Color-over-angle (CoA) variation in the light output of white LEDs is a common and unsolved problem. In this article we introduce a new method to reduce CoA variation using a special collimator. The method is based on analytical inverse design methods. We present a numerical algorithm to solve the differential equations arising from this method and verify the results using Monte Carlo raytracing.
Prins, C. R., Thije Boonkkamp, ten, J. H. M., Tukker, T. W., & IJzerman, W. L. (2013). An inverse method for the design of TIR collimators to achieve a uniform color light beam. Journal of Engineering Mathematics, 81(1), 177-190. https://doi.org/10.1007/s10665-012-9584-7