Ray mapping with surface information for freeform illumination design

A novel approach to incorporate surface information into the ray mapping method is proposed. This method calculates irradiance at the physical optical surface and target plane instead of the usually flat or hemispherical dummy surface, resulting in a mapping relationship which reflects the true geometry of the system. The robustness of the method is demonstrated in an extreme example (60° off axis) where the uniformity is as high as 82%.