Open AccessImproved computation of the adaptation coefficient in the CIE system of mesopic photometry
Author(s) -
Cheng Gao,
Xu Yang,
Zhifeng Wang,
Manuel Melgosa,
Michael Pointer,
Ming Ronnier Luo,
Kaida Xiao,
Changjun Li
Publication year - 2017
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.25.018365
Subject(s) - mesopic vision , scotopic vision , photometry (optics) , photopic vision , computation , bisection method , mathematics , repeatability , luminance , optics , computer science , algorithm , physics , statistics , retina , stars , computer vision
New values of parameters a and b are proposed for the CIE system of mesopic photometry MES2 [CIE Publication 191:2010], because from the original values this model may have no solution or multi-solutions. From the new values of parameters a and b it is shown that the CIE MES2 system has a unique solution. The difference however, between the original and the new values of parameters a and b is very small and the changes do not affect previous conclusions based on the MES2 model. To compute such a solution, we propose a Bisection-Newton method which exhibits fast convergence (8 iterations in the worst case), and improves the fixed-point method recommended by the CIE MES2 system, which has convergence problems for high values of the photopic luminance and very high values of the scotopic/photopic ratio. Comparative results for the fixed-point method, the Bisection method, the Newton method, and the Bisection-Newton method, in terms of the number of iterations necessary for convergence and the computation time used, are reported.