UV Light Detection for Paper Watermark Authentication
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Solution Overview
Problem
Existing devices fail to reliably distinguish genuine watermarks in paper documents from simulated ones, as they cannot differentiate between authentic fiber structure changes and those created by printing, especially when both the genuine and forged documents appear similar under transmitted light detection.
Innovation Solution
A device equipped with a lighting system, transport mechanism, and a sensor, where the light is directed through a reflector to detect the transmission of light through the document, utilizing UV light to interact more strongly with the paper substrate than with printing inks, allowing for the differentiation of security features inherent to the fiber structure from those simulated by printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If transmitted light detection is used to examine watermarks, then the detection process is simple, but genuine watermarks cannot be distinguished from simulated ones
Solution Approach 1:
The patent changes the detection parameter from simple transmitted light intensity to the spatial distribution pattern of transmitted light. By analyzing how light transmits through different fiber density areas, the system can distinguish genuine watermarks (with characteristic fiber patterns) from simulated ones (with uniform printing), resolving the contradiction between simple detection and accurate authentication.
2Ease of manufacture
If printing inks are used to simulate watermarks, then counterfeit documents can be created, but the simulation is visually indistinguishable from genuine watermarks
Solution Approach 1:
The patent applies local quality analysis by examining the micro-level fiber structure characteristics in different areas of the document. Genuine watermarks show specific fiber density patterns and textures that differ from the uniform appearance of printed simulations, even when both have similar visual appearance. This local structural analysis restores authentication reliability.
3Reliability
If UV-dark paper is used for genuine documents, then UV light detection can distinguish them from UV-light paper forgeries, but it cannot detect forgeries made of UV-dark paper
Solution Approach 1:
The patent introduces fiber structure analysis as an intermediary detection method that works independently of the paper's UV properties. By examining the light transmission patterns through the fiber structure, the system can authenticate watermarks on both UV-dark and UV-light papers, making the detection method versatile against all types of paper forgeries.
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 the reliable detection of genuine security features in the fiber structure of paper documents, effectively distinguishing them from forged ones, even when both are made of UV-dark paper, by focusing on the interaction between UV light and the paper substrate, reducing the influence of printing inks.
Implementation Method 1
Paper substrates have special properties in terms of the reflection, transmission, absorption and luminescence of light, which can be influenced by the targeted addition of additives during paper manufacture and by coatings.
Implementation Method 2
The transparency of the paper depends on the density of the paper fibers, so that the watermark can be seen with the naked eye, especially in transmitted light.
Data Source
Figure 1~2
AI summary
A device and a method for detecting security features embedded in the fiber structure of flat paper objects are proposed. The device is equipped with at least one lighting device (1, 11) that illuminates the flat objects (4) with light, with a transport device that transports the flat objects (4) relative to the lighting device (1, 11) along a transport plane (6, 18) in the transport direction (5), with at least one sensor (3, 13) for the light from the lighting device (1, 11) arranged offset from and downstream of the lighting device (1, 11) in the transport direction (5), and with at least one reflector (2, 12) arranged in the light beam path between the lighting device (1, 11) and the sensor (3, 13), which reflects the light from the lighting device (1, 11) in the direction of the sensor (3, 13).The path of the light beam between the reflector (2, 12) and the sensor (3, 13) crosses the transport plane (6, 18) at least once.