Hermetically-sealed flexible food packages require very effective seal integrity testing to extend the shelf stability of thermally processed food. The initial goal of this study was to estimate the detection limits of laboratorygenerated channels which simulate defects in food packages using pulse-echo ultrasonic imaging techniques. Packages with well characterized (via transmission optical microscopy) laboratory-generated channels that simulate defects with diameters between 9 and 325 fj,m in the seal plane traversing the major axis of the heat seal were generated in heat-sealed microwavable retort-pouch plastic film (trilaminate). Pulse-echo techniques in the 13-17 MHz center frequency range were investigated. The samples were examined with a conventional B-mode imaging technique, which was found to be inadequate for subwavelength imaging of the types of typical channel defects found in shelfstable food packages. Based on conventional B-mode image features, a new goal of this study was established to develop and evaluate an imaging technique which would exhibit subwavelength imaging capabilities. The new imaging technique called backscattered amplitude integral (BAI) is introduced here. It was observed that BAI-mode imaging has the ability for subwavelength detection of channel defects, e.g., detection of a W-/-tm diameter channel defect at a center frequency of 13.1 MHz (A = 182 μm).
|Original language||English (US)|
|Number of pages||11|
|Journal||IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control|
|State||Published - 1998|
ASJC Scopus subject areas
- Acoustics and Ultrasonics
- Electrical and Electronic Engineering