AbstractsPhysics

Abstract

This dissertation is divided in two parts: The first one deal with two main characteristics of the light sources for general lighting: Color quality and luminous efficacy. The second one deals with technical aspects of the mesopic photometry applied in street lighting. The first part begins by proposing a method to generate a new color rendering index, consisting of a three-dimensional visual index, which was named 3D-CRM. In order to illustrate the use of this method and index, three examples of lighting application were performed: Artwork, meat and fruit. The results show the goodness of the visual index 3D-CRM, that is also accompanied by a numeric index that indicates how the light source tested fits with the gamut of colors required by the specific lighting application. Complementing the preceding proposal, a statistical analysis was performed in order to define the parameters that make up the color quality of light sources. This statistical study was based on a collection of more than 100 real and ideal spectra of light sources. As a result, it was found that there is another variable that can complement the CRI index to indicate the color quality. This is the proposed index Oc (Optimal Color), which is based on the calculation of volumes generated with the spectrum of test source and several ideal spectra of reflectance to get optimal colors (high saturated colors) at different luminance levels. This fisrt part of the dissertation ends by proposing an index to generate a classification of light sources according to the requirements of the lighting application and the parameters such as correlated color temperature (CCT), luminous efficacy of radiation (LER) and color quality (CQ). It was demonstrated that the new proposed index called ECQ (Efficacy and Color Quality), is able to generate a useful ranking when assessing a collection of spectra, by giving a desired CCT and the weight that efficacy and color quality have in the lighting application studied. By using some examples of different lighting applications (i.e. different weights for color quality and efficacy) it was demonstrated how versatile and useful the ECQ index is. In the second part of this dissertation, a comparison of laboratory measurements between two different types of goniophotometers is made. The first one is a standard and photometer-based one, which uses the far-field for measurement. The second one has a more recent technology, uses a CCD camera and photometer as sensors, as well as the near field for measurement. This comparison exercise validates the measurements from the near-field goniophotometer, since up to moment, for this type of measurement and type of sensor (CCD camera), there are no laboratories with international traceability that can verify or calibrate this measurement system. The comparison exercise shows that there is a very good fit between both measures performed to standard light bulbs; therefore results of the near-field goniophotometer are validated. In recent measures performed at the Light and lighting laboratory…