Optical Fingerprint Sensor Pixel Array Liveness Detection

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Solution Overview

Problem

Existing optical fingerprint identification systems face security risks due to the inability to distinguish between genuine and forged fingerprints, particularly those made of artificial materials, which can mimic the reflection properties of human skin.

Innovation Solution

Incorporating a pixel array with both common and characteristic pixel points, where the characteristic pixel points have a reduced optical signal intensity due to a filter layer or polarizer, allowing for the detection of differences in signal intensity to determine the authenticity of a fingerprint, thereby enhancing security by distinguishing between live and artificial materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional optical fingerprint sensors are used, then fingerprint identification is simple and fast, but security is poor due to inability to distinguish forged fingerprints

Engineering Contradiction:

ImprovesecurityVSAvoidpixel array structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pixel array is segmented into two distinct types: first type pixel points for capturing optical signals from the fingerprint, and second type pixel points with filters for detecting material properties. This segmentation allows the system to simultaneously perform basic fingerprint capture and advanced liveness detection, resolving the contradiction between security improvement and device complexity by organizing the complexity into functional segments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the pixel array are assigned different functional qualities: first type pixel points are optimized for general optical signal detection, while second type pixel points are equipped with filters specifically for detecting material properties. This local differentiation of quality allows the system to enhance security through material property detection without requiring all pixels to be complex, thus balancing security improvement with manageable device complexity.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If characteristic pixel points with filters are added, then ability to detect material properties improves, but device complexity increases

Engineering Contradiction:

Improvematerial property detectionVSAvoidpixel array structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of equipping all pixel points with filters, the patent applies filters only to certain second type pixel points. This partial action approach provides sufficient material property detection capability to distinguish forged fingerprints while avoiding the excessive complexity that would result from universal filter implementation. The selective placement of filtered pixel points achieves the necessary measurement precision with minimized added complexity.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If multiple types of pixel points are used, then fingerprint authenticity verification is enhanced, but manufacturing complexity increases

Engineering Contradiction:

Improvefingerprint authenticity verificationVSAvoidpixel array fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent differentiates pixel points by optical parameters (filter presence, sensitivity characteristics) rather than using fundamentally different hardware components. This parameter-based differentiation allows for enhanced fingerprint authenticity verification while maintaining compatibility with standard pixel array manufacturing processes. By varying optical parameters rather than structural complexity, the system achieves improved reliability without proportionally increasing manufacturing difficulty.

Inventive Principle:

Principle #35Parameter changes

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 effectively improves the security of fingerprint identification by accurately differentiating between real and artificial fingerprints based on the intensity ratios of optical signals received by characteristic and adjacent pixel points, reducing false acceptance and enhancing user safety.

Implementation Method 1

a pixel array including a plurality of first type of pixel points and at least one second type of pixel point, wherein a filter layer or polarizer is disposed above the at least one second type of pixel point

Methodology Applied

Scientific EffectOptical filtration: Filter (optical)

Implementation Method 2

Methodology Applied

Scientific EffectPolarization: Polarisation

Data Source

PatentEP3657381B1Fingerprint recognition apparatus and method, and terminal device

Publication Date: 2022.08.17 SHENZHEN GOODIX TECH CO LTD

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AI summary

Provided are an apparatus and a method of fingerprint identification and a terminal device, the fingerprint identification apparatus including: an optical sensor including a pixel array, where the pixel array includes a plurality of first type of pixel points and at least one second type of pixel point, and the plurality of first type of pixel points and the at least one second type of pixel point are configured to receive optical signals from an object; and a color filter layer or a polarizer plate disposed above the at least one second type of pixel point; where an intensity of an optical signal received by the at least one second type of pixel point and an intensity of an optical signal received by at least one first type of pixel point adjacent to the at least one second type of pixel point are used to determine whether the object is a real finger.