White Light Interferometry for Security Document Verification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing verification methods for security documents are often specialized and inadequate for detecting sophisticated counterfeits, particularly in documents with opaque or metallic layers, where surface features alone are insufficient for authentication.
Innovation Solution
A verification method utilizing white-light interferometry to create depth profiles of security documents, allowing non-destructive examination of both surface and internal structures, which can distinguish between genuine and forged documents by analyzing intensity value distributions and layer transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface-based verification methods are used, then the verification process is simple and fast, but the method is inadequate for detecting sophisticated counterfeits in documents with opaque or metallic layers
Solution Approach 1:
The patent transitions from two-dimensional surface verification to three-dimensional depth profile analysis using white-light interferometry. By measuring optical path differences at multiple depths, the system creates vertical cross-sections of document layers, enabling detection of internal structures and manipulations that surface methods cannot detect.
Solution Approach 2:
The patent replaces contact-based or simple optical surface scanning with non-contact white-light interferometry. This optical measurement technique uses coherent light sources and interferometric patterns to measure surface and subsurface topography with nanometer precision, eliminating mechanical contact while achieving deeper verification.
2Measurement precision
If white-light interferometry is used to examine internal structures, then verification precision is improved, but the device complexity increases
Solution Approach 1:
The patent designs the white-light interferometer to serve multiple verification functions simultaneously: measuring layer thicknesses, detecting voids and delaminations, analyzing printing depth, and identifying material compositions. This multi-functionality justifies the device complexity by providing comprehensive document authentication in a single system.
Solution Approach 2:
The patent creates optical copies (interferograms) of the document's internal structure that can be digitally processed and analyzed. These virtual depth profiles serve as replicas of the physical document layers, allowing detailed examination without physical contact or damage to the original document.
3Reliability
If comprehensive depth profiling is performed, then detection capability for manipulations is enhanced, but the verification time increases
Solution Approach 1:
The patent implements selective depth profiling where the system focuses measurements on specific regions of interest or suspicious areas rather than uniformly scanning entire documents. This partial action approach maintains high detection capability for manipulations while reducing overall verification time by concentrating resources on critical verification points.
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 precise verification of complex security features, including those within opaque or metallic layers, by generating detailed depth profiles that reveal manipulations or forgeries, enhancing the reliability of document authentication.
Implementation Method 1
The invention relates to a method for verifying security documents and a verification device for security documents, which perform and use white-light interferometry in order to verify security features present in a security document
Data Source
Figure 1
Figure 2~3b
Figure 4~7
AI summary
The invention relates to a verification apparatus and a verification method. The verification method comprises the following steps: the security document (13) is oriented relative to a white light interferometer (2), an examination by means of white light interferometry is performed in at least one location (P1 -P3) on a surface to be examined (15), wherein a depth profile is produced in a direction of examination (19-1 to 19-3), a feature is derived from the depth profile, and the at least one derived feature is compared with one or more specifications in order to derive a verification decision.