System and technique for detecting the presence of foreign material

The present invention is directed to the detection of foreign material. More particularly, but not exclusively, it is directed to the detection of foreign material in heterogeneous process streams such as process streams of foodstuffs. In one particular application the invention is directed to the detection of bone in a slurry of chicken meat. A system and technique for detecting the presence of foreign material is presented. An ultrasound transmitter interrogates the bulk material and an array of detectors receives the off angle ultrasound scattering response of the bulk material. The presence of foreign material is determined when the off angle scattering response exceeds a predetermined threshold. The technique is especially suitable for the detection of bone in meat.