Method and apparatus for checking value documents

A method for checking a value document having a security element with several magnetic region, said magnetic regions having at least one high-coercive magnetic region which contains a high-coercive magnetic material with a first coercive field strength and at least one low-coercive magnetic region which contains a low-coercive magnetic material with a second coercive field strength which is lower than the first coercive field strength and at least one combined magnetic region which contains both the high-coercive and the low-coercive magnetic material, comprising the steps:

• first, magnetizing the security element by a first magnetic field whose magnetic field strength is greater than the first coercive field strength, so that the magnetization of the high-coercive magnetic material and the magnetization of the low-coercive magnetic material are aligned in a first magnetization direction,
• then, magnetizing the security element by a second magnetic field whose magnetic field strength is lower than the first coercive field strength but is greater than the second coercive field strength, the second magnetic field being oriented such that the magnetization of the low-coercive magnetic material through the second magnetizing is aligned antiparallel to the first magnetization direction,
• detecting first magnetic signals of the security element by a first magnetic detector, and
• detecting second magnetic signals of the security element by a second magnetic detector, before the detection of the second magnetic signals a third magnetic field acting on the security element,
• wherein a magnetic region whose second magnetic signal exceeds a second upper threshold and/or undershoots a second lower threshold, and whose first magnetic signal neither exceeds a first upper threshold nor undershoots a first lower threshold, is identified as a combined magnetic region, and
• wherein the first magnetic signal of the security element has a first signal offset and that the first upper threshold lies above the first signal offset and the first lower threshold lies below the first signal offset.

An apparatus for checking a document of value which has a security element with high-coercive magnetic material of a first coercive field strength and with low-coercive magnetic material of a second coercive field strength, wherein the apparatus comprises successively along a transport direction of the value document:

• a first magnetization device arranged to make available a first magnetic field which is configured for the first magnetizing of the high-coercive and of the low-coercive magnetic material in a first magnetization direction, the magnetic field strength employed for the first magnetizing being greater than the first coercive field strength,
• a second magnetization device arranged to make available a second magnetic field which is configured for the second magnetizing of the low-coercive magnetic material in a second magnetization direction which is oriented antiparallel to the first magnetization direction, the magnetic field strength employed for the second magnetizing being lower than the first coercive field strength, but greater than the second coercive field strength, and
• a first magnetic detector arranged to detect first magnetic signals of the security element,
• a second magnetic detector arranged to detect second magnetic signals of the security element, and
• a third magnetization device arranged to make available a third magnetic field, which is configured such that the third magnetic field, upon checking of the value document, acts on the security element before the detection of the second magnetic signals,
• wherein the magnetic field strength of the third magnetic field is greater than the second coercive field strength and the third magnetic field is oriented such that the magnetization of the low-coercive magnetic material is aligned by the third magnetic field in a third magnetization direction which is oriented non-antiparallel to the first magnetization direction.