing system suitable to capture the liquid crystal signal.

Laboratory Study of Anchor Ice Growth

A counterrotating flume housed in a cold room was used to study anchor ice growth. The rate of anchor ice growth was monitored and quantified over time using a digital image processing system. The laboratory experiments were conducted over Froude numbers ranging from 0.18 to 0.76 using air temperatures of −15 and −20°C. The data suggest that the rate of anchor ice growth and the density of the resulting anchor ice have a dependence on the Froude number. The rate of anchor ice growth is observed to be a maximum at a Froude number of approximately 0.27. The qualitatively observed density of the anchor ice increases with increasing Froude number. The release of anchor ice is related to the Reynolds number; anchor ice was released for Reynolds number less than approximately 42,000, but remains attached for larger Reynolds numbers.

Advanced digital photoelastic investigations on the tooth-bone interface.

The purpose of this study was to investigate the behavior of the tooth-bone interface on the nature of stress distribution in the tooth and its supporting alveolar bone for various occlusal loads using an advanced digital photoelastic technique. A digital image processing system coupled with a circular polariscope was used for the stress analysis. The phase shift technique and a phase unwrapping algorithm was utilized for fringe processing. This aids in obtaining qualitative and quantitative information on the nature of stress distribution within the dento-osseous structures. The experiments revealed bending stresses within dento-osseous structures. However, the compressive stress magnitude was larger than the tensile stress. Zero stress regions were also identified within the dento-osseous structures. The results suggest that the geometry of the dento-osseous structures and the structural gradients at the tooth-bone interface play a significant role in the distribution of stresses without stress concentrations. Further, the application of an advanced image-processing system with the circular polariscope showed notable advantages and could be applied in other biomechanical investigations.

Effects of nicotinamide and carbogen on oxygenation in human tumor xenografts measured with luminescense based fiber-optic probes

Background and purpose: In head and neck cancer, addition of both carbogen breathing and nicotinamide to accelerated fractionated radiotherapy showed increased loco-regional control rates. An assay based on the measurement of changes in tumor pO 2 in response to oxygenation modification could be helpful for selecting patients for these new treatment approaches. Materials and methods: The fiber-optic oxygen-sensing device, OxyLite™, was used to measure changes in pO 2, at a single position in tumors, after treatment with nicotinamide and carbogen in three human xenograft tumor lines with different vascular architecture and hypoxic patterns. Pimonidazole was used as a marker of hypoxia and was analyzed with a digital image processing system. Results: At the position of pO 2 measurement, half of the tumors showed a local increase in pO 2 after nicotinamide administration. Steep increases in pO 2 were measured in most tumors during carbogen breathing although the increase was less pronounced in tumor areas with a low pre-treatment pO 2. A trend towards a faster local response to carbogen breathing for nicotinamide pre-treated tumors was found in all three lines. There were significant differences in hypoxic fractions, based on pimonidazole binding, between the three tumor lines. There was no correlation between hypoxic marker binding and the response to carbogen breathing. Conclusion: Temporal changes in local pO 2 can be measured with the OxyLite™. This system was used to quantitate the effects of oxygen modifying treatments. Rapid increases in pO 2 during carbogen breathing were observed in most tumor areas. The locally measured response to nicotinamide was smaller and more variable. Bio-reductive hypoxic cell marker binding in combination with OxyLite™ pO 2 determination gives spatial information about the distribution patterns of tumor hypoxia at the microscopic level together with the possibility to continuously measure changes in pO 2 in specific tumor areas.

Stress distribution in the dento-alveolar system using digital photoelasticity.

Past research has confirmed that the governing factors in cellular modelling and remodelling adhere to sound principles of engineering mechanics. Hence studies of stress distributions would provide better understanding of the functional adaptation of dental supporting structures. Photoelasticity is an established experimental tool to study whole-field stress distribution in structures subjected to forces. However, it has certain limitations that make its application in biological specimens tedious. In this investigation an advanced digital photoelastic system is used to visualize and study the nature of the stress distribution in dental supporting structures. These digital fringe patterns are analysed using a phase-shift technique. The present biomechanical study shows that dental supporting structures exhibit a characteristic stress distribution, promoting structural adaptation based on needs. Furthermore, the advantage of using a digital image processing system along with the circular polariscope is discussed.

Dynamic Ca2+changes in neutrophil phagosomes A source for intracellular Ca2+during phagolysosome formation?

An increase in cytosolic Ca2+concentration periphagosomally is critical for phagolysosomal formation and neutrophil elimination of microbes. The Ca2+increase could be achieved through release of Ca2+from mobilized intracellular stores. Alternatively, Ca2+that passively enter the phagosome during phagocytosis could be provided by the phagosome. Intraphagosomal Ca2+changes in single human neutrophils was measured during phagocytosis of serum opsonized Fura-2-conjugated zymosan particles, using a digital image processing system for microspectrofluorometry. A decrease in phagosomal Ca2+down to nanomolar concentrations was seen within minutes following phagosomal closure. Blockage of plasma membrane Ca2+channels by econazole abolished this decrease. The fluorescence properties of Fura-2 zymosan were retained after phagocytosis and stable to pH changes, reactive oxygen species, and proteolytic enzymes. We suggest that Ca2+ions present in the phagosome enter the cell cytosol through Ca2+channels in the phagosomal membrane, achieving a localized Ca2+rise that is important for phagosome processing.

Compensatory head posture changes in patients with obstructive sleep apnea.

The upper airway narrowing and changes in head posture and their relationship with apnea severity in patients with obstructive sleep apnea (OSA) were investigated. In 86 male OSA patients and 37 healthy men, one-night polysomnographic examination was performed and a lateral cephalogram by digital image processing system was taken in each subject. Fifteen variables concerning the upper airway dimensions, area and head postures were measured by using a computer software (NIH Image). The results showed that upper airway dimensions in the OSA group at all levels were significantly smaller than those in the control group and the results hold true when the age and body mass index were well controlled in these two groups. Significant forward inclination of the cervical column was found in the patients with an apnea index (AI) greater than 35 episodes/h. And changes in the head posture variables in the whole study group were significantly correlated with AI and airway dimensions at various levels. It was suggested that there exist significant and extensive upper airway narrowing in OSA patients even in upright position and awake state; And as the apnea severity progresses, patients may assume certain compensatory head postures in an attempt to maintain an adequate airway patency.

三色照明光を用いたＰＴＶ法による三次元流速測定技術の開発

We developed a technique for measuring instantaneous, three-dimensional velocity components in liquid flows by using a digital image processing system, and here we describe a particle tracking velocimery technique improving the tracking of the initial and terminal positions of tracer particles. By using color cameras and a RGB flashlight source three images of the tracer particles are obtained: one at their initial positions; their ter-minal positions, and along their pathline. The images of the initial and the terminal posi-tions are paired by using the pathline image, and the velocity vectors are calculated. We studied image processing algorithms for obtaining three-dimensional-flow vectors from the images produced by the two cameras and for distinguishing duplicate images of the tracer particles. We confirmed this technique is useful for three-dimensional flow observa-tion.

The effect of nozzle aspect ratio on stagnation region heat transfer characteristics of elliptic impinging jet

The local heat transfer characteristics of an elliptic impinging jet on a heated flat plate were experimentally investigated for various nozzle aspect ratios. Five elliptic nozzles of aspect ratio ( AR) of 1, 1.5, 2, 3 and 4 having the same equivalent diameter ( D e) were tested at jet Reynolds number of 10,000 to study the effect of nozzle aspect ratio on the local heat transfer enhancement in the stagnation region. The temperature distributions on the heated flat plate were measured using a thermochromic liquid crystal thermometry with a digital image processing system. The flow structure was visualized using a smoke-wire technique to get a better understanding on the impinging elliptic jet. With varying the nozzle-to-plate spacing, the isothermal contours on the heated flat plate showed the axis-crossover in heat transfer due to the self-induced curvature variation of a three-dimensional jet structure. For smaller nozzle-to-plate spacing ( L/D e <4 ), as the nozzle aspect ratio AR of elliptic jet increases, the heat transfer rate was increased larger than that for the axisymmetric jet ( AR = 1) in the stagnation region. This was mainly attributed to the engulfing large entrainment and enhanced large-scale mixing of the elliptic jet. The stagnation point Nusselt number was correlated for the nozzle aspect ratio and the nozzle-to-plate spacing as Nu o ∝ AR −0.082 L/D e −0.077 .

Effect of astigmatism on multifocal intraocular lenses

Purpose To study the effect of astigmatism on multifocal intraocular lens (MIOL) function. Setting Laser Laboratory, Department of Electronics, Electrotechnics and Informatics, University of Trieste, Italy. Methods Using an experimental optical system, this study compared the division of a laser beam in the focal spots of 1 monofocal IOL (Pharmacia 722A), 1 bifocal IOL (Pharmacia 811E), and 2 MIOLs (AMO Array MPC25NB and Domilens Progress 1). The model consists of a helium–neon laser and an optical system: a triangular optical bench with a precision collimator, a micropositionable immersion stage to support the IOL, and a digital image-processing system. Astigmatism was induced by interposing a +1.0 diopter (D) cylinder lens between the IOL and the television camera. Astigmatism was corrected by adding a −1.0 D cylinder lens in front of the IOL on the same axis. Results Astigmatism creates pairs of focal lines, 1 for each focal spot in the IOL. In the multifocal IOL, the posterior focal line of the nearest focus interfered with the anterior line of the next focus. Correcting the astigmatism led to a significant reduction (mean 20%) in light intensity. Conclusions Astigmatically neutral surgery or surgical correction of pre-existing astigmatism is essential in MIOL implantation to minimize the decrease in contrast sensitivity.

Digitally enhanced type-I magnetic contrast in SEM as a method of domain investigation

In this paper, the type-I magnetic contrast for studying domain structures in a scanning electron microscope (SEM) is reviewed. The application of digital image processing (DIP) system, which has become common in recent years, brings some new possibilities. Owing to this, it is now possible to perform detailed study of domain behavior in the cases of very low magnetic contrast and complicated domain patterns. The features of type-I magnetic contrast are illustrated by the examples of domain images at the (0 0 0 1) surface of cobalt monocrystals. The main advantages and limitations of the method are discussed in more detail.

A vegetation map of Central Africa derived from satellite imagery

Summary Aim This paper presents the Joint Research Centre's TREES Project satellite derived Vegetation Map of Central Africa, at 1:5,000,000 scale, with a detailed description of the vegetation classes and their distribution. The information content of the map is compared with other conventional and satellite derived maps of the region for validation and evaluation purposes. Location The map focuses on the Guineo‐Congolian ecological domain and covers the following countries: Cameroon, Central African Republic, Republic of Congo, Equatorial Guinea, Gabon and the Democratic Republic of Congo. Methods Using coarse resolution satellite imagery a map of vegetation cover has been produced based upon the spectral response of the vegetation cover. Digital image processing and geographical information systems techniques were employed, together with local knowledge, high resolution imagery and expert consultation, to compile a cartographic map product. Results The TREES Vegetation Map of Central Africa has been shown to be strongly correlated with the FAO Forest Resources Assessment for 1990. Comparison with other map sources indicates that the map contains greater spatial detail and is more consistent than conventionally compiled maps. The conventional maps however, contain more thematic information content relating to vegetation type. Main conclusions The map improves our state of knowledge of the vegetation cover of Central Africa and presents the most consistent and spatially detailed view yet published at this scale. Thematic information content on forest type is limited but should be improved in the near future with the inclusion of data from new satellite sensors. This first version of the map and future planned updates should provide an important input for regional stratification and planning purposes for forest resources, biodiversity and climate studies.

Technical NoteTurbulent heat transfer from a convex hemispherical surface to a round impinging jet

As an effective method to enhance heat and mass transfer, impinging jets have been widely used in a variety of engineering applications such as cooling of hot steel plates, tempering of glass, drying of papers and textiles, cooling of turbine blades and electronic components, and manufacturing of TFT-LCD plate. Numerous studies of the heat transfer and flow characteristics for the jet impingement on surfaces have been reported. These studies have dealt with the effects of Reynolds number, nozzle-to-surface distance, nozzle geometry, jet orientation, multiple jets, cross flow, and impinging surface shape on the resulting flow and heat transfer. Several review and summary papers on the impinging jet heat transfer have been published by Martin [1], Jambunathan et al. [2], and Viskanta [3]. Although many different jet characteristics have been considered, a great majority of impinging jet studies in the past were on the flat surface. However, many engineering applications of jet impingement cooling on curved surfaces may be encountered. A few papers have studied the impinging jet heat transfer from the curved surface. Chupp et al. [4]studied the heat transfer characteristics with an array of round jets impinging on a concave surface. Thomann [5]and Hrycak [6]reported the total heat transfer on the concave surface is higher than on the flat surface due to larger surface area especially for small nozzle-to-surface distances. For a highly concave surface, the optimum distance is less than for the equivalent flat surface case. With decreasing surface curvature and increasing nozzle-to-surface distance, the heat transfer characteristics approach those for the flat surface. Gau and Chung [7]investigatged the effects of surface curvature on the slot jet impingement heat transfer along semi-cylindrical concave and convex surfaces. They observed a series of three-dimensional counterrotating vortices near the stagnation point region on the convex surface. And they also found Taylor–Görtler vortices initiated along the concave surface. Yang et al. [8]investigated jet impingement cooling on the semi-cylindrical concave surface with two different nozzles (round edged nozzle and rectangular edged nozzle) . In the present study, the local Nusselt numbers are measured for an air jet issuing from a long straight pipe and impinging perpendicular on the convex hemispherical surface. The experiments are made for Re = 11 000–87 000, L⧹ d = 2–10, and D⧹ d = 10.6. An electrically heated gold film Intrex (a very thin gold-coated polyester substrate sheet) is used to create a uniform heat flux on the convex surface. The temperature on the surface is measured using a thermochromic liquid crystal and a digital color image processing system.

Monitoring Of Hazards And Urban Growth In Villavicencio, Colombia, Using Scanned Air Photos And Satellite Imagery

A method is presented to monitor the development of geomorphic hazard areas by overlaying time series of air photos in a digital image processing system. The present study deals with such hazards affecting an urban area, Villavicencio at the foot of the eastern Andes in Colombia. The relevant windows of the air photos are digitized by flat-bed scanning and then transformed geometrically to be overlain on SPOT panchromatic imagery where available. The 10 m resolution of the satellite imagery allows, in practice, sufficient detail to bring out the differences, which are a yardstick to monitor the development of the phenomenon over time. Where no SPOT panchromatic imagery is available, one of the photos may be taken as a reference; registration to a topographic base map is also possible. A development over time to the present hazardous situations can be read from the analyzed imagery. Air photo series dating back to 1937 are available for this research, in the context of a geomorphic hazards study currently undertaken in the eastern Colombian Andes front where it pushes against the Llanos Orientales. The mountain front is quite steep and high, and the contact with the plains is very abrupt. A thrust fault zone in which the rocks are strongly mylonitized, marks the eastern front. Villavicencio lies just below this zone, but its main access road has to cross it. The terrain is mostly made up of Mesozoic and Palaeozoic sedimentary series, with prominent black lutites; Tertiary sedimentaries are found in the foreland. All rocks are strongly folded and faulted. Precipitation is in the order of 3500–5500 mm per year. Records on river discharge events are scarce or absent. Seismic events are frequent in the area. This area is prone to strong and rapid geomorphic processes posing hazards to the inhabitants. The town of Villavicencio is the gateway to the Llanos Orientales. It is the major town for hundreds of kilometres around, and a commercial, educational and health centre for the whole eastern region of Colombia. It is connected to Santa Fe de Bogota, the national Capital, by the only highway to the Llanos, which traverses very difficult terrain through the Eastern Andes, and is cut frequently by landslides, bridge collapse etc., as a result of the torrential rainfall and the instability of the terrain. A major hazard is a big landslip known as the Mirador, close to Villavicencio, on the main road to Bogota. Its rapid advancement has caused numerous road closures; its growth could be monitored on the scanned and registered air photos. The shifting and flooding of the Guatiquia River threatens the left bank, on which the airport of Villavicencio is situated. The development of the flood hazard, and the areal extent of the area threatened, is monitored and measured on the scanned and referenced air photos. The areal growth of the town of Villavicencio itself could likewise be monitored and measured.

Digital image processing system for magnetic domain observation in SEM

A digital image processing (DIP) system and its application for domain observation in cobalt monocrystals by the type-I magnetic contrast in a scanning electron microscope (SEM) is presented. The system capabilities shown include contrast enhancement, noise reduction, removal of tilted illumination and undesirable periodic patterns from the image, Fourier analysis and determination of the magnetic domain width. In particular, it is demonstrated for the first time that even as the SEM possesses a single secondary electron detector it is possible to obtain images with type-I magnetic contrast only (i.e. without topographic contrast), owing to combining image alignment with image subtraction. Other advantages of using DIP systems are also mentioned.

Data analysis system for film

A simplified setup for an automatic film analysis system is described. It is composed of a digital image processing system and a film transmission mechanism. The film, which records the movement of an impact or explosion is driven by a film transmission mechanism and is converted to digital images. The signaled points with variable shape are matched by correlative matching in sequential images and data representing the movement is obtained. In this system, some practical methods such as subpixel location and distortion elimination for the camera lens are implemented to improve the measurement precision.

Analysis of light energy distribution by multifocal intraocular lenses through an experimental optical model

Purpose: To analyze and compare the light energy distribution generated by multifocal intraocular lenses (IOLs).Setting: Laser Laboratory of the Department of Electronics, Electrotechnics and Informatics, University of Trieste, Italy.Methods: An optic system to examine the division of a laser beam in the various focal spots of multifocal IOLs was developed. The model consists of a helium-neon laser and an optical system: a triangular optical bench with a precision collimator, a micropositionable immersion stage supporting the IOL to be measured, and a digital image-processing system. Four bifocal and three multifocal IOLs were studied. This system is able to expand the distance between foci, leading to a sharper separation of the focal spots. The resolution of the images makes it possible to analyze the distribution of total light energy among the foci.Results: Results showed the variation in light intensity of the focal spots of multifocal and bifocal IOLs, as well as their disposition in the dioptric range.Conclusion: Light distribution among various focal distances corresponded to the foci provided by monofocal, bifocal, and multifocal IOLs. The percentage of light energy distribution was related to the importance of each focus.

Magnetic domain structure of Co/Ni(110)

The magnetic domain structures of ultrathin Co films, epitaxially grown on Ni(110) substrate, were studied by a Kerr microscope combined with a digital image processing system for the first time. The digital image processing system allows us to subtract contrast of nonmagnetic origin from the magneto–optic image. It was found that the Co(110)/Ni(110) system exhibits domain structures different from that of the Ni(110) substrate. Irregular domains of ultrathin Co films larger than 2 mm were observed, while plate(stripe)-like domains were found for the Ni(110) substrate. Furthermore, the domain patterns of the Co(110)/Ni(110) system are strongly influenced by the adsorption of gas and variation of temperature.