Contactless Fingerprint Imaging with Structured Light Hand Positioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional contactless fingerprint recording devices face challenges in real-time hand position control in 3D space due to the need for additional hardware like distance sensors and complex scanning procedures, which hinder efficient 3D image data recording.
Innovation Solution
A camera-projector combination with structured illumination is used to determine hand position without additional sensors, allowing for real-time 3D image data recording by measuring the structure size of structured lighting on the camera sensor, which is a function of the camera's distance to the hand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional distance sensors and complex scanning procedures are used for contactless fingerprint recording, then hand position detection accuracy is improved, but device complexity increases and real-time recording efficiency deteriorates
Solution Approach 1:
The patent merges the distance detection function into the existing camera system by using structured light projection and analyzing the deformation of light patterns captured by the camera. This eliminates the need for separate distance sensors while maintaining measurement precision, directly resolving the contradiction between measurement accuracy and device complexity
Solution Approach 2:
The patent introduces structured light patterns as an intermediary medium between the camera and the hand. By projecting known light patterns and analyzing their deformation upon contact with the hand surface, the system indirectly measures hand position and distance without requiring direct sensor-to-hand contact, thus simplifying the device while preserving measurement accuracy
2Measurement precision
If additional distance sensors and complex scanning procedures are used, then hand position detection accuracy is improved, but productivity decreases due to slower processing time
Solution Approach 1:
The patent pre-projects structured light patterns onto the hand before actual fingerprint capture. This preliminary action of projecting known patterns allows the camera to immediately capture and analyze light deformation for rapid distance and position calculation, enabling real-time processing without waiting for complex sensor readings, thus improving productivity while maintaining precision
Solution Approach 2:
The patent replaces mechanical distance sensors and complex scanning mechanisms with an optical computation approach. By using light pattern deformation analysis and mathematical processing of camera images, the system achieves fast, real-time hand position detection without the mechanical complexity and processing delays of conventional sensor-based systems
3Manufacturing precision
If a narrow depth of field is used for high-resolution fingerprint imaging, then manufacturing precision of the image is improved, but the ease of operation deteriorates as hand positioning becomes more critical
Solution Approach 1:
The patent implements a feedback mechanism where the camera first captures the hand's position and orientation by analyzing structured light pattern deformation. Based on this feedback information, the system provides guidance to the user for proper hand positioning before triggering the high-resolution fingerprint capture, making the process more tolerant to initial positioning errors while maintaining final image quality
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
Enables real-time hand distance detection and accurate 3D image data recording of fingerprints without requiring additional distance sensors, ensuring high-resolution and efficient image capture.
Implementation Method 1
a camera (2) for detecting light that is diffusely reflected from a hand (3) or a part of the hand (3) in an object plane (21)
Data Source
AI summary
A device, for contactless optical recording of a papillary structure of a hand or parts thereof, includes a lighting unit illuminating the hand or parts thereof with emitted structured light, and a camera detecting structured light emitted from the lighting unit, which is diffusely reflected from the hand or parts thereof in an object plane of the camera. A nonzero difference in distances between the camera along an optical axis of an optical path of the camera and the lighting unit along an optical axis of an optical path of the lighting unit from the object plane of the camera is present in order to determine a position of the hand or parts thereof along the optical axis of the optical path of the camera in relation to a range of depth of field of the camera using a structure size determined in the light detected by the camera.