Segmented Ultrasonic Fingerprint Sensor for Flexible Displays

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Solution Overview

Problem

Ultrasonic fingerprint sensor systems face challenges in integrating with flexible and curved displays due to acoustic coupling issues and power management limitations, particularly with large electrode areas requiring high drive voltages and peak currents, which can lead to image distortions and inefficiencies.

Innovation Solution

The implementation of an ultrasonic fingerprint sensor system with a substrate having a piezoelectric layer and an electrode layer divided into segmented electrodes, where the electrode segments are selectively driven with voltage bursts, reducing power consumption and minimizing image discontinuities, and using an electrically nonconductive acoustic layer for enhanced acoustic coupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If a large electrode area is used for ultrasonic fingerprint sensing, then the sensor active area is increased, but the drive voltage and peak current requirements increase leading to power management limitations

Engineering Contradiction:

Improvesensor active areaVSAvoidpower consumption

Core Design Contradiction:

Area of stationary objectVSUse of energy by stationary object

Solution Approach 1:

The electrode layer is divided into multiple segmented electrodes instead of using a single large electrode. This segmentation allows the ultrasonic transmitter to activate only specific electrode segments corresponding to the detected finger position, rather than driving the entire large electrode area. Consequently, the peak current and drive voltage requirements are reduced while maintaining the large sensor active area capability.

Inventive Principle:

Principle #1Segmentation

2Area of stationary object

If a large electrode area is used for ultrasonic fingerprint sensing, then the sensor active area is increased, but image distortions and discontinuities occur

Engineering Contradiction:

Improvesensor active areaVSAvoidimage quality

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If flexible and curved displays are used, then adaptability is improved, but acoustic coupling issues arise affecting ultrasonic wave propagation

Engineering Contradiction:

Improvedisplay flexibilityVSAvoidacoustic coupling

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces an acoustic matching layer with specific acoustic impedance properties between the ultrasonic transmitter and the flexible display. This layer is designed with acoustic impedance that is intermediate between the piezoelectric material and the flexible display material, thereby improving acoustic coupling and reducing reflections. This allows effective ultrasonic wave propagation even when the display is flexible or curved.

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 configuration enables efficient ultrasonic wave propagation and reflection across flexible and curved displays, improving image quality and user experience by reducing power requirements and minimizing image artifacts, while allowing for larger sensor active areas and continuous authentication across full display areas.

Implementation Method 1

The ultrasonic transceiver includes a piezoelectric layer and an electrode layer coupled to the piezoelectric layer, where the electrode layer is divided into a plurality of electrode segments, where one or more of the electrode segments are configured to be selected to receive a voltage burst from an integrated circuit electrically coupled to the electrode layer, where the voltage burst causes the piezoelectric layer to generate ultrasonic waves.

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The transmitter may be operatively coupled with an ultrasonic sensor configured to detect portions of the ultrasonic wave that are reflected from the object.

Methodology Applied

Scientific EffectPiezoelectric effect: Converse Piezoelectric Effect

Data Source

PatentUS10891458B2Module architecture for large area ultrasonic fingerprint sensor

Publication Date: 2021.01.12 QUALCOMM INC

AI summary

An ultrasonic fingerprint sensor system of the present disclosure may be provided with an ultrasonic transmitter or ultrasonic transceiver having an electrode layer divided into a plurality of electrode segments. The ultrasonic fingerprint sensor system may detect an object over one or more electrode segments and provide a voltage burst to one or more selected electrode segments for localized generation of ultrasonic waves. The localized generation of ultrasonic waves may facilitate localized readout for imaging. In some implementations, the voltage burst may be provided in a single-ended drive scheme or differential drive scheme.