Magnetic Sensor Arrangement for Banknote Authentication Interference Compensation
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Solution Overview
Problem
Existing banknote handling devices face difficulties in reliably detecting magnetic security features due to interference from other magnetic fields, such as those generated by drive motors and fans, which complicates the authentication process.
Innovation Solution
A device and method utilizing a combination of security feature sensors and compensation sensors to detect and compensate for interfering magnetic fields, allowing for the reliable detection of magnetic security features without additional magnetic shielding. The sensors are arranged to differentiate between the security feature signals and interference, using a transport device to position the document and calculate compensation values based on measured interference variables and weighting factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetoresistive sensors are used to detect magnetic security features, then the detection capability is provided, but interference from other magnetic fields (drive motors, fans) reduces detection reliability
Solution Approach 1:
The sensor system is segmented into two distinct groups: security feature sensors positioned to detect magnetic security features on banknotes, and compensation sensors positioned to detect only interference magnetic fields. This segmentation allows each sensor group to perform its specialized function, with the evaluation unit processing signals from both groups to separate security feature signals from interference signals.
Solution Approach 2:
The compensation sensors act as intermediaries that detect the interference magnetic fields generated by drive motors and fans. By measuring these interference fields separately, the system can compensate for their effect on the security feature sensors, effectively using the compensation sensors as mediators to isolate and eliminate the harmful magnetic interference.
2Measurement precision
If sensors are positioned close to the transport plane for detecting security features, then detection sensitivity increases, but interference from nearby magnetic sources increases
Solution Approach 1:
Different regions of the sensor arrangement are assigned different functions based on their local characteristics. Security feature sensors are positioned at a first distance from the transport plane where they can detect security features, while compensation sensors are positioned at a second distance where they primarily detect interference fields. This local differentiation allows each sensor to optimize its detection capability for its specific purpose.
Solution Approach 2:
The solution adds a spatial dimension to the sensor arrangement by positioning sensors at different distances from the transport plane. Rather than trying to solve interference problems in the same plane, the system uses the distance dimension to create separate detection zones: one for security features and one for interference fields, allowing simultaneous detection of both phenomena.
3Object-affected harmful factors
If additional magnetic shielding is implemented to block interference, then interference reduction is achieved, but device complexity and cost increase
Solution Approach 1:
Instead of using mechanical magnetic shielding structures to block interference fields, the system substitutes a sensor-based measurement and compensation approach. Compensation sensors measure the interference fields, and the evaluation unit calculates compensation values that are subtracted from security feature sensor signals, replacing the need for physical shielding with an electronic compensation system.
Solution Approach 2:
The system uses itself to compensate for its own interference problems. The compensation sensors are part of the same sensor arrangement and detect the interference fields that affect the security feature sensors. By using components within the system itself to measure and compensate for interference, the solution avoids adding external shielding structures.
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
Enables secure and automatic detection of magnetic security features, enhancing the authenticity verification of banknotes and other documents of value by effectively filtering out interfering magnetic fields, thus improving the accuracy of authentication processes.
Implementation Method 1
The magnetic security feature in the handling device is checked, for example, by means of magnetoresistive sensors
Implementation Method 2
For example, the sensors can be designed as Hall sensors, which detect a magnetic field without contact
Data Source
Figure 1~1B
Figure 2
Figure 3
AI summary
A device (15) for detecting a magnetic security feature (17') of a valuable document (17) can comprise: a transport device (21) configured to transport the valuable document (17) through the device (15), sensors (1-12, AC) configured as magnetic sensors and comprising at least two security feature sensors (1-12) and at least one compensation sensor (AC), and an evaluation unit (23) configured to receive the signals output by the sensors (1-12, AC), wherein the sensors (1-12, AC) are arranged and configured in a line (L) parallel to the transport plane (TE) and transverse to the transport direction, and wherein the sensors (1-12, AC) are arranged at a distance (D1, D2) from the transport plane (TE) such that the distance (D1) of the security feature sensors (1-12) is configured to detect a security feature (17') by at least one of the security feature sensors. (1-12) to record,and that the distance (D2) of the compensation sensor (AC) is set so that a safety feature (17') is not detected by the compensation sensor (AC).