Design of a composite lighting system based on a freeform and a rod lens for machine vision

Abstract

Light-emitting diodes (LEDs) have been widely utilized in machine vision lighting systems such as the process monitoring system in the additive manufacturing field, owing to their long life, high illumination efficiency, and controllable dimming. The quality of the lighting system directly affects the efficiency and accuracy of the entire monitoring system. However, existing designs cannot meet the optical efficiency and uniformity requirements at short lighting distances and small inspection areas with mixed multi-spectrum channels. This paper thus proposes a novel, to the best of our knowledge, design method of integrating a freeform surface lens and a square-shaped rod lens. The optical characteristics under different working distances and targeting surface types have been optimized and evaluated. Meanwhile, tolerance analysis has been utilized to demonstrate the feasibility of installation. With the use of the software Tracepro, simulation results showed that the designed composite machine vision lighting system can obtain an optical efficiency of 81.704% and an illuminance uniformity of 95.804% within the inspection area at a distance of 250 mm. Furthermore, verification experiments with a prototype were performed, demonstrating the feasibility of the proposed machine vision lighting system.

Online synchronous inspection and system optimization of flexible food packaging bags by using machine vision and sensing technique

“…Pengfei et al [27] made an effort to move object monitoring and intelligent tracking measurement for video supervision with algorithms through formulas and comparison between the accuracy and success rate, and experiment. Xing et al [28] researched and supplied a specific design method for the coalescence of two kinds of lenses with different features by optimizing operating distances and targeting surfaces, obeying rather strict requirements.…”

Design of multi-spectral LED lighting system with high color uniformity for microscopic imaging

“…For instance, spotlights based on TIR lenses and reflectors have been designed to mix RGB light sources uniformly [7]. Incorporating a free-form surface lens and a square rod can produce a light spot with uniform illumination at a distance of 250 mm [8]. Various optical mixing devices are employed for multi-spectral LED light mixing, such as microlens arrays [9], light rods, and combinations of the above optical devices.…”