Freeform Optics-Based Microlens Array Lighting System Design and Optimization for Machine Vision

The performance of the lighting system significantly impacts the efficiency and accuracy of the overall defect detection process in additive manufacturing. However, achieving both high optical efficiency and exceptional illuminance uniformity within compact detection areas at typical working distances remains challenging with conventional designs. This paper proposes a novel uniform lighting system design utilizing a freeform optics-based microlens array. Optical performance, focusing on efficiency and uniformity, was optimized across key distances using the Taguchi method. Simulation results demonstrate that the optimized uniform illumination system, featuring a 13 × 13 array with microlens of 2 mm radius positioned 300 mm from the target plane, achieves a high optical efficiency of 93.7% and an outstanding illuminance uniformity of 98.9%. Furthermore, the system maintains good uniformity across different wavelengths, enhancing its versatility. These findings strongly support the feasibility of the proposed freeform optics-based microlens array lighting system for machine vision in laser additive manufacturing defect detection, significantly contributing to improved image contrast.