FOOD CONTAINER INTERNAL PRESSURE ANALYSIS

A sensor structure for use with container inspection systems utilizes a continuous-wave (CW) microwave radar to measure the curvature or the vibration characteristics of a container wall through a thick corrugated cardboard case top or on a single item container processing line. A radar antenna directs RF energy toward cans moving along a conveyor. The antenna emits a beam which, over time, illuminates a narrow region along a line from one outer edge of the can to the opposing outer edge, as the can passes the antenna. During this time, a continuous measurement of the relative change in distance from the antenna to the top of the can is generated and sampled for acquisition by a computer, and an estimate of the profile is made from changes in the distance measurement. The profile is used as a measure of the internal pressure of the can or as an indication of the presence of manufacturing defects. In a second embodiment, the resonant vibration frequencies and amplitudes of the container are measured and analyzed from the changes in distance measurement. The vibration characteristics are an alternative measure of the internal pressure of the container or indication of the presence of manufacturing defects. The sensor embodiment is chosen to obtain the most reliable detection criteria for a specific type of container or product.