A New S Model Of Mesopic Photometry And Its Application

This research present two main ideas.One is to establish a new S model for mosopic photometry based on visual performance experiments.Second is the practical application of S model in street lighting and automotive lighting by calculating a mesopic efficiency coefficient(R_m) for different light sources at different mesopic light levels.This work started by investigating the main researchs have been done in this topic internationlly,then discussed the characteristic of human vision system and the development history of CIE photometry.Three main methods of establishing phptometry(brightness matching,flicker and visual performance) have been introduced in this work.The objective of this work is to establish a new system of mesopic photometry that bridges those established for the photopic and scotopic vision.In this work a projector experimental system was designed and set up, which could control the experimental conditions(light level,contrast, visual angle,eccentricity and spectrum) and record the subjects' reaction time and detection rate.A new mesopic visual performance index (MVP,the ratio of reaction time to dectection reate) was introduced in this work to evaluate the visual performance around threshold.The experimental results indicate that MVP can reflect the effect of experimental conditions more correct and stable than reaction time or detection rate.A new S model for mosopic photometry was established based on the results of visual performance experiments.This model can be described by two simple equations and easily applied to calculate L_m(mesopic luminance) when L_p(photopic luminance) and r(s/p ratio) of any light source are measured.After compared to other two main models(X model and MOVE model) published recently,S model has a more simple form and could bridge photopic and scotopic domains more smoonthly.The mesopic luminance caculated by S model were in the median of results by X model and MOVE model.The modelling process of S model shows that the relationship of x and L_m is the key point of establishing a mesopic model based on visual performance methods.The relationship of x and L_m could be derived from the results of background spectrum's effect on reaction time.The effect of spectrum on reaction time is not only depend on light levels,but also depend on other experimental conditions(like contast,visual angle and eccentricity).At this moment,the simple way to establish an agreed system of photometry for the mesopic region is to take the average results of x and L_m from different published models.The S model introduced in this work is based on currently CIE photometry system V_(λ) and V'_(λ).The simple form of S model make it easy for application in lighting field.When L_p(photopic luminance) and r(s/p ratio) of any light source are measured,L_m(mesopic luminance) could be caculated by S model.A mesopic efficiency coefficient(R_m,the ratio of mesopic luminance to photopic luminance) was also introduced for the application of mesopic photometry.When R_m is caculated by S model for different light sources at different ligh levels,the photopic luminance, efficiency and luminous flux could be modified to mesopic values.Beside the theoretical research,this work also tried to applied the S model to practical lighting project.The performance of induction lamps and high pressure soidum lamps were disscussed in road tunnel lighting. The performance of high intensity discharge headlamps and halogen headlamps were compared in real road by two-alternative-forced-choice methods.The application of white LED in street lighting were also discussed base on S model.This work may have some contributions to the establishment of a standard for mesopic photometry,which will be benefit for the energy saving and safety in street lighting.