Finger Verifier Using Projected Fringe Pattern Analysis
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Solution Overview
Problem
Existing methods for verifying the authenticity of fingerprints, such as those using three-dimensional reconstruction, are time-consuming and prone to fraud detection issues due to the need for precise calibration and are not suitable for contactless verification.
Innovation Solution
A method employing a projection device to project parallel lines onto the finger, capturing the image, extracting fringes, calculating physical characteristics like variance and deflection, and comparing them with reference values to determine authenticity, without requiring three-dimensional reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If three-dimensional reconstruction methods are used for finger verification, then detection accuracy is improved, but calculation time increases significantly
Solution Approach 1:
The patent extracts only the essential two-dimensional fringe pattern information from the projected lines, eliminating the need for complex three-dimensional reconstruction. By focusing solely on analyzing the 2D fringe characteristics (curvature, spacing, orientation) directly captured by the camera, the system achieves sufficient detection accuracy while dramatically reducing calculation time and computational complexity.
Solution Approach 2:
Instead of projecting lines and then performing complex 3D reconstruction to analyze surface geometry, the patent inverts the approach by directly analyzing the 2D fringe patterns formed by the projected lines. This inversion allows the system to detect finger authenticity through simpler 2D image processing of fringe characteristics rather than through time-consuming 3D reconstruction algorithms.
2Measurement precision
If precise calibration between projector and camera is performed, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the verification system universally applicable by eliminating the need for precise calibration between the projector and camera. The method works with various projector-camera configurations without requiring complex calibration procedures, making the system easier to deploy and maintain while maintaining sufficient measurement precision for fraud detection.
Solution Approach 2:
The patent adopts a pragmatic approach by using standard, easily obtainable projectors and cameras without requiring precision calibration equipment or procedures. The system accepts that the calibration may not be perfectly precise but demonstrates that this level of precision is sufficient for the intended application of finger verification, thereby reducing device complexity and cost.
3Ease of operation
If contactless verification is implemented, then ease of operation is improved, but detection reliability decreases
Solution Approach 1:
The patent maintains reliable fraud detection in contactless mode by analyzing the two-dimensional spatial characteristics of the fringe patterns. The curvature, spacing, and orientation of the fringes captured in the 2D image plane provide sufficient information to distinguish real fingers from fake ones, even without physical contact. This 2D analysis compensates for the lack of tactile feedback while preserving detection reliability.
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 enables faster and more effective detection of fraud, including decoys like latex or paper, by analyzing two-dimensional data, reducing calculation time and improving contactless verification accuracy.
Implementation Method 1
a projection device designed to project a test pattern consisting of a plurality of lines parallel to each other on the finger
Implementation Method 2
a capture device provided for capturing an image of the finger and of the crosshairs
Data Source
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Figure 3a~4c
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AI summary
The invention relates to a method for verifying (200) the veracity of a finger by a verification device comprising a projection device projecting a pattern of lines which are parallel and orthogonal to the longitudinal direction of the finger, a capture device capturing an image of the finger and the pattern, and a processing unit, the method comprising: a lighting step (201) in which the projection device lights up the finger with the pattern, a contactless capture step (202) in which the capture device captures a pattern image of the projected pattern, a step of extracting fringes (206) in which the processing unit extracts fringes from the pattern image, a feature calculation step (208) in which the processing unit calculates a feature relative to the physical structure of the fringes, a comparison step (210) during which the processing unit compares the calculated feature with reference values, and a decision-making step (212) in which the processing unit makes a decision regarding the veracity of the finger.