Finger Vein Authentication Device with Variable Irradiation Angle
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Solution Overview
Problem
Conventional finger vein authentication devices face challenges in obtaining sufficient contrast for vein pattern extraction and are bulky, making them unsuitable for thin digital devices like smartphones.
Innovation Solution
A finger vein authentication device with an imaging unit and an illumination unit on the same plane, featuring a variable irradiation angle and image selection based on brightness and contrast evaluation, along with a MEMS mirror for controlled near-infrared light distribution, allowing for thinner and more efficient vein pattern capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light from the light source directly illuminates the finger surface to be photographed, then the illumination is simple and direct, but it is not possible to obtain sufficient contrast and it is difficult to extract a clear vein pattern
Solution Approach 1:
The patent employs a MEMS mirror to dynamically adjust the irradiation angle of the light source, enabling the system to adapt to different finger positions and sizes. This dynamic adjustment allows optimal illumination angles to be selected for different scenarios, improving vein pattern contrast without requiring multiple fixed light sources
Solution Approach 2:
The system changes the irradiation angle parameter of the light source to optimize vein pattern extraction. By varying the angle at which light strikes the finger, the system can enhance the contrast of vein patterns in captured images, directly addressing the contrast problem while using a single adjustable light source
2Length of moving object
If an optical reduction system is used as the optical system of the imaging unit, then the imaging capability is achieved, but the device thickness increases making it unsuitable for thin digital devices
Solution Approach 1:
The patent combines the illumination unit and imaging unit on substantially the same plane, eliminating the need for separate optical reduction systems. This integration allows the system to achieve both thinness and effective vein pattern capture by using the illumination light that has passed through the finger directly for imaging
Solution Approach 2:
The system captures the vein pattern by imaging the light that has transmitted through the finger, creating an optical copy of the vein structure. This approach eliminates complex reduction optics while maintaining imaging capability, as the transmitted light itself carries the vein pattern information
3Length of moving object
If the illumination unit and imaging unit are disposed on the same plane, then the device can be made thinner, but the irradiation angle control becomes more challenging
Solution Approach 1:
The patent replaces complex mechanical angle adjustment mechanisms with a MEMS (Micro-Electro-Mechanical System) mirror. This substitution enables precise irradiation angle control through electrostatic actuation rather than bulky mechanical components, allowing the units to be on the same plane while maintaining angle control capability
Solution Approach 2:
The MEMS mirror utilizes thin film structures to achieve angular deflection of the light beam. This thin-film approach allows for compact angle control without adding significant thickness to the device, consistent with the overall thinness goal
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
The solution enables a smaller, thinner finger vein authentication device capable of improving authentication accuracy and compatibility with thin digital devices by optimizing vein pattern illumination and image processing.
Implementation Method 1
a light source which irradiates a person's finger with near-infrared light
Data Source
AI summary
Provided is a device which performs vein authentication by using a downward irradiation-type thin module and selecting an image of a proper angle by varying the irradiation direction of near-infrared illumination. Realized are a photographing method and control method of a finger vein image suitable for thin devices such as a smartphone. Adopted is a finger vein authentication device comprising an imaging unit, an illumination unit which is disposed on a substantially same plane as the imaging unit, and irradiates a finger to be captured by the imaging unit with light in which an irradiation angle is variable, an image selection unit which selects an image according to the irradiation angle of the illumination unit, and an authentication processing unit which performs authentication processing using the image selected by the image selection unit.