Wide Area Metal Detection

Reference#: P01766

With the recent terrorist attacks, providing a safe environment in large settings such as stadiums, amusement parks, airports and other areas where large groups of people are moving through has taken on renewed importance. Currently, perhaps the most effective portal that has an electromagnetic induction (EMI) metal detector. Typically only one person can walk through the metal detector at a time, so this creates a "choke" point where a line typically forms. For large sporting events and anywhere where large crowds gather and must be screened, the use of portable type metal detectors are time consuming and create additional problems with delays.

The Wide Area Metal Detecting (WAMD) System, invented by the Johns Hopkins Applied Physics Laboratory, provides for large-scale metal weapon screening which can be used to locate potential individuals in a crowd that merit further investigation. This mass pre-screening would greatly reduce the need for meticulous scanning of each individual with a high sensitivity portal-type detector or a hand-held metal detector to identify potential weapons. The invention comprises a series of closely spaced current carrying wires configured as a horizontal magnetic field generator (HMFG), which is designed to be buried in an area where people are walking, such as the entrances to ballparks or amusement parks. An array of magnetic field detectors is also buried with the HMFG. A nonmagnetic surface (such as asphalt) covers the hardware and can be patterned with a grid to assist in locating the magnetic fields. The HMFG is powered either by a pulsed current source or a continuous wave current source to create eddy currents in nearby metal objects such as weapons being carried by people walking toward the entrance and over the area.

Dr. G. R. Jacobovitz
Phone: (443) 778-9899