Simplified irradiance/illuminance calculations in optical systems

The optical engineer can apply unit sphere methods, used to find geometrical configuration factors in radiant heat transfer calculations, to calculate similar factors for irradiance and illuminance distributions in many optical systems. This paper illustrates how using a dummy reference sphere of arbitrary radius, and direct ray trace analysis, can greatly simplify photoradiometric calculations while achieving accuracies of better than 1%. Uniform and non- uniform light sources are treated. Examples are presented using different optical configurations and light sources including projection systems, scanners, illuminators, and several imagers.