Academic literature on the topic 'Spatial photometry'
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Journal articles on the topic "Spatial photometry"
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Liu, Long, Yun Cui Zhang, and Jun Xiao. "The Influencing Factor Analyses of Narrow Beam LED Luminaire Performance Test." Advanced Materials Research 694-697 (May 2013): 3283–86. http://dx.doi.org/10.4028/www.scientific.net/amr.694-697.3283.
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The beam angle of the luminaire is an important factor to influence testing method. This paper mainly discusses the narrow beam luminaire test methods, especially luminaires space photometric, chromaticity characteristic test method. The factors step length and test time which influence spatial distribution photometer are analyzed. An example is introduced which show how to set electrical parameter, photometry parameter test efficiency for a narrow beam LED luminaire.
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Tinbergen, J. "Array Polarimetry and Optical-Differencing Photometry." Symposium - International Astronomical Union 167 (1995): 197–205. http://dx.doi.org/10.1017/s0074180900056448.
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Array detectors have improved the efficiency of optical polarimetry sufficiently for this technique to become part of the standard arsenal of observational facilities. However, we could gain even more: spatially-differentiating photometry can be implemented as an option of array Polarimeters and low-noise, high-frame-rate array detectors will allow extremely high precision both in polarimetry and in such differentiating photometry. The latter would be valuable for analyzing many kinds of optical or infrared images of very low contrast; the essence of the technique is to use optical (and extremely stable) means to produce the spatial derivative of the flux image, in the form of a polarization image which is then presented to a “standard” array polarimeter. The polarimeter should incorporate a polarization modulator of sufficient quality for the photometric application in mind. If developed properly, using a state-of-the-art array detector and the most sensitive type of polarization modulator (stress-birefringence), optical differencing will allow levels of relative photometric precision not otherwise obtainable. With the optical differencing option taken out of the beam, the same instrument can be used for high-quality polarimetry.
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Bezugla, Natalia, Serhii Poluectov, Vladyslav Chornyi, and Mikhail Bezuglyi. "MONTE CARLO SIMULATION OF LIGHT SCATTERING IN HUMAN SKIN LAYERS BY SPATIAL PHOTOMETRY METHODS." Bulletin of Kyiv Polytechnic Institute. Series Instrument Making, no. 61(1) (June 30, 2021): 91–100. http://dx.doi.org/10.20535/1970.61(1).2021.237112.
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The ability to register and analyze the spatial distribution of light scattered within the full solid angle is the basis for the development and improvement of information-measuring systems and software and hardware complexes for problems of optical biomedical diagnostics. The greatest contribution to light scattering at non-invasive methods of biomedical research are made by the layers of human skin, affecting the depth of probing and the resolution of diagnostic systems. The significant individual variability of the optical properties of biological tissues does not allow practically (clinically) assessing their effect on the light scattering characteristics; therefore, the use of methods for modeling the optical radiation propagation in media in the measuring tools functioning context makes it possible to provide such a prognostic analysis. The goal of this work is a comparative evaluation of the results of the light propagation in human skin layers by Monte Carlo simulation using information-measuring systems of a biomedical photometer with ellipsoidal reflectors and a goniophotometer.
The Monte Carlo simulation results of light scattering in dermis and epidermis at a wavelength of 632.8 nm using spatial photometry methods and the "BT_Mod" software, as well as coordinates, direction, and statistical weight of photons, allows the ray-tracing in a biomedical photometer with ellipsoidal reflectors are presented in this work.
As a result of modeling, graphs of the dependence of optical coefficients (transmission T, diffuse reflection Rd, and absorption A) for the studied tissues of various thicknesses on the value of the scattering anisotropy factor were obtained, as well as photometric images of the second focal plane of ellipsoidal reflectors when receiving a scattering spot in reflected and transmitted light. Diagrams of the averaged scattering indicatrix at three thicknesses of the epidermis and dermis were obtained for a set of biophysically significant values of the scattering anisotropy factor, based on which the integral distribution of the photons statistical weight in diffuse scattered light was analyzed. A quantitative assessment of the illuminance level of images is carried out according to the zone analysis principles in photometry by ellipsoidal reflectors. The resulting graphs of the illuminance dependence the external and middle rings of photometric images in reflected and transmitted light.
The results of the research make it possible to analyze the spatial distribution of light scattered by the human skin layers (epidermis and dermis) within the full solid angle, which can be used in problems of optical dosimetry and medical imaging in diagnostic, endoscopic, and therapeutic methods of biophotonics.
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Xiao, Kai, and Haibo Yuan. "Validation and Improvement of the Pan-STARRS Photometric Calibration with the Stellar Color Regression Method." Astronomical Journal 163, no. 4 (March 22, 2022): 185. http://dx.doi.org/10.3847/1538-3881/ac540a.
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Abstract As one of the best ground-based photometric data set, Pan-STARRS1 (PS1) has been widely used as the reference to calibrate other surveys. In this work, we present an independent validation and recalibration of the PS1 photometry using spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR7, and photometric data from the corrected Gaia Early Data Release 3 (EDR3) with the Stellar Color Regression (SCR) method. Using per band typically a total of 1.5 million LAMOST-PS1-Gaia stars as standards, we show that the PS1 photometric calibration precisions in the grizy filters are around 4 ∼ 5 mmag when averaged over 20′ regions. However, significant large- and small-scale spatial variation of magnitude offset, up to over 1%, probably caused by the calibration errors in the PS1, are found for all the grizy filters. The calibration errors in different filters are uncorrelated, and are slightly larger for the g and y filters. We also detect moderate magnitude-dependent errors (0.005, 0.005, 0.005, 0.004, 0.003 mag per magnitude in the 14–17 mag range for the grizy filters, respectively) in the PS1 photometry by comparing with the Gaia EDR3 and other catalogs. The errors are likely caused by the systematic uncertainties in the PSF magnitudes. We provide two-dimensional maps to correct for such magnitude offsets in the LAMOST footprint at different spatial resolutions from 20′ to 160′. The results demonstrate the power of the SCR method in improving the calibration precision of wide-field surveys when combined with the LAMOST spectroscopy and Gaia photometry.
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Thanjavur, Karun, Željko Ivezić, Sahar S. Allam, Douglas L. Tucker, J. Allyn Smith, and Stephen Gwyn. "Photometric cross-calibration of the SDSS Stripe 82 Standard Stars catalogue with Gaia EDR3, and comparison with Pan-STARRS1, DES, CFIS, and GALEX catalogues." Monthly Notices of the Royal Astronomical Society 505, no. 4 (May 22, 2021): 5941–56. http://dx.doi.org/10.1093/mnras/stab1452.
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ABSTRACT We extend the SDSS Stripe 82 Standard Stars catalogue with post-2007 SDSS imaging data. This improved version lists averaged SDSS ugriz photometry for nearly a million stars brighter than r ∼ 22 mag. With 2–3 times more measurements per star, random errors are 1.4–1.7 times smaller than in the original catalogue, and about three times smaller than for individual SDSS runs. Random errors in the new catalogue are $\lesssim$0.01 mag for stars brighter than 20.0, 21.0, 21.0, 20.5, and 19.0 mag in u, g, r, i, and z-bands, respectively. We achieve this error threshold by using the Gaia Early Data Release 3 (EDR3) Gmag photometry to derive grey photometric zeropoint corrections, as functions of RA and Declination, for the SDSS catalogue, and use the Gaia BP–RP colour to derive corrections in the ugiz bands, relative to the r-band. The quality of the recalibrated photometry, tested against Pan-STARRS1, DES, CFIS, and GALEX surveys, indicates spatial variations of photometric zeropoints ≦ 0.01 mag (rms), with typical values of 3–7 millimag in the RA, and 1–2 millimag in the Declination directions, except for $\lesssim$6 millimag scatter in the u-band. We also report a few minor photometric problems with other surveys considered here, including a magnitude-dependent ∼0.01 mag bias between 16 ≤ GGaia ≤ 20 in the Gaia EDR3. Our new, publicly available catalogue offers robust calibration of ugriz photometry below 1 per cent level, and will be helpful during the commissioning of the Vera C. Rubin Observatory Legacy Survey of Space and Time.
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Rau, M. M., C. B. Morrison, S. J. Schmidt, S. Wilson, R. Mandelbaum, Y.-Y. Mao, David Alonso, et al. "A composite likelihood approach for inference under photometric redshift uncertainty." Monthly Notices of the Royal Astronomical Society 509, no. 4 (November 12, 2021): 4886–907. http://dx.doi.org/10.1093/mnras/stab3290.
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ABSTRACT Obtaining accurately calibrated redshift distributions of photometric samples is one of the great challenges in photometric surveys like LSST, Euclid, HSC, KiDS, and DES. We present an inference methodology that combines the redshift information from the galaxy photometry with constraints from two-point functions, utilizing cross-correlations with spatially overlapping spectroscopic samples, and illustrate the approach on CosmoDC2 simulations. Our likelihood framework is designed to integrate directly into a typical large-scale structure and weak lensing analysis based on two-point functions. We discuss efficient and accurate inference techniques that allow us to scale the method to the large samples of galaxies to be expected in LSST. We consider statistical challenges like the parametrization of redshift systematics, discuss and evaluate techniques to regularize the sample redshift distributions, and investigate techniques that can help to detect and calibrate sources of systematic error using posterior predictive checks. We evaluate and forecast photometric redshift performance using data from the CosmoDC2 simulations, within which we mimic a DESI-like spectroscopic calibration sample for cross-correlations. Using a combination of spatial cross-correlations and photometry, we show that we can provide calibration of the mean of the sample redshift distribution to an accuracy of at least 0.002(1 + z), consistent with the LSST-Y1 science requirements for weak lensing and large-scale structure probes.
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DENIEL, Jean-Marc. "Computing spatial distribution of tube and louvre luminaires efficiency from their description." International Journal of Sustainable Lighting 22, no. 1 (June 15, 2020): 12–27. http://dx.doi.org/10.26607/ijsl.v22i1.94.
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Lighting computation requires photometry data that are not always available. Lacking photometry data limits lighting study to in situ measurement, luminaire measurement or use of similar luminaire photometry. This is not satisfactory, neither for convenience nor cost and accuracy reasons. Fitting the spatial distribution of luminaire efficiency to their description would allow lighting computations in this kind of situation. An efficiency spatial distribution model is proposed for grid and louvre tube luminaires, taking optic width, louvre between-axis and gloss as parameters. It is constructed over 12 measured efficiency spatial distributions and the corresponding luminaire descriptors. Even if optic and louvre gloss cannot be differentiated, this model fits to measurements and allows for computed irradiance close to experiments within −5% to +19%. In addition, luminaire descriptors can freely vary inside their experimental range and even be extrapolated.
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Caldwell, John A. R., and C. David Laney. "Cepheids in the Magellanic Clouds." Symposium - International Astronomical Union 148 (1991): 249–57. http://dx.doi.org/10.1017/s0074180900200545.
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Cepheid variables provide a key to understanding the structure and distance of the Magellanic Clouds, as well as providing accurate reddenings there. Recent major observing programs have continually expanded the data base of photometry and velocities. It is important to try to reconcile the plethora of Cepheid data into a consonant picture of the three-dimensional spatial structure of the Clouds and to compare in a consistent manner the bulk Cloud distance moduli found by several photometric methods.
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Bezuglyi, Mikhail, and Natalia Bezuglaya. "Raman Spectroscopy Principles for in vivo Diagnostic by Ellipsoidal Reflectors." Electrical, Control and Communication Engineering 15, no. 1 (September 1, 2019): 39–46. http://dx.doi.org/10.2478/ecce-2019-0006.
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AbstractThe paper presents the analysis of the functional abilities of measurement tools with ellipsoidal reflectors for Raman spectroscopy. The investigated structural scheme of the setup is intended for use in Raman spectroscopy in vivo by ellipsoidal reflectors. The setup can be used as a prototype for development of a device for non-invasive control of sugar level. Additionally, the investigation demonstrates the efficiency of ellipsoidal photometry method for registration of Raman scattering signal on test-solutions. The testing was performed for different sugar concentrations with the laser radiation wavelength 980 nm. In addition, the selecting principles of laser radiation source parameters (including beam diameter and power) were investigated. During the research, the data about spatial distribution of the backscattered light in human shoulder and finger tissues during photometry by ellipsoidal reflectors were received. The procedure involves application of Monte Carlo simulation. The dependency of the external and middle ring illuminance of photometric images on the diameter and power of the laser beam is represented based on the zone analysis.
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Mimica, P., and K. Pavlovski. "Reconstruction of an Accretion Disk Image in AU Mon from CoRoT Photometry." Proceedings of the International Astronomical Union 7, S282 (July 2011): 63–64. http://dx.doi.org/10.1017/s1743921311026901.
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AbstractThe long-period binary system AU Mon was photometrically observed on-board the CoRoT satellite in a continuous run of almost 60 days long which has covered almost 5 complete cycles. Unprecedented sub milimag precision of CoRoT photometry reveals all complexity of its light variations in this, still active mass-transfer binary system. We present images of an accretion disk reconstructed by eclipse mapping, and an optimization of intensity distribution along disk surface. Time resolution and accurate CoRoT photometric measurements allow precise location of spatial distribution of ‘hot’ spots on the disk, and tracing temporal changes in their activity. Clumpy disk structure is similar to those we detected early for another W Serpentis binary W Cru (Pavlovski, Burki & Mimica, 2006, A&A, 454, 855).
Dissertations / Theses on the topic "Spatial photometry"
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Zangari, Amanda Marie. "Investigating spatial variation in the surface and atmosphere of Pluto through stellar occultations and PSF photometry." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82305.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 231-239).
Stellar occultations provide a high-resolution view of a single chord through Pluto's atmosphere. This thesis presents three projects related to stellar occultation observations of Pluto. The first project concerns the ground testing of the High-speed Imaging Photometer for Occultations (HIPO), a camera aboard the Stratospheric Observatory For Infrared Astronomy (SOFIA). Differential photometry was found to be reliable to one part in 104. The second project is a modern determination of the light ratio of Charon and Pluto, essential for predicting future occultations. The final project considers twenty years worth of Pluto stellar occultation results, including new measurements using HIPO, and determines whether temperature asymmetries can be seen in fits for the upper atmosphere. These measurements allow the first Earth-based assessment of Pluto's geographic temperature distribution. Included is a description of the extensive test modeling to determine the boundary selection methods for the upper atmosphere for each differently-shaped light curve. The temperature asymmetries or lack thereof, are considered in the context of time of day, average insolation and surface features in the vicinity of the area near the occultation half-light radius. No clear correlation was found for any of the three metrics, suggesting that Pluto's atmosphere is spatially isothermal.
by Amanda Marie Zangari.
Ph.D.
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Безугла, Наталя Василівна. "Просторова фотометрія біологічних середовищ." Thesis, НТУУ "КПІ", 2016. https://ela.kpi.ua/handle/123456789/15918.
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Дисертаційна робота присвячена розробці методу фотометричного аналізу біологічних середовищ шляхом розширення простору визначення їх оптичних властивостей, що дозволило одночасно врахувати характеристики відбитого та пропущеного середовищем оптичного випромінювання в межах повного тілесного кута. У роботі розроблено методики реалізації математичного базису просторової фотометрії біологічних середовищ за принципами визначення інтенсивності розсіяння по паралелях (кільцевих смугах) та меридіанах (перетинах).
Запропоновані схемо-технічні рішення двох- та восьми-канальної інформаційно-вимірювальних систем для просторової фотометрії за перетинами, реалізовані на рівні експериментальних установок. Розроблено програмне забезпечення фотометричного паралельного аналізу, що дозволяє досліджувати індикатриси розсіяння за перетинами.
Проведено аналіз індикатрис розсіяння лазерного випромінювання товщинними зразками м’язових тканини на різних довжинах хвиль та з різним розміщенням волокон. Здійснено перехід від індикатриси розсіяння товщинними зразками до фактору анізотропії однократного розсіяння. Доведено ідентичність експериментально-визначених величин оптичних коефіцієнтів дифузного відбиття та повного пропускання та визначених за результатами Монте-Карло моделювання з використанням усередненої за перетинами величини фактору анізотропії однократного розсіяння.The thesis is devoted to developing the method of photometric analysis of biological media by expansion the space of definition their optical properties. That made possible the simultaneously consider the characteristics of the optical radiation, reflected and transmitted by biological media, within the full solid angle. In the work the main methods of solution the basic equation of radiative transfer theory in problems of optical biomedical diagnostics, were analyzed. Thus, the main attention focused on optical parameters of biological media: scattering (μs), absorption (μa) coefficients, and the anisotropy factor of single scattering (g), which are responsible for spatial distribution of scattered radiation by normal and pathology tissues or media (first order approximation, diffuse approximation, small angle approximation, flux models, Monte Carlo method). Conditions of use depending the type of biological media are described. The phase functions of single scattering (Mie, Henyey-Greenstein, Gegenbauer kernel, Delta-Eddington, Eddington), which used to describe the propagation the optical radiation in different types of biological media, were considered. Systematized the methods and tools of biophotonics with the possibilities of spatial-oriented analysis of radiation, scattered by sample of biological media, organs and body parts. Goniometric and spherical types of experimental setup are the most appropriated types that can used for spatial photometry. Photometric image of varying thickness samples of biological media by ellipsoidal reflectometry were received. Based on experimental research, the axial asymmetry of anisotropy of scattering by porcine and chicken muscle tissues of varying thickness in vitro at a wavelength of 632.8 nm was found. The influence of anisotropy of scattering on accuracy of determination the optical coefficients of diffuse reflection and total transmission by method Monte Carlo was demonstrated. Study of spatial anisotropy scattering by method of photometry was suggested. On this basis, has developed methods of implementing of the mathematical basis of spatial photometry of biological media by determining the scattering intensity along parallels (circular bands) and meridians (sections). The mechanism of the transition from experimentally determined indicatrix of scattering of thick sample to the anisotropy factor of single scattering by designed methods is proposed. The proposed scheme-technical versions of information-measurement system for spatial photometry along sections with two and eight channel, which were realized in experimental setups of goniometric and spherical type. The features of element synthesis, exploitation and calibration of setups are described. The interfaces and methods of application of developed software for parallel photometric analysis "IMSOB" and "IMSOB-2", to support research the scattering indicatrix along sections in reflected or transmitted light for two- and eight-channel systems respectively are given. The method of sample preparation of biological media and features of experiment for different experimental setups of spatial photometry are given. The methodology of preparation the biological samples used for research in this paper were detail described. The analysis of the indicatrix of laser light scattering by thick samples of muscle tissue at different wavelengths with transverse and longitudinal placement of fibers was made. The data obtained by method of spatial photometry, which realized the principle of analyses of the sections. Experimental studies conducted on goniometric type setup. For phase function of single scattering Henyey-Greenstein, modified by isotropic component in each sections, the transition from indicatrix scattering of thick sample to the single scattering anisotropy factor g was made. Identity of experimentally-determined values of the optical coefficients of diffuse reflection and total transmission and determined by the results of Monte Carlo simulation using the average values by sections of the anisotropy factor of single scattering are approved.
Диссертация посвящена разработке метода фотометрического анализа биологических сред путем расширения пространства определения их оптических свойств, что позволило одновременно учесть характеристики отраженного и пропущенного средой оптического излучения в пределах полного телесного угла. В работе разработаны методики реализации математического базиса пространственной фотометрии биологических сред по принципу определения интенсивности рассеяния по параллелям (кольцевым полосам) и меридианам (сечениям). Предложены схемотехнические решения двух- и восьмиканальной информационно-измерительных систем для пространственной фотометрии по сечениям, реализованные на уровне экспериментальных установок. Разработано программное обеспечение фотометрического параллельного анализа, позволяющее исследовать индикатрисы рассеяния по сечениям. Проведен анализ индикатрис рассеяния лазерного излучения толщинными образцами мышечных тканей на различных длинах волн и с разным размещением волокон. Осуществлен переход от индикатрисы рассеяния толщинных образцов к фактору анизотропии однократного рассеяния. Доказана идентичность экспериментально определенных величин оптических коэффициентов диффузного отражения и полного пропускания и определенных по результатам моделирования Монте-Карло с использованием усредненной по сечениям величины фактора анизотропии однократного рассеяния.
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PEFFERKORN, STEPHANE. "Photometrie mesopique, evaluation liee a la structure spatiale des sources de lumiere." Paris, CNAM, 1995. http://www.theses.fr/1995CNAM0223.
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La sensibilite spectrale de l'il n'etant pas uniforme, la photometrie visuelle heterochrome a pour objet de quantifier l'effet visuel des rayonnements du spectre. Des solutions existent pour la vision photopique (diurne), et la vision scotopique (nocturne) mais la vision mesopique (crepusculaire), ou fonctionnent les cones et les batonnets, pose probleme. Si l'on dispose de resultats de photometrie mesopique obtenus par comparaison directe de luminosite (dcb), ou l'efficacite lumineuse d'un test monochromatique est comparee visuellement a celle d'une source de reference sur grand champ, aucun resultat n'existe pour des scenes visuelles composees de champs structures spatialement. Nous avons donc mis au point une nouvelle methode de photometrie visuelle fondee sur la sensibilite au contraste spatial lumineux (hssp) pour mesurer la sensibilite spectrale de l'il aux niveaux mesopiques. Pour cela, nous avons concu et construit un dispositif de mesure optique avec des mires heterochromes associe au recepteur visuel humain. Le protocole experimental a ete automatise et valide. Nous montrons, en recueillant des resultats a 6 niveaux stables d'adaptation mesopiques pour 3 frequences spatiales, qu'il est possible de mesurer la sensibilite spectrale de l'il avec un champ structure spatialement en vision mesopique, a condition d'etablir un protocole experimental strict. Les mesures photometriques visuelles montrent clairement des differences suivant la frequence spatiale de la stimulation. D'une part, nous confirmons l'influence des parametres tels que la longueur d'onde et le niveau lumineux d'adaptation sur l'equilibre photometrique. D'autre part, nous montrons qu'un controle de l'excentricite est necessaire et qu'un nouveau parametre, la frequence spatiale, est susceptible de conditionner l'etat d'adaptation a l'obscurite du systeme des cones et du systeme des batonnets. Nous proposons a la commission internationale de l'eclairage, un cadre normatif pour la photometrie mesopique
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Pavelka, Adam. "Numerické modelování zdrojů světla." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219144.
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The master’s thesis deals with photometry units used in light engineering. There are defined the methods of modelling the illumination systems, their advantages, disadvantages and possibilities of using. Furthermore, the thesis deals with modelling of two illumination systems by ray-tracing in programming environment of MATLAB. The master’s thesis describes the analysis of the problem and the program designing process. Acquired model results are then compared with the real measurements of both illumination systems which allow the discussion of the results and the deviations of the models.
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Zong, Weikai. "Amplitude and frequency modulations of oscillation modes in hot B subdwarf and white dwarf stars from Kepler photometry." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30306/document.
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Les interactions non linéaires entre modes de pulsation, induisant des modulations d'amplitude et de fréquence, sont difficiles à mettre en évidence avec les télescopes au sol en raison des temps caractéristiques en jeu, de l'ordre de la semaine, du mois, ou même de l'année. L'avènement des télescopes spatiaux comme KEPLER (opéré par la NASA) a considérablement changé la donne en apportant de nouvelles données pour ce domaine de recherche. Dans cette thèse, nous analysons les données photométriques obtenues avec KEPLER pour 24 étoiles compactes pulsantes, incluant 18 étoiles sous-naines de type B (sdB) et 6 naines blanches. Nous établissons que les modulations d'amplitude et de fréquence des modes d'oscillation sont un phénomène courant dans ces étoiles. Nous étudions en particulier deux étoiles : KIC 0862602, une naine blanche pulsante de type DB, et KIC 10139564, une étoile sdB variable à courtes périodes. KIC 0862602 et KIC 10139564 ont été observées sans interruption par KEPLER en cadence rapide pendant deux années pour la première et plus de trois ans pour la seconde. En analysant en détail ces données photométriques de très haute précision, nous mettons en évidence différents types de comportements affectant les composantes de triplets induits par la rotation stellaire. Les fréquences et amplitudes de ces modes montrent des variations soi périodiques soi irrégulières, ou demeurent constantes. Ces comportements peuvent être connectés à ceux prédits par les équations d'amplitude dans le cas de couplages non linéaires résonants entre modes, en particulier pour les temps caractéristiques des modulations. De plus, nous montrons que les modes en résonance constituant les triplets peuvent également interagir avec des modes extérieurs par le biais d'autres formes de résonances telle que la résonance à trois modes v 0 ~ v 1 + v 2 , une situation qui n'est pas prise en compte dans le cadre théorique existant. Ces études apportent pour la première fois une preuve claire de l'existence de mécanismes de couplages non linéaires entre modes d'oscillations dans les pulsateurs compacts. Cette découverte résonne comme un avertissement pour les projets visant à mesurer les taux de changement des périodes dus à l'évolution dans les étoiles compactes en général. Les modulations de fréquence d'origine non linéaire peuvent potentiellement empêcher toute mesure fiable de ces taux, à moins de corriger ces effets auparavant. Les modulations observées caractérisées dans cette thèse apportent un regard nouveau sur "l'astérosismologie non linéaire" et appellent à revisiter les méthodes d'analyse des courbes de lumière pour en extraire les modes d'amplitude et de fréquence variables. Dans un futur proche, nous anticipons davantage d'attention portée à ces phénomènes non inéaires dans différents types d'étoiles pulsantes observées depuis l'espace, ainsi qu'un regain d'intérêt pour la théorie non linéaire des oscillations stellaires en généralNonlinear mode interactions, inducing amplitude and frequency modulations, are difficult to observe from ground-based telescopes as these typical timescales of the modulations are of the order of weeks, months, or even years. The launch of space telescopes such as Kepler (operated by NASA) has tremendously changed the situation by providing new data for this research field. In this thesis, we analyze the Kepler photometric data observed for 24 compact pulsators, including 18 hot B subdwarf (sdB) stars and six white dwarf stars. We find that it is a common phenomenon that oscillation modes in these pulsating stars show amplitude and/or frequency variations. We focus in particular on two stars, KIC 08626021, a DB white dwarf, and KIC 10139564, a short period sdB star. KIC 08626021 and KIC 10139564 have been monitored by Kepler in short-cadence mode for nearly two years and more than three years without interruption, respectively. By analyzing in depth these high-quality photometric data, we find that the modes within triplets induced by rotation clearly reveal different types of behaviors : their frequency and amplitude may exhibit either periodic or irregular modulations, or remain constant. These various behaviors can be linked to those predicted within the amplitude equation formalism in the case of the nonlinear resonant mode coupling mechanism, particularly for the modulation timescales. Furthermore, we find that the triplet resonance modes can also interact with outside modes through other types of resonances such as the three-mode resonance v 0 ~ v 1 + v 2 , which is not considered within the current nonlinear theoretical frameworks. These findings constitute the first clear evidence of nonlinear resonant mode couplings occurring in compact pulsators. This should resonate as a warning to projects aiming at measuring the evolutionary change rate of pulsation periods in compact stars in general. Nonlinear modulations of the frequencies can potentially jeopardize any attempt to measure reliably such rates, unless they can be corrected beforehand. The observed modulations characterized in this thesis provide new insights to "nonlinear asteroseismology" and call for new methods to process the signals of variable modes from the observed light curves. We foresee that increasing attention will focus on these nonlinear phenomena in various types of pulsating stars observed from space in the near future, thus reviving interest in the nonlinear oscillation theory in general
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Belgacem, Ines. "Etude photométrique des lunes glacées de Jupiter." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS386/document.
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Les satellites glacés de Jupiter sont d'un grand intérêt scientifique dans la recherche d'habitabilité au sein de notre système solaire. Elles abritent probablement toutes trois des océans d'eau liquide sous leur croûte glacée. Leurs surfaces présentent différents stades d’évolution – celle de Callisto est très ancienne et entièrement recouverte de cratères, celle de Ganymede est un mélange de terrains sombres et cratérisés et de plaines claires et plus jeunes et la surface d’Europa est la plus jeune et présente des signes d’activité récente. Cette thèse porte sur la photométrie, c’est à dire l’étude de l’énergie lumineuse réfléchie par une surface, en fonction des géométries d’éclairement et d’observation. Les études photométriques permettent de déterminer l’état physique et la microtexture des surfaces (porosité, structure interne, forme des grains, rugosité, transparence…). Une bonne connaissance photométrique est également d'une importance cruciale dans la correction des jeux de données pour toute étude cartographique ou spectroscopique ainsi que pour les futures missions de cette décennie : Europa Clipper de la NASA et JUpiter ICy Moons Explorer de l’ESA.Deux types d’information sont nécessaires pour réaliser une étude photométrique : des données de réflectance et des données géométriques (conditions d’illumination et d'observation). Pour obtenir les premières, nous avons utilisé et calibré des images de missions spatiales passées - Voyager, New Horizons et Galileo. Pour obtenir les secondes, nous avons développé des outils permettant de corriger les métadonnées de ces images (ex : la position et l'orientation des sondes) afin d’obtenir des informations géométriques précises. Nous avons, d’autre part, développé un outil d’inversion pour estimer les paramètres photométriques de Hapke sur des régions d’Europa, Ganymede et Callisto sur l’ensemble du jeu de données en un seul calcul. Enfin, nous discutons des liens possibles entre les paramètres photométriques estimés, la microtexture de la surface et les processus endogènes/exogènes mis en jeuJupiter's icy moons are of great interest in the search for habitability in our Solar System. They probably all harbor liquid water ocean underneath their icy crust. Their surfaces present different stages of evolution – Callisto is heavily cratered and the oldest, Ganymede shows a combination of dark cratered terrain and younger bright plains and Europa’s surface is the youngest with signs of recent and maybe current activity. This work focuses on photometry, i.e. the study of the light scattered by a surface in relation to the illumination and observation geometry. Photometric studies give us insight on the physical state and microtexture of the surface (compaction, internal structure, shape, roughness, transparency…). A good photometric knowledge is also of crucial importance in the correction of datasets for any mapping or spectroscopic study as well as for the future missions of this decade – NASA’s Europa Clipper and ESA’s JUpiter ICy moons Explorer.Two pieces of information are necessary to conduct a photometric study – reflectance data and geometric information (illumination, viewing conditions). For the former, we have used and calibrated images from past space missions – Voyager, New Horizons and Galileo. For the latter, we have developed tools to correct these images metadata (e.g. spacecraft position and orientation) to derive precise geometric information. Moreover, we have developed a Bayesian inversion tool to estimate Hapke’s photometric parameters on regions of Europa, Ganymede and Callisto. We estimate all parameters on our entire dataset at once. Finally, we discuss the possible links between the photometric parameters, the surface microtexture and endogenic/exogenic processes
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Pipien, Sarah. "A la recherche de quasars à grand décalage spectral dans le sondage CFHQSIR." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0376/document.
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J'ai consacré mon travail de thèse à la recherche de quasars à haut redshift dans le sondage Canada France High-z Quasar Survey in the Near Infrared (CFHQSIR). L'objectif principal de ce programme est de découvrir des quasars de redshift de l'ordre de z $\sim$ 7 dans les champs larges du CFHTLS (CFHTLS Wide) en utilisant des images réalisées dans le proche infrarouge avec la caméra WIRCam installée au foyer du CFHT. J'ai tout d'abord effectué la calibration photométrique de l'ensemble des données de CFHQSIR. J'ai ensuite étudié la qualité des images ainsi que leur propriété de bruit et leur profondeur. J'ai dans un deuxième temps calculé le nombre de quasars qu'il serait possible de détecter avec CFHQSIR et en ai déduit les contraintes envisageables sur la fonction de luminosité des quasars à z $\sim$ 7. J'ai ensuite procédé à l'identification de candidats quasars parmi les dizaines de milliers de sources que comptent les 130 degrés carrés couvert par CFHQSIR. Des observations de suivi photométriques des candidats ont finalement permis de révéler une cinquantaine d’objets, dont une quinzaine a été sélectionnée pour des observations spectroscopiques au Very Large Telescope (VLT). Celles-ci n’ayant, pour la plupart, pas encore été realisées, la nature exacte de ces sources ne pourra être connue que dans les prochains mois. Pour finir, la dernière partie de ma thèse s’est focalisée sur l’étude de modèles statistiques bayésiens afin de compléter ma méthode de sélection de candidats quasars. Cette étude m'a finalement permis de vérifier que la majorité des objets retenus pour des observations spectroscopiques étaient effectivement les candidats les plus probablesMy PhD work is focused on the search for high-redshift quasars in the Canada France High-z Quasar Survey in the Near Infrared (CFHQSIR). The main scientific objective of this CFHT Large Program is to search for quasars at redshift z $\sim$ 7 with near-infrared images of the CFHTLS Wide fields acquired with the CFHT WIRCam camera. Firstly, I carried out the photometric calibration of the CFHQSIR images. I performed a detailed analysis of the CFHQSIR data by studying their quality, as well as their noise properties and their depths.Secondly, I computed the number of high-redshift quasars that could be detected with CFHQSIR and the corresponding constraints which could be put on the z $\sim$ 7 quasar luminosity function. Then, I proceeded to the identification of quasar candidates among the many thousands of sources in the 130 square degrees covered by CFHQSIR. Photometric follow-up observations of the candidates revealed about fifty objects, of which fifteen were chosen to be spectroscopically observed with the Very Large Telescope (VLT). Given that this spectroscopic follow-up is not yet completed, the exact nature of these sources will only be known in the coming months. To finish, I applied Bayesian model comparison to my sample in order to complete and consolidate my selection procedure. My candidates were finally classified according to their probability to be a high-redshift quasar. I verified that the majority of the most likely candidates were selected for spectroscopic observations
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Jasinghege, Don Prasanna Deshapriya. "Spectrophotometric properties of the nucleus of the comet 67P/Churyumov-Gerasimenko observed by the ROSETTA spacecraft." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC007/document.
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Cette thèse s'inscrit dans le cadre de la mission spatiale Rosetta et porte sur les propriétés spectrophotométriques de la comète 67P/Churyumov-Gerasimenko à l’aide de l’instrument OSIRIS. Cet instrument est composé de deux caméras pour les observations du noyau et de la coma de la comète. Elles permettent d’acquérir des images avec des filtres qui opèrent dans la gamme du proche UV au proche IR. Dans un premier temps, j'ai analysé les courbes spectrophotométriques des taches claires qui sont apparues sur le noyau de la comète. Une étude comparative de celles-ci grâce aux données du spectro-imageur VIRTIS a ainsi permis de constater que les taches claires sont liées à la glace de H2O. Dans un second temps, j’ai entrepris une étude spectrophotométrique de la région Khonsu, qui a mis en évidence les variations saisonnières de la pente spectrale de différents terrains. Par la suite, j’ai élargi mon analyse des taches à tout le noyau de la comète. J’ai détecté plus de 50 taches claires dues à la présence de glace de H2O et j’ai produit une carte pour repérer leurs emplacements sur le noyau, afin d’étudier plus en détail leur répartition et leur évolution au cours de temps. Ceci m’a permis d’identifier quatre types de taches regroupés en fonction de leur morphologie et de constater qu'elles sont dues à différentes sources d'activité cométaireThis thesis is based on the spectrophotometric properties of the comet 67P/Churyumov-Gerasimenko, using the OSIRIS instrument of Rosetta space mission. Composed of two scientific cameras to observe the nucleus and the coma of the comet, OSIRIS images are acquired with multiple filters, that span the near-UV to near-IR wavelength range. They were used to study the spectrophotometric curves of the exposed bright features that appeared on the surface of the cometary nucleus, leading to a comparative study, that was carried out in collaboration with the VIRTIS spectro-imager aboard Rosetta, that demonstrated, that these exposures are related to H2O ice, using its absorption band located at 2 microns. The thesis further details a spectrophotometric study of the Khonsu region in the southern latitudes of the comet, where the seasonal variation of the spectral slope of different types of terrains is explored. Finally, the results of an extended survey of exposed bright features are presented. More than 50 individual features are presented under four morphologies along with an albedo calculation, suggesting that different activity sources are responsible for their appearance on the nucleus
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Radonjić, Ana. "Spatial and photometric factors modulating the effect of depth on lightness." 2009. http://hdl.rutgers.edu/1782.2/rucore10002600001.ETD.000051313.
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Jetté, Pomerleau Vincent. "Étude électrophysiologique de l’impact de la couleur dans le déploiement attentionnel." Thèse, 2014. http://hdl.handle.net/1866/10726.
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L’influence de la couleur dans les mécanismes perceptuels et attentionnels a été étudiée. Quatre couleurs (le rouge, le vert, le bleu et le jaune) ont été calibrées individuellement à travers la technique heterochromatic flicker photometry. Suivant cela, les participants ont déployé leur attention à une cible (un cercle de couleur avec une ligne orientée). Les données électrophysiologiques ont été enregistrées pendant que les sujets performaient la tâche de recherche visuelle, et les analyses ont été basées sur les potentiels évoqués (PÉs). Trois composantes des PÉs ont été examinées : la posterior contralateral positivity (Ppc); la N2pc, reflétant le déploiement de l’attention visuo-spatiale et la temporal and contralateral positivity (Ptc). Des conditions dans lesquelles la cible était bleu ou rouge, lorsque comparées à des conditions avec une cible jaune ou verte suscitaient une N2pc plus précoce. Une amplitude plus élevée est aussi observée pour les cibles rouges pour les composantes Ppc et Ptc, reflétant une sélectivité pré-attentionelle. Ces résultats suggèrent de la prudence dans l’interprétation de données comparant des cibles de différentes couleurs dans des tâches de PÉs, et ce même lorsque les couleurs sont équiluminantes.We investigated how target color affected behavioral and electrophysiological results in a visual search task. Perceptual and attentional mechanisms were tracked using the N2pc component of the event-related potential and other lateralized components. Four colors (red, green, blue, or yellow) were calibrated for each participant for luminance through heterochromatic flicker photometry and equated to the luminance of grey distractors. Each visual display contained 10 circles, 1 colored and 9 grey, each of which contained an oriented line segment. The task required deploying attention to the colored circle, which was either in the left or right visual hemifield. Three lateralized ERP components relative to the side of the lateral colored circle were examined: a posterior contralateral positivity (Ppc) prior to N2pc, the N2pc, reflecting the deployment of visual spatial attention, and a temporal and contralateral positivity (Ptc) following N2pc. Red or blue stimuli, as compared to green or yellow, had an earlier N2pc. Both the Ppc and Ptc had higher amplitudes to red stimuli, suggesting particular selectivity for red. The results suggest that attention may be deployed to red and blue more quickly than to other colors and suggests special caution when designing ERP experiments involving stimuli in different colors, even when all colors are equiluminant.
Books on the topic "Spatial photometry"
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Spehar, Branka, and Colin W. G. Clifford. The Wedding Cake Illusion. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0059.
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Lightness induction is the shift in surface appearance caused by adjacent or nearby surfaces. Spatial context can make a surface appear more different from (contrast) or more similar to (assimilation) its surround. Although assimilation effects tend to occur with more complex contexts, often containing repetitive patterns, we are still generally unable to ascertain the circumstances in which assimilation or contrast will occur. This chapter explores the interaction of geometric and photometric characteristics leading to contrast and assimilation in lightness induction. Concepts covered include the wedding cake illusion, White’s effect, the checkerboard illusion, the bull’s eye illusion, and luminance contrast.
Book chapters on the topic "Spatial photometry"
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Gruneisen, Rachel. "High Precision Photometry from Space with COROT: Effect of the Spatial Image Jitter on the Photometric Performances of CCDs." In Optical Detectors for Astronomy, 217–22. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5262-4_33.
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Santo, Hiroaki, Michael Waechter, and Yasuyuki Matsushita. "Deep Near-Light Photometric Stereo for Spatially Varying Reflectances." In Computer Vision – ECCV 2020, 137–52. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-58598-3_9.
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Quéau, Yvain, François Lauze, and Jean-Denis Durou. "A $$L^1$$ -TV Algorithm for Robust Perspective Photometric Stereo with Spatially-Varying Lightings." In Lecture Notes in Computer Science, 498–510. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-18461-6_40.
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Fukunishi, H., Y. Watanabe, A. Uchida, and Y. Takahashi. "Spatial and temporal structures of sprites and elves observed by array photometers." In Space Weather Study Using Multipoint Techniques, Proceedings of the COSPAR Colloquium, 283–88. Elsevier, 2002. http://dx.doi.org/10.1016/s0964-2749(02)80230-x.
Full textConference papers on the topic "Spatial photometry"
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Magunov, Alexander N., and A. Y. Gasilov. "Spatial scanning microspectrophotometer." In Photometry: Selected Papers from the 8th and 9th CIS Conferences, edited by Leonid S. Ushakov. SPIE, 1993. http://dx.doi.org/10.1117/12.166355.
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Bezuglaya, N. V., and M. A. Bezuglyi. "Spatial photometry of scattered radiation by biological objects." In 1st International Conference "Biophotonics Riga 2013", edited by Janis Spigulis and Ilona Kuzmina. SPIE, 2013. http://dx.doi.org/10.1117/12.2044609.
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Ganeev, Rashid A. "Express photometric method for determination spatial characteristics of laser radiation." In Photometry: Selected Papers from the 8th and 9th CIS Conferences, edited by Leonid S. Ushakov. SPIE, 1993. http://dx.doi.org/10.1117/12.166356.
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Andreeva, L. I., V. A. Belokon, F. A. Ermalitski, and V. A. Shevtsov. "Spatial and spectral variations on zone characteristics of fast-response one-quantum photomultiplier 28ELUF-15." In Photometry: Selected Papers from the 8th and 9th CIS Conferences, edited by Leonid S. Ushakov. SPIE, 1993. http://dx.doi.org/10.1117/12.166364.
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Montinaro, Cinzia, Barbara Spagnolo, Marco Pisanello, Filippo Pisano, Antonio Balena, Marco Bianco, Virgilio Brunetti, et al. "Estimating the Spatial Behavior of Fiber Photometry Across Different Brain Regions." In Optics and the Brain. Washington, D.C.: OSA, 2021. http://dx.doi.org/10.1364/brain.2021.btu1b.3.
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Gontcharov, G., A. Mosenkov, V. Il’in, A. Marchuk, S. Savchenko, A. Smirnov, and P. Usachev. "Interstellar extinction at high Galactic latitudes across the whole dust layer in the Galaxy." In ASTRONOMY AT THE EPOCH OF MULTIMESSENGER STUDIES. Proceedings of the VAK-2021 conference, Aug 23–28, 2021. Crossref, 2022. http://dx.doi.org/10.51194/vak2021.2022.1.1.181.
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By use of various methods we estimate interstellar extinction at high Galactic latitudes across the whole dust layer inthe Galaxy in a variety of photometric filters. First, we compare reddening estimates from the 3D map of Green-2019(i) inside and (ii) around 23 Galactic globular clusters, i.e. where (i) the estimates are obtained from the Pan-STARRSphotometry of the cluster stars and (ii) estimates from the Schlegel-1998 (SFD98) map are used due to the lack of thestars in Pan-STARRS. The estimates (i) turn out to be systematically higher than (ii) by E(B − V ) = 0.04 mag. Thismeans that SFD98 underestimates low reddenings by the value E(B − V ) = 0.04 mag. Second, we estimate extinction fromcomparison of photometric observations and theoretical isochrones for 43 Galactic globular clusters. The lowest extinctionis A V = 0.1 mag. Third, we analyze the spatial variations of the observed colours for an unprecedentedly large and completesample of 101810 clump giants with precise parallaxes and photometry from Gaia DR2 and WISE. This sample is selectedby us in the space cylinder with a radius of 700 pc around the Sun and a height of 3600 pc across the whole Galacticdust layer. Until now, complete samples of stars with precise distances and photometry have not been considered at such alarge distance from the Galactic plane. This explains our unexpected results: the Galactic dust layer appears thicker thanpreviously thought - the extinction continues to increase even at a distance of |Z| > 400 pc from the plane of the Galaxy;the mean extinction across the whole half-layer below or above the Sun is A V = 0.2 mag. Fourth, by use of the 3D reddeningmaps of Gontcharov-2017, Lallement-2019, and Green-2019 we calculate the most probable parameters for a new version ofour 3D model of the dust spatial distribution in a wide Galactic neighbourhoods of the Sun. Comparing with other models,our model provides the most accurate predictions of the observed colours of the above mentioned sample of 101810 clumpgiants. This comparison predicts the median reddening E(B − V ) = 0.06 mag for high latitudes |b| > 50 deg, and the dustcontainer of the Gould Belt provides up to a half of this reddening.
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Mansy, May M., Hongjae Kim, and Karim G. Oweiss. "Spatial detection characteristics of a single photon fiber photometry system for imaging neural ensembles*." In 2019 9th International IEEE/EMBS Conference on Neural Engineering (NER). IEEE, 2019. http://dx.doi.org/10.1109/ner.2019.8717005.
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Bezuglyi, M., N. Bezuglaya, and A. Viruchenko. "On the possibility of ellipsoidal photometry and Monte Carlo simulation to spatial analysis of biological media." In 2017 IEEE 37th International Conference on Electronics and Nanotechnology (ELNANO). IEEE, 2017. http://dx.doi.org/10.1109/elnano.2017.7939771.
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Kling, Kerstin, and Dieter Mewes. "Visualization of Micro- and Macromixing in Liquid Mixtures of Reacting Components (Keynote Paper)." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45216.
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Micromixing is visualized inside a stirred vessel by using two different optical measurement techniques, the optical tomography and the Planar Laser Induced Fluorescence technique (PLIF). In order to distinguish between macro- and micromixing, a mixture of two dyes is injected into the mixing vessel. One of the dyes is an inert dye whereas the second dye is undergoing a fast chemical reaction with the vessel content. The distribution of the inert dye serves as a tracer for the macromixing but does not predicate the mixing quality on the nano scale. The chemical reaction requires mixing on the molecular scale. Therefore the reacting dye, which is changing its emission characteristics during the reaction, indirectly visualizes the micromixing. The tomographical dual wavelength photometry is used to measure the three-dimensional, transient concentration fields in the whole vessel at the same time. Measurements with the Planar Laser Induced Fluorescence technique are performed in an arbitrary plane of the vessel. This restriction on a two-dimensional concentration field is recompensed with a much higher spatial resolution which allows to visualize small scale structures in the order of mm. For both techniques low Reynolds number measurements are performed in a mixing vessel equipped with a Rushton turbine. Results are presented as two- or three-dimensional concentration fields. Areas of micromixing are detected by calculating the local degree of deviation from the concentration fields. They are depending on the injection position of the dye and are mainly found in the boundary layer of the lamellas.
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Honzatko, David, Engin Turetken, Pascal Fua, and L. Andrea Dunbar. "Leveraging Spatial and Photometric Context for Calibrated Non-Lambertian Photometric Stereo." In 2021 International Conference on 3D Vision (3DV). IEEE, 2021. http://dx.doi.org/10.1109/3dv53792.2021.00049.
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