cMUT Ultrasonic Fingerprint Detection Circuit

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Solution Overview

Problem

Ultrasonic fingerprint detection circuits face challenges in determining whether a detected subject is a living body due to insufficient vertical resolution, which is crucial for accurate fingerprint identification and integration with display apparatuses.

Innovation Solution

The ultrasonic fingerprint detection assembly combines an ultrasonic fingerprint detection circuit with a living body detection circuit, utilizing a capacitive micromachined ultrasonic transducer (cMUT) array and a mutual capacitance touch circuit to perform living body detection simultaneously with fingerprint detection, by detecting changes in capacitance between electrodes during a rest stage of the ultrasonic emission process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If ultrasonic fingerprint detection circuit uses cMUT array for fingerprint detection, then fingerprint identification capability is achieved, but vertical resolution for living body detection is insufficient

Engineering Contradiction:

Improvevertical resolutionVSAvoidliving body detection accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent combines ultrasonic fingerprint detection circuit and capacitive living body detection circuit into a single integrated assembly. The cMUT array serves dual purposes: fingerprint detection through ultrasonic waves and living body verification through capacitance changes during rest stages, thereby improving vertical resolution without sacrificing detection reliability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The cMUT array is designed to perform multiple functions: primary ultrasonic fingerprint detection and secondary capacitive living body detection. By utilizing the rest stage of the ultrasonic emission cycle for capacitance measurement, the system achieves multi-functionality that resolves the contradiction between measurement precision and reliability

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If separate living body detection circuit is added to ultrasonic fingerprint detection system, then living body detection capability is improved, but device complexity increases

Engineering Contradiction:

Improveliving body detection capabilityVSAvoiddetection system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the living body detection function with the existing ultrasonic fingerprint detection circuit by utilizing the same cMUT array structure. The first and second electrodes of the cMUT serve as both ultrasonic transducers and capacitive sensors, eliminating the need for completely separate detection circuits and reducing overall device complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Speed

If ultrasonic emission process is continuous, then fingerprint detection speed is improved, but living body detection during rest stage becomes impossible

Engineering Contradiction:

Improvefingerprint detection speedVSAvoidrest stage availability

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The patent employs periodic ultrasonic emission with distinct active and rest stages. During each cycle, the ultrasonic waves are emitted for fingerprint detection, followed by a rest stage where capacitance changes are measured for living body detection. This periodic action ensures both fingerprint detection speed and living body detection capability are maintained

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system maintains continuous detection capability by utilizing every phase of the ultrasonic emission cycle. The fingerprint detection occurs during ultrasonic emission while living body detection occurs during the rest stage, ensuring that no time is wasted and both functions are performed continuously without interruption

Inventive Principle:

Principle #20Continuity of useful action

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 enhances the vertical resolution for living body detection, allowing for accurate identification of living subjects and integration with display apparatuses, while maintaining compatibility with glass-based processes and reducing the complexity of the detection system.

Implementation Method 1

an ultrasonic fingerprint detection circuit sends a nearly planar ultrasonic wave to a finger

Methodology Applied

Scientific EffectUltrasonic wave emission: Ultrasound

Implementation Method 2

The planar ultrasonic wave interacts with valleys and ridges of the fingerprint, which have different reflectivity. Accordingly, different echo signals are generated

Methodology Applied

Scientific EffectAcoustic echo: Echo

Implementation Method 3

determine whether a subject being detected is a living body by detecting a change of capacitance between the first touch electrodes and the second touch electrodes of the living body detection circuit

Methodology Applied

Scientific EffectCapacitance change detection: Capacitance

Data Source

PatentUS11301662B2Ultrasonic fingerprint detection circuit, ultrasonic fingerprint detection method, and display apparatus

Publication Date: 2022.04.12 BOE TECHNOLOGY GROUP CO LTD

AI summary

The present disclosure is related to an ultrasonic fingerprint detection assembly. The ultrasonic fingerprint detection assembly may include an ultrasonic fingerprint detection circuit and a living body detection circuit. The living body detection circuit may be configured to carry out living body detection at a rest stage of the ultrasonic fingerprint detection circuit.