Reaction time based model for mesopic photometry

Abstract

1 INSTRUCTIONS Photometry combines the optical properties and radiation energy of the lighting source by spectral luminous efficiency function.[1~ 2] The visibility function is defined in order to express the difference of the eye’s sensitivity for different radiation, which can compare the strong and weak of vision inducing by two radiators with different wavelength.[3] According to the International Commission on illumination (CIE), the vision over level of luminance 10 cd/m 2 is defined photopic vision and the vision below level of luminance 10 -3 cd/m 2 is defined scotopic vision. In fact, levels of luminance of much outdoor lighting and some indoor lighting are at the region of 0.001~3cd/m 2 , which is defined mesopic vision. Especially, the road lighting belongs to the mesopic vision region.[4~5] The refore, more and more attentions are paid on the mesopic vision and the public voice of establishing photometry standard based on the mesopic vision becomes higher and higher.[7~8] Two main methods are used to measure spectral luminous efficiency function including heterochromatic brightness matching methods and scintillation method.[9] However, it is difficult to compare the brightness of two different colors light when the heterochromatic brightness matching method is used. The scintillation method is better than the heterochromatic brightness matching method and it matches the additivity in the br ightness region of photopic vision. But it becomes complex at mesopic vision state using scintillation method. The main method of building mesopic vision function is vision efficacy method in the international.[10] The spectral luminous efficiency func tion can be represented by a certain combination of photopic vision function V(λ) and scotopic vision function V’(λ) by some mathematical treatment and the combined formula.[11] There are three main mesopic vision model based on the vision efficacy method including X model, MOVE model and S model. In this paper, we investigated the influence of the luminance, contrast and eccentric angle on the reaction time. A new mesopic vision model was built based on the measure of familiar five lighting source.