Raman Sensor Parallel Spectral Channels High-Speed Document Verification
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Solution Overview
Problem
Current sensors are unable to detect Raman or SERS markers on valuable documents, such as banknotes, in a spatially resolved manner at high speeds exceeding 11 m/s, which is necessary for authenticating and identifying the documents effectively.
Innovation Solution
A Raman sensor design that illuminates the document with excitation light and disperses the resulting Raman light in a spectrometer, using multiple spectral channels to detect light from the same surface area synchronously, allowing for parallel readout and achieving a spatial resolution of less than 12 mm, with a detector optimized for high signal/noise ratio and rapid readout to prevent spatial/spectral smearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Raman sensors are used for detecting security features on moving valuable documents, then measurement precision can be achieved, but the measurement time becomes too long (seconds to minutes) to be suitable for high-speed processing (>11 m/s)
Solution Approach 1:
The patent divides the detection process into multiple spectral channels (e.g., 3-10 channels) that simultaneously detect different wavelength ranges. This segmentation allows parallel processing of spectral information, reducing total measurement time while maintaining detection precision through multi-channel simultaneous acquisition
Solution Approach 2:
The patent employs periodic scanning of the valuable document combined with synchronous detection in multiple spectral channels. The periodic motion is synchronized with the detection system to capture spatially resolved Raman signals at high speed, enabling measurement times in the millisecond range suitable for documents moving at >11 m/s
2Productivity
If high-speed detection is implemented to match document processing speeds (>11 m/s), then productivity increases, but spatial resolution deteriorates due to motion blur and temporal smearing
Solution Approach 1:
The patent pre-synchronizes the detection system with the periodic motion of the document conveyor. By anticipating the document position and timing the spectral channel acquisitions accordingly, the system captures spatially resolved signals without motion blur, maintaining sub-12mm spatial resolution at processing speeds exceeding 11 m/s
Solution Approach 2:
The patent implements feedback control where the detection system continuously monitors document position and adjusts the timing of spectral channel acquisitions in real-time. This feedback mechanism compensates for variations in document speed and positioning, preventing spatial/spectral smearing and maintaining measurement precision at high productivity rates
3Productivity
If multiple spectral channels are used for parallel detection to reduce measurement time, then measurement speed increases, but device complexity increases
Solution Approach 1:
The patent designs a universal sensor platform where multiple spectral channels share common optical components (illumination source, collection optics, detector). This multi-functional design allows simultaneous spectral detection across multiple channels while minimizing redundant components, achieving high measurement speed without proportional increases in device complexity
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 reliable identification of Raman or SERS-active features and authenticity recognition of valuable documents even at high speeds, providing a spatial resolution sufficient for detecting composite counterfeits and reading barcode information.
Implementation Method 1
a sensor (12) for mechanically testing moving valuable documents (150) with at least one security feature based on Raman or SERS spectroscopy... illuminate the valuable document (150) for testing with excitation light from a laser source (101)... and disperse the resulting Raman light from the security features
Implementation Method 2
disperse the resulting Raman light from the security features in a spectrometer (110) with spectral resolution into a plurality of spectral channels
Implementation Method 3
the light collected in the spectral channels from the same surface area of the valuable document is detected synchronously by the detector... the spectral channels are read out simultaneously and in parallel
Data Source
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Figure 3A~3B
Figure 4~5B
AI summary
The invention relates to a device and a method for verifying documents of value that are marked with feature substances, and to the corresponding feature substances. The feature substances are detected and reliably identified at a spatial resolution in the low millimeter range or lower even at high conveying velocities on the basis of Raman or SERS spectroscopy techniques.