Photochromic materials exist in two different color states, with switching between states being achieved by irradiation, with ultra-violet and visible light. By printing patterns and data using both photochromic ink a...
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ISBN:
(纸本)0819413208
Photochromic materials exist in two different color states, with switching between states being achieved by irradiation, with ultra-violet and visible light. By printing patterns and data using both photochromic ink and ordinary ink, it is possible to create a document that is difficult to forge and easy to authenticate. Security is achieved only by public ignorance about and the relative rarity of photochromic materials. Very high levels of security are possible, using modern data encipherment techniques. These are so secure that no known algorithmic method exists for breaking them in a practical amount of time. It should be understood that encipherment algorithms provide a way of protecting a message. Guaranteeing the authenticity of a complete document is better achieved using photochromic materials. This article describes a scheme which employs both techniques to achieve higher overall security than either can provide individually. Central to this idea is the ability to sense the presence of photochromic materials using machines, prior to recognizing specified patterns and reading text.
One of the central problems of computervision is object recognition. A catalogue of model objects is described as a set of features such as edges and surfaces. The same features are extracted from the scene and match...
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ISBN:
(纸本)0819413208
One of the central problems of computervision is object recognition. A catalogue of model objects is described as a set of features such as edges and surfaces. The same features are extracted from the scene and matched against the models for object recognition. Edges and surfaces extracted from the scenes are often noisy and imperfect. In this paper algorithms are described for improving low level edge and surface features. Existing edge extraction algorithms are applied to the intensity image to obtain edge features. Initial edges are traced by following directions of the current contour. These are improved by using corresponding depth and intensity information for decision making at branch points. Surface fitting routines are applied to the range image to obtain planar surface patches. An algorithm of region growing is developed that starts with a coarse segmentation and uses quadric surface fitting to iteratively merge adjacent regions into quadric surfaces based on approximate orthogonal distance regression. Surface information obtained is returned to the edge extraction routine to detect and remove fake edges. This process repeats until no more merging or edge improvement can take place. Both synthetic (with Gaussian noise) and real images containing multiple object scenes have been tested using the merging criteria. Results appeared quite encouraging.
The development of software that would be to computervision what expert system shells are to expert systems has been the subject of considerable inquiry over the last ten years; this paper reviews the pertinent publi...
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ISBN:
(纸本)0819413208
The development of software that would be to computervision what expert system shells are to expert systems has been the subject of considerable inquiry over the last ten years; this paper reviews the pertinent publications and tries to present a coherent view of the field. We start by outlining two major differences between would be `vision shells' and conventional expert system shells. The first is the need for an intermediate level of symbolic representation between image pixels and the knowledge base. The second is that the mental operations that people perform to interpret images lie almost totally below the threshold of consciousness. vision system designers therefore cannot, as domain experts normally do, examine their own mental processes and cast them into rules to extract information from images. The vision shell should thus contain, in addition to the usual knowledge engineering toolbox, knowledge on the pertinence of specific imaging operations towards various goals. After a review of the role of explicit knowledge in artificial vision, we examine the architecture a vision shell should have, and look at ways of facilitating the entry of domain-pertinent knowledge into it. Final remarks are made on knowledge representation and acquisition aspects particular to industrial applications.
A fundamental task in studying the action of cancer chemotherapy is to determine the quantity and spatial relationship of tumor-infiltrating lymphocyte populations. Classically this is performed by staining thin tissu...
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ISBN:
(纸本)0819413208
A fundamental task in studying the action of cancer chemotherapy is to determine the quantity and spatial relationship of tumor-infiltrating lymphocyte populations. Classically this is performed by staining thin tissue sections with antibodies by immunoperoxidase amplification. The staining technique is practically limited to locating a single cell type per tissue section. Full immunophenotyping requires successive staining of serial sections, using statistical analysis to correlate the results. This paper describes a system that brings together multi- parameter fluorescence imaging and morphological segmentation techniques to provide a fast, accurate, and automatic analysis of the lymphocyte infiltrate in tissue sections. With fluorescence techniques a single section can be stained with up to four distinct fluorescently labelled antibodies to determine cell phenotypes. To harness this potential computervisiontechniques are required to analyze the images. A routine based on the water shed algorithm has been developed that segments the nuclei image with an accuracy of greater than 90%. By matching the nuclei boundaries to the local peak fluorescence, cell boundary estimates are obtained in the antigen images. By then extracting two measurements from the boundary signal the cells can be classified according to their antigen expression. Determining cell expression of multiple antigens simultaneously provides a more detailed and accurate picture of the tumor infiltrate than single parameter analysis, and increases understanding of the immune response associated with the chemotherapy.
Color images can be analyzed using two kinds of coordinate systems: rectangular systems based on primary colors (RGB), and cylindrical systems based on hue, saturation, and intensity (HSI). HSI systems match our intui...
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ISBN:
(纸本)0819413208
Color images can be analyzed using two kinds of coordinate systems: rectangular systems based on primary colors (RGB), and cylindrical systems based on hue, saturation, and intensity (HSI). HSI systems match our intuitive understanding of colors and make it possible to name colors in knowledge bases, a significant advantage given the mushrooming use of declarative knowledge for image analysis. On the other hand, HSI systems give rise to singularities which result in undesirable instabilities, notably with respect to the statistical properties of hue distributions. Computing the mean and variance of a split distribution in the conventional manner would yield an unrealistically large variance and a mean hue in the blue-green region. The paper presents alternative ways of computing means and variances that avoid these effects. At the cost of a relatively slight numerical overhead, these computations generate results in agreement with our intuitive understanding of colors in split peak situations, and reduce to the standard definitions in well-behaved histograms. Recursive formulas are given for the calculation of these statistics, and an efficient algorithm is presented. Equivalence conditions between the results of the introduced procedures and conventional calculations are stated. Examples are given using actual color images.
Inspired from the time delays that occur in neurobiological signal transmission, we describe an adaptive time delay neural network (ATNN) which is a powerful dynamic learning technique for spatiotemporal pattern trans...
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ISBN:
(纸本)0819413208
Inspired from the time delays that occur in neurobiological signal transmission, we describe an adaptive time delay neural network (ATNN) which is a powerful dynamic learning technique for spatiotemporal pattern transformation and temporal sequence identification. The dynamic properties of this network are formulated through the adaptation of time-delays and synapse weights, which are adjusted on-line based on gradient descent rules according to the evolution of observed inputs and outputs. We have applied the ATNN to examples that possess spatiotemporal complexity, with temporal sequences that are completed by the network. The ATNN is able to be applied to pattern completion. Simulation results show that the ATNN learns the topology of a circular and figure eight trajectories within 500 on-line training iterations, and reproduces the trajectory dynamically with very high accuracy. The ATNN was also trained to model the Fourier series expansion of the sum of different odd harmonics. The resulting network provides more flexibility and efficiency than the TDNN and allows the network to seek optimal values for time-delays as well as optimal synapse weights.
This paper presents a computervision system for the acquisition and processing of 3-D images of wax dental imprints. The ultimate goal of the system is to measure a set of 10 orthodontic parameters that will be fed t...
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ISBN:
(纸本)0819413208
This paper presents a computervision system for the acquisition and processing of 3-D images of wax dental imprints. The ultimate goal of the system is to measure a set of 10 orthodontic parameters that will be fed to an expert system for automatic diagnosis of occlusion problems. An approach for the acquisition of range images of both sides of the imprint is presented. Range is obtained from a shape-from-absorption technique applied to a pair of grey-level images obtained at two different wavelengths. The accuracy of the range values is improved using sensor fusion between the initial range image and a reflectance image from the pair of grey-level images. The improved range image is segmented in order to find the interstices between teeth and, following further processing, the type of each tooth on the profile. Once each tooth has been identified, its accurate location on the imprint is found using a region- growing approach and its shape is reconstructed with third degree polynomial functions. The reconstructed shape will be later used by the system to find specific features that are needed to estimate the orthodontic parameters.
In the design and construction of mobile robotsvision has always been one of the most potentially useful sensory systems. In practice however, it has also become the most difficult to successfully implement. At the M...
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ISBN:
(纸本)0819413208
In the design and construction of mobile robotsvision has always been one of the most potentially useful sensory systems. In practice however, it has also become the most difficult to successfully implement. At the MIT Mobile Robotics (Mobot) Lab we have designed a small, light, cheap, and low power Mobot vision System that can be used to guide a mobile robot in a constrained environment. The target environment is the surface of Mars, although we believe the system should be applicable to other conditions as well. It is our belief that the constraints of the Maitian environment will allow the implementation of a system that provides vision based guidance to a small mobile rover. The purpose of this vision system is to process realtime visual input and provide as output information about the relative location of safe and unsafe areas for the robot to go. It might additionally provide some tracking of a small number of interesting feature, for example the lander. The system is designed t.o be self contained. It has its own camera and on board processing unit. It draws a small amount of power and exchanges a very small amount of information with the host robot. The project has two parts, first the construction of a hardware platform, and second the implementation of a successful vision algorithm. For the first part of the project, which is nearly complete, we have built a small self contained vision system. It employs a cheap but fast general purpose microcontroller (a 68332) connected to a Charge Coupled Device (CCD). The CCD provides the CPU with a continuous series of medium resolution gray-scale images (64 by 48 pixels with 256 gray levels at 10-15 frames a second). In order to accommodate our goals of low power, light weight, and small size we are bypassing the traditional NTSC video and using a purely digital solution. As the frames are captured any desired algorithm can then be implemented on the microcontroller to extract the desired information from the image
Low level edge detection operators usually do not generate contiguous edges, leaving objects in images with discontinuous borders. This, coupled with inherent signal noises, makes it difficult to identify objects in i...
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ISBN:
(纸本)0819413208
Low level edge detection operators usually do not generate contiguous edges, leaving objects in images with discontinuous borders. This, coupled with inherent signal noises, makes it difficult to identify objects in images. Here we describe a new algorithm that connects disjoint edge pixels to form continual object boundaries. We model the edge images as potential fields deployed with energies at the edge pixel positions all over the images. Pixels at the edge disjoint positions are charged by the combining forces of these edge pixels in proportion to the relative distances and directions of these pixels. An intrinsic part of the process is the identification of terminal edge pixels (TEP), accompanying with a classification of edge pixels in terms of the pixel connection patterns, to provide critical information for possible connectivity of edge segments. The algorithm applies a potential evaluation function to measure the likelihood of edge linking in certain directions for given TEPs. To reduce the computational overhead and improve the efficiency of the algorithm, an informed search method is used to locate significant edge pixels that present the most strong linking forces to a given TEP. The potential value for the TEP is calculated with respect to the edge directions dominated by the linking forces. When the potential value exceeds a given threshold in a direction, an extension is made at the TEP position in that direction. The process iterates until desired results are attained, using a global edge pattern evaluation scheme.
The conference materials contain 69 papers grouped into twelve sessions dealing with different topics in computervision. Pattern recognition;human face recognition algorithms and systems;image processing including fe...
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ISBN:
(纸本)0819407445
The conference materials contain 69 papers grouped into twelve sessions dealing with different topics in computervision. Pattern recognition;human face recognition algorithms and systems;image processing including feature spaces, edge and contour methods, optical character recognition and morphology;Packaging, materials handling, software and manipulation;fuzzy image processing and image understanding are the main topics covered.
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