A real-time approach to detect seal defects in food packages using ultrasonic imaging

The microbial integrity of many types of flexible food packages depends on a zero defect level in the fused seam seal. Human inspection for defects in these seals is marginal at best, and secondary incubation protocols are of ten used to spot packages with compromised integrity before releasing produ ct for sale. A new type of inspection method has been developed and is bein g evaluated for robustness. The purpose of the study was to evaluate a new raster scanning geometry to simulate continuous motion, online ultrasonic i nspection of the seal region in flexible food package seals. A principal en gineering tradeoff of scanning inspection systems is between increased line speed that results from decreased spatial sampling (less acquired data to process) and decreased image quality. The previously developed pulse-echo B ackscattered Amplitude Integral (BAI) mode imaging technique is used to for m ultrasound images using the new scanning geometry. At an ultrasonic frequ ency of 22.9 MHz, 38- and 50-mum-diameter air-filled channel defects in all -plastic transparent trilaminate are evaluated. The contrast-to-noise ratio (CNR) of the processed BAI-mode image is used to quantify image quality as a function of spatial sampling. Results show seal defects (38- and 50-mum diameter) are still detectable for undersampled conditions, although image quality degrades as spatial sampling decreases. Further, it is concluded th at the raster scanning geometry is feasible for online inspection.