A Corróns

Publications (13)21.9 Total impact

• Article: Principal Components Analysis on the spectral Bidirectional Reflectance Distribution Function of ceramic colour standards.

  A Ferrero, J Campos, A M Rabal, A Pons, M L Hernanz, A Corróns
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  ABSTRACT: The Bidirectional Reflectance Distribution Function (BRDF) is essential to characterize an object's reflectance properties. This function depends both on the various illumination-observation geometries as well as on the wavelength. As a result, the comprehensive interpretation of the data becomes rather complex. In this work we assess the use of the multivariable analysis technique of Principal Components Analysis (PCA) applied to the experimental BRDF data of a ceramic colour standard. It will be shown that the result may be linked to the various reflection processes occurring on the surface, assuming that the incoming spectral distribution is affected by each one of these processes in a specific manner. Moreover, this procedure facilitates the task of interpolating a series of BRDF measurements obtained for a particular sample.
  Optics Express 09/2011; 19(20):19199-211. · 3.59 Impact Factor
• Article: Spectral Responsivity Calibration of Ge Photodiodes with Respect to an Electrically-calibrated Pyroelectric Radiometer and to a Black-body Source

  J Campos, P Corredera, A Pons, A Corróns
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  ABSTRACT: The absolute spectral responsivity at some infrared wavelengths of two germanium photodiodes has been determined by two different methods: comparison with an absolute radiometer (ECPR) and calibration with respect to a black-body simulator. The same geometry and spectral width have been used in both methods. The results, uncertainty sources and their evaluation, and the agreement between the methods, are discussed in this paper.
  Metrologia 01/2005; 28(3):141. · 1.75 Impact Factor
• Article: Realization of the candela from a partial filtering V(λ) detector traceable to a cryogenic radiometer

  J Campos, A Corróns, A Pons, P Corredera
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  ABSTRACT: This paper describes the approach used to realize the candela from illuminance measurements made with a large-area, partial-filtering photometer. The methods followed to determine the absolute responsivity at 555 nm, traceable to an absolute cryogenic radiometer, and to measure the relative spectral responsivity are discussed, including the uncertainty values of the measured quantities. Finally, preliminary results obtained on comparing the photometer measurements with the previous luminous intensity scale are presented.
  Metrologia 04/2003; 32(6):675. · 1.75 Impact Factor
• Article: Calibration of near-infrared transfer standards at optical-fibre communication wavelengths by direct comparison with a cryogenic radiometer

  P Corredera, J Campos, M L Hernanz, J L Fontecha, A Pons, A Corróns
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  ABSTRACT: This paper describes an experimental setup, based on an optical-fibre system, to calibrate infrared photodiodes at 1300 nm and 1550 nm by comparison with a cryogenic radiometer. An integrating-sphere radiometer used as a transfer standard for optical-fibre power measurements has been characterized and calibrated, obtaining an uncertainty of less than 0.1% at these wavelengths.
  Metrologia 03/2003; 35(4):273. · 1.75 Impact Factor
• Article: Reflectance dependencies of silicon trap detectors

  J Campos, P Corredera, A Pons, A Corróns, J L Fontecha
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  ABSTRACT: This work analyses the reflectance of silicon photodiodes as a function of incident beam polarization, angles of incidence and acceptance, and thickness of the passivating layer. The contributions of these effects to the polarization sensitivity of real trap devices are considered. An analytical model is used to calculate changes in responsivity due to polarization in traps with angular misalignments and traps constructed from different types of silicon photodiode. The results show that sensitivity to polarization should be considered when high-accuracy measurements are required.
  Metrologia 03/2003; 35(4):455. · 1.75 Impact Factor
• Article: Absolute power measurements at wavelengths of 1300 nm and 1550 nm with a cryogenic radiometer and a tuneable laser diode

  P Corredera, M L Hernanz, J Campos, A Corróns, A Pons, J L Fontecha
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  ABSTRACT: An experimental set-up designed for the calibration of near-infrared detectors against a cryogenic radiometer, using a tuneable laser diode as source, is described. A complete characterization of the cryogenic radiometer has been performed at the Instituto de Fisica Aplicada (IFA, Madrid), at wavelengths of 1300 nm and 1550 nm. Two different secondary standards, an electrically calibrated pyroelectric radiometer and an InGaAs-based integrating-sphere radiometer, have been calibrated with relative uncertainties of less than 10−3 at these wavelengths.
  Metrologia 03/2003; 37(5):519. · 1.75 Impact Factor
• Article: Ultraviolet calibration of detectors with respect to a cryogenic radiometer

  A Corróns, J L Fontecha, P Corredera, J Campos, A Pons, M L Hernanz
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  ABSTRACT: A facility has been designed to perform a variety of detector characterizations in the air-ultraviolet in the spectral range 230 nm to 400 nm. The facility allows the measurement of spatial uniformity, linearity and the spectral responsivity of different detectors, irradiated by a He-Cd laser or by a monochromator and Xe discharge lamp. With this technique, a set of Si photodiodes, Si detectors in trap configuration, and ultraviolet (UV) radiometers built with SiC detectors in an integrating sphere, have been calibrated and their absolute responsivity at the He-Cd laser UV line has been determined with respect to an absolute cryogenic radiometer.
  Metrologia 03/2003; 37(5):555. · 1.75 Impact Factor
• Article: Comparison between absolute thermal radiometers at wavelengths of 1300 nm and 1550 nm

  P Corredera, M L Hernanz, J Campos, A Corróns, A Pons, J L Fontecha
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  ABSTRACT: In 1991, the last international comparison of spectral responsivity with germanium detectors showed relative differences between national laboratories of up to 10−2 at wavelengths of 1300 nm and 1550 nm. The 1997 EUROMET international comparison of optical-fibre power meters showed relative differences between European laboratories of 10−2. The coincidence of the results from the two comparisons suggests that the radiometric standards used by these laboratories in the calibration of their power meters are the main cause of such differences, rather than the optical-fibre or transfer devices used in the comparisons. To test this assumption, three different electrical-substitution radiometers (ESRs), working at room temperature and used at the same wavelengths as radiometric standards in optical-fibre laboratories, were compared. The radiometers were an optical calorimeter, a pyroelectric radiometer and a thermopile. The relative differences obtained were within 5 × 10−3.
  Metrologia 03/2003; 37(5):543. · 1.75 Impact Factor
• Article: An analytical method for estimating correlated colour temperature uncertainty

  J Fontecha, J Campos, A Corróns, A Pons
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  ABSTRACT: Correlated colour temperature (CCT) is an important parameter of light sources. It is estimated from the position of the chromatic coordinates (u, v) in the Commission Internationale de l'Éclairage (CIE) 1960 colour space. The International Organization for Standardization (ISO) Guide is difficult to use when trying to obtain CCT uncertainty from chromaticity coordinates and their uncertainties because there is no clear analytical expression relating them. In this paper, an analytical method of obtaining the CCT uncertainty from the coordinates (u, v) and their uncertainties, without approximations, is proposed. The validity of the method is proven by comparing results with examples in the literature and with those obtained using a geometrical projection method.
  Metrologia 02/2003; 39(6):531. · 1.75 Impact Factor
• Article: Measurement of standard aluminium mirrors, reflectance versus light polarization

  J Campos, J Fontecha, A Pons, P Corredera, A Corróns
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  ABSTRACT: The dependence of the reflectance of standard aluminium mirrors on the polarization status of the incident light has been calculated and measured for an angle of incidence close to normal , so that the systematic uncertainty introduced by not controlling the light polarization status in spectrophotometric measurements of specular reflectance can be known and then eliminated or minimized.
  Measurement Science and Technology 12/1998; 9(2):256. · 1.49 Impact Factor
• Source

  Available from: Joaquin Campos

  Article: Absolute spectral irradiance scale in the 700-2400 nm spectral range.

  P Corredera, A Corróns, A Pons, J Campos
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  ABSTRACT: An absolute spectral irradiance scale for the 700-2400 nm range has been developed. The scale is based on an absolute radiometer and a series of interference filters, which were used to determine the spectral irradiance of quartz halogen incandescent lamps at a number of discrete wavelengths. Values at intermediate wavelengths have been obtained by interpolation. This new scale was compared with NIST standards based on blackbody radiance. Both scales were found to agree within +/- 1%.
  Applied Optics 08/1990; 29(24):3530-4. · 1.41 Impact Factor
• Source

  Available from: Joaquin Campos

  Article: Response uniformity of silicon photodiodes.

  J Campos, A Corróns, A Pons
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  ABSTRACT: The response uniformity of four silicon photodiodes, previously calibrated by using the self-calibration technique, has been measured. The response nonuniformity over the sensitive surface is not a negligible source of uncertainty in this case.
  Applied Optics 12/1988; 27(24):5154-6. · 1.41 Impact Factor
• Article: Solar irradiance spectrum at Madrid

  A. Pons, A. Corróns
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  ABSTRACT: An experimental study of the spectrum of direct solar irradiance in Madrid on dear days has been made. The expression is proposed to describe more realistically the real direct solar spectral irradiance in Madrid.
  Atmospheric Environment (1967) 16(9):2237-2240.