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Gdeisat M.A.,Colleges of Applied science | Burton D.R.,Liverpool John Moores University | Lilley F.,Liverpool John Moores University | Arevalillo-Herraez M.,University of Valencia | And 2 more authors.
Measurement Science and Technology | Year: 2016

The number of phase wraps in an image can be either reduced, or completely eliminated, by transforming the image into the frequency domain using a Fourier transform, and then shifting the spectrum towards the origin. After this, the spectrum is transformed back to the spatial domain using the inverse Fourier transform and finally the phase is extracted using the arctangent function. However, it is a common concern that the spectrum can be shifted only by an integer number, meaning that the phase wrap reduction is often not optimal. In this paper we propose an algorithm than enables the spectrum to be frequency shifted by a rational number. The principle of the proposed method is confirmed both by using an initial computer simulation and is subsequently validated experimentally on real fringe patterns. The technique may offer in some cases the prospects of removing the necessity for a phase unwrapping process altogether and/or speeding up the phase unwrapping process. This may be beneficial in terms of potential increases in signal recovery robustness and also for use in time-critical applications. © 2016 IOP Publishing Ltd.

Arevalillo-Herraez M.,University of Valencia | Gdeisat M.,Colleges of Applied science | Lilley F.,Liverpool John Moores University | Burton D.R.,Liverpool John Moores University
Optics and Lasers in Engineering | Year: 2016

In this paper, we present a novel algorithm to reduce the number of phase wraps in two dimensional signals in fringe projection profilometry. The technique operates in the spatial domain, and achieves a significant computational saving with regard to existing methods based on frequency shifting. The method works by estimating the modes of the first differences distribution in each axial direction. These are used to generate a tilted plane, which is subtracted from the entire phase map. Finally, the result is re-wrapped to obtain a phase map with fewer wraps. The method may be able to completely eliminate the phase wraps in many cases, or can achieve a significant phase wrap reduction that helps the subsequent unwrapping of the signal. The algorithm has been exhaustively tested across a large number of real and simulated signals, showing similar results compared to approaches operating in the frequency domain, but at significantly lower running times. © 2015 Elsevier Ltd. All rights reserved.

Gdeisat M.,Colleges of Applied science | Burton D.,Liverpool John Moores University | Lilley F.,Liverpool John Moores University | Arevalillo-Herraez M.,University of Valencia
Optics Communications | Year: 2016

This paper suggests the use of FIR Hilbert transformers to extract the phase of fringe patterns. This method is computationally faster than any known spatial method that produces wrapped phase maps. Also, the algorithm does not require any parameters to be adjusted which are dependent upon the specific fringe pattern that is being processed, or upon the particular setup of the optical fringe projection system that is being used. It is therefore particularly suitable for full algorithmic automation. The accuracy and validity of the suggested method has been tested using both computer-generated and real fringe patterns. This novel algorithm has been proposed for its advantages in terms of computational processing speed as it is the fastest available method to extract the wrapped phase information from a fringe pattern. © 2015 Elsevier B.V.

Elhag M.F.,Colleges of Applied science | Ahmed A.H.A.,University of Khartoum
Proceedings - 2013 International Conference on Computer, Electrical and Electronics Engineering: 'Research Makes a Difference', ICCEEE 2013 | Year: 2013

Instructor's teaching experience or instructional style (INST) is an essential factor in the knowledge transfer for T-learning [1], so in this paper I tried to cope (INST) in E-learning system as well. Specifically, this paper proposed (Methodological approach based on Fuzzy logic to Select the Optimum Instructional style(s) for Designing a Specific E-learning system (MFSOI-DSE). The proposed (MFSOI-DSE) extends the fuzzy logic concepts and techniques in E-learning field, explicitly, in selecting an optimum (INST) for developing a specific courseware. In this paper I proposed a new procedure for representing the (INST) in quantitative values instead of qualitative description, using Frame of cognition/knowledge. In this paper, a conducted case study using the proposed procedure has met the selection of INST for developing a specific courseware with an expertise decision. Moreover, the paper specified the best software tools for building an automated system based on the above mentioned procedure in order to facilitate the (MFSOI-DSE). The topic of this paper lies on a multidisciplinary area of research, so it needs a solid background in computer science, Fuzzy logic and Instructional design field. Finally, I hope this paper will improve the quality of the E-learning systems based on IQP (Instructional Quality Profile) [1]. © 2013 IEEE.

Jebari C.,Colleges of Applied science
Procesamiento de Lenguaje Natural | Year: 2015

This paper presents a new method for genre identification that combines homogeneous classifiers using OWA (Ordered Weighted Averaging) operators. Our method uses character n-grams extracted from different information sources such as URL, title, headings and anchors. To deal with the complexity of web pages, we applied MLKNN as a multi-label classifier, in which a web page can be affected by more than one genre. Experiments conducted using a known multi-label corpus show that our method achieves good results. © 2015 Sociedad Española para el Procesamiento del Lenguaje Natural.

Gdeisat M.,Colleges of Applied science | Qudeisat M.,Purdue University | Alsa'D M.,University of Cambridge | Burton D.,Liverpool John Moores University | And 2 more authors.
Optics and Lasers in Engineering | Year: 2016

This paper suggests a novel absolute empirical calibration method for a multi-sensor fringe projection system. The optical setup of the projector-camera sensor can be arbitrary. The term absolute calibration here means that the centre of the three dimensional coordinates in the resultant calibrated volume coincides with a preset centre to the three-dimensional real-world coordinate system. The use of a zero-phase fringe marking spot is proposed to increase depth calibration accuracy, where the spot centre is determined with sub-pixel accuracy. Also, a new method is proposed for transversal calibration. Depth and transversal calibration methods have been tested using both single sensor and three-sensor fringe projection systems. The standard deviation of the error produced by this system is 0.25 mm. The calibrated volume produced by this method is 400 mm×400 mm×140 mm. © 2015 Elsevier Ltd. All rights reserved.

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