Multi-Wavelength Hologram Verification for Security Documents
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Solution Overview
Problem
Existing methods for verifying the authenticity of holograms in identification, security, or other documents are inefficient and lack the ability to rapidly and reliably determine the spectral position of the peak wavelength and diffraction efficiency, leading to potential forgery and manipulation.
Innovation Solution
A device and method using a set of light emitters emitting different wavelengths to illuminate the hologram, with a photodetector and control system to determine the diffraction efficiency and peak wavelength, allowing for rapid and reliable verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple light sources with different wavelengths are used to illuminate the document, then the spectral position of peak wavelength and diffraction efficiency can be determined, but the device complexity increases
Solution Approach 1:
The illumination system is segmented into multiple independent light sources, each emitting at a specific wavelength range. This allows the spectral characteristics of the hologram to be probed at discrete wavelength points, enabling determination of peak wavelength and diffraction efficiency through sequential illumination and detection
Solution Approach 2:
A beam combining element (such as a dichroic mirror or optical fiber bundle) serves as an intermediary to merge the output of multiple light sources into a single illumination beam. This mediator enables the complex multi-wavelength illumination to be delivered through a simplified optical path to the document
2Measurement precision
If a photodetector is positioned to detect transmitted light at specific angles, then diffraction efficiency can be measured, but the device complexity and alignment requirements increase
Solution Approach 1:
The photodetector is positioned to detect light at specific angles corresponding to the diffraction orders of the hologram. By sequentially illuminating with different wavelengths and detecting at predetermined angular positions, the system measures diffraction efficiency periodic to the hologram's grating structure without requiring continuous angular scanning
Solution Approach 2:
The system measures diffraction efficiency by changing the wavelength parameter of incident light and detecting the corresponding diffracted light intensity at fixed angles. This approach converts a potentially complex angular measurement problem into a simpler wavelength-dependent intensity measurement
3Productivity
If rapid sequential illumination with different wavelengths is performed, then verification speed increases, but the light source switching complexity increases
Solution Approach 1:
Multiple light sources are switched on and off in a periodic sequence, with each source illuminating the document for a brief interval. The photodetector integrates or sequentially records the transmitted light intensity for each wavelength, enabling rapid spectral characterization through time-multiplexed illumination without requiring complex mechanical switching mechanisms
Solution Approach 2:
The light sources are dynamically controlled to switch between different operational states (on/off) in a predetermined sequence. This dynamic switching enables the system to rapidly probe multiple wavelength points during a single verification cycle, achieving high productivity through temporal modulation rather than spatial 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 rapid and reliable verification of hologram quality by determining the peak wavelength and diffraction efficiency without expensive equipment, detecting manipulation or defects, and ensuring authenticity.
Implementation Method 1
a set of light emitters (104) configured to emit light in the direction of the component (102)
Implementation Method 2
The efficiency of light diffraction at the holographic film is a measure of its visual perceptibility
Implementation Method 3
A photodetector (106) is directed towards the detection chamber (108) and is configured to detect light transmitted through the component (102)
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a device (100) for the optical verification of at least one component (102) of an identification, security, or other document (102), comprising a detection chamber (108) into which at least the component (102) of the identification, security, or other document can be placed, a set of light emitters (104) configured to emit light in the direction of the component (102) of the identification, security, or other document, wherein at least one first light emitter (104) is configured to emit light from a first wavelength range, and wherein at least one second light emitter (104) is configured to emit light from a second wavelength range that differs from the first wavelength range, and a photodetector (106) directed towards the detection chamber (108), which is configured to detect light transmitted through the component (102) of the identification, security, or other document.to detect light reflected from or deflected by it. The invention also relates to a method for optically verifying the authenticity of at least one component (102) of an identification, value, or security document.