Reflective freeform optics tailoring for off-axis illumination systems

Freeform surfaces have been driving substantial changes in illumination design over the past few decades. Compared to their refractive counterparts, freeform reflective optics can yield larger angle of deflection, and more flexible geometry in three-dimensional space. Besides, they are dispersion-free, and superior in thermal management. However, designing freeform reflective optics in highly tilted geometry still faces many unresolved challenges. Here, a general formulation is proposed to design freeform off-axis reflective optics for precise illumination/intensity tailoring in highly tilted geometry. The superiority and effectiveness of the proposed method are verified by three interesting but challenging designs. Furthermore, we apply this method in the design of a highly collimated, uniform, and compact backlight.