Patent ID: 6622913
Filing Date: 2003-09-23
Classification: G06K

Abstract:
A security system for protecting an item by forming it with a predetermined code pattern, the system comprising:a plurality of space-apart magnetic elements forming said code pattern, wherein said magnetic elements are made of at least one magnetic material having a coercivity substantially less than 10 A/m and a permeability substantially higher than 20000; a reading head comprising: a magnetic means comprising two permanent magnets magnetized in opposite directions and arranged in a spaced-apart parallel relationship along an axis perpendicular to the magnetization axes, said magnetic means producing a high gradient static magnetic field defining an extended narrow region, which is located between the permanent magnets and extends parallel to said magnetization axes, and in which the static magnetic field vector is substantially equal to zero, to thereby effect the magnetic element located within the static magnetic field outside the zero-field region; and a sensing element being mounted substantially within said region and operable to be responsive to signals generated by the magnetic element that has been affected by the static magnetic field and is located within said extended narrow region being oriented substantially parallel to said region, and a detector detecting the response of said sensing element and generating data representative thereof the system being thereby capable of detecting the code pattern during a relative displacement between the magnetic elements and the sensing element in a reading direction perpendicular to the longitudinal axis of the magnetic element, when the magnetic elements successively pass said zero-field region with the magnetic elements' orientation substantially parallel to the narrow zero-field region.