Trends in automated visual inspection

Automated visual inspection (AVI) or automated optical inspection (AOI) systems offer significant advantages over human inspection from a fatigue, throughput, speed and accuracy point of view. This area has matured considerably over the last decade or so, due to advances in enabling technologies like sensors, processor hardware, software methodologies, and networking to name a few. These advances in cost, performance and design methodologies have resulted in an explosion of application areas, where AVI and AOI systems have become an integral component of quality control schemes in product inspection and certification. AVI systems represent a quantitative feedback node to identify and eliminate problems at different stages in the production process. Commercial systems The major application areas for AVI include but are not limited to: (a) Packaging: medical containers (pill strips, bottles), food cans (hole detection, shape defects, finish), chips (pad contacts), etc. (b) Electronics: semiconductor wafers, dies, chips, PCB inspection, etc. (c) Web and surface inspection: metal, textiles, paper etc. AVI systems can be further classified based on whether they detect gross defects using relatively global features or fine defects based on fine local features. Print inspection and die inspection are examples of the latter and typically require greater algorithmic support. Commercial systems can also be classified based on the level of integration. Custom systems are complete solutions for a specific industrial application available for high-volume industries like semiconductors. On the other hand, the AVI industry has always had a large number of system integrators and consultants that design systems based on off-theshelf vision processors, sensors, software and varying degrees of proprietary contributions. Commercial AVI systems have always had to operate under ‘‘hard’’ realtime conditions and harsh plant environments and have become mature and reliable over the years. Increasingly, industry trends have led to further de facto requirements: (a) systems have to be networked and accessible remotely, (b) systems have to be integrated with manufacturing software or processes and (c) systems have to interface with databases. While these trends raise the bar for any developer, they have made defect classification and statistical analysis, a real possibility. This presents an opportunity to AVI system developers to ‘‘add value’’ to the manufacturing process.