Object detection method

A method for detecting objects passing through an inspection zone comprising:

• providing an inspection zone having a first side and an opposing second side, and wherein the opposing second side is spaced apart from the first side by a known and predetermined distance;
• providing a reflective background at the opposing second side of the inspection zone;
• providing a stream of individual objects of interest and moving the stream of individual objects of interest along a first supported path of travel from a first position to a second position, and releasing the stream of individual objects of interest from the second position into an unsupported path of travel so that the stream of individual objects of interest pass through the inspection zone, between the first side and the opposing second side thereof, generally vertically under the influence of gravity;
• providing an emitter of pulsed electromagnetic radiation at the first side of the inspection zone that, when actuated, generates pulses of electromagnetic radiation which are directed across the inspection zone and toward the reflective background at the opposing second side of the inspection zone and toward the stream of individual objects of interest passing through the inspection zone so that at least a portion of the emitted pulses of electromagnetic radiation pass through the stream of individual objects of interest and strike the reflective background, or at least a portion of the emitted pulses of electromagnetic radiation impact one or more of the individual objects of interest within the inspection zone, and the emitted electromagnetic radiation pulses that strike the reflective background are at least partially reflected, and the emitted electromagnetic radiation pulses that impact one or more of the individual objects of interest within the inspection zone are at least partially reflected;
• providing a detector of electromagnetic radiation positioned at the first side of the inspection zone and oriented to receive electromagnetic radiation pulses that are reflected by the reflective background and that are reflected by striking individual objects of interest within the inspection zone, and the detector of electromagnetic radiation is positioned a known distance from the reflective background and wherein the detector of electromagnetic radiation generates a reflection receipt signal upon detection of a reflected electromagnetic radiation pulse that has been at least partially reflected from the reflective background, and the detector of electromagnetic radiation generates a reflection receipt signal upon detection of a reflected electromagnetic radiation pulse that has been at least partially reflected from an individual object of interest within the inspection zone;
• providing a controller operatively communicating with the detector of electromagnetic radiation to receive reflection receipt signals therefrom, and wherein the controller periodically generates an emission signal which is communicated to the emitter of electromagnetic radiation which responsively causes the emitter of electromagnetic radiation to emit a pulse of electromagnetic radiation directed toward the reflective background at the second side of the inspection zone and wherein the controller determines a time duration between each emission signal communicated to the emitter of electromagnetic radiation and each reflection receipt signal received from the detector of electromagnetic radiation, and wherein any determined time duration that varies from a known time duration for each emitted pulse electromagnetic radiation to travel from the electromagnetic radiation emitter to the reflective background and to travel from the reflective background to the detector of electromagnetic radiation is evidence that an object of interest is present in the inspection zone.