Computer modeling of integrating spheres

I present a Monte Carlo model for predicting the performance of integrating spheres as a function of incident flux direction. The model was developed specifically to aid in the design of integrating spheres used as cosine collectors but is of general applicability. I discuss a method of generating uncorrelated random numbers. The probability density functions associated with uniform irradiance over a circular entrance port and Lambertian reflectors or emitters are presented. A comparison of the model with analytic equations predicting performance for an unbaffled integrating sphere is included. The average of the data generated by the model agrees with the analytic solution for sphere throughput to better than 0.25% (ς = 8.3%).