Optical Sensor Self-Test for Valuable Document Light Correction
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Solution Overview
Problem
Existing optical sensors for valuable documents struggle to accurately correct measured values due to varying light source intensities over their operating life, especially when multiple light sources are used simultaneously, leading to inconsistent and difficult-to-calculate corrections.
Innovation Solution
An optical sensor design with a photodetector row, light source row, and monitor detector row, where each monitor element is assigned to a light source, allows for a self-test to detect light intensities, and uses correction factors based on these intensities to adjust measured values, accounting for light source aging and other factors like temperature sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple light sources are used to illuminate the valuable document, then the illumination coverage and measurement capability are improved, but the complexity of correcting measured values increases due to varying light intensities from each source
Solution Approach 1:
The system divides the illumination task among multiple light sources (first light source, second light source, etc.) and assigns separate monitor diodes to each source. Each monitor diode independently monitors its corresponding light source's intensity, enabling separate tracking of each source's characteristics over time.
Solution Approach 2:
Monitor diodes provide real-time feedback on the light intensity of each light source by detecting the light emitted by their respective sources. This feedback is used to determine correction factors that compensate for intensity variations, enabling accurate correction of measured values despite using multiple light sources with different intensity characteristics.
2Measurement precision
If light source intensity is monitored using a monitor diode, then the light intensity compensation is improved, but the solution becomes inadequate when multiple light sources with different intensity developments are used
Solution Approach 1:
Instead of using a single monitor diode for all light sources, the system segments the monitoring function by assigning one monitor diode to each light source. This allows each light source's intensity characteristics to be tracked independently, making the system adaptable to multiple light sources with different intensity development patterns.
Solution Approach 2:
Each monitor diode is positioned to specifically monitor the light from its corresponding light source, creating a localized monitoring relationship. This local quality approach ensures that each light source's unique intensity characteristics are captured by its dedicated monitor diode, enabling precise compensation for each source.
3Adaptability or versatility
If subsequent calculation is used to correct measured values, then the adaptability to different light source conditions is improved, but the calculation becomes difficult when multiple light sources with overlapping emitted light are used
Solution Approach 1:
The correction process is segmented by light source, with each light source having its own monitor diode providing independent intensity data. This segmentation simplifies the calculation by allowing the system to handle each light source's contribution separately rather than dealing with complex overlapping intensity patterns from multiple sources simultaneously.
Solution Approach 2:
Monitor diodes act as intermediaries between the light sources and the measurement system. Each monitor diode translates its corresponding light source's intensity characteristics into measurable signals that can be used to determine correction factors, simplifying the overall correction calculation process.
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
The solution effectively corrects measured values by compensating for light source intensity variations, ensuring accurate and reliable verification of valuable documents, enhancing the sensor's ability to distinguish genuine from counterfeit documents.
Implementation Method 1
The light emitted by the valuable document as a result of the illumination is detected by a photodetector
Implementation Method 2
the emitted light intensity is monitored using a monitor diode arranged near the light source
Implementation Method 3
The term luminescence is understood as a generic term for the radiation emitted back from the valuable document after optical stimulation, e.g. fluorescence or phosphorescence
Implementation Method 4
The term luminescence is understood as a generic term for the radiation emitted back from the valuable document after optical stimulation, e.g. fluorescence or phosphorescence
Data Source
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AI summary
The invention relates to an optical sensor for examining valuable documents. At a point in time before the examination of the valuable documents, a self-test of the optical sensor is carried out, during which the light sources thereof are switched on, and monitor elements are used to detect the light intensity, incident on each monitor element at the time of the self-test, of the light source assigned to the particular monitor element. During the examination of a valuable document following the self-test, the light sources of the optical sensor are switched on to illuminate the valuable document, and measurement values of the respective valuable document are recorded. The recorded measurement values of the valuable document are then corrected with the aid of the light intensities detected by the monitor elements at the time of the self-test, in order to take into account a change, occurring over the operating time of the light sources, in the light intensity emitted by the light sources.