Gonio-Espectrofotómetro para Medida de BSDF con Baja Incertidumbre

La función BSDF (Bidirectional Scatter Distribution Function) de una superficie describe la dispersión de la radiación óptica que se produce en esa superficie en todas las direcciones del espacio para cualquier dirección de iluminación de la muestra. Por tanto, el conocimiento de esta función es muy importante porque a partir de ella se pueden determinar todos los factores de reflectancia de la superficie y obtener la información que se necesita para aplicaciones en las que intervenga esa superficie, como es el caso de modelos de iluminación o estimación de apariencia.Peer reviewe

Principal components analysis on the spectral bidirectional reflectance distribution function of ceramic colour standards

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. © 2011 Optical Society of America.The authors are grateful to the “Plan Nacional de F´ısica” for funding this work (FIS2007- 66671-C02-01), and to the CSIC’s JAE Program for providing the group with a training researcher.Peer Reviewe

Distribución angular de la intensidad radiante espectral de leds blancos de alta luminosidad

6 pags., 7 figs.In this paper we study the angular and spectral distribution of the emission of conventional white LEDs using the low uncertainty Spanish Gonio-spectro-photometer (GEFE). With this instrument we obtain the emission profiles for different observation planes, so that you can get the information needed to characterize the emissions from any source in the visible range (380 nm to 780 nm). This study was achieved in order to determine a measurement protocol that will allow uslater to generate an irradiance model for LEDs based on the distance to the source. We show preliminary results obtainedby using high brightness white LEDs and the instrument above mentioned. © Sociedad Española de Óptica.En este trabajo abordamos el estudio de la distribución angular y espectral de la emisión de LEDs blancos convencionales empleando el Gonio‐espectrofotómetro Español de baja incertidumbre (GEFE). Con este instrumento se obtienen los espectros de emisión para diferentes planos de observación, de manera que contamos con la información necesaria para caracterizar la emisión de cualquier fuente que emita en el rango visible (380 nm a 780 nm). Este estudio se lleva a cabo con la finalidad de determinar un protocolo de medida, que nos permita, más adelante, generar un modelo de irradiancia para LEDs en función de la distancia al emisor. Presentamos los resultados preliminares que se obtienen empleando LEDs blancos de alta luminosidad y el instrumento de medida antes mencionado.Esta investigación ha sido financiada por el Plan Nacional I+D+i mediante la subvención FIS2010‐ 19756 y el programa JAE del CSIC a través de los contratos JAE‐DOC

Automatic gonio-spectrophotometer for the absolute measurement of the spectral BRDF at in-out-of-plane and retroreflection geometries

This paper presents the description and the characterization of the gonio-spectrophotometer GEFE (the acronym for 'Gonio-EspectroFotómetro Español'). This device has been designed and built for the low-uncertainty absolute measurement of the bidirectional reflectance distribution fuction (BRDF).It comprises a fixed, collimated and uniform light source, a six-axis robot-arm to rotate the sample and a spectroradiometer that may revolve around the sample to be able to vary the source-to-detector angular separation. This gonio-spectrophotometer makes it possible to perform spectral measurements in the visible range,both inside and outside the incidence place, as well as measurements in retroreflection conditions. This fully automated system is able to measure automously a sample's complete spectral BRDF (comprising around 1000 different angular configurations) in less than 4 h. © 2012Peer Reviewe