For the measurement of effective intensity of flashing lights, the Blondel-Rey, Blondel-Rev-Douglas, Form Factor, and Allard methods are adopted in various applications. These methods produce significantly different results depending on the pulse waveforms. These methods have been studied and compared by computation using ten different pulse waveforms including a train of pulses and a modulated pulse, at varied duration from 0.001 s to 10s. The results indicate obvious failures of the Blondel-Rey-Douglas and Form Factor methods for a train of pulses. Form Factor method show a problem with a slow pulse with a sharp peak added. Allard method show reasonable results for all forms of pulses except that it show results 20% to 30% higher than the Blondel-Rey results for a rectangular pulse at 0.1 s to 1 s duration. Assuming that the Blondel-Rey equation is accurate for rectangular pulses, the problem in the Allard method has been solved by modifying its visual impulse response function q (f) so that the calculation results for rectangular pulses match the results of the Blondel-Rey equation. A function for q (t) has been found that perfectly matches the Blondel-Rey results, and an approximation of the function has been achieved by two exponential functions that can be realized by a simple resistor-capacitor circuit. This modified method is practically equivalent to the Blondel-Rey equation for rectangular pulses, yet, solving all the problems identified with the other methods for non-rectangular pulses.
Proceedings Title: Temporal and Spatial Aspects of Light and Coulour Perception and Measurement, Expert Symposium ||| Commission Internationale de I'eclairage
Conference Dates: August 27-28, 2002
Conference Location: Veszprem, HU
Conference Title: Commission Internationale de L'Eclairage
Pub Type: Conferences
blondel-rey, effective intensity, flashing light, photometry, pulsed light, visual range