A method for configuring J electromagnetic radiation sources (J≧2) to simultaneously irradiate a substrate. Each source has a different function of wavelength and angular distribution of emitted radiation. The substrate includes a base layer and I stacks (I≧2) thereon. Pj denotes a same source-specific normally incident energy flux on each stack from source j. For simultaneous exposure of the I stacks to radiation from the J sources, Pj is computed such that an error E being a function of |W1−S1|, |W2−S2, . . . , |WI−SI| is about minimized with respect to Pj=1, . . . , J). Wi and Si respectively denote an actual and target energy flux transmitted into the substrate via stack i (i=1, . . . , I). The stacks are exposed to the radiation from the sources characterized by the computed Pj (j=1, . . . , J).