Calculation of the indirect component of the horizontal illuminance

This paper presents a new theoretical method for calculating the indirect component of the horizontal illuminance. The method is based on examination of the paths of the selected light beams of every luminaire and on the calculation of their contribution to the horizontal illuminance at the working plane points. On the basis of the theory presented, a computer program was developed, whose main output data are matrices of the direct and indirect components of the horizontal illuminance at chosen points on the working plane. The illustrative examples show excellent agreement of the results obtained by the proposed method with those achieved experimentally, confirming that the method is of high accuracy.