Transparent Ultrasonic Fingerprint Stack for Artifact-Free Displays

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Solution Overview

Problem

Existing fingerprint sensors are not transparent and therefore not suitable for use with transparent display devices, leading to issues with visible artifacts and background light cancellation, and silicon-based optical sensors are not transparent.

Innovation Solution

A transparent fingerprint sensor stack is developed, comprising transparent fingerprint sensor circuitry, electrodes, a piezoelectric layer, and an adhesive layer, configured to produce ultrasonic waves at frequencies between 1 MHz to 20 MHz, with an optional high-impedance layer and ultraviolet light blocking, suitable for use with transparent displays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional fingerprint sensors are used, then fingerprint authentication function is provided, but the sensors are not transparent causing visible artifacts and background light cancellation issues

Engineering Contradiction:

Improvefingerprint authentication functionVSAvoidvisible artifacts

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies transparency changes to the fingerprint sensor components. The sensor stack includes transparent electrodes (such as ITO, graphene, silver nanowires), transparent piezoelectric materials, and transparent adhesive layers, allowing visible light to pass through without creating visible artifacts while maintaining fingerprint authentication capability

Inventive Principle:

Principle #32Color changes

Solution Approach 2:

The patent uses composite material structures where multiple transparent materials are stacked together. The fingerprint sensor comprises transparent fingerprint sensor circuitry, transparent electrodes, transparent piezoelectric layer, and transparent adhesive layer, creating a composite transparent sensor stack that maintains functionality while achieving optical transparency

Inventive Principle:

Principle #40Composite materials

2Reliability

If silicon-based optical sensors are used, then fingerprint sensing is achieved, but transparency is not possible

Engineering Contradiction:

Improvefingerprint sensing capabilityVSAvoidlack of transparency

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces silicon-based optical sensing with an ultrasonic-based sensing mechanism. The transparent piezoelectric layer generates and detects ultrasonic waves to sense fingerprint patterns, eliminating the need for opaque silicon components while maintaining reliable fingerprint sensing capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces ultrasonic waves as an intermediary medium for fingerprint detection. Instead of using visible light that requires opaque silicon sensors, the system uses ultrasonic waves that can propagate through transparent materials, enabling both transparency and sensing functionality

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If transparent materials are used for the fingerprint sensor stack, then optical transparency is achieved, but ultrasonic wave transmission power may be reduced

Engineering Contradiction:

Improveoptical transparencyVSAvoidultrasonic wave transmission power

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The patent utilizes mechanical vibration principles where the transparent piezoelectric layer is driven to vibrate at ultrasonic frequencies to generate strong ultrasonic waves. The acoustic resonator structure amplifies these vibrations, maintaining high transmission power despite using transparent materials

Inventive Principle:

Principle #18Mechanical vibration

Solution Approach 2:

The patent optimizes parameters of the transparent materials and their layer configurations to enhance ultrasonic transmission. By adjusting material properties, layer thicknesses, and resonant frequencies, the system achieves both optical transparency and sufficient ultrasonic wave transmission power

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

The transparent fingerprint sensor stack enhances ultrasonic wave transmission power and avoids visible artifacts, making it suitable for transparent displays, while being flexible for non-planar surfaces.

Implementation Method 1

a transparent piezoelectric layer... configured to produce ultrasonic waves at frequencies between 1 MHz to 20 MHz

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

an acoustic resonator that is configured to produce a local maximum of ultrasonic wave transmission

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS20260030913A1Transparent fingerprint sensor

Publication Date: 2026.01.29 QUALCOMM INC

AI summary

An apparatus may include a transparent display stack and a transparent fingerprint sensor stack. The transparent fingerprint sensor stack may include transparent fingerprint sensor circuitry, transparent fingerprint sensor electrodes, a transparent piezoelectric layer and a transparent adhesive layer proximate the transparent display stack. In some examples, at least some layers of the transparent fingerprint sensor stack may be, or may include, an acoustic resonator configured to produce a local maximum of ultrasonic wave transmission at a frequency in a range from 1 MHz to 20 MHz.