Andrzej Walczak

Adaptive edge detection method for images

The novel two-dimensional (2D) wavelet with anisotropic property and application of it has been presented. Wavelet is constructed in the polar coordinate system to obtain anisotropic properties. A novel edge detection method has been developed with the aid of this wavelet. This method detects gradient jump and than follows along this jump. In this way the number of calculation for edge localization is reduced. Moreover, the presented method is able to detect all edges in an image in multi-scale together with its spatial orientation. Proposed wavelet as well as edge extraction method seems to be new way to edge detection for an image.

New Low Melting Nematics 2-Chloro-4-Alkylphenyl 4-Alkylbicyclo-[2,2,2]Octane-1-Carboxylates with Negative Dielectric Anisotropy

Abstract Synthesis of a new class of stable, low melting nematics with a negative dielectric anisotropy is described. The basic physical properties of 2-chloro-4-heptylphenyl 4-pentylbicy-clo-[2,2,2]octane-1-carboxylate (7CP5BOC) are presented.

An ontology building system for structuring medical diagnostic knowledge

The paper gives an overview of research devoted to developing a semi-automatic methodology of building a semantic model of medical diagnostic knowledge. The methodology can serve multiple purposes. First of all it can be a foundation for building ontologies of diseases. The same methodology can also be used for building ontologies of medical diagnostic technologies. The semantic model is applied because it allows for uniform representation of heterogenic data. In the context of medicine this allows for the fusion of heterogenic data coming from different diagnostic technologies. In consequence all the data gathered for a particular patient can be further processed with the aid of the same mathematical techniques. Thus it is easy to construct a reasoning mechanism that diagnoses the possible diseases by comparing the data obtained for a patient with the semantic models of diseases. The process of an ontology building is automatic and uses a set of natural language processing methods. The described methodology was developed specifically for the Polish language.

Waveguide couplers induced optically over organic junction

A new kind of waveguide and waveguide coupler formed in a nematic liquid crystal (lc) cell is created by means of a weak-intensity laser beam that propagates along the flat boundary between layers of lc and photoconductive polymer. To obtain a waveguide, the connection between the lc and polymer must be driven by the properly polarized voltage. The examined lc cells were of a common kind with indium-tin-oxide (ITO) uniform electrodes on both inner sides of a glass plate. The planar homogeneous alignment of the lc layer was confined by a poly (N-vinyl carbazole) (PVC) layer on one side and a polyimide layer on the opposite side. We applied the PVC doped with a photosensitizer as the photoconductive polymer and a nematic lc mixture of high birefringence. A waveguide was created along a light beam propagation path, and coupling between the waveguides was fabricated in the same way. The energy transfer between the waveguides was proved in properly prepared experiments for laser beam wavelengths equal to 532 nm and 632.8 nm. For both wavelengths, the outcomes of the experiments were of the same quality.

2-D wavelet with position controlled resolution

Wavelet transformation localizes all irregularities in the scene. It is most effective in the case when intensities in the scene have no sharp details. It is the case often present in a medical imaging. To identify the shape one has to extract it from the scene as typical irregularity. When the scene does not contain sharp changes then common differential filters are not efficient tool for a shape extraction. The new 2-D wavelet for such task has been proposed. Described wavelet transform is axially symmetric and has varied scale in dependence on the distance from the centre of the wavelet symmetry. The analytical form of the wavelet has been presented as well as its application for details extraction in the scene. Most important feature of the wavelet transform is that it gives a multi-scale transformation, and if zoom is on the wavelet selectivity varies proportionally to the zoom step. As a result, the extracted shape does not change during zoom operation. What is more the wavelet selectivity can be fit to the local intensity gradient properly to obtain best extraction of the irregularities.

Medical data preprocessing for increased selectivity of diagnosis

Abstract In this review, we present a framework that will enable us to obtain increased accuracy of computer diagnosis in medical patient checkups. To some extent, a new proposition for medical data analysis has been built based on medical data preprocessing. The result of such preprocessing is transformation of medical data from descriptive, semantic form into parameterized math form. A proper model for digging of hidden medical data properties is presented as well. Exploration of hidden data properties achieved by means of preprocessing creates new possibilities for medical data interpretation. Diagnosis selectivity has been increased by means of parameterized illnesses patterns in medical databases.

Digital images interpolation with wavelet edge extractors

We present an interpolation algorithm for digital images based on the extended Edge-Directed Interpolation. The proposed algorithm utilises localisation and orientation of edges extracted with wavelet edge extractors. The algorithm chooses an interpolation method of a given point of an image, depending on localisation with respect to extracted edges. We apply our method to grey scale digital images. In this paper we present only the first stage of this algorithm. This stage is focused on interpolation along almost straight edges without corners. We present the results obtained with this part of our algorithm, in comparison to a few popular interpolation algorithms and we propose a plan of further algorithm extensions.

Design of the liquid crystal band-pass optical filter

Dispersion of the refraction indices n (λ) as well as dispersion of the imaginary part of the refection coefficient r = r0*exp(-iφR(λ)) have to be determined to design band-pass Fabry-Perot filter. In the case when liquid crystal is placed in the filter gap then both ordinary and extraordinary indices have to be determined. Consequently one must find imaginary part of the coefficient r for ordinary and extraordinary waves transmitted by the filter. Imaginary part of the refraction coefficient is called also phase of reflection. Proposed method exploits a Fabry-Perot filter to obtain examined values. It has been proved that both values, phase of reflection, and refraction indices must be determined in the same procedure from data obtained in the same measurement. The procedure consists of: determination of the transmission peaks position in the Fabry-Perot filter spectrum; nonlinear fit procedure which optimize dispersions of the n(λ), and φR(λ) to minimize the differences between theoretical and experimental transmissions of the filter; simulation of the free spectral range (FSR), and finesse of the filter spectrum in dependence on dispersions of n(λ), and φR(λ). Results have been presented in the case of four different liquid crystal substances and two different mirrors applied in the filter. The way for determination of the φR (λ) seems to be interesting as this value is really hard to measure. Presented data for the examined liquid crystals are also new.

EDGE DETECTION WITH LIQUID CRYSTAL POLARIZING FILTER

The liquid crystalline filter exhibiting particular optical properties is presented. Their basis application is the multiresolution image analyzer based on a wavelet transform (WT). In co-operation with the phase shifter such a filter allows to rotate the polarization of the transmitted light. The resulted intensity distribution has been exploited as a tool to span the transmitted image onto the space of the circular Haar wavelets. It provides new possibilities in an optical signal processing. The analysis of the light transmission in considered filter as well as the wavelet space creation are also described.

Analysis and model of the photorefractive-like effect in non-conductive asymmetric liquid crystal hybrid cell

The paper presents the way that colour can serve solving the problem of calibration points indexing in a camera geometrical calibration process. We propose a technique in which indexes of calibration points in a black-and-white chessboard are represented as sets of colour regions in the neighbourhood of calibration points. We provide some general rules for designing a colour calibration chessboard and provide a method of calibration image analysis. We show that this approach leads to obtaining better results than in the case of widely used methods employing information about already indexed points to compute indexes. We also report constraints concerning the technique. Nowadays we are witnessing an increasing need for camera geometrical calibration systems. They are vital for such applications as 3D modelling, 3D reconstruction, assembly control systems, etc. Wherever possible, calibration objects placed in the scene are used in a camera geometrical calibration process. This approach significantly increases accuracy of calibration results and makes the calibration data extraction process easier and universal. There are many geometrical camera calibration techniques for a known calibration scene [1]. A great number of them use as an input calibration points which are localised and indexed in the scene. In this paper we propose the technique of calibration points indexing which uses a colour chessboard. The presented technique was developed by solving problems we encountered during experiments with our earlier methods of camera calibration scene analysis [2]-[3]. In particular, the proposed technique increases the number of indexed points points in case of local lack of calibration points detection. At the beginning of the paper we present a way of designing a chessboard pattern. Then we describe a calibration point indexing method, and finally we show experimental results. A black-and-white chessboard is widely used in order to obtain sub-pixel accuracy of calibration points localisation [1]. Calibration points are defined as corners of chessboard squares. Assuming the availability of rough localisation of these points, the points can be indexed. Noting that differences in distances between neighbouring points in calibration scene images differ slightly, one of the local searching methods can be employed (e.g. [2]). Methods of this type search for a calibration point to be indexed, using a window of a certain size. The position of the window is determined by a vector representing the distance between two previously indexed points in the same row or column. However, experiments show that this approach has its disadvantages, as described below. * E-mail: A.Nowakowski@ire.pw.edu.pl Firstly, there is a danger of omitting some points during indexing in case of local lack of calibration points detection in a neighbourhood (e.g. caused by the presence of non-homogeneous light in the calibration scene). A particularly unfavourable situation is when the local lack of detection effects in the appearance of separated regions of detected calibration points. It is worth saying that such situations are likely to happen for calibration points situated near image borders. Such points are very important for the analysis of optical nonlinearities, and a lack of them can significantly influence the accuracy of distortion modelling. Secondly, such methods may give wrong results in the case of optical distortion with strong nonlinearities when getting information about the neighbouring index is not an easy task. Beside this, the methods are very sensitive to a single false localisation of a calibration point. Such a single false localisation can even result in false indexing of a big set of calibration points. To avoid the above-mentioned problems, we propose using a black-and-white chessboard which contains the coded index of a calibration point in the form of colour squares situated in the nearest neighbourhood of each point. The index of a certain calibration point is determined by colours of four nearest neighbouring squares (Fig.1). An order of squares in such foursome is important. Because the size of a colour square is determined only by the possibility of correct colour detection, the size of a colour square can be smaller than the size of a black or white square. The larger size of a black or white square is determined by the requirements of the exact localisation step which follows the indexing of calibration points [3]. In this step, edge information is extracted from a blackand-white chessboard. This edge information needs larger Artur Nowakowski, Wladyslaw Skarbek Institute of Radioelectronics, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warszawa, A.Nowakowski@ire.pw.edu.pl Received February 10, 2009; accepted March 27, 2009; published March 31, 2009 http://www.photonics.pl/PLP