Method and system for sliding door pattern cancellation in metal detection

A metal detection system comprising:

• a transmitter operable to transmit an interrogation signal, the interrogation signal establishing a detection region and being used to detect transitory metal objects within the detection region;
• a receiver operable to receive instantaneous signals in response to the interrogation signal, the instantaneous signals representing electromagnetic field disturbances during operation of the metal detection system, the instantaneous signals including electromagnetic field disturbances attributed to the movement of metal doors;
• and
• a metal detection module operable to:
• determining a resulting waveform, the resulting waveform representing a difference between the instantaneous signals received during operation of the metal detection system and a recorded pattern of signals representing electromagnetic field disturbances over time caused by a pattern of movement of the metal doors in the detection region when a transitory metallic object is not present, the movement of the metal doors during operation of the metal detection system being substantially the same as the pattern of movement of the metal doors during the recording of the pattern of signals;
• and
• determine if a metal object is present in the detection region based on the resulting waveform.

An integrated EAS/metal detection system comprising:

• a transmitter operable to transmit an interrogation signal, the interrogation signal establishing an interrogation zone and being used to detect EAS markers and transitory metal objects within the interrogation zone;
• a receiver operable to receive instantaneous signals in response to the interrogation signal, the instantaneous signals representing electromagnetic field disturbances during operation of the metal detection system, the instantaneous signals including electromagnetic field disturbances attributed to the movement of metal doors;
• and
• a metal detection module operable to:
• determining a resulting waveform, the resulting waveform representing a difference between the instantaneous signals received during operation of the metal detection system and a recorded pattern of signals representing electromagnetic field disturbances over time caused by a pattern of movement of the metal doors in the detection region when a transitory metallic object is not present, the movement of the metal doors during operation of the metal detection system being substantially the same as the pattern of movement of the metal doors during the recording of the pattern of signals;
• and
• determine if a metal object is present in the detection region based on the resulting waveform.