Under-Glass Fingerprint Button Layout Without Physical Key Travel

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Solution Overview

Problem

Existing terminal devices integrate fingerprint identification with physical buttons, affecting aesthetic appearance and user convenience due to the need for a fixed stroke and structural design that compromises both form and function.

Innovation Solution

A method and device that integrates a fingerprint identification sensor and a capacitive button sensor beneath the cover glass, allowing for simultaneous fingerprint and button information collection through capacitive coupling, without overlapping, enhancing aesthetic appearance and structural strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a physical button is combined with fingerprint identification function, then button functionality is achieved, but aesthetic appearance and structural strength are affected

Engineering Contradiction:
Improvebutton functionalityVSAvoidaesthetic appearance
Core Design Contradiction:
Adaptability or versatilityVSShape

Solution Approach 1:

The patent replaces the mechanical physical button with a capacitive button sensor that detects touch through capacitance changes. This substitution eliminates the need for a physical protruding button, maintaining the cover glass's aesthetic appearance while preserving button functionality through electrical field detection.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a capacitive sensor layer as an intermediary between the user's finger and the button function. This intermediary detects touch through capacitance coupling without requiring direct mechanical contact or physical button structure, thus preserving both appearance and functionality.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Adaptability or versatility

If a physical button is combined with fingerprint identification function, then button functionality is achieved, but structural strength of cover glass is affected

Engineering Contradiction:
Improvebutton functionalityVSAvoidstructural strength
Core Design Contradiction:
Adaptability or versatilityVSStrength

Solution Approach 1:

The patent replaces the mechanical button structure with a capacitive sensing system that requires no physical openings or protrusions in the cover glass. This maintains the cover glass's structural integrity while achieving button functionality through electrical field detection beneath the glass surface.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent nests the capacitive button sensor and fingerprint sensor within the cover glass structure itself, placing them beneath the glass surface. This nesting approach allows both sensors to function while the cover glass remains intact, preserving structural strength.

Inventive Principle:
Principle #7Nested doll (Nesting)

3Shape

If fingerprint identification sensor and capacitive button sensor are integrated beneath cover glass, then aesthetic appearance is enhanced, but sensor placement complexity increases

Engineering Contradiction:
Improveaesthetic appearanceVSAvoidsensor placement complexity
Core Design Contradiction:
ShapeVSDevice complexity

Solution Approach 1:

The patent moves both sensors to a different dimensional plane beneath the cover glass surface. The capacitive button sensor and fingerprint sensor are positioned in the same subsurface layer, allowing them to share the same structural space and simplifying integration while maintaining aesthetic appearance.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent creates a multi-functional sensor layer beneath the cover glass that serves both capacitive button detection and fingerprint identification purposes. This universal sensor integration reduces overall system complexity by combining multiple functions into a single integrated structure.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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

Enables seamless integration of fingerprint identification and button functionality, improving user convenience by allowing operation with any strength and enhancing the terminal device's appearance and structural integrity.

Implementation Method 1

the capacitive button sensor being configured to collect button information applied to the cover glass based on a coupling capacitance formed between a finger of a user and a surface of the touch screen

Methodology Applied
Scientific EffectCapacitive coupling: Capacitance

Implementation Method 2

the coupling capacitance causes currents flowing through four electrodes at four corners of the touch screen, the currents flowing through the four electrodes being proportional to distances from the finger to the four corners

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentEP3901824B1Method and device for realizing touch button and fingerprint identification, and terminal device
Publication Date: 2025.12.10 XIAOMI INC
  • EP3901824B1 patent drawingFigure 1~3
  • EP3901824B1 patent drawingFigure 4~6
  • EP3901824B1 patent drawingFigure 7

AI summary

The present disclosure relates to a method and a device for realizing a touch button and a fingerprint identification and a terminal device. The device includes: a fingerprint identification sensor (21), disposed below a cover glass (23) of a terminal device; a capacitive button sensor (22), disposed below the cover glass (23) and located on at least one side of the fingerprint identification sensor (21).