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New types of shelf-stable food packages have been developed that offer the processor lower energy, storage and packaging costs, and offer the consumer better nutrition, increased product quality and easier preparation. The major restraint on the implementation of these types of packages is the regulatory requirement for 200% manual visual inspection for seal defects during production. Human inspectors suffer from unpredictable performance variations. What is needed is an automatic, on-line, nondestructive evaluation technique. This study evaluated all available types of package testing methods, and found ultrasonic imaging be the best available choice of nondestructive methods.
Scanning Laser Acoustic Microscopy (SLAM) is a successful method for the evaluation of defects, but need for access to both sides of the material, and the cost and complexity of the equipment make it of limited usefulness. We have developed a new method of signal processing (termed the Boundary Integral Amplitude (BAI) method) that makes the generation of a 3-D image of the material possible using a simple pulse-echo transducer. This method will image subwavelength sized defects,using backscattered acoustic energy, and provides a promising path for high speed sensor development. Future plans are to develop this into a demonstration-scale unit, using a phased-array transducer to determine the design parameters for successful high-speed on-line scanning.