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Unconstrained Licence Plate and Text Localization and Recognition
Matas, Jiří; Zimmermann, Karel
2005 -
Licence plates and traffic signs detection and recognition have a number of different applications relevant for transportation systems, such as traffic monitoring, detection of stolen vehicles, driver navigation support or any statistical research. A number of methods have been proposed, but only for particular cases and working under constraints (e.g. known text direction or high resolution). Therefore a new class of locally threshold separable detectors based on extremal regions, which can be adapted by machine learning techniques to arbitrary shapes, is proposed. In the test set of licence plate images taken from different viewpoints (-45°,45°), scales (from seven to hundreds of pixels height) even in bad illumination conditions and partial occlusions, the high detection accuracy is achieved (95%). Finally we present the detector generic abilities by traffic signs detection. The standard classifier (neural network) within the detector selects a relevant subset of extremal regions, i.e. regions that are connected components of a thresholded image. Properties of extremal regions render the detector very robust to illumination change and partial occlusions. Robustness to a viewpoint change is achieved by using invariant descriptors and/or by modelling shape variations by the classifier. The time-complexity of the detection is approximately linear in the number of pixel and a non-optimized implementation runs at about 1 frame per second for a 640 × 480 image on a high-end PC.
Available in digital repository of ČVUT.
Unconstrained Licence Plate and Text Localization and Recognition
Licence plates and traffic signs detection and recognition have a number of different applications relevant for transportation systems, such as traffic monitoring, detection of stolen vehicles, driver ...
WaldBoost – Learning for Time Constrained Sequential Detection
Šochman, Jan; Matas, Jiří
2005 -
In many computer vision classification problems, both the error and time characterizes the quality of a decision. We show that such problems can be formalized in the framework of sequential decision-making. If the false positive and false negative error rates are given, the optimal strategy in terms of the shortest average time to decision (number of measurements used) is the Wald's sequential probability ratio test (SPRT). We built on the optimal SPRT test and enlarge its capabilities to problems with dependent measurements. We show how to overcome the requirements of SPRT - (i) a priori ordered measurements and (ii) known joint probability density functions. We propose an algorithm with near optimal time and error rate trade-off, called WaldBoost, which integrates the AdaBoost algorithm for measurement selection and ordering and the joint probability density estimation with the optimal SPRT decision strategy. The WaldBoost algorithm is tested on the face detection problem. The results are superior to the state-of-the-art methods in the average evaluation time and comparable in detection rates.
Available in digital repository of ČVUT.
WaldBoost – Learning for Time Constrained Sequential Detection
In many computer vision classification problems, both the error and time characterizes the quality of a decision. We show that such problems can be formalized in the framework of sequential ...
Left-Handed Coplanar Waveguide
Macháč, Jan; Hudlička, Martin; Zehentner, Ján; Spiliotis, Nikolaos G.; Omar, Abbas S.
2005 -
This paper proposes a new version of a left-handed coplanar waveguide. The line has a fully uniplanar structure without vias and lumped elements. The series capacitors are represented by interdigital capacitors and the parallel inductors by short circuited CPW stubs connected to a ground metallization. The measured frequency dependences of S21 and S11 agree well with the data predicted by simulation. The simple equivalent circuit of the line unit cell was set up by fitting its dispersion characteristic to the dispersion characteristic of the first left-handed mode calculated by the CST Microwave Studio.
Keywords:
coplanar waveguide; metamaterial; left-handed transmission line
Available in digital repository of ČVUT.
Left-Handed Coplanar Waveguide
This paper proposes a new version of a left-handed coplanar waveguide. The line has a fully uniplanar structure without vias and lumped elements. The series capacitors are represented by interdigital ...
Flat Waveguide with a Longitudinal Slot
Zehentner, Ján; Mrkvica, Jan; Macháč, Jan
2005 -
This paper presents an analysis of a flat slotted waveguide by the spectral domain method finalized by a complex root search procedure. Matching of fields from bounded and unbounded regions at the common interface is explained and applied to satisfy the boundary conditions in the spectral domain. New theoretical findings are reported, and the dispersion characteristics of particular modes are shown and discussed with regard to their potential application. The different behaviour of the odd and even modes is pointed out. Their affinity to the modes in a standard rectangular waveguide is noted. A hint is given of a modification of the line cross-section resulting in the propagation of a bound mode besides the propagation of the space leaky modes.
Keywords:
boundary conditions; complex propagation constants; flat slotted waveguide; leaky waves; spectral domain method
Available in digital repository of ČVUT.
Flat Waveguide with a Longitudinal Slot
This paper presents an analysis of a flat slotted waveguide by the spectral domain method finalized by a complex root search procedure. Matching of fields from bounded and unbounded regions at the ...
Two-view Geometry Estimation Unaffected by a Dominant Plane
Chum, Ondřej; Werner, Tomáš; Matas, Jiří
2005 -
A RANSAC-based algorithm for robust estimation of epipolar geometry from point correspondences in the possible presence of a dominant scene plane is presented. The algorithm handles scenes with (i) all points in a single plane, (ii) majority of points in a single plane and the rest off the plane, (iii) no dominant plane. It is not required to know a priori which of the cases (i)-(iii) occurs. The algorithm exploits a theorem we proved, that if five or more of seven correspondences are related by a homography then there is an epipolar geometry consistent with the seven-tuple as well as with all correspondences related by the homography. This means that a seven point sample consisting of two outliers and five inliers lying in a dominant plane produces an epipolar geometry which is wrong and yet consistent with a high number of correspondences. The theorem explains why RANSAC often fails to estimate epipolar geometry in the presence of a dominant plane. Rather surprisingly, the theorem also implies that RANSAC-based homography estimation is faster when drawing nonminimal samples of seven correspondences than minimal samples of four correspondences.
Available in digital repository of ČVUT.
Two-view Geometry Estimation Unaffected by a Dominant Plane
A RANSAC-based algorithm for robust estimation of epipolar geometry from point correspondences in the possible presence of a dominant scene plane is presented. The algorithm handles scenes with (i) ...
Matching with PROSAC – Progressive Sample Consensus
Chum, Ondřej; Matas, Jiří
2005 -
A new robust matching method is proposed. The progressive sample consensus (PROSAC) algorithm exploits the linear ordering defined on the set of correspondences by a similarity function used in establishing tentative correspondences. Unlike RANSAC, which treats all correspondences equally and draws random samples uniformly from the full set, PROSAC samples are drawn from progressively larger sets of top-ranked correspondences. Under the mild assumption that the similarity measure predicts correctness of a match better than random guessing, we show that PROSAC achieves large computational savings. Experiments demonstrate it is often significantly faster (up to more than hundred times) than RANSAC. For the derived size of the sampled set of correspondences as a function of the number of samples already drawn, PROSAC converges towards RANSAC in the worst case. The power of the method is demonstrated on wide-baseline matching problems.
Available in digital repository of ČVUT.
Matching with PROSAC – Progressive Sample Consensus
A new robust matching method is proposed. The progressive sample consensus (PROSAC) algorithm exploits the linear ordering defined on the set of correspondences by a similarity function used in ...
Processing of Alumina Nano-films
Mach, P.; Rozkošný, T.
2005 -
There are different technologies for processing of alumina thin films. It has been found that only some of them are usable for reliable and reproducible processing of nano-films with the thickness of 2 through 3 nm. Such the films are used for fabrication of tunneling junctions with high sensitivity to humidity, which can be used for fabrication of humidity sensors. The alumina films are mostly prepared on evaporated or sputtered aluminum electrode by oxidization. Quality of tunneling junctions with alumina tunneling barrier fabricated of air-oxidized, oxygen-oxidized and oxygen plasma-oxidized Al electrodes has been examined by the measurement of resistances and capacitances of the junctions. Sensitivity of the junctions to external humidity has been examined, too. It has been found that the best technology for fabrication of alumina nano-films is plasmatic oxidation of aluminum evaporated thin films. It has been also found that the alumina nano-thin films are very sensitive to humidity.
Available in digital repository of ČVUT.
Processing of Alumina Nano-films
There are different technologies for processing of alumina thin films. It has been found that only some of them are usable for reliable and reproducible processing of nano-films with the thickness of ...
Influence of Interconnection Surface Finishes on Quality of Adhesive Joints
Mach, P.; Bušek, D.; Duraj, A.
2005 -
Electrically conductive adhesives electrically connect and mechanically bond circuits to a variety of substrates. Four different silver-filled isotropically conductive adhesives have been used for attaching of 1206 chip components (resistors with "zero" values -jumpers) on printed-circuit boards with six different interconnection surface finishes: Cu (standard cleaning), oxidized Cu, Cu after degradation vapors of H2SO3, Ni, Au over Ni, Sn (HAL). The resistances, nonlinearity, and noise of joints have been investigated before and after application of the dynamic mechanical load, which has been realized by periodical deflection of the printed circuit boards with assembled resistive chips. The load of the individual joints has been calculated. It has been found that degradation of Cu surface does not cause significant changes of electrical properties of the joints. The worst electrical parameters as well as the lowest resistance against the dynamic mechanical load have been found for the joints realized on Ni and Sn surface finishes.
Available in digital repository of ČVUT.
Influence of Interconnection Surface Finishes on Quality of Adhesive Joints
Electrically conductive adhesives electrically connect and mechanically bond circuits to a variety of substrates. Four different silver-filled isotropically conductive adhesives have been used for ...
Ontology Driven Voice-Based Interaction in Mobile Environment
Kopsa, Jiří; Míkovec, Zdeněk; Slavík, Pavel
2005 - English
In this paper we are presenting a prototype of a voice user interface that allows users to interact with the mobile knowledge management system, which is being developed at Czech Technical University in Prague. The primary application domain of the system is facility and construction site management. The knowledge handled by the system consists of a domain ontology, site plans and their semantic descriptions (application ontology). The site plans are stored in the SVG format; the semantic descriptions along with the domain ontology are stored in the OWL format. The knowledge (described by the corresponding ontology) is used for efficient control of the voice based interaction with the knowledge management system. The implementation of the voice user interface is based on the existing VoiceXML platform.
Available in digital repository of ČVUT.
Ontology Driven Voice-Based Interaction in Mobile Environment
In this paper we are presenting a prototype of a voice user interface that allows users to interact with the mobile knowledge management system, which is being developed at Czech Technical University ...
First results of microwave measurement of broadband radio interference filters
Hoffmann, Karel; Škvor, Zbyněk
2004 -
A vector measurement method for testing multiport interference filters for shielded chambers has been used. Measured data up to 3 GHz are presented. The authors believe that this is the first time such results have been published.
Available in digital repository of ČVUT.
First results of microwave measurement of broadband radio interference filters
A vector measurement method for testing multiport interference filters for shielded chambers has been used. Measured data up to 3 GHz are presented. The authors believe that this is the first time ...
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