Merit function for the evaluation of color uniformity in the far field of LED spot lights

Abstract

The scope of the present paper is the derivation of a merit function which predicts the visual perception of LED spot lights. The color uniformity level Usl is described by a linear regression function of the spatial color distribution in the far field. Hereby, the function is derived from four basic functions. They describe the color uniformity of spot lights through different features. The result is a reliable prediction for the perceived color uniformity in spot lights. A human factor experiment was performed to evaluate the visual preferences for colors and patterns. A perceived rank order was derived from the subjects' answers and compared with the four basic functions. The correlation between the perceived rank order and the basic functions was calculated resulting in the definition of the merit function U sl . The application of this function is shown by a comparison of visual evaluations and measurements of LED retrofit spot lamps. The results enable a prediction of color uniformity levels of simulations and measurements concerning the visual perception. The function provides a possibility to evaluate the far field of spot lights without individual subjective judgment.

Color uniformity in spotligths - visual perception and system design

“…As a non parametric test, it does not assume normal distribution of the residuals. The Kruskal-Wallis test was performed with two parameter chroma level (1)(2)(3) and number of hues (1)(2)(3). The null hypothesis H 0 stated that there is no difference between the values of the parameters.…”