The evaluation of light parameters in the public lighting in the sphere of mesopic vision

Recently more and more specialists deal with questions of the road lighting. They design methodics that should be followed during the projection of the public lighting. The way of projection of road lighting according to the newest norms is more effective, it eliminates lighting pollution and helps to reach safer operation. The road lighting is a specific case of lighting system where an observer stands in the area of rather low adaptation luminance. That means that lighting parameters of road lighting system are not evaluated according to the photopic curve of human eye sensitivity but according to curves that can be found in mesopic area of sensitivity. Therefore a measurement of roads lighting was carried out. Here the illuminance was evaluated according to a chosen mesopic curve of sensitivity of human sight that was chosen according to the level of the observers adaptation luminance. In terms of observation of changes in sensitivity of the human eye during conversion from photopic to mesopic vision it is necessary to point out the fact that it is a peripheral area of the human eye. The central part of the eye (fovea) must be excluded from the observation of these changes as there are only photoreceptors (cones) of photopic sight to be found in this area.