Optical Fingerprint Recognition Using Adaptive Scan Conditions
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Solution Overview
Problem
Optical fingerprint recognition systems face challenges with dry fingerprints, as they result in unclear or blurred images due to reduced light reflection and absorption, and existing solutions like dispersive optical systems and Adaptive Gain Control (AGC) either do not fully address the issue or introduce inefficiencies such as prolonged image capture times and the need for feedback processes.
Innovation Solution
Implementing a method and apparatus that uses multiple scans with different scan conditions, such as normal and long exposure conditions, to determine if a fingerprint is dry and adjust the recognition process accordingly, allowing for immediate and reliable fingerprint recognition without the need for additional feedback or cyclic adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an absorption optical system is used, then the recognition rate is improved for normal fingerprints, but the image quality deteriorates for dry fingerprints
Solution Approach 1:
The patent applies parameter changes by switching between different optical system configurations (absorption vs. dispersive) depending on the fingerprint condition. The controller detects dry fingerprint conditions and changes the optical parameter by activating the dispersive optical system, which uses a different light interaction mechanism (scattering vs. absorption) to produce clear images of dry fingerprints.
2Manufacturing precision
If a dispersive optical system is used, then the image quality improves for dry fingerprints, but the fundamental vulnerability to dry fingerprints is not fully solved
Solution Approach 1:
The patent implements dynamics by making the optical system adaptive and switchable rather than fixed. The controller dynamically selects between absorption and dispersive optical systems based on real-time detection of fingerprint moisture conditions, ensuring optimal performance across varying fingerprint states.
3Reliability
If AGC (Adaptive Gain Control) is used, then the vulnerability to dry fingerprints is improved, but the image capture time increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple optical systems (absorption and dispersive) ready for immediate switching, rather than using iterative feedback adjustment. The controller detects dry fingerprint conditions and switches to the appropriate pre-prepared optical system, eliminating the need for cyclic feedback processes and exposure time adjustments required by AGC.
4Manufacturing precision
If AGC (Adaptive Gain Control) is used, then the image quality is improved for dry fingerprints, but the system complexity increases due to feedback processes
Solution Approach 1:
The patent uses copying by creating parallel optical system copies (absorption and dispersive systems) that both exist simultaneously in the device. This allows direct switching between pre-configured systems rather than using complex feedback loops to iteratively adjust a single system, simplifying the control architecture.
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 fast and reliable fingerprint recognition by using the appropriate scan conditions to enhance image clarity, eliminating the need for prolonged feedback processes and ensuring effective recognition of dry fingerprints.
Implementation Method 1
an incident light on a portion with which a fingerprint does not come in contact is totally reflected from a surface of a prism
Implementation Method 2
an incident light on ridges is refracted from or absorbed in moisture or oil
Implementation Method 3
an incident light on a portion with which a fingerprint does not come in contact is totally reflected from a surface of a prism
Implementation Method 4
condenses on lens the light scattered at the ridges portions of the fingerprint contacted thereto
Data Source
AI summary
A method for an optical fingerprint recognition, the method includes scanning a fingerprint image using a multiple scan which allows alternating a first scan condition and a second scan condition different from each other; determining whether an input fingerprint is a dry fingerprint depending on a darkness level of a fingerprint image derived from the first scan condition; and performing a fingerprint recognition using a fingerprint image derived from the first scan condition or a fingerprint image derived from the second scan condition in accordance with the determination result as to the dry fingerprint.