Design of freeform LED illumination lenses without glare

Conventional freeform lenses paired with high-brightness LEDs offer precise illumination control, but the high source luminance is maintained at the output of the lens. This is a significant issue for general lighting, where glare must be minimized. By combining a freeform lens with a diffuser, the observed peak luminance can be reduced, but this compromises illumination accuracy. This study investigates illumination lenses with a continuous freeform topology at the output of the lens. This freeform topology incorporates multiple convex and concave regions to ensure that each point in the resulting far-field distribution is illuminated by multiple lens regions. The freeform topology is designed with differentiable ray-tracing by considering specific height constraints on the optimized surface. The resulting reduction in the observed peak luminance, as well as the degree of illumination control compared to conventional freeform surfaces, are analyzed in detail.