Search results for "Names"
showing 10 items of 6843 documents
Continuous Refocusing for Integral Microscopy with Fourier Plane Recording
2018
Integral or light field imaging is an attractive approach in microscopy, as it allows to capture 3D samples in just one shot and explore them later through changing the focus on particular depth planes of interest. However, it requires a compromise between spatial and angular resolution on the 2D sensor recording the microscopic images. A particular setting called Fourier Integral Microscope (FIMic) allows maximizing the spatial resolution for the cost of reducing the angular one. In this work, we propose a technique, which aims at reconstructing the continuous light field from sparse FIMic measurements, thus providing the functionality of continuous refocus on any arbitrary depth plane. Ou…
Phase error analysis of clipped waveforms in surface topography measurement using projected fringes
2021
Abstract When working with the method of projected fringes outside the optical laboratory one often encounters the problem of uncontrollable ambient light. This might cause saturation of the camera which in turn results in clipping of the fringes. Since standard theories describing phase-shifting techniques assume the projected fringes to be purely sinusoidal, such clipping will result in measurement error. In this paper a detailed analysis of this problem is given, and relations between phase errors, the amount of fringe clipping and the number of phase steps are found. Moreover, the phase difference between the clipped and the unclipped fringes is described. This investigation is based on…
Anamorphic fractional Fourier transform: optical implementation and applications
1995
An additional degree of freedom is introduced to fractional-Fourier-transform systems by use of anamorphic optics. A different fractional Fourier order along the orthogonal principal directions is performed. A laboratory experimental system shows preliminary results that demonstrate the proposed theory. Applications such as anamorphic fractional correlation and multiplexing in fractional domains are briefly suggested.
A Hybrid Frequency-Space Approach for Shape Measurement by Shadow Moiré Technique with Carrier Fringe Pattern
2006
In this paper, a novel methodology to process fringe pattern is presented. The core of the signal processing technique is the use of the direction information, a modulo 2pi quantity that locally informs about the direction along which fringes grow with maximum rate. By using this information, it was possible to perform adaptive, direction- and orientation-based operations on fringe images in order to remove unwanted effects, to enhance the contrast and to extract the phase information encoded. The method has been applied on shadow moire interferograms with carrier fringes in order to measure the surface of small objects. The developed algorithm allows to process fringes whose phase informat…
Space–bandwidth product of optical signals and systems
1996
The space–bandwidth product (SW) is fundamental for judging the performance of an optical system. Often the SW of a system is defined only as a pure number that counts the degrees of freedom of the system. We claim that a quasi-geometrical representation of the SW in the Wigner domain is more useful. We also represent the input signal as a SW in the Wigner domain. For perfect signal processing it is necessary that the system SW fully embrace the signal SW.
A Direction/Orientation-Based Method for Shape Measurement by Shadow MoirÉ
2008
In this paper, a methodology to process fringe patterns is presented. The core of the signal processing technique is the use of the direction information, which is a modulo quantity that locally indicates the direction along which fringes grow at a maximum rate. By using this information, it was possible to perform adaptive and direction/orientation-based operations on fringe images to remove unwanted effects (mainly distortions at the image borders), to enhance the contrast, and to extract the phase information encoded. The method has been applied on shadow-moire interferograms with carrier fringes in order to measure the surface of small objects. The developed algorithm allows processing …
Spectral estimators for Doppler analysis of intracoronary ultrasound catheters
2002
With the zero-cross-detection method (ZCD) it has been shown that it is not possible to achieve a reproducible quantitative, and robust evaluation of an inter-coronary audio signal. The authors define spectral estimators to analyze the Doppler-audio signal. Measurements in a blood flow model have shown that the ZCD method underestimates the expected velocity at all speeds. Spectral analysis allows the determination of the actual and peak velocity more robustly and precisely. >
Nazwy skrzypu 'Equisetum' w dialekcie śląskim
2018
Na Śląsku, podobnie jak w innych regionach Polski, odnotowujemy sporą liczbę nazw nazywających skrzyp ‘Equisetum’. Według danych Atlasu językowego Śląska A. Zaręby nazwy skrzypu układają się w dość przejrzyste strefy geograficzne. Na północ od izoleksy Chocianowice (pow. kluczborski) i Stare Budkowice (pow. opolski) występują warianty leksemu kostka. Na Śląsku środkowym, po Chełm Śląski (pow. tyski), Bełk (pow. rybnicki), Rogów (pow. wodzisławski) spotykamy przęckę. Zaś poniżej tej linii, na Śląsku południowym, mamy strefę mieszaną z wariantami nazw kocur, chwost i kocycoł. Opis materiałów zgromadzonych w kartotece Słownika gwar śląskich uzupełnia ten obraz. Analiza pokazuje powiązania półn…
Raman spectroscopy study of β-irradiated silica glass
2003
International audience; Natural and synthetic silica glass samples with different OH content have been submitted to β-irradiation at different doses from 106 to 5 × 109 Gy in a Van de Graaff accelerator. Structural changes under irradiation have been analyzed by Raman spectroscopy. The main findings are: (i) a decrease of the Si–O–Si angular dispersion and the average Si–O–Si angle as a function of dose and (ii) an increase of number of three-membered SiO4 ring concentration during irradiation. These results show therefore that purely electronic excitation from β-irradiation induces in a-SiO2 small but significant structural changes of the SiO4 membered ring statistics (size and dispersion)…
Photoelectron lifetime determination of Ag(1 1 1) films at the Fermi surface
2001
The electronic properties of 10 monolayers Ag(111) films deposited onto Si(111)-7 x 7 substrates at room temperature have been studied by scanning the photoelectron intensity at the Fermi level in different symmetry directions. The main features observed in these profiles correspond to Lorentzian-like peaks produced by the pass of the sp band through the Fermi level. A simple model has been developed, which connects the photoemission peak linewidth with the lifetime of photoelectrons excited from the Fermi level. The obtained inverse photoelectron lifetime values have been found to be in excellent agreement with the typical values of the Ag single crystals. These results support the fact th…