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The Division of Nuclear and Medical Electronics of Warsaw
University of Technology is an institution where a capacitance process
tomograph was first designed in Poland. The design of this capacitance
tomograph, its performance and first results are presented in the paper.
The tomograph can operate with one or two probes with up to 32 electrodes
altogether. Twelve or sixteen electrode configuration is commonly used
and a two times twelve or two times sixtheen electrode set up is provided
for flowmeter applications. Additionally, the device has functionality
of a 16-channel capacitance meter for industrial applications. The tomograph
has a novel modular structure. It consists of 16 analogue signal cards,
a motherboard and a control module with an analogue to digital converter.
The measurement is based on a standard charge ñ discharge method.
The signal card is capable to work both as a transmitter and a receiver
during the measurement process. The motherboard provides communication
between signal cards and the control module using a custom digital bus.
The control module contains a 16-bit analogue to digital converter, a control
logic, and a serial communication interface. All digital electronic circuits
have been designed using programmable logic devices (PLDs).
Keywords: capacitance measurement, capacitance tomography, measurement system.
The general concept of 3D data acquisition and processing system which enables us gathering information about shape, morphing, and movement of 3D object for virtual environment is presented. The methodology based on combined structured light, spatio-temporal phase analysis, and photogrametry is described. For virtual reality the concept of a virtual camera, as the mean for interactive object visualization is introduced. The exemplary initial results of implementation of such a system are presented.
Keywords: 3D shape measurement, digital fringe projection, spatio-temporal fringe pattern analysis, movement trajectories, virtual reality.
The paper presents an algorithm for estimation of temperature of image. Colour temperature is important, perceptual feature describing colour and content of images. The main idea of the algorithm is to average pixel values of image, omitting the values which have meaningless influence on perception of colour temperature. It is done in an iterative procedure. The convergence of the procedure is discussed. The algorithm can be applied in image search/retrieval tasks and is proposed in the MPEG-7 colour temperature descriptor for estimation of colour temperature of images.
Keywords: colour temperature, colour perception, image retrieval.
This paper presents the robust colour image segmentation algorithm which can be used extensively in automated optical inspection system on the printed circuits boards (PCB) assembly line. The robustness of the presented algorithm is increased by low computational effort what dedicates this approach to on-line vision systems explored in high-speed production lines. The second advantage of the proposed algorithm is the non-parametric solution which is invariant to changes of light and colour of the inspected components. This condition should be fulfilled with the vectoral imaging approach where the most important task is the segmentation process which divides image space into disjoint regions with similar colour or texture.
Keywords: image analysis, colour image segmentation, clustering, optical inspection.
Problems of quality improvement in holographic images and a reconstruction time reduction are discussed. The convolution and Fresnel approaches are presented. For both methods the algorithm improvement is proposed. Basing on a special transmittance function calculation, a computation time significantly decreases. For the Fresnel approximation, an autocorrelation factor from the reconstructed image is removed. The presented ideas are illustrated by exemplary images for each step of computation. Advantages and disadvantages of the methods are discussed.
Keywords: digital holography, convolution approach, response function, image filtration.
The paper presents technological achievements in fabrication
of cryogenically-cooled and ambient temperature HgCdTe photodiodes carried
out during the last four years at the Institute of Applied Physics, Military
University of Technology. Because of the complicated and expensive fabrication
process, numerical simulation has become a critical tool for the development
of HgCdTe bandgap engineering devices. Therefore in the second part of
the paper, an original iteration scheme is used to predict the effect of
composition and doping profiles on the heterojunction detector parameters.
A novel tipping boat for liquid phase epitaxial (LPE) growth of HgCdTe
from Te-rich solutions has been proposed. The
successful fabrication of long wavelength infrared (LWIR)
Hg1-yCdyTe/Hg1-xCdxTe heterostructures
(y > x) on semi-insulating (111)CdZnTe substrates is presented. The performance
of p-on-n double-layer heterojunction (DLHJ) photodiodes at temperature
77 K is analysed. It is also shown that LPE can be used to realise advanced
bandgap engineered multi-junction structures. The parameters and characteristics
of the new type of HgCdTe buried photodiodes, operated at near-room temperature
(T = 200-300 K) in
LWIR spectral range, are reported. Finally, an effective
numerical model for performance predictions of HgCdTe heterostructure device
is presented. The model is used to analyse the performance of dual-band
HgCdTe photovoltaic detector and mid wavelength infrared (MWIR) HgCdTe
heterostructure device. In the last case, it is shown that excess 1/f noise
of MWIR non-equilibrium heterostructure device is connected with fluctuation
of carrier mobility.
Keywords: liquid epitaxy, HgCdTe photodiodes, multi-junction
photodiodes, heterostructure photodiodes, dual-band
detectors.
Microcalcifications are one of more important signs enabling
detection of breast cancer at an early stage. The main goal of the research
was designing and realization of a system for automatic detection and classification
of microcalcifications, taking advantage of the proposed automatic feature
selection algorithm. The first step of the detection algorithm is to segment
the individual objects: potential microcalcifications. This is achieved
by applying opening by reconstruction top-hat technique
and image thresholding based on approximation of an image
local histogram with a probability density function of Gauss distribution.
Selected features of the segmented objects are used as inputs to neural
networks. The first classifier verifies the initial detection and the others
assess a diagnosis of the input objects. The algorithm results are locations
of suggested microcalcifications and optionally automatic diagnosis. The
presented form of the system was verified in clinical tests using diagnosed
databases (DDSM from the University of South Florida and own digitised
database of mammograms). The
achieved results are promising and comparable with other
known systems. Efficiency of icrocalcifications detection was up to 90%.
Keywords: computer-aided diagnosis, microcalcification detection, digital mammography.
The complex algorithm for estimating a length of blood vesselsí newly created in angiogenesis process has been presented. A filtering method using two-dimensional matched filter is a fundamental process in the presented algorithm. For proper extraction of blood vesselsí network more image processing techniques has been used including spatial low-pass filtering, binarisation, skeletonisation, and, developed by the author, algorithms for cleaning vessel network obtained in this process and for removing vessels false detected in the previous steps. The presented algorithm can be used for fully automatic vesselsí length estimating in medical images and can be helpful for angiogenesis processís research.
Keywords: biomedical imaging, digital filters, image processing.
Dynamic optical data storage and other applications in the field of optical data processing would be possible due to development of suitable nonlinear optical materials. The experimental investigations of the orientation photorefractive effect in nematic liquid crystals have been presented. The investigations showed that the orientational optical sensitivity of liquid crystals can be greatly enhanced by an external electric and optical applied field. The photorefractive volume space charge field in the LC cell is the result of charge generation in the bright regions of interference pattern and charge transportation.
Keywords: photorefractive liquid crystals, dynamic holography.
Novel, fast, accurate, and low complexity face localisation algorithm is presented. It is robust for hard scene conditions, such as complex background, different lighting, and face poses. It exploits spatial masking of face colour areas in normalised perceptually plausible tint-saturation-luminance (TSL) space where Canny filter is applied. Then, facial areas are approximated by ellipses of constrained proportions using fuzzy Hough transform on detected edges. Finally eye localisation technique is applied in Cr-Cb colour space in order to determine face pose, confirm face presence, and it enables us normalisation of face recognition.
Keyword: face localisation, Hough transform, TSL colour space.
Increasing application of non-invasive medical techniques
(like stereotactic radiosurgery) generates a high demand for modern image
processing algorithms. Image registration and segmentation are the two
essential examples of this. The algorithms need to be reasonably fast,
reliable, accurate, and highly automated. Information theory provides a
means to create such systems. In this paper we present thresholding segmentation
using image entropy and a registration technique based on maximization
of mutual information. Then we show some experimental
results using real-world computed tomography (CT) and medical resonance
imaging (MRI) data.
Keywords: image segmentation, image registration, entropy, mutual information.