A STUDY ON NEW BEAM PARAMETERS

At present, manufacturers of reflector lamps (R and PAR) provide two p arameters describing the beam pattern: beam angle and center-beam cand lepower. These parameters, however; have little to do with human perce ption of the beam. New parameters that connect photometric data and hu man perception of the beam pattern of reflector lamps are necessary fo r better lighting applications. For this purpose, this paper proposes two new beam parameters, the visual beam angle and the sharpness of th e edge of the visual beam, for reflector lamps. Hypotheses for the vis ual beam angle and the sharpness of the edge of the visual beam are es tablished based on van Kernenade's first derivative method and the the ory of the Cornsweet illusion. An experiment was conducted to test the se hypotheses and to compare the predicted visual beam angle to both t he manufacturer-claimed and the measured beam angle. Seventeen young s ubjects participated in the experiment. Twelve PAR lamps ranging from wide to narrow beamspread were selected as test lamps for the experime nt. The results of the experiment show the potential for using the pre dicted visual beam angle and the predicted edge sharpness as the new p arameters for characterizing reflector lamps. This paper also makes re commendations for further research.