Banknote Imaging Using RGB Camera Infrared Wavelength Separation

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Solution Overview

Problem

Conventional banknote validators struggle to accurately identify banknotes with infrared variable inks due to the inability of RGB cameras to resolve between multiple infrared wavelengths simultaneously, leading to reduced throughput and increased costs with the use of multiple light sources or infrared filters.

Innovation Solution

A method utilizing a conventional RGB camera with a Bayer filter matrix to separate infrared images from visible images by manipulating the relative differences in color filter efficiencies, allowing simultaneous illumination and extraction of images at different infrared wavelengths without the need for sequential illumination or additional filters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If sequential illumination with multiple infrared wavelengths is used, then measurement precision of infrared variable inks is improved, but productivity decreases due to reduced throughput speed

Engineering Contradiction:

Improveinfrared image resolutionVSAvoidthroughput speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent enables continuous simultaneous illumination of the banknote with multiple infrared wavelengths (e.g., 785nm and 850nm) using separate LED sources, allowing the RGB camera to capture both wavelength components in a single exposure. This eliminates the need for sequential illumination, maintaining continuous useful action and preserving high throughput speed while achieving precise differentiation of infrared variable inks through spectral unmixing algorithms.

Inventive Principle:

Principle #20Continuity of useful action

2Measurement precision

If infrared filters are introduced into the optical sensor arrangement, then measurement precision of infrared wavelengths is improved, but device complexity and cost increase

Engineering Contradiction:

Improveinfrared wavelength discriminationVSAvoidoptical sensor arrangement complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/optical filtering approach (using physical infrared filters in the optical path) with an electronic/digital processing approach. By using LEDs with narrow spectral emission profiles and applying spectral unmixing algorithms to the RGB camera output, the system achieves infrared wavelength discrimination without requiring any infrared filters, beam splitters, or complex optical switching mechanisms, thereby reducing device complexity and cost.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If a single incandescent infrared light source is used, then device complexity is reduced, but reliability decreases due to variable output and difficulty of control

Engineering Contradiction:

Improvelight source configurationVSAvoidillumination control stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the fundamental parameters of the light source by replacing a single broadband incandescent source with multiple narrowband LED sources operating at specific infrared wavelengths (e.g., 785nm and 850nm). LEDs provide stable, controllable, and energy-efficient illumination with long lifetimes. The independent control of each LED channel allows precise regulation of illumination intensity and timing, significantly improving reliability and control stability compared to incandescent sources.

Inventive Principle:

Principle #35Parameter changes

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 efficient and cost-effective acquisition of distinct infrared images of banknotes, improving throughput and eliminating the need for infrared filters, thus enhancing the banknote validation process.

Implementation Method 1

separate infrared images from visible images by manipulating the relative differences in color filter efficiencies

Methodology Applied

Scientific EffectBayer filter matrix wavelength separation: Filter (optical)

Implementation Method 2

illuminate the banknote with, for example, two distinct wavelengths of infrared light

Methodology Applied

Scientific EffectInfrared radiation detection: Infrared Radiation

Data Source

PatentUS11544985B2Banknote imaging

Publication Date: 2023.01.03 INNOVATIVE TECH LTD

AI summary

A method of obtaining a plurality of infrared images of a banknote that involves simultaneously illuminating the banknote with infrared light at a first wavelength and infrared light at a second wavelength, capturing an image of the banknote with an RGB camera, obtaining from both a first output channel signal and a second output channel signal of the RGB camera sensor where the intensity distribution of the infrared light at the first wavelength and the intensity distribution of the infrared light at the second wavelength uses a first calibration coefficient and a second calibration coefficient of the RGB camera sensor, producing separate infrared images of the banknote at the first wavelength and the second wavelength from the respective intensity distributions.