Sensor Luminescence Decay Verification
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Solution Overview
Problem
Existing document verification systems inaccurately determine the decay time of luminescence at high transport speeds due to movement effects, leading to falsified intensity profiles.
Innovation Solution
A method using a sensor that excites a document with a first and second luminescence at different wavelengths, evaluating their intensity profiles relative to each other to calculate characteristic time constants, thereby compensating for movement effects and ensuring accurate authenticity checks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the document transport speed is increased to improve productivity, then the checking throughput is improved, but the measurement precision of luminescence decay time deteriorates due to movement effects falsifying the intensity profile
Solution Approach 1:
The patent applies dynamics by making the excitation source movable, tracking the document's position during transport. The excitation source moves synchronously with the document, maintaining constant spatial relationship and enabling accurate intensity profile measurement even at high transport speeds. This dynamic adaptation resolves the contradiction by allowing high productivity while preserving measurement precision.
Solution Approach 2:
The patent implements feedback through position detection systems that monitor document location and transport speed, using this information to control the excitation source movement and timing. The system continuously adjusts excitation parameters based on real-time position feedback, ensuring accurate luminescence decay time measurement despite high-speed transport conditions.
2Device complexity
If a stationary sensor is used to detect luminescence while the document moves at high speed, then the device complexity is reduced, but the measurement precision deteriorates because the intensity profile is falsified by the relative movement
Solution Approach 1:
Instead of using a stationary sensor, the patent employs a movable excitation source that tracks the document position. This dynamic approach maintains the excitation-detection relationship despite document movement, preserving measurement precision without requiring complex multi-sensor arrays or sophisticated stationary detection systems.
Solution Approach 2:
The patent effectively creates a moving reference frame by synchronizing the excitation source movement with document transport. This copying of the document's motion by the excitation source allows the system to treat the relative position as static, simplifying the detection system while maintaining accuracy.
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 precise determination of luminescence decay times even at high transport speeds, enhancing the accuracy of document authenticity verification by eliminating movement-induced errors.
Implementation Method 1
The value document has a security feature that contains one or more luminescent substances that emit luminescence
Implementation Method 2
The luminescence which the value document illuminated with the excitation light emits is detected by the sensor
Data Source
Figure 1a~1d
Figure 2a~2c
Figure 3~5
AI summary
The invention relates to a method and a sensor for checking a valuable document, which is moved in relation to the sensor. The sensor is designed to detect the luminescence of the valuable document in two different spectral ranges simultaneously at the same detection location. The two curves of intensity versus time of the first and second luminescence detected in different spectral ranges are evaluated in relation to each other. The motion effects that distort both curves of intensity in the same or at least a very similar manner are thereby eliminated by calculation.