Biometric Image Alignment Using Frequency-Based Affine Stitching
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Solution Overview
Problem
Existing methods for combining images of different portions of a biometric feature, such as fingerprints or irises, result in approximate alignment, leading to reduced identification accuracy.
Innovation Solution
A computer-implemented method involving resizing and affine transformation of images based on frequency analysis and curvature correction to align and combine biometric features accurately, using a device with a processor and memory to execute the method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Ransac algorithm is used for aligning different portions of an object from different images, then the alignment process can be completed, but only approximate alignment is achieved which reduces identification accuracy
Solution Approach 1:
The patent transforms the alignment problem from spatial domain to frequency domain by applying Fourier transformation. This parameter change allows for precise frequency matching between corresponding portions of different images, enabling exact alignment rather than approximate alignment. The frequency domain representation reveals periodic patterns (ridges in fingerprints) that can be precisely matched through frequency comparison and phase adjustment.
Solution Approach 2:
The patent replaces the iterative geometric matching mechanism of the Ransac algorithm with a frequency-based transformation approach. Instead of repeatedly sampling and testing geometric transformations, the method uses Fourier transformation to convert spatial alignment into frequency domain correlation, which can be solved more precisely through frequency matching and phase adjustment.
2Quantity of substance
If multiple images are combined to improve biometric identification, then more characteristics are available, but misalignment reduces the effectiveness of these additional characteristics
Solution Approach 1:
By transforming images to the frequency domain, the patent enables precise alignment of multiple biometric images through frequency matching. This allows all characteristics from multiple images to be correctly positioned and combined, maximizing the benefit of having more characteristics available for identification.
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
Improves the accuracy of combined images for user identification by ensuring precise alignment and representation of biometric features, enhancing the number of characteristics available for identification.
Implementation Method 1
modifying at least a portion of the second image using the Fourier transformation
Data Source
AI summary
A method for obtaining a combined image comprises: obtaining two original images of a user's biometric feature comprising a plurality of characteristics; determining a frequency of the characteristics in the first original image and in the second original image; resizing, based on the determined frequency, the first and/or second original images to obtain a first image and a second image; identifying, in the first image and in the second image, a subset of the plurality of characteristics; for some of the identified characteristics in the first image, identifying corresponding identified characteristics in the second image; deriving an affine transformation for transforming the identified characteristics in the second image into the corresponding identified characteristics in the first image; modifying a portion of the second image using the affine transformation; and obtaining the combined image comprising one portion of the first image and the modified portion of the second image.