Capacitive Fingerprint Sensor Eliminates Backlight Module

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current fingerprint sensors require high-resolution optical sensing, which necessitates a costly backlight module, resulting in a thicker and more expensive sensor mechanism.

Innovation Solution

A capacitive fingerprint sensor utilizing capacitive sensing pixels composed of transistors, sensing capacitors, and current sources, eliminating the need for a backlight module by using low-circuit-area capacitive sensing pixels to achieve high-resolution fingerprint detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If optical sensing is used for high-resolution fingerprint collection, then measurement precision is improved, but device complexity and cost increase due to the backlight module

Engineering Contradiction:

Improvefingerprint collection resolutionVSAvoidsensor mechanism structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the optical sensing system (which requires a backlight module and complex optical path) with a capacitive sensing system. The capacitive sensing pixels directly detect fingerprint patterns through electrical capacitance changes, eliminating the need for optical components and significantly simplifying the sensor mechanism while maintaining high-resolution fingerprint collection capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If optical sensing with backlight module is used, then measurement precision is improved, but manufacturing cost increases

Engineering Contradiction:

Improvefingerprint collection resolutionVSAvoidhardware cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The capacitive sensing system replaces expensive optical components (backlight module, lenses, filters) with simple capacitive sensing pixels that can be manufactured using standard semiconductor fabrication processes, significantly reducing hardware costs while maintaining high measurement precision

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the sensing principle from optical parameter detection to electrical capacitance parameter detection. This parameter change enables the use of simpler, cheaper materials and manufacturing processes while achieving the same high-resolution fingerprint detection capability

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If optical sensing is used for high-resolution fingerprint collection, then measurement precision is improved, but the thickness of the sensor mechanism increases

Engineering Contradiction:

Improvefingerprint collection resolutionVSAvoidsensor mechanism thickness

Core Design Contradiction:

Measurement precisionVSLength of stationary object

Solution Approach 1:

The capacitive sensing system replaces the thick optical path (requiring backlight module, optical elements, and protective layers) with a thin capacitive sensing structure that can be integrated directly into the device housing, dramatically reducing sensor mechanism thickness while maintaining high-resolution fingerprint collection

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent transitions from a three-dimensional optical path structure to a two-dimensional capacitive sensing plane, eliminating the need for vertical space required by optical components and enabling ultra-thin sensor integration

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 solution reduces hardware costs and mechanism thickness while maintaining high-resolution fingerprint sensing, providing a more efficient and cost-effective capacitive fingerprint sensing panel.

Implementation Method 1

the sensing capacitor is coupled between the sensing node and a sensing control signal

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS12131572B1Capacitive fingerprint sensor

Publication Date: 2024.10.29 AU OPTRONICS CORP

AI summary

A capacitive fingerprint sensor is provided. The capacitive fingerprint sensor includes a plurality of capacitive sensing pixels. Each of the capacitive sensing pixels includes a sensing node, a first transistor, a sensing capacitor and a second transistor. The first transistor has a first terminal receiving a first system voltage, a control terminal receiving a reset control signal, and a second terminal coupled to the sensing node. The sensing capacitor is coupled between the sensing node and a sensing control signal. The second transistor has a first terminal receiving a second system voltage, a control terminal receiving a sensing voltage of the sensing node, and a second terminal providing a sensing output signal.