Abstract

CHIU, Yuan-Shyi Peter; LIN, Hong-Dar  and  CHENG, Hsu-Hung. Optical inspection of appearance faults for auto mirrors using Fourier filtering and convex hull arithmetic. J. appl. res. technol [online]. 2021, vol.19, n.4, pp.279-293.  Epub Feb 14, 2022. ISSN 2448-6736.  https://doi.org/10.22201/icat.24486736e.2021.19.4.958.

Auto mirrors are indispensable and essential for the reflection of objects behind the car and act as a crucial part in driving security. In manufacturing stages of auto mirrors, certain tasks operated unusually will cause scratches, chips, pinholes, bubbles and damaged edges on the general surface and profile faults on auto mirrors. Those appearance faults sometimes will severely have an impact on the standard of the mirror reflection and increase the driving hazard. During the traditional examination of auto mirrors in the manufacturing process, almost all work is performed by human examiners. Manual examination can be easily affected by foreign objects reflected on the mirror surfaces which can cause mistaken determinations of fault examination. Hence, this study works toward investigating the automatic appearance fault detection of auto mirrors. We propose a fault enhancement technique based on Fourier high-pass filtering and the convex hull arithmetic to inspect appearance faults on auto mirrors. This approach only utilizes their own information of testing images to judge whether there are any irregular appearance changes without the need of standard patterns for matching. Experimental outcomes illustrate that the appearance fault detection rate increases by 95.13%, the false alarm rate decreases to 1.88% and the correct classification rate attains to 98.11%.

Keywords : Industrial inspection; auto mirrors; appearance faults; Fourier filtering; convex hull arithmetic.

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