AI-based Automatic Optical Inspection of Glass Bubble Defects

Abstract

Automatic Optical Inspection (AOI) offers a range of solutions to meet the requirements of every production facility, attracting significant interest of manufacturers of various industries. One important AOI application in the glass industry is to detect bubble defects in spherical glass, especially those used for making high-end lenses. Nevertheless, the AOI process must make the inspection decision in a reliable manner. Another challenge is that glass bubble defects are nearly transparent and can be captured by cameras only from certain viewing angles and with the aid of a specially engineered lighting mechanism. In this paper, an Artificial Intelligence method based on AOI (AI-AOI) is proposed to address the need of the glass industry as aforementioned. In specifics, our proposed method employs (1) a specially designed back-lighting mechanism to illuminate the hardly visible glass bubble defects, (2) Otsu thresholding image-segmentation method to obtain the distortion part and the core part of the defects and eliminate the fake defects caused by dust particles, and (3) a novel AI-based bubble-defect detection method capable of capturing the bubble defects as small as a few millimeters in diameter. The initial experimental results validate the feasibility of the proposed AOI method with an accuracy of 95%. If we exclude factors such as scratches by humans or the presence of dust particles in the inspection room, our method can achieve a recognition rate of 100%.