Person: Zoido Chamorro, Jesús Manuel
Universidad Complutense de Madrid
Faculty / Institute
Óptica y Optometría
Now showing 1 - 10 of 20
- PublicationOn MacAdam`s ellipses(Sociedad Española de Óptica, 1996) Zoido Chamorro, Jesús Manuel; Carreño Sánchez, Fernando; Bernabeu Martínez, EusebioA systematic analysis of the results obtained by MacAdam is presented. We repeat the calculations with the aid of a computer using the data supplied in his paper and the same equations. Significative differences emerge between the results obtained by us and those given by MacAdam. These discrepancies arise from the fact that the straight lines on which he carried out the different color matchings around a given chromaticity do not have a common intersection that could be considered as the center of the ellipse. A detailed study of the data leads us to question the geometry apnd the size of the curves of equally noticeable chromaticity differences proposed in Mac Adam's original study.
- PublicationChromatic perception of non-invasive lighting of cave paintings(SPIE, 2009-08-22) Zoido Chamorro, Jesús Manuel; Vázquez Moliní, Daniel; Álvarez Fernández-Balbuena, Antonio; Bernabeu Martínez, Eusebio; García Botella, Ángel; Herráenz Ferreiro, Juan Antonio; Egido Rodríguez, Marian, delThis work is intended to deal with the problems which arise when illuminanting Paleolithic cave paintings. We have carried out the spectral and colorimetric characterization of some paintings located in the Murcielagos (bats) cave (Zuheros, Córdoba, Spain). From this characterization, the chromatic changes produced under different lighting conditions are analysed. The damage function is also computed for the different illuminants used. From the results obtained, it is proposed an illuminant whose spectral distribution diminishes the damage by minimizing the absorption of radiation and optimises the color perception of the paintings in this cave. The procedure followed in this study can be applied to optimise the lighting systems used when illuminating any other art work.
- PublicationSpatial characterization of light detectors with nanometric resolution(SPIE, 2004-04-15) Alda, Javier; López Alonso, José Manuel; Rico García, José María; Zoido Chamorro, Jesús Manuel; Boreman, GlennThe miniaturization of light detectors in the visible and infrared has produced devices with micrometric and sub-micrometric spatial features. Some of these spatial features are closely linked with the physical mechanism of detection. An example of these devices is an optical antennas. To spatially characterize optical antennas it is necessary to scan a probe beam on the plane of the optical antenna. The mapping of this response is then treated and analyzed. When the response of the antenna is monitorized at visible or near-infrared frequencies, a sub-micron scanning step is necessary. In this paper we show the experimental set-up of a measurement station having a spatial resolution of 50 nanometers. This station is devoted to spatially characterize micrometric detectors, and specially optical antennas. The origin of the uncertainties of the measurement protocol is shown and practically analyzed. This station is also applied for characterizing the temporal, spectral, and polarization sensitivity specifications of light detectors with the previously mentioned resolution.
- PublicationIntra-observer and inter-observer variability of color-matching experimental data(Sociedad Española de Óptica, 2004-06) Carreño Sánchez, Fernando; Zoido Chamorro, Jesús ManuelWe present a discussion on the intra-observer and inter-observer variability in judging small color-differences when considering the experimental data provided by Wyszeky and Fielder. By using standard techniques in statistical theory we evaluate the size and shape of the regions of colorimetric indistinguishability in (x, y, Y) space. In the case of intra-observer variability we show that a low number of matches provides thresholds with a high degree of variation from one session to another. The analysis of data obtained for several observers reveals that thresholds vary in a non systematic way from one observer to another.
- PublicationCounting statistics and fluctuations in Bose–Einstein condensation(Elsevier, 2003-03) Zoido Chamorro, Jesús ManuelFor a system of N Bose atoms, we propose a natural probability distribution for the occupation numbers. The counting statistics only depends on the probabilities of occupation of the single-particle states. Fluctuations of the occupation numbers are related in a simple way with the corresponding probabilities. The case of N ideal bosons trapped in a symmetric three-dimensional harmonic potential is analyzed. In this case, fluctuations of the condensate display a physically expected behavior. When the thermodynamic limit is considered, we obtain analytic expressions for the counting statistics and fluctuations of the ground estate occupation number. The temperature of maximum fluctuations of the ground state occupation number is proposed in order to characterize in an unambiguous way the apparition of a macroscopic condensate fraction.
- PublicationOptimization of color-representation systems when comparing different observers(John Wiley & Sons, Inc., 2000-10-13) Zoido Chamorro, Jesús ManuelDue to the variability in the sets of color-matching functions, different real observers have associated different color-representation systems. This fact darks the true interpretation of the experimental results obtained for different observers. In this work, we propose a transforming operator, which optimizes the mapping of the color-representation system associated with an arbitrary observer into the system spanned by a standard set of color-matching functions. When comparing the experimental results for different observers, this transformation allows us to obtain more reliable conclusions. If the the data are analyzed in the systems obtained by applying the optimized operator, the differences between the colorimetric behavior of two real observers are less than when, as usual, the results are compared in the systems spanned by the sets of color-matching functions of the individual observers.
- PublicationTheoretical analysis of inter-observer variability in the determination of luminance thresholds(John Wiley & Sons, Inc., 2006-12) Carreño Sánchez, Fernando; Ezquerro Rodríguez, José Miguel; Zoido Chamorro, Jesús ManuelWe present an analytical method to analyze, from a theoretical point of view, the influence of color-matching functions on the perception of luminance thresholds. We show that the thresholds depend on the spectral responsivities of each observer. We also analyze the influence of luminance level on the thresholds: a strong inter-observer variability is found at low or moderate luminance levels (0.02 < Y < 1 ft-L) whereas at high intensities (1 < Y < 7 ft-L) the thresholds are observer-independent.
- PublicationThe use of metamers to compare the color vision of observers(John Wiley & Sons, Inc., 2001-08) Ezquerro Rodríguez, José Miguel; Carreño Sánchez, Fernando; Zoido Chamorro, Jesús Manuel; Bernabeu Martínez, EusebioIn this research we compare the colorimetric behavior of several observers. For color centers recommended by CIE we have produced large sets of spectral distributions, which are metameric for the CIE 1931 standard observer. For each one of the color centers, we compare the clouds of chromaticity coordinates with the chromaticity thresholds. We define a parameter that provides a quantitative measure of the interobserver variability. This parameter is used to arrange the observers by their degree of likeness. A similar procedure has been used to compare two real observers. It is shown how there is no reciprocity between the colorimetric behavior of two real observers
- PublicationVariations on the adiabatic invariance: the Lorentz pendulum(American Association of Physics Teachers, 2012-12-20) Sánchez Soto, Luis Lorenzo; Zoido Chamorro, Jesús ManuelWe analyze a very simple variant of the Lorentz pendulum, in which the length is varied exponentially, instead of uniformly, as it is assumed in the standard case. We establish quantitative criteria for the condition of adiabatic changes in both pendula and put in evidence their substantially different physical behavior with regard to adiabatic invariance.
- PublicationThe Weber fraction and asymmetries in luminance thresholds(John Wiley & Sons, Inc., 2002-10) Carreño Sánchez, Fernando; Zoido Chamorro, Jesús ManuelPresented in this article is a method for the determination of the Weber fraction by analyzing data obtained from color-matching experiments. The method is based on a rigorous analysis of the probability density function derived from discrimination judgments made in the xyY space. Analysis shows the thresholds for luminance increments and decrements are shown to be different and asymmetric and the Weber fraction to depend on the target's level of luminance and chromaticity.