Curved Photosensitive Layer Fingerprint Sensor Design

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Solution Overview

Problem

Fingerprint recognition technologies face accuracy issues due to parasitic capacitances in capacitive systems and poor sensitivity in optical systems, particularly in electronic devices with display panels, leading to signal crosstalk and reduced recognition accuracy.

Innovation Solution

A fingerprint recognition device with a photosensitive detector structure featuring a curved photosensitive layer and a loop-shaped frame to enhance light reception, comprising N-type, intrinsic, and P-type semiconductor layers, and a thin film transistor for improved signal transfer, integrated into a display panel manufacturing process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If capacitive fingerprint recognition is used, then fingerprint detection capability is provided, but parasitic capacitances cause signal crosstalk between fingerprint detection signal and display signal, reducing recognition accuracy

Engineering Contradiction:

Improvefingerprint detection capabilityVSAvoidrecognition accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces capacitive sensing with optical sensing technology. The fingerprint sensor uses photoelectric converters (photodiodes) to detect light reflected from the fingerprint pattern on the user's finger, eliminating the parasitic capacitance issue inherent in capacitive sensing. This substitution of sensing mechanism resolves the signal crosstalk problem between fingerprint detection and display signals.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If optical fingerprint recognition is used, then signal crosstalk is avoided, but sensitivity and accuracy of fingerprint detection are poor

Engineering Contradiction:

Improvesignal crosstalkVSAvoidsensitivity and accuracy

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The patent applies curvature to the light-receiving surface of the photosensitive layer. The curved surface (concave or convex) increases the effective light-receiving area and improves light collection efficiency, thereby enhancing the sensitivity and accuracy of fingerprint detection while maintaining the optical sensing approach that avoids signal crosstalk.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent introduces a loop-shaped reflective frame structure that reflects light onto the photosensitive layer from additional angles and paths. This adds another dimension to light reception, increasing the effective detection area and improving sensitivity without introducing signal crosstalk issues.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Measurement precision

If photosensitive layer area is increased to improve light reception, then sensitivity improves, but device area and complexity increase

Engineering Contradiction:

ImprovesensitivityVSAvoiddevice area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The curved surface of the photosensitive layer increases the effective light-receiving area within a compact footprint. By curving the surface, the sensor can capture more reflected light from the fingerprint pattern without proportionally increasing the device's planar area, thus improving sensitivity while controlling device size.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The loop-shaped reflective frame structure utilizes vertical and angular dimensions to redirect light onto the photosensitive layer. This allows the sensor to effectively increase its light-receiving capability without proportionally increasing the horizontal device area, as the light reflection occurs in three-dimensional space rather than simply expanding the planar sensor area.

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

The solution increases the light receiving area and improves sensitivity and accuracy of fingerprint recognition by minimizing signal crosstalk and enhancing the detection of fingerprint patterns.

Implementation Method 1

optical fingerprint recognition sensors have problems of poor sensitivity and accuracy... each of the at least one photosensitive detector comprising a first electrode, a photosensitive layer on the first electrode, and a second electrode on the photosensitive layer

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

the loop-shaped frame has a reflective inner surface such that light impinging on the inner surface is reflected to the photosensitive layer

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS11328530B2Fingerprint recognition device, manufacturing method thereof, and display panel

Publication Date: 2022.05.10 BEIJING BOE TECH DEV CO LTD

AI summary

A fingerprint recognition device includes a first substrate and at least one photosensitive detector on the first substrate, each of the at least one photosensitive detector including a first electrode, a photosensitive layer on the first electrode, and a second electrode on the photosensitive layer. A side of the photosensitive layer facing away from the first electrode has a curved shape.