Biometric Sensor Diverging Optical Element Aperture

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Solution Overview

Problem

Conventional optical fingerprint sensors are too bulky for mobile devices and struggle to detect fine ridge and valley features through thick cover glass, requiring mechanical buttons and cutouts that compromise device design and functionality.

Innovation Solution

The use of a diverging optical element with an aperture array between the light sensing elements and the object to be imaged, which limits the acceptance angle of light beams and reduces blurring, allowing for sharper image capture and thinner sensor profiles suitable for mobile devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If conventional optical fingerprint sensors are used, then imaging capability is achieved, but sensor size becomes too bulky for mobile devices

Engineering Contradiction:

Improvesensor sizeVSAvoidimaging capability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The optical sensor is segmented into distinct functional layers: a light blocking layer with apertures, a light guiding layer with light pipes, and a sensing array. This segmentation allows each layer to perform its specific function efficiently while reducing the overall sensor volume suitable for mobile devices.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from conventional lateral light blocking to vertical light guiding through light pipes. By directing light vertically through the cover glass and using light pipes to guide it to the sensing array, the sensor achieves compact form factor while maintaining imaging capability through thick cover glasses.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If capacitive sensors are used to reduce size, then sensor compactness is improved, but sensing capability through thick cover glass deteriorates

Engineering Contradiction:

Improvesensor sizeVSAvoidsensing capability

Core Design Contradiction:

Volume of moving objectVSMeasurement precision

Solution Approach 1:

Light pipes serve as intermediary structures that bridge the gap between the finger surface and the sensing array through thick cover glass. These light pipes guide optical signals from the fingerprint ridges and valleys to the photodetectors, enabling precise sensing through distances that would be impossible for direct capacitive coupling.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces capacitive sensing (electrical field-based) with optical sensing (light-based). This substitution allows the sensor to see through thick non-conductive cover glass that would block electrical fields, while maintaining compact form factor through efficient light guiding structures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Speed

If pinhole camera approach is used to create aperture effect, then light directionality is improved, but light transmission efficiency deteriorates due to blocking layer

Engineering Contradiction:

Improvelight directionalityVSAvoidlight transmission efficiency

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The patent converts the harmful effect of the light blocking layer (which blocks most light in pinhole cameras) into a beneficial structure. The blocking layer is designed with optimized apertures that, combined with light pipes, actually enhance light guidance by preventing stray light while efficiently transmitting useful light signals to the sensors.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent optimizes the aperture size, shape, and distribution parameters in the light blocking layer, along with the light pipe dimensions and refractive indices, to achieve the optimal balance between light directionality and transmission efficiency. These parameter adjustments maximize the useful light reaching the sensors while minimizing losses.

Inventive Principle:

Principle #35Parameter changes

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 enables reliable optical fingerprint sensing through thick cover layers without the need for mechanical buttons, providing improved image quality and a more compact sensor design for mobile devices.

Implementation Method 1

an array of diverging optical elements above an aperture (between the object to be imaged and the aperture) for each sensing element or pixel to enhance the effect of the aperture to preferentially remove contributions of light from object features far from the central axis of the sensing element or pixel

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10108841B2Biometric sensor with diverging optical element

Publication Date: 2018.10.23 FINGERPRINT CARDS IP AB

AI summary

An optical biometric sensor includes an array of light sensing elements, an array of diverging optical elements, and an array of apertures disposed between the array of light sensing elements and the array of diverging optical elements. Light incident on the diverging optical elements within a limited acceptance angle passes through the apertures and towards the light sensing elements and light incident on the diverging optical elements outside of the limited acceptance angle diverges away from the apertures.