Multi-spectral Document Authentication Using Linear LED Arrays
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Solution Overview
Problem
Current methods for multi-spectral imaging of documents, especially in high-speed moving conditions, face challenges in capturing well-resolved images spectrally and optically due to limited light collection efficiency and spatial resolution, particularly in confined spaces.
Innovation Solution
The use of structured illumination with a linear array of LEDs of different wavelengths, coupled with cylindrical optics and time-division multiplexing, allows for simultaneous imaging of multiple wavelengths with high optical and spectral resolution, enabling the creation of multi-spectral image stacks from scattered light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional multi-spectral imaging methods are used in high-speed moving conditions, then spectral resolution can be maintained, but light collection efficiency deteriorates and spatial resolution is lost
Solution Approach 1:
The patent segments the imaging process by using a linear array of LEDs with different wavelengths to illuminate different portions of the document sequentially. Each LED wavelength corresponds to specific sensor elements, dividing the spectral measurement task across multiple time steps and spatial zones, thereby improving light collection efficiency while maintaining spectral resolution
Solution Approach 2:
The patent employs time-division multiplexing where LEDs of different wavelengths are activated in periodic sequences. Each wavelength is measured at specific time intervals as the document moves through the imaging system, allowing efficient light collection at each wavelength while maintaining overall spectral resolution through temporal separation
2Manufacturing precision
If bright illumination and high-speed acquisition are used for two-dimensional imaging, then spatial resolution can be maintained, but device complexity and power consumption increase
Solution Approach 1:
The patent replaces complex two-dimensional illumination arrays with a simple linear array of LEDs. Each LED illuminates a line across the document, and the linear sensor array captures the reflected light. This segmentation reduces the illumination system from a complex 2D arrangement to a simple 1D linear array, significantly reducing device complexity while maintaining spatial resolution
Solution Approach 2:
The patent substitutes mechanical/complex optical illumination systems with a simpler electronic control system. Instead of using complex optical components and multiple light sources arranged in two dimensions, the system uses a linear LED array controlled by electronic timing signals, replacing mechanical complexity with electronic simplicity
3Measurement precision
If multiple lines of illumination and multiple sensors are used for line scan imaging, then spectral resolution can be improved, but device complexity increases
Solution Approach 1:
The patent merges multiple spectral measurement functions into a single linear sensor array. Instead of using separate sensors for each wavelength, the system combines all spectral detection capabilities into one linear array, with each sensor element responding to multiple wavelengths through time-division multiplexing. This merging reduces device complexity while maintaining spectral resolution
Solution Approach 2:
The patent makes each sensor element in the linear array universal by enabling it to detect multiple wavelengths at different time intervals. Through time-division multiplexing, a single sensor element serves multiple spectral detection functions, eliminating the need for dedicated sensors for each wavelength and thereby reducing overall 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
This approach enables the capture of high-resolution, multi-spectral images of moving documents with improved light collection efficiency, reducing power usage and noise, and maintaining spatial resolution, even in confined spaces.
Implementation Method 1
A linear array of LEDs of different wavelengths is used to create a line of illumination
Implementation Method 2
Each LED is coupled with cylindrical optics to create a line illumination
Implementation Method 3
measurement of the light scattered from the surface of the document
Implementation Method 4
A linear sensor array is used to detect light produced by the at least one LED
Data Source
AI summary
A device detects multi-spectral imaging by using scan elements. The device may include an illumination module and a detection module to detect light scattered from an object illuminated by the illumination module. The device may also include an array of light sources to produce light at a plurality of different wavelengths, and create a line of illumination with each of the different wavelengths. The light detection may be applied to authenticate and validate documents, such as banknotes moving along a document conveyer.