Single Detector Sensor for Document Luminescence and Remission
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Solution Overview
Problem
Current methods for detecting the authenticity of value documents, particularly bank notes, face challenges in simultaneously measuring luminescence and remission using separate detectors, which complicates the identification of composed forgeries and is difficult to perform without relative movement between the document and detectors.
Innovation Solution
A sensor system that uses a single detector for both luminescence and remission measurements, allowing remission measurement during illumination with excitation light and luminescence measurement after illumination, with a spectral detection filter that allows a significant portion of excitation light to pass through, reducing distortion from simultaneous luminescence and enabling accurate comparison of measurement values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate detectors are used for remission and luminescence measurements, then both measurements can be performed, but the device complexity increases and it becomes difficult to measure at the same document position
Solution Approach 1:
The patent merges the remission detector and luminescence detector into a single detector that performs both measurement functions. The detector is configured to measure remission during illumination and luminescence after illumination, eliminating the need for separate detectors and enabling measurements at the same document position.
Solution Approach 2:
The single detector is designed with multi-functionality to perform both remission measurement during illumination and luminescence measurement after illumination. This universal detector replaces what would traditionally require two separate specialized detectors, simplifying the device while maintaining measurement capabilities.
2Measurement precision
If a blocking filter is used to block excitation light during remission measurement, then luminescence distortion is reduced, but the remission measurement value is distorted by simultaneous luminescence
Solution Approach 1:
The patent uses periodic illumination with excitation light pulses, measuring remission during the illumination phase and luminescence during the dark phase between pulses. This periodic measurement approach allows the same detector to capture both signals at different times without interference from simultaneous luminescence during remission measurement.
Solution Approach 2:
The patent introduces a half-value filter as an intermediary element that transmits a controlled portion of excitation light during remission measurement. This filter allows sufficient excitation light to reach the document for luminescence excitation while blocking enough to reduce luminescence distortion in the remission measurement, serving as a mediator between the conflicting requirements.
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 allows for improved detection of remission and luminescence at nearly the same document position, reducing the need for additional detectors and minimizing distortion, thereby enhancing the accuracy of authenticity checks, including the identification of composed forgeries.
Implementation Method 1
an illumination device for illuminating a document, e.g. a value document, with one or several excitation light pulses of an excitation light which is suitable for exciting the document, e.g. value document, to emit luminescent light
Implementation Method 2
for detecting at least one remission measurement value of the document, e.g. value document, at at least one point in time at which the document, e.g. value document, is illuminated with an excitation light pulse
Implementation Method 3
for detecting at least one luminescence measurement value of the document, e.g. value document, at at least one point in time after the end of the respective excitation light pulse
Implementation Method 4
a detection filter which is located in a detection ray path formed between the document, e.g. value document, and the detector
Data Source
AI summary
A method and a sensor for checking documents are provided in which the same detector is used for a remission measurement and a luminescence measurement of the value document. The remission measurement value being detected during the illumination of the value document with an excitation light used for luminescence excitation, and the luminescence measurement value after switching off the illumination. In order to reduce a distortion of the remission measurement value by the luminescence, a spectral detection filter is incorporated into the detection ray path, which has a transmission of at least 0.5% in the spectral region of the excitation light. The increased transmission of the spectral detection filter achieves that the excitation intensity impinging on the detector far exceeds the luminescence intensity occurring simultaneously with the excitation and thus reduces the mentioned distortion.