Fresnel‐Loss–Constrained Freeform Lens Design Based on NSGA‐II Multiobjective Optimization

Freeform lenses play a critical role in LED packaging due to their beam‐shaping capabilities. However, existing packaging designs commonly neglect the Fresnel loss effect at multi‐interface boundaries. Addressing this gap, this study establishes a synergistic freeform lens design methodology based on a multi‐objective optimization framework, achieving breakthroughs in both high light extraction efficiency and optical quality control. Leveraging the Fresnel equations, a multi‐interface energy transmission model is constructed to quantitatively characterize the coupled mechanism of total internal reflection and refraction losses. A triobjective optimization scheme was implemented, targeting flux loss minimization, surface curvature regularization, and illuminance uniformity enhancement. Pareto‐optimal solutions were generated via the NSGA‐II algorithm, balancing Snell's law compliance, differential geometry constraints, and ray‐mapping optimization. Experimental validation demonstrated reduced total flux loss from 8.98 to 4.41 lm, suppressed peak surface curvature from 25.4 to 2.42, and improved illuminance uniformity from 0.84 to 0.91. The proposed methodology provides a systematic approach for designing high‐efficiency freeform optics with balanced photometric performance.