Ridge Direction Extraction for Unstable Fingerprint Zones
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Solution Overview
Problem
Conventional ridge direction extraction methods struggle to accurately determine ridge directions in unstable areas like the core and delta, where high curvature leads to erroneous extractions and limited accuracy, even after smoothing processing.
Innovation Solution
A ridge direction extraction device and method that calculates direction confidence and expectation by considering multiple reference zones in various directions, recalculation of direction confidence based on direction expectation, and weighting contributions to improve continuity and accuracy, especially near core and delta regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ridge directions are extracted locally using only nearby pixel groups, then calculation amount is reduced, but erroneous ridge directions are easily extracted due to wrinkles, scars, and high ridge curvature in areas near core and delta
Solution Approach 1:
The fingerprint image is divided into multiple zones, and ridge direction extraction is performed for each zone independently. This segmentation allows local processing to reduce calculation amount while maintaining accuracy by confining the analysis to manageable regions where ridge patterns are more consistent
Solution Approach 2:
The patent introduces a new dimension of consideration by evaluating ridge direction consistency across multiple zones and comparing extracted directions with expected directions based on ridge flow patterns. This multi-dimensional verification approach enables accurate ridge direction extraction even in challenging areas with high curvature or noise
2Reliability
If smoothing processing is applied to correct erroneous ridge directions, then some errors are reduced, but accuracy remains limited in areas affected by wide-area noises such as wrinkles and in direction unstable areas near core and delta
Solution Approach 1:
The patent performs preliminary ridge direction extraction for multiple zones before applying smoothing or correction. By pre-calculating ridge directions in surrounding zones and establishing expected direction patterns, the system can more effectively identify and correct erroneous directions without being misled by wide-area noises or high curvature effects
3Measurement precision
If ridge directions are extracted by considering all pixels, then accuracy is improved, but calculation amount increases significantly
Solution Approach 1:
The fingerprint image is divided into multiple zones, and ridge direction extraction is performed for each zone independently. This segmentation allows local processing to reduce calculation amount while maintaining accuracy by confining the analysis to manageable regions where ridge patterns are more consistent
Solution Approach 2:
Instead of processing all pixels uniformly, the patent applies ridge direction extraction to selected zones and uses propagation to determine directions in other areas. This partial action approach reduces calculation amount by focusing detailed analysis only where necessary while deriving other directions from established patterns
Data Source
AI summary
A ridge direction extraction device capable of extracting ridge directions accurately even in direction unstable areas is provided. In the ridge direction extraction device, a zone direction extractor calculates ridge directions and direction confidence of each zone, and a high confidence zone area determiner determines a high confidence zone area. A direction expectation calculator selects a propagation candidate zone and a reference zone, and calculates direction expectation of the ridge direction of the propagation candidate zone based on the ridge direction and distance of the reference zone. A propagation zone direction extractor recalculates the direction confidence calculated by the zone direction extractor based on the direction expectation of each propagation candidate zone, and extracts the ridge direction of a propagation candidate zone based on the direction confidence recalculated.