Digital luminance photometry in the context of the human visual system

Abstract

Almost all solutions in modern lighting systems are based on LED technology. Luminance and obvious ease of control are the
key characteristics of this light source. At the same time, luminances at the level of 108cd/m2 are a significant advantage of LED in design applications, where high luminous intensity amplification is important. However, in general and in road lighting applications, LED luminaires represent a source of potential discomfort glare. Unfortunately, lighting technology’s metrology lags behind LED parameter development and optimization. The results of luminance measurements of the same luminaires, made with a luminance camera and meters with a measuring field, differ. The differences even appear for the same imaging luminance measuring devices with different lenses. This article presents the results of experiments and detailed analyzes related to modern digital luminance photometry based on the use of digital image sensors. Luminance tests were conducted on multi-source research models of luminaires. Traditional luminance measuring equipment with a measuring field was used in the experiment. The research was also supplemented with the measurements made using CCD/CMOS luminance cameras with selected components where the angular field of view of each pixel was a 0.45 min arc corresponding to the highest average human sight parameters. The results confirm that the average luminance value for multi-source luminaires depends on the measurement system configuration. It has been proposed to standardize the angular field of view parameters of all measurement systems, where the measurement aims to obtain a value that
directly relates to human visual impressions (e.g. glare).