Anti-Light-Scattering Layer for Fingerprint Sensor Crosstalk Reduction

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Solution Overview

Problem

Fingerprint imaging systems face issues with light scattering and crosstalk due to angle deviations in fiber-optical plates, which degrade image quality and contrast ratio.

Innovation Solution

An anti-light-scattering layer with alternating first and second portions is introduced, where the first portions cover photodiodes and have higher refractivity than the second portions, reducing light penetration and scattering by reflecting light back onto the first portions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fiber-optical plate is used as a protective plate, then the sensor array is protected and light scattering is reduced, but light scattering and crosstalk still occur due to angle deviation in the gratings

Engineering Contradiction:

Improveprotection of sensor arrayVSAvoidlight scattering and crosstalk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The protective plate is segmented into multiple independent microlens units, each corresponding to a photodiode. This segmentation prevents light from adjacent pixels from entering the wrong photodiode, thereby reducing crosstalk while maintaining protection functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each microlens is individually designed with specific optical properties to focus light from its corresponding photodiode. The local optimization of light focusing at each pixel location improves signal quality while reducing overall light scattering in the system.

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If light transmission regions are provided between adjacent photodiodes, then light transmission is improved, but light scattering and crosstalk increase

Engineering Contradiction:

Improvelight transmissionVSAvoidlight scattering and crosstalk

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The microlens acts as an intermediary optical element between the light transmission region and the photodiode. It focuses the transmitted light precisely onto the photodiode surface, ensuring that improved light transmission does not result in increased crosstalk or scattering.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively reduces light scattering and crosstalk, enhancing the contrast ratio and image quality by preventing light from entering adjacent pixel cells.

Implementation Method 1

refractivity of the plurality of first portions is greater than refractivity of the plurality of second portions

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

reducing light penetration and scattering by reflecting light back onto the first portions

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS9922232B2Fingerprint imaging system and forming method thereof having a plurality of light transmission regions between adjacent photodiodes on a backlight system

Publication Date: 2018.03.20 SHANGHAI OXI TECH

AI summary

A fingerprint imaging system and a method for forming the same. The system includes: a backlight system; a sensor array on the backlight system, wherein the sensor array comprises a plurality of photodiodes and a plurality of light transmission regions between adjacent photodiodes; and an anti-light-scattering layer formed on the sensor array, wherein the anti-light-scattering layer comprises a plurality of first portions and a plurality of second portions disposed between adjacent first portions, wherein the plurality of first portions cover at least the plurality of photodiodes respectively, and refractivity of the plurality of first portions is greater than refractivity of the plurality of second portions.