Yazar "Coskun, Emre" seçeneğine göre listele

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    3D Profile Measurements of Objects by Using Zero Order Generalized Morse Wavelet
    (Amer Inst Physics, 2017) Kocahan, Ozlem; Durmus, Cagla; Elmas, Merve Naz; Coskun, Emre; Tiryaki, Erhan; Ozder, Serhat
    Generalized Morse wavelets are proposed to evaluate the phase information from projected fringe pattern with the spatial carrier frequency in the x direction. The height profile of the object is determined through the phase change distribution by using the phase of the continuous wavelet transform. The phase distribution is extracted from the optical fringe pattern choosing zero order Generalized Morse Wavelet (GMW) as a mother wavelet. In this study, standard fringe projection technique is used for obtaining images. Experimental results for the GMW phase method are compared with the results of Morlet and Paul wavelet transform.
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    A new method to determine the continuous refractive index of an absorbing film by Generalized Stockwell Transform
    (Elsevier Sci Ltd, 2023) Coskun, Emre; Emir, Cansu; Selamet, Semanur; Parlak, Mehmet; Ozder, Serhat
    Generalized Stockwell Transform (GST) was adapted to analyze a transmittance signal to continuously determine the refractive index and extinction coefficient. The process is built by analyzing oscillation frequencies of the transmission signal where oscillations exist. The simulation studies clearly show the advantage of the locally referenced phase property of the presented method. The validity of the method was checked for a CdS thin film. The results determined by the GST method are consistent with the results determined by envelope and other signal analyzing methods, and the literature. The noise and relative error analysis of the method was also discussed.
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    A Simulation Study for Determination of Refractive Index Dispersion of Dielectric Film from Reflectance Spectrum by Using Paul Wavelet
    (Amer Inst Physics, 2017) Tiryaki, Erhan; Coskun, Emre; Kocahan, Ozlem; Ozder, Serhat
    In this work, the Continuous Wavelet Transform (CWT) with Paul wavelet was improved as a tool for determination of refractive index dispersion of dielectric film by using the reflectance spectrum of the film The reflectance spectrum was generated theoretically in the range of 0.8333 - 3.3333 mu m wavenumber and it was analyzed with presented method. Obtained refractive index determined from various resolution of Paul wavelet were compared with the input values, and the importance of the tunable resolution with Paul wavelet was discussed briefly. The noise immunity and uncertainty of the method was also studied.
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    An Improved Method For Determination Of Refractive Index Of Absorbing Films: A Simulation Study
    (Amer Inst Physics, 2017) Ozcan, Seckin; Coskun, Emre; Kocahan, Ozlem; Ozder, Serhat
    In this work an improved version of the method presented by Gandhi was presented for determination of refractive index of absorbing films. In this method local maxima of consecutive interference order in transmittance spectrum are used. The method is based on the minimizing procedure leading to the determination of interference order accurately by using reasonable Cauchy parameters. It was tested on theoretically generated transmittance spectrum of absorbing film and the details of the minimization procedure were discussed.
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    An Improved Method For The Determination Of Birefringence Dispersion Of Liquid Crystal Cell: A Simulation Study
    (Amer Inst Physics, 2016) Ozcan, Seckin; Coskun, Emre; Kocahan, Ozlem; Ozder, Serhat
    An improved approach to determine the birefringence dispersion of a liquid crystal cell was presented. Using the local maxima or minima of the transmittance spectrum of liquid crystal cell is a very convenient method for this aim with the proviso that at least one birefringence value must be known in advance from which the interference orders corresponding to maxima or minima are determined. Presented approach overcomes this problem. The improved method was based on the minimizing procedure leading to the determination of interference order and Cauchy parameters accurately. It was tested on a theoretically generated transmittance spectrum of liquid crystal cell and the details of the fitting procedure were discussed.
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    Determination of birefringence dispersion in nematic liquid crystals by using an S-transform
    (Optical Soc Amer, 2007) Ozder, Serhat; Coskun, Emre; Koysal, Oguz; Kocahan, Ozlem
    An analysis of the transmittance signal of the 5CB-coded nematic liquid crystal by using an S-transform is presented. The transmittance spectrum of this liquid crystal is acquired in the 1.26-2.22 mu m(-1) region at room temperature. The dispersion curve of birefringence is obtained for 5CB by this analysis, and data are fitted to the Cauchy formula, whereby the dispersion parameters are extracted. The result is found to be in favorable accordance with the Merck catalog value. (c) 2007 Optical Society of America.
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    Determination of phase from the ridge of CWT using generalized Morse wavelet
    (Iop Publishing Ltd, 2018) Kocahan, Ozlem; Tiryaki, Erhan; Coskun, Emre; Ozder, Serhat
    The selection of wavelet is an important step in order to determine the phase from the fringe patterns. In the present work, a new wavelet for phase retrieval from the ridge of continuous wavelet transform (CWT) is presented. The phase distributions have been extracted from the optical fringe pattern by choosing the zero order generalized morse wavelet (GMW) as a mother wavelet. The aim of the study is to reveal the ways in which the two varying parameters of GMW affect the phase calculation. To show the validity of this method, an experimental study has been conducted by using the diffraction phase microscopy (DPM) setup; consequently, the profiles of red blood cells have been retrieved. The results for the CWT ridge technique with GMW have been compared with the results for the Morlet wavelet and the Paul wavelet; the results are almost identical for Paul and zero order GMW because of their degree of freedom. Also, for further discussion, the Fourier transform and the Stockwell transform have been applied comparatively. The outcome of the comparison reveals that GMWs are highly applicable to the research in various areas, predominantly biomedicine.
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    Determination of the refractive index of a dielectric film continuously by the generalized S-transform
    (Optical Soc Amer, 2010) Coskun, Emre; Sel, Kivanc; Ozder, Serhat
    The generalized S-transform was improved as a method to determine the refractive index of a dielectric film continuously by using the transmittance spectrum, and the applicability of the method was demonstrated on mica. The result determined from the generalized S-transform method was compared with the results determined from the S-transform and the fringe counting methods and published values. The advantage of the proposed method was explained, and the absolute error of the presented method was also calculated. (c) 2010 Optical Society of America
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    Generalized Morse wavelet for the determination of the birefringence of a liquid crystal cell
    (Iop Publishing Ltd, 2015) Kocahan, Ozlem; Coskun, Emre; Ozder, Serhat
    The generalized Morse wavelet (GMW) was improved as an alternative tool to determine the birefringence dispersion of a liquid crystal (LC) material by using the transmittance spectrum. The GMW has two degrees of freedom and the advantage of this additional degree of freedom was clearly exhibited in the simulation study. The validity of the presented method was shown by using the transmittance spectrum of the ZLI-6000 coded nematic LC and the acquired results were compared with the results of other methods. The noise immunity and uncertainty of the presented method were also studied.
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    Generalized Morse wavelets for the phase evaluation of projected fringe pattern
    (Iop Publishing Ltd, 2014) Kocahan, Ozlem Yilmaz; Coskun, Emre; Ozder, Serhat
    Generalized Morse wavelets are proposed to evaluate the phase information from projected fringe pattern with the spatial carrier frequency in the x direction. The height profile of the object is determined through the phase change distribution by using the phase of the continuous wavelet transform. The choice of an appropriate mother wavelet is an important step for the calculation of phase. As a mother wavelet, zero order generalized Morse wavelet is chosen because of the flexible spatial and frequency localization property, and it is exactly analytic. Experimental results for the Morlet and Paul wavelets are compared with the results of generalized Morse wavelets analysis.
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    Nanowire geometry effects on devices and transport mechanisms: SnS2/SiNW heterojunction
    (Springer, 2023) Coskun, Emre; Emir, Cansu; Terlemezoglu, Makbule; Parlak, Mehmet
    The semiconductor nanowire technology has become essential in developing more complex and efficient devices. In this study, the Si nanowire (SiNW) heterojunction structure with a two-dimensional SnS2 thin film was investigated. The SiNW array was created by the metal-assisted etching method because of length control and production over large areas of nanowires. The created SiNW has more diminishing reflectivity compared with Si planar substrate. The diode characteristics of SnS2/SiNW and SnS2/Si planar heterojunctions were investigated by dark current analysis at room temperature, and the improving diode characteristics by the three-dimensional interface between SiNW and SnS2 thin film were discussed. Transport mechanisms of the SiNW heterojunction were also studied for various methods. Thermionic emission and thermally assisted tunneling models are the dominant mechanisms for low voltages (0.02-0.20 V), and the space charge limiting current mechanism dominates the current for comparingly high voltages (0.20-0.40 V). All the values reveal the significant impact of the SiNW on heterojunctions for improving efficiency.
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    Optical phase distribution evaluation by using an S-transform
    (Optical Soc Amer, 2007) Ozder, Serhat; Kocahan, Ozlem; Coskun, Emre; Goktas, Hilal
    An experimental study of the use of an S-transform to evaluate the phase distribution from a two-dimensional fringe pattern by introducing the carrier frequencies in two spatial directions, x and y, is presented. The phase distribution is extracted from the optical fringe pattern by using an S-transform gradient and S-transform phase methods. The experimental result for the Fourier transform profilometry algorithm is compared with the results of the S-transform. analysis. (c) 2007 Optical Society of America
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    Optical phase distribution evaluation by using S-transform
    (Amer Inst Physics, 2007) Kocallan, Ozlem; Ozder, Serhat; Coskun, Emre
    A simulation study to evaluate phase distribution from two dimensional fringe pattern by introducing the carrier frequencies in two spatial directions, x and y, is presented. The phase distribution is extracted from the optical fringe pattern by using S-transform gradient and S-transform phase methods. Furthermore, a Gaussian white noise is added to the fringe pattern to test the noise immunity of S-transform. The recovered phase distributions both by S-transform gradient method and phase method are compared with the simulated one.
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    Optical Phase Distribution Evaluation by Using Zero Order Generalized Morse Wavelet
    (Amer Inst Physics, 2017) Kocahan, Ozlem; Elmas, Merve Naz; Durmus, Cagla; Coskun, Emre; Tiryaki, Erhan; Ozder, Serhat
    When determining the phase from the projected fringes by using continuous wavelet transform (CWT), selection of wavelet is an important step. A new wavelet for phase retrieval from the fringe pattern with the spatial carrier frequency in the x direction is presented. As a mother wavelet, zero order generalized Morse wavelet (GMW) is chosen because of the flexible spatial and frequency localization property, and it is exactly analytic. In this study, GMW method is explained and numerical simulations are carried out to show the validity of this technique for finding the phase distributions. Results for the Morlet and Paul wavelets are compared with the results of GMW analysis.
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    Paul wavelet algorithm for the determination of birefringence dispersion of a liquid crystal cell
    (Optical Soc Amer, 2011) Coskun, Emre; Ozder, Serhat
    The Paul wavelet algorithm was prepared as a method to obtain the birefringence values continuously for a liquid crystal sample by using the transmittance spectrum in visible and near-infrared regions at room temperature. The obtained results determined from the Paul wavelet algorithm are harmonious with the 5CB-coded liquid crystal catalog value and the results determined from the fringe counting method. The controlling on the resolution of the working space is possible with the Paul wavelet, and the presented work attempts to depict the importance of control. Noise effect and absolute errors of the presented method and the fringe counting method are also studied and compared. (C) 2011 Optical Society of America
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    Profile Measurement of Objects by Using Stockwell and Continuous Wavelet Transforms
    (IEEE, 2008) Kocahan, Ozlem; Coskun, Emre; Oezder, Serhat
    In this study, 3D profile measurements of objects are tested with integral transforms by using a standard fringe projection technique consisting of a CCD (charge-coupled device) camera and a projector. The surface profile of a rough object is studied experimentally with crossed optical axes geometry. A two dimensional fringe pattern by introducing the carrier frequencies in two spatial directions, x and y, is analyzed with S-transform and continuous wavelet transform based on Model wavelet algorithms. Phase gradient and phase methods are presented for continuous wavelet transform (CWT) and S-transform of the fringe pattern. At the end, results of experimental application of these techniques are compared.
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    Quantitative Phase Imaging of Red Blood Cell by Diffraction Phase Microscopy
    (IEEE, 2017) Kocahan, Ozlem; Tiryaki, Erhan; Durmus, Cagla; Elmas, Merve Naz; Coskun, Emre; Ozder, Serhat
    Diffraction phase microscopy maintains the single shot measurement and low speckle noise associated with white light. A microscope with halogen lamp and a Mach-Zehnder interferometer were combined to obtain images of red blood cell with fringe pattern. From these images, the phase values were retrieved by using continuous wavelet transform (CWT) phase method. In the analysis of CWT, Paul wavelet is chosen as a mother wavelet. Experimental results of the CWT phase method with Paul wavelet are discussed at the end of the study.
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    Refractive index and extinction coefficient determination of an absorbing thin film by using the continuous wavelet transform method
    (Optical Soc Amer, 2008) Coskun, Emre; Sel, Kivanc; Ozder, Serhat; Kurt, Mustafa
    We present the continuous wavelet transform (CWT) method for determining the dispersion curves of the refractive index and extinction coefficient of absorbing thin films by using the transmittance spectrum in the visible and near infrared regions at room temperature. The CWT method is performed on the transmittance spectrum of an a - Si1-xCx:H film, and the refractive index and extinction coefficient of the film are continuously determined and compared with the results of the envelope and fringe counting methods. Also the noise filter property of the method is depicted on a theoretically generated noisy signal. Finally, the error analyses of the CWT, envelope, and fringe counting methods are performed. (C) 2008 Optical Society of America
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    S-transform analysis of projected fringe patterns
    (Spie-Int Soc Optical Engineering, 2007) Kocahan, Oezlem; Oezder, Serhat; Coskun, Emre
    3D profile measurement of an object is studied experimentally by using a standard fringe projection technique consisting of a CCD camera and a digital projector. The height profile of the object is calculated through the phase change distribution of the projected fringes with two dimensional fringe pattern by introducing the carrier frequencies in two spatial directions, x and y. The phase distribution is extracted from the optical fringe pattern by using S-transform gradient and S-transform phase methods. Experimental result for the Fourier transform profilometry algorithm is compared with the results of the S-transform analysis.
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    Simultaneous determination of the thickness and refractive index dispersion of dielectric films by the Paul wavelet transform
    (Elsevier Science Sa, 2019) Ozcan, Seckin; Coskun, Emre; Kocahan, Ozlem; Ozder, Serhat
    The continuous wavelet transform with Paul wavelet was proposed as a method for the simultaneous determination of physical thickness and refractive index dispersion of dielectric films in the visible and near infrared region. Transmittance spectrums, acquired at two different incident angles, were used for the calculations. By this way refractive index dispersion was obtained without knowing the film thickness. The method was tested with simulated data and experimentally applied to a sample of borosilicate glass. The obtained thickness and refractive index dispersion values were compared to the values obtained by the envelope method and the ones provided by the manufacturer.