Estimation of spatial distribution of spectrocolorimetric characteristics of LED lamps in MacAdam steps

Abstract

Modern light sources, such as LEDs, make it possible to create highly efficient lighting devices with a high color rendering index (at least 85), and a luminous efficiency of up to 250 lm/W. Insufficient lighting can cause visual discomfort. A long stay in conditions of visual discomfort and tension leads to a lack of concentration, visual and general fatigue. The main challenge facing lighting manufacturers is to minimize color differences between individual lighting fixtures or between production batches. In this work, it was necessary to evaluate the spatial distribution of the spectrocolorimetric characteristics of LED lamps in MacAdam steps. To do this, at the beginning, such concepts as a comfortable light environment, correlated color temperature and MacAdam ellipses were considered. Further, it was necessary to measure 10 samples of the LED emitting element. The measurements were carried out using such instruments as a goniophotometer and a spectrocolorimeter. As a result, the main colorimetric characteristics, such as color coordinates, were obtained. Based on the chromaticity coordinates, the color deviation in MacAdam steps was calculated for each sample. Also, a regression analysis was carried out and an approximating expression for the chromaticity coordinates was obtained. On the basis of the approximating expression for the chromaticity coordinates, the average color deviation in MacAdam steps was calculated. The value made up 5 steps. The deviation for the values –40 and 40 was also calculated. In order to reduce the color deviation (reduce the number of McAdam steps), it is necessary to make changes in the technological process of manufacturing the phosphor composition. For example, to reduce the thickness of the phosphor coating or reduce the concentration of phosphor. The results of these studies can be used by the developers of LED lamps based on LED emitting elements in order to improve the uniformity of the spatial distribution of color.