Magnetic Testing of Valuable Documents Using Dual Magnetization
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Solution Overview
Problem
Existing magnetic testing methods for valuable documents, such as banknotes, struggle with accurately reading finely structured magnetic codes due to the complexity and limited spatial resolution of magnetic detectors, particularly inductive detectors.
Innovation Solution
A method involving a dual-magnetization process using magnetic fields of different strengths to align low- and high-coercivity magnetic materials differently, followed by evaluation of magnetic signals from multiple measurement tracks to identify and differentiate between magnetic areas, allowing for the determination of magnetic coding through comparison values and thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetoresistive detectors (AMR, GMR, TMR) or Hall effect sensors are used to achieve high spatial resolution for reading finely structured magnetic encodings, then measurement precision is improved, but device complexity increases due to the complex manufacturing requirements of these detectors
Solution Approach 1:
The patent changes the operating parameters of the inductive magnetic detector by applying different magnetic field strengths (first stronger field, then weaker field) to different types of magnetic materials. This parameter-based differentiation allows the simple inductive detector to distinguish between high-coercivity and low-coercivity magnetic areas, achieving accurate reading of magnetic encodings without requiring complex magnetoresistive or Hall effect sensors.
2Ease of manufacture
If inductive magnetic detectors are used to simplify device structure, then ease of manufacture is improved, but measurement precision deteriorates due to insufficient spatial resolution for reading finely structured magnetic encodings
Solution Approach 1:
The patent overcomes the spatial resolution limitation of inductive detectors by changing the magnetic field parameters applied during measurement. By using a two-stage magnetization process with different field strengths, the system extracts more information from the magnetic signal, enabling the simple inductive detector to accurately identify both high- and low-coercivity magnetic areas that form the magnetic encoding.
Solution Approach 2:
The patent applies a preliminary strong magnetic field to magnetize both high- and low-coercivity magnetic areas before the actual measurement. This preliminary action ensures that all magnetic areas are properly magnetized and will produce detectable signals, allowing the inductive detector to achieve sufficient measurement precision for reading magnetic encodings.
3Device complexity
If a single magnetic field strength is used for magnetization, then device complexity is reduced, but measurement precision deteriorates because both high- and low-coercivity magnetic areas cannot be differentiated
Solution Approach 1:
The patent employs periodic action by applying magnetic fields in two distinct stages: first a stronger field to magnetize both types of magnetic areas, then a weaker field to selectively affect only low-coercivity areas. This periodic application of different field strengths creates characteristic signal patterns that enable precise differentiation between high- and low-coercivity magnetic materials, improving measurement precision while maintaining relatively simple device architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate identification and categorization of magnetic coding on valuable documents, improving the detection of both low- and high-coercivity areas, and distinguishing between different coercive materials, enhancing the security verification process.
Implementation Method 1
magnetized by a first magnetic field area whose magnetic field strength is greater than both the first and second coercive field strengths
Implementation Method 2
low-coercive magnetic material with a first coercive field strength, and one or more high-coercive magnetic areas made of a high-coercive magnetic material with a second coercive field strength greater than the first
Implementation Method 3
inductive magnetic detector, which has several measuring tracks transverse to the transport direction of the valuable document and is configured to detect a magnetic signal in each measuring track
Data Source
Figure 1~2
Figure 3a~3d
Figure 4a~5b
AI summary
The invention relates to the testing of valuable documents which have a security element with a number of magnetic regions, for example high-coercivity and/or low-coercivity magnetic regions. When all magnetic regions have been magnetised in a first direction, second magnetisation is performed, in which only the low-coercivity magnetic material is remagnetised, but the high-coercivity magnetic material remains oriented in the first direction of magnetisation. Magnetic signals of the security element are then detected using an inductive magnetic detector, which has a plurality of measuring tracks transverse to the direction of transport of the valuable document. In order to evaluate the magnetic signals of the measuring tracks, the strongest two local minima and maxima of a magnetic signal detected by a measuring track as a function of time are determined. By comparing the amplitudes of the particular magnetic signal in the minima and maxima, a minima comparison value and maxima comparison value of the measuring track are determined. The magnetic coding of the security element is checked on the basis of the minima comparison values and maxima comparison values.