Lateral Light Diffusion for Live Finger Detection
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Solution Overview
Problem
Current fingerprint authentication systems face difficulties in distinguishing live fingers from artificial fingers made of gummy material, as these artificial fingers are conductive and similar in composition to human epidermis, making detection challenging, especially when thin and attached to real fingers.
Innovation Solution
A fingerprint authenticating apparatus that irradiates light from the lateral side of the finger and measures the diffusion pattern to determine whether the object is a live finger or an artificial finger based on the size of the light-diffusion pattern area, utilizing a light source and multiple light receiving elements to differentiate between live and artificial fingers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance fingerprint sensors or weak-electric-field fingerprint sensors are used to detect artificial fingers, then detection capability is improved for non-conductive materials, but detection capability deteriorates for conductive gummy material artificial fingers
Solution Approach 1:
The patent replaces electrical detection methods (capacitance or weak-electric-field sensors) with optical detection methods. A light source illuminates the finger from the lateral side, and light receiving elements detect the diffusion pattern of light passing through the finger. This substitution allows detection of artificial fingers made of conductive gummy material, which cannot be detected by electrical methods.
Solution Approach 2:
The patent utilizes optical property differences between live fingers and artificial fingers. By measuring the diffusion pattern of light, the system detects variations in light transmission characteristics that differ between biological tissue and artificial materials, even when the artificial material is conductive and compositionally similar to human epidermis.
2Measurement precision
If light is applied in almost normal direction to detect artificial fingers, then detection capability is improved for surface-level artificial fingers, but detection capability deteriorates when thin artificial fingerprint is attached to real finger
Solution Approach 1:
Instead of applying light from the normal direction (perpendicular to the surface) as in conventional methods, the patent applies light from the lateral side (parallel to the surface). This inversion of the lighting direction allows the light to pass through the thin artificial fingerprint layer and detect the underlying finger structure, enabling detection even when the artificial fingerprint is thin and transmissive.
Solution Approach 2:
The patent changes the dimension of light application from normal incidence (one-dimensional penetration) to lateral incidence (two-dimensional path through the object). This dimensional change allows light to traverse the thin artificial fingerprint layer and reach the underlying finger, capturing diffusion patterns that reveal the presence of a live finger beneath the artificial coating.
3Ease of manufacture
If gummy material artificial fingers are used, then ease of manufacture is improved (similar to human epidermis), but detection difficulty increases due to electrical conductivity and compositional similarity
Solution Approach 1:
The patent replaces electrical detection systems with optical detection systems. By using a light source and light receiving elements to measure diffusion patterns, the system can detect artificial fingers made of conductive gummy material that would otherwise be undetectable to electrical sensors.
Solution Approach 2:
The patent exploits optical property differences between live fingers and artificial fingers. The diffusion pattern of light passing through the finger provides a signature that differs between biological tissue and artificial materials, enabling detection despite compositional and electrical property similarities.
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
Effectively prevents fraudulent use of artificial fingers by accurately distinguishing between live and artificial fingers, even when thin gummy material is attached, by exploiting differences in light transmission characteristics.
Implementation Method 1
a light source that irradiates a light to the object from a lateral side of the fingerprint sensor; a measuring unit that measures a diffusion pattern of the light passing through the object
Data Source
AI summary
A fingerprint sensor acquires fingerprint information of an object being in contact. A light source irradiates a light to the object from a lateral side of the fingerprint sensor. A measuring unit measures a diffusion pattern of the light passing through the object. A determining unit determines whether the object is a live finger or an artificial finger based on the diffusion pattern measured by the measuring unit.