Influence of Lighting Sources Spectra on the Human Visual Brightness Identification under the Mesopic Vision

Based on the MOVE models and the measurement of emission spectra of various light sources, the photopic function weights x and the mesopic equivalent brightness of human visual spectral luminous efficiency in different background brightness were calculated. Results showed that in the mesopic scope, human visual function peak value gradually increases with the brightness decreasing, and is moving towards the short-wave direction. The change rate is inversely proportional to the s/p index. In the case of ambient brightness for 0.5 cd center dot m(-2), peak values increase by 30% compared to the photopic function. Compared to the traditional test results, the mesopic equivalent brightness of fluorescent lamp and other different color temperature white light LED showed a positive gain that reaches 40%. On the other hand, the high pressure sodium lamp showed a negative gain. Results also showed that there was a decreasing trend when the ambient light level increased, and once the brightness level reaches that when cone cells play a full role, the equivalent brightness will equal photopic brightness. The methods and conclusions of this paper can help evaluate light sources, light-emitting material spectrum and characteristics of apparent brightness.