PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 92 NR 9/2016 173 Dariusz SAWICKI 1 , Agnieszka WOLSKA 2 Warsaw University of Technology (1), Central Institute for Labour Protection - National Research Institute (2) doi:10.15199/48.2016.09.44 Problems related to the angular resolution of the ILMD for GR index determination Abstract. The article presents problems of angular resolution of a photometer matrix (imaging luminance measurement device – ILMD) used for glare rating GR determination based on luminance distribution measurements. The analysis was carried out, how the various measured parameters influence on the uncertainty of the GR index determination. Analysis and conducted experiments showed that in specific cases the impact of angular resolution on the result of the GR is completely negligible. Streszczenie. W artykule przedstawiono problemy rozdzielczości kątowej fotometru matrycowego przy wyznaczaniu wskaźnika olśnienia GR na podstawie pomiaru rozkładu luminancji. Przeprowadzono analizę wpływu poszczególnych mierzonych parametrów na niepewność wyznaczania wskaźnika olśnienia GR. Analiza oraz przeprowadzone eksperymenty pokazały, że w szczególnych przypadkach wpływ rozdzielczości kątowej matrycy na wynik GR jest całkowicie pomijalny. (Problemy rozdzielczości kątowej miernika matrycowego przy wyznaczaniu wskaźnika olśnienia GR). Keywords: GR index, ILMD, matrix angular resolution Słowa kluczowe: wskaźnik olśnienia GR, matrycowy miernik luminancji, rozdzielczość kątowa matrycy Introduction Glare phenomenon is caused by the appearance of light sources of a very high luminance in the field of view. It occurs both on: the indoor and outdoor workplaces. It can cause different effects depending on the geometric and photometric parameters of a lighting system. Discomfort glare is the sensation of annoyance, while disability glare is the reduction in visibility caused by intense light sources in the field of view for a short but noticeable time. Glare limitation to a level appropriate to the visual task difficulty is an important measure of lighting quality. Unfortunately, glare as the lighting quality parameter may not always be assessed in an objective way in the working environment, although there are standardized requirements for it [1, 2]. In conditions of exposure to glare on the outdoor workplaces can work approx. 3.7% of the total employment in the national economy in Poland. Poor visibility due to glare is considered as one of the indirect reasons of the occupational accidents, in particular at outdoor workplaces when work is carried out after twilight. Our study [3], including an analysis of the occupational accidents as well as numerous expert opinions in workplaces showed that such incidents are often not reported in the statistics. To a large extent the irregularity corresponds to the lack of adequate knowledge and measurements methods for the evaluation of discomfort glare at the workplaces. A numerical measure used to determine the degree of discomfort glare on indoor workplaces is UGR index [1, 4]. On outdoor workplaces it is GR index [2, 5, 6, 7]. Both indexes depend on a luminance of glare sources (or veiling luminance by the glare source) and on a luminance of the background / environment (veiling luminance by the environment). In both cases the background luminance (veiling luminance by the environment) can be determined based on the illuminance measurements. The glare source position in relation to observation line is also taken into consideration, but in a different way for both indexes. Lighting design of the working environment should include the calculation of the relevant glare index. This index should be verified after the installation of the lighting equipment. The most reliable verification of calculated glare index is that which can be carried out based on measurements in the real workplace environment. Verification by measurement of UGR index (except for LED sources) is currently possible but it hasn’t been possible for GR index until now. One of the basic problems, which makes difficult determination of the glare indexes, is taking into account the geometrical relations between parameters and the angular resolution of the equipment used for the luminance measurement. Distant location of the luminaires from the observer makes angular dimensions of the light sources very small. Therefore, the selection of appropriate optical system for GR measurements is important. Two important measurement aspects must be provided: the proper angular resolution of an array photometer and the large enough photometer field of view. The article presents the analysis of the main angular relations associated with photometer’s optical system which are necessary to take into consideration for GR measurement. Glare index for the outdoor workplaces The principles for glare assessment on outdoor workplaces are described in CIE publications [6, 7] and in European Standard EN 12464-2 [2]. GR index, which describes the level of glare is based on the formula (1) [2, 6, 7]. (1)           9 . 0 ve vl 10 L L log 24 27 GR where: L vl – the veiling luminance (cd/m 2 ) caused by the lighting installation, it can be calculated by the formula (2) as the sum of the veiling luminances produced by each individual luminaire L vi . L ve – the equivalent veiling luminance of the environment (cd/m 2 ), determined from formula (6) or (7). (2) vn 2 v 1 v vl L ... L L L     The veiling luminance of the individual luminaire L vi is calculated by (3). (3) 2 i eyei vi E 10 L      where: E eyei – the illuminance at the observer's eye in a plane perpendicular to the line of sight (2˚ below the horizon – Fig. 1.) from the individual luminaire.  i – the angle between the observer’s line of sight and the direction to the individual luminaire. CIE publication [6] and standard [2] define this angle to be in range between 1.5° and 60°. The angle  is defined according to Figure 1. [2, 7]. This angle in formula (3) is expressed in degrees [6, 8].