Detection of metal,glass and plastic pieces in bottled beverages using ultrasound

The detection system is composed of a pulse/echo transducer, a water jet nozzle and an x–y table. Foreign bodies such as glass, metal and plastic pieces were detected by scanning the flat bottom of the beverage container. Based on acoustic modeling, a method for detection and identification of foreign bodies is developed and tested. A signal processing algorithm for time–frequency analysis is used to discriminate between beverage and contaminants from ultrasound echoes. Effective detection ability for materials such as glass, metals, and plastic, with sizes from 10 to 2.5 mm² is demonstrated. Experiments were also performed using ultrasonic beam penetrating glass material to detect steel balls of different sizes. This is closer to the case of real foreign body in terms of orthogonality and cross-section to ultrasound beam.