Collimator Filter Layer for Thin Optical Fingerprint Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical fingerprint sensors are too bulky for integration in mobile devices due to their inability to effectively sense fine ridge and valley features through thick cover glass, requiring cutouts and mechanical buttons, which compromise device design and user experience.
Innovation Solution
Integration of a collimator filter layer with light collimating apertures aligned with light sensing elements in the image sensor wafer, allowing for optical sensing through thick cover layers without blurring, enabling a lower-profile fingerprint sensor suitable for mobile devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional optical fingerprint sensors are used, then fingerprint sensing capability is achieved, but sensor size becomes too bulky for mobile devices
Solution Approach 1:
The optical sensor is divided into multiple functional layers: cover glass layer, collimator layer with microlenses, and sensor layer with photodetectors. This segmentation allows each layer to be optimized independently, reducing overall sensor thickness while maintaining sensing capability through thick cover glass
Solution Approach 2:
A collimator layer with microlenses is introduced as an intermediary between the cover glass and the sensor layer. This intermediate structure collimates light rays reflected from the fingerprint, enabling effective sensing through thick cover glass without requiring the sensor to be in direct contact with the fingerprint
2Length of stationary object
If sensor thickness is reduced for mobile devices, then device integration is improved, but sensing capability through thick cover glass deteriorates
Solution Approach 1:
The collimator layer performs preliminary light conditioning by collimating reflected light rays before they reach the photodetectors. This preliminary optical processing compensates for the distance through thick cover glass, maintaining measurement precision despite reduced sensor thickness
Solution Approach 2:
The microlenses in the collimator layer are designed with specific focal lengths and aperture sizes optimized for the cover glass thickness. By adjusting these optical parameters, the system maintains high measurement precision through thick cover glass while keeping the sensor thin
3Reliability
If cutouts and mechanical buttons are used to achieve fingerprint sensing, then sensing reliability is improved, but device design and user experience deteriorate
Solution Approach 1:
The optical sensor structure integrates multiple functions into a single thin module: fingerprint sensing, light reflection collection, and optical signal conditioning. This universal design eliminates the need for separate cutouts and mechanical buttons, simplifying device design while maintaining sensing reliability
Solution Approach 2:
The system uses optical reflection from the fingerprint surface to create an optical copy of the ridge and valley pattern. This optical copying mechanism allows fingerprint sensing through the cover glass without physical contact, eliminating the need for cutouts and mechanical buttons
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 enables optical fingerprint sensing through thick cover layers, improving sensitivity and resolution while maintaining a thin sensor profile, suitable for mobile devices without the need for cutouts or mechanical buttons, thus enhancing user experience and device design.
Implementation Method 1
forming a collimator filter layer on an image sensor wafer, wherein a plurality of light collimating apertures in the collimator filter layer are aligned with a plurality of light sensing elements in the image sensor wafer
Implementation Method 2
a plurality of light sensing elements in the image sensor wafer... detect absolute capacitance... capacitance at each sensing element in the array varies depending on whether a ridge or valley is present
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Methods and systems for integrating image sensor structures with collimator filters, including manufacturing methods and associated structures for forming collimator filters at the wafer level for integration with image sensor semiconductor wafers. Methods of making an optical biometric sensor include forming a collimator filter layer on an image sensor wafer, wherein a plurality of light collimating apertures in the collimator filter layer are aligned with a plurality of light sensing elements in the image sensor wafer, and after forming the collimator filter layer on the image sensor wafer, singulating the image sensor wafer into a plurality of individual optical sensors.