Non-Contact Fingerprint Imaging With Adaptive Focus Steps
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Solution Overview
Problem
Existing biometric systems face challenges in capturing clear fingerprint images due to variations in finger size and thickness among users, leading to difficulties in focusing and adjusting fingertip position for effective fingerprint authentication.
Innovation Solution
A biometric information acquisition device and method that employs a camera with first and second focus controls to capture multiple images at varying focus distances, determining optimal focus step sizes based on fingertip size, and selecting the most focused image for fingerprint data acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single focus control is used to capture fingertip images, then the device complexity is reduced, but the measurement precision of fingerprint data deteriorates due to variations in finger size and thickness
Solution Approach 1:
The patent implements dynamic focus control by capturing images at multiple focus distances rather than using a single fixed focus point. The focus distance is dynamically adjusted to accommodate variations in fingertip size and thickness, ensuring that the fingerprint imaging surface falls within the focused region regardless of user characteristics.
Solution Approach 2:
The system changes the focus distance parameter based on detected fingertip characteristics. By measuring fingertip size and thickness and subsequently adjusting the focus distance accordingly, the system optimizes image clarity for diverse users without requiring complex mechanical focus adjustment mechanisms.
2Measurement precision
If multiple images are captured at different focus distances, then the fingerprint data quality is improved, but the loss of time increases due to multiple capture cycles
Solution Approach 1:
The system performs preliminary actions by first capturing a reference image to detect fingertip characteristics (size, thickness, curvature) before determining the optimal focus distance. This preliminary detection enables subsequent images to be captured at the correct focus point, avoiding unnecessary multiple capture cycles and reducing overall time loss.
Solution Approach 2:
The system uses feedback from the captured images to iteratively refine focus distance determination. By analyzing the clarity and characteristics of initially captured images, the system adjusts the focus distance for subsequent captures, ensuring optimal fingerprint image quality while minimizing the number of capture cycles required.
3Ease of operation
If the focus distance is fixed, then the ease of operation is improved, but the adaptability to different user characteristics deteriorates
Solution Approach 1:
The system performs self-service by automatically detecting fingertip characteristics and determining the optimal focus distance without requiring user intervention. Users simply need to place their fingers on the imaging surface, and the system autonomously adjusts parameters to accommodate different finger sizes, thicknesses, and curvatures, maintaining ease of operation while achieving high adaptability.
Solution Approach 2:
The system dynamically adapts the focus distance based on detected fingertip characteristics rather than using a fixed focus point. This dynamic adjustment occurs automatically in response to varying user characteristics, providing both ease of operation and high adaptability across diverse user populations.
Data Source
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AI summary
This biological information acquisition device is provided with: a camera that captures an image of a fingertip of a subject in a non-contact state by each of a first focus control and a second focus control; an acquisition unit that acquires a first captured image captured by the first focus control; a measurement unit that measures the size of the fingertip with respect to the entire area of the first captured image; a determination unit that determines, on the basis of the size of the fingertip, the increment range of focus of the camera for capturing an image during the second focus control; and a control unit that acquires one of second captured images captured by the second focus control.