Fingerprint Sensor Liveness Detection via Multi-Wavelength Optical Analysis
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Solution Overview
Problem
Existing fingerprint recording systems face challenges in reliably distinguishing between genuine and fake fingerprints, particularly in rejecting counterfeits such as replicated fingerprints, thin plastic film overlays, and cadaver fingers, due to similarities in optical properties.
Innovation Solution
The method combines multiple reflectance measurements in different wavelength ranges with transmittance measurements to determine authenticity criteria characteristic of oxidized blood, using a camera-based fingerprint recording unit with a prism body, where light is radiated into the finger beyond the contact surface to measure transmission and absorption coefficients, and evaluates these criteria to differentiate between genuine and fake fingerprints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple reflection measurements in different wavelength ranges are performed, then authenticity detection capability is improved, but device complexity increases
Solution Approach 1:
The camera sensor is designed to perform multiple functions: it captures both the fingerprint image pattern and the optical absorption characteristics across different wavelength ranges. By making the sensor multi-functional, the system achieves improved authenticity detection without proportionally increasing device complexity, as the same hardware component serves multiple measurement purposes.
Solution Approach 2:
The patent combines the fingerprint imaging function with the spectral analysis function into a single integrated measurement process. The camera sensor simultaneously captures spatial fingerprint information and spectral absorption information, merging two measurement functions into one unified system that reduces overall device complexity while maintaining high reliability.
2Reliability
If transmittance measurements are performed through the finger, then discrimination between genuine and fake fingerprints is improved, but measurement precision requirements increase
Solution Approach 1:
The system measures optical absorption characteristics across multiple wavelength ranges (400-700nm, 700-1000nm, 1000-1400nm) to capture the spectral fingerprint of living tissue. By changing the measurement parameter from simple transmittance to wavelength-dependent absorption coefficients, the system achieves better discrimination capability while the automated evaluation algorithm handles the precision requirements.
Solution Approach 2:
The patent replaces complex mechanical or contact-based authentication methods with optical field-based measurements. By using light transmission and absorption measurements instead of mechanical pressure sensors or contact switches, the system achieves higher reliability in distinguishing genuine from fake fingerprints while the optical measurement process inherently provides sufficient precision through spectral analysis.
3Measurement precision
If light is radiated into the finger beyond the contact surface, then transmission measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The light source is positioned to illuminate the finger from the side beyond the contact surface, utilizing the lateral dimension rather than only the vertical dimension through the prism. This geometric arrangement allows transmission measurements through the finger tissue while keeping the optical path straightforward, improving measurement accuracy without requiring complex multi-layer optical systems.
Solution Approach 2:
The finger itself acts as an intermediary medium between the light source and the camera sensor. By positioning the light source to radiate through the finger tissue laterally, the system uses the finger's own structure as the measurement path, eliminating the need for additional complex optical intermediaries or transmission windows while achieving accurate transmission measurements.
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 effectively discriminates between genuine fingers and all forms of counterfeits by utilizing the unique transmission behavior of living tissue, particularly in the NIR range and specific wavelength ratios, ensuring high-probability authenticity detection and counterfeit rejection.
Implementation Method 1
The at the interface between prism body 2, as shown schematically in figure 1 shown, and the surrounding air or finger surface incident light is scattered by means of diffuse scattering in some areas, namely in the areas of the skin ridges, and falls on a bevelled, mirrored side 4 of the prism body.
Implementation Method 2
at least one transmission measurement is carried out in a predetermined transmission wavelength range for determination of an absorption coefficient in the transmission wavelength range, in each case for authentication
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The method involves applying an authenticity identification of a finger on a fingerprint recorder. Multiple reflection measurements are recorded in a predetermined preset for authenticity identification at multiple reflection wavelength ranges. A transmission measurement is recorded in a preset transmission wavelength range from the applied finger. An independent claim is included for a device for automatic recording of a fingerprint by a camera-based fingerprint recorder attached to a data processing unit.