Design of random microlens arrays with large scattering angles

Microlens arrays exhibit significant potential for applications in laser beam expansion, shaping, homogenization, and decoherence. Unfortunately, an increase in the target scattering angle of the microlens results in higher surface curvature. This can lead to a significant reduction in transmittance over a specific scattering angle range, directly affecting beam shaping and homogenization processes. In this paper, a design method for randomized microlens array homogenizing optical element with large scattering angles is proposed. A combination of transmission and total internal reflection (TIR) is used to significantly increase the scattering angle of the microlens arrays while maintaining high transmittance. A method of generating microlens arrays using random edge-length ratios is used to eliminate interference and improve the uniformity of the spot. The study explores the uniformity and energy utilization of random microlens arrays during random degree alteration and analyzes the influence of machining errors on homogenization. To validate the novel method, a random microlens array has been developed, featuring a scattering angle range of ± 41°, remarkable uniformity at 82.31 %, and an energy utilization rate of 85.48 %. This research lays a solid foundation for developing random microlens arrays with large scattering angles.