Calibration function for an experimental setup for the measurement of irradiance distributions via a transmitting...

We describe a procedure to estimate the calibration function for an experimental setup that contains a transmitting diffuser whose bidirectional transmittance distribution function for light transmitted in normal direction is nearly independent of the incidence angle. This type of diffusing screen may be used in experimental setups to measure the irradiance distribution in the focal plane of concentrator optics that have large angles of incidence in the focal plane. It is shown that the influence of this screen and of the remaining components on the irradiance distribution may be described empirically by a Gaussian function and thus may be corrected for. Furthermore, it is demonstrated that the correction is necessary to avoid an underestimation of the concentrator optics' ability to concentrate the incoming radiation.