Infrared Waveguide Biometric Imaging for Under-Display Fingerprint

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Solution Overview

Problem

Biometric sensors under electronic device displays face challenges in providing non-disturbing illumination for fingerprint imaging, especially in dark environments, due to the need for efficient and unobtrusive light sources within cramped spaces.

Innovation Solution

A biometric imaging arrangement utilizing an image sensor with a waveguide structure that orthogonally redirects infrared light for illumination, allowing for invisible lighting and assembly in tight spaces, with the waveguide integrated directly on the image sensor to ensure precise illumination of the finger.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If visible light from the display is used for illumination, then sufficient illumination is provided for fingerprint capture, but user disturbance increases in dark environments

Engineering Contradiction:

Improveillumination for fingerprint captureVSAvoiduser disturbance

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the wavelength parameter of the illumination light from visible spectrum to infrared spectrum. The display is driven to emit infrared light at wavelengths between 700nm-1000nm, which is invisible to the human eye but detectable by the image sensor. This resolves the contradiction by maintaining sufficient illumination intensity for fingerprint capture while eliminating visible light disturbance in dark environments

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent effectively changes the 'color' (wavelength) of the display light from visible colors to infrared. By adjusting the display's emission characteristics to produce infrared radiation, the system provides illumination that cannot be seen by users, thereby eliminating the harmful effect of visible light leakage while maintaining the useful function of illuminating the fingerprint

Inventive Principle:

Principle #32Color changes

2Illumination intensity

If additional light sources are added under the display, then sufficient illumination is provided, but device complexity and assembly difficulty increase

Engineering Contradiction:

Improveillumination for fingerprint captureVSAvoidassembly complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent makes the display serve multiple functions: it acts as both the user interface display and the illumination light source. By driving the display to emit infrared light, the system eliminates the need for separate illumination components, reducing device complexity and assembly difficulty while providing sufficient illumination for fingerprint capture

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The display serves itself by generating the illumination light needed for fingerprint capture. Instead of requiring external or additional light sources, the display generates infrared light that illuminates the fingerprint, making the system self-sufficient and reducing overall complexity

Inventive Principle:

Principle #25Self-service

3Object-affected harmful factors

If infrared light is used for illumination, then user disturbance is reduced, but assembly space requirements become more constrained

Engineering Contradiction:

Improveuser disturbanceVSAvoidassembly space

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The display performs dual functions as both display element and infrared illumination source. This eliminates the need for separate illumination components that would require additional space, allowing the system to benefit from infrared illumination while maintaining compact assembly space under the display

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

This solution provides a cost-effective and unobtrusive biometric imaging system that effectively illuminates the finger without disturbing the user, enabling reliable fingerprint capture even in low-light conditions while maintaining a compact design.

Implementation Method 1

The waveguide structure comprises optical decoupling areas configured to orthogonally redirect infrared light received from a side of the waveguide structure towards the object

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

an image sensor comprising a detector pixel array configured to detect infrared radiation transmitted from an object for capturing an image

Methodology Applied

Scientific EffectInfrared radiation detection: Infrared Radiation

Data Source

PatentUS12008835B2Biometric imaging arrangement for infrared imaging comprising a waveguide formed on an image sensor

Publication Date: 2024.06.11 FINGERPRINT CARDS ANACATUM IP AB

AI summary

The present invention relates to a biometric imaging arrangement comprising: an image sensor comprising a detector pixel array configured to detect infrared radiation transmitted from an object for capturing an image, a waveguide structure arranged on the image sensor to cover the detector pixel array, the waveguide structure comprising optical decoupling areas configured to orthogonally redirect infrared light received from a side of the waveguide structure towards the object when being placed for imaging.