Method and apparatus for sensing a magnetic field

Abstract

A magnetic screening system uses directional gradiometers with high resolution and accuracy to measure magnetic field signatures of target objects (e.g., gun, knife, cell phone, keys) in a volume of interest. The measured signatures can be compared to signatures of known objects stored in a local database. Various mathematical processes may be used to identify or classify target object signatures. In a network of magnetic screening systems, the magnetic screening systems can transmit signatures to a central signature database, and a management computer can share the central signature database with all of the magnetic screening systems on the network. The magnetic screening system can operate in multiple modes, such as a tracking mode, measurement mode, and self-test mode. Through use of unique processes and designs, the magnetic screening system can achieve a high rate of processing persons for target objects.

1 . A gradiometer comprising:
 at least three magnetometers; and   a processor unequally weighting outputs of the at least three magnetometers and combining the unequally weighted outputs to orient a direction of sensitivity toward at least one direction of interest.   
     
     
         2 . The gradiometer according to  claim 1  wherein the processor weights the outputs with non-integer weights. 
     
     
         3 . The gradiometer according to  claim 1  wherein the processor uses output weights calculated using a deterministic mathematical technique. 
     
     
         4 . The gradiometer according to  claim 1  wherein the processor adjusts the output weights digitally. 
     
     
         5 . The gradiometer according to  claim 1  wherein spacing of the magnetometers is determined before the weights are determined. 
     
     
         6 . The gradiometer according to  claim 1  wherein the number of magnetometers and associated weights are selectable to develop arbitrary response patterns. 
     
     
         7 . A method of sensing a magnetic field, the method comprising:
 applying unequal weights to outputs of at least three magnetometers in a gradiometer; and   combining the unequally weighted outputs to orient a direction of sensitivity toward at least one direction of interest.   
     
     
         8 . The method according to  claim 7  wherein applying the outputs includes applying the outputs with non-integer weights. 
     
     
         9 . The method according to  claim 7  further including calculating the output weights in a deterministic mathematical manner. 
     
     
         10 . The method according to  claim 7  further including adjusting the output weights digitally. 
     
     
         11 . The method according to  claim 7  further including determining spacing of the magnetometers before determining the weights. 
     
     
         12 . The method according to  claim 7  further including selecting a number of magnetometers and associated weights to develop arbitrary response patterns. 
     
     
         13 . A gradiometer comprising:
 means for applying unequal weights to outputs of at least three magnetometers in a gradiometer; and   means for combining the unequally weighted outputs to orient a direction of sensitivity toward at least one direction of interest.