Differentiable optimization of multiple freeform lenses for high-performance tilted illumination

We present an optimization framework for designing multiple freeform lenses to achieve high-performance oblique illumination. The optimization process involves two steps: optimizing the irradiance distribution on an intermediate plane and fine-tuning the surface parameters to achieve the desired tilted target irradiance distribution. The framework could be used to design freeform illumination systems with an arbitrary number of lenses without significantly increasing the computational resource requirements. Leveraging differentiable ray tracing (DRT), we design a compact system with double freeform lenses, realizing a high tilt angle (TA) of 78.86^∘ and an average spacing-to-height ratio (SHR) of 3.77. It holds significant potential for applications in the design of vehicle headlights, industrial vision inspection, and decoration lighting.