Fingerprint Block Direction Estimation Using Adjacent DFT Cues
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Solution Overview
Problem
Existing fingerprint image processing methods require repetitive calculations for each block to determine direction, leading to high computational overhead and increased latency.
Innovation Solution
A fingerprint image processing method that determines the direction of a current block using Discrete Fourier Transform (DFT) energies based on the directions of adjacent blocks, reducing the need for full traversal and incorporating a primal method for blocks where DFT fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If repetitive calculations are performed for each block to determine direction separately, then direction accuracy can be maintained, but computational overhead increases and latency increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing direction information for blocks in the first row and first column before processing subsequent blocks. This allows interior blocks to leverage pre-computed directional data from adjacent blocks, reducing the need for complete re-calculation and thereby decreasing computational overhead while maintaining direction accuracy.
Solution Approach 2:
The patent merges the direction determination process by combining results from multiple sources: DFT energies calculated for candidate directions and primal method results from adjacent blocks. This fusion of computational approaches allows the system to maintain high accuracy through multi-source validation while reducing overall processing time by avoiding redundant independent calculations for each block.
2Measurement precision
If DFT method is used to calculate direction for each block, then measurement precision is high, but calculation time increases due to full traversal requirement
Solution Approach 1:
The patent applies partial action by calculating DFT energies only for a limited set of candidate directions (initial direction plus directions from adjacent blocks) rather than performing full traversal of all possible directions. This selective DFT calculation maintains sufficient direction accuracy for most blocks while significantly reducing calculation time compared to exhaustive search methods.
Solution Approach 2:
The patent uses an intermediary approach by introducing a direction prediction mechanism that leverages spatial relationships between adjacent blocks. The initial direction for a block is predicted based on directions from left and upper adjacent blocks, serving as a mediator that guides the DFT calculation toward the most likely correct direction, thereby reducing the search space and calculation time while maintaining precision.
3Productivity
If gradient method is used to calculate direction, then processing speed is fast, but sensitivity to noise increases reducing accuracy
Solution Approach 1:
The patent employs a composite approach by combining multiple direction calculation methods (DFT method and primal method) and using results from adjacent blocks to validate and supplement individual block calculations. This composite strategy leverages the speed advantage of gradient-based methods while compensating for noise sensitivity through cross-validation with neighboring blocks and selective DFT analysis, achieving both efficiency and accuracy.
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 accuracy and reduces calculation time by leveraging adjacent block directions and using DFT energies, with a primal method as a fallback, thereby optimizing computational efficiency.
Implementation Method 1
determining a direction of the current block from among the plurality of candidate directions using Discrete Fourier Transform (DFT) energies in the plurality of candidate directions
Data Source
AI summary
A fingerprint image processing method includes: receiving a plurality of blocks of a block matrix representing a fingerprint image; and processing a first set of blocks of the plurality of blocks, the processing comprising: obtaining a plurality of candidate directions of a current block, wherein the plurality of candidate directions include an initial direction of the current block, and directions of at least a respective predetermined number of blocks on a left of the current block and a right of the current block, and the initial direction is determined using a direction of a left adjacent block and a direction of an upper adjacent block of the current block; and determining a direction of the current block from among the plurality of candidate directions based on Discrete Fourier Transform (DFT) energies in the plurality of candidate directions.