# Multi-surface catadioptric freeform lens design for ultra-efficient off-axis road illumination

## TL;DR

This paper introduces a new multi-surface freeform lens design method for off-axis road lighting that improves uniformity and efficiency using analytic surfaces, energy partitioning, and genetic algorithm optimization.

## Contribution

It presents a novel multi-surface lens design approach combining analytic surfaces, energy partitioning, and optimization for enhanced off-axis illumination efficiency.

## Key findings

- Significant improvement in illuminance uniformity.
- Ultra-high transfer efficiency achieved.
- Optimized surfaces reduce Fresnel losses and errors.

## Abstract

We propose a novel design methodology to tackle the multi-surface catadioptric freeform lens design for off-axis road illumination applications based on an ideal source. The lens configuration contains an analytic refractive entrance surface, an analytic total internal reflective (TIR) surface and two freeform exit surfaces. A curl-free energy equipartition is established between the source and target plane and divided to implement the composite ray mapping mechanism. Furthermore, the analytic TIR surface and refractive entrance surface are optimized for the minimal Fresnel losses and surface error based on genetic algorithm (GA). The results show a significant improvement on illuminance uniformity and ultra-high transfer efficiency compared to our proposed result in [Zhu et al., Opt. Exp. 26, A54-A65 (2018)].