Optical Fingerprint Sensor Array for Display Devices
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Solution Overview
Problem
Conventional optical fingerprint sensors face challenges in accurately recognizing fingerprints due to their size limitations and complexity, while capacitive sensors struggle with thin protective films that compromise fingerprint recognition in portable display devices.
Innovation Solution
An optical image sensor device utilizing a directional light unit with a light source, a low refractive layer, and an optical film to converge collimated light for fingerprint recognition without increasing the thickness of the cover substrate, and a display device configuration that allows easy connectivity between PCBs for efficient integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If collimated light with high directionality is used for fingerprint sensing, then measurement precision is improved, but the size of the fingerprint recognition area is extremely limited and device complexity increases due to required scanning function
Solution Approach 1:
The optical fingerprint sensor is divided into multiple independent sensing regions arranged in an array on the display surface. Each region can sense fingerprints independently using collimated light, eliminating the need for a scanning mechanism while maintaining high measurement precision across the entire display area.
Solution Approach 2:
The fingerprint sensing capability is extended from a single point or line to a two-dimensional array of sensing regions distributed across the display surface. This dimensional expansion allows simultaneous fingerprint recognition across multiple areas without requiring mechanical scanning.
2Area of stationary object
If optical fingerprint sensor with scanning function is added to achieve wide area coverage, then area of stationary object is improved, but device complexity and size increase
Solution Approach 1:
The fingerprint sensor array is integrated directly into the display device structure, merging the sensing function with the display surface. Multiple sensing regions are arranged in an array that covers a wide area of the display, eliminating the need for separate scanning devices while achieving both large coverage and simple structure.
3Device complexity
If capacitive fingerprint sensor is used to eliminate scanning device, then device complexity is reduced, but measurement precision is compromised due to thin protective films in portable devices
Solution Approach 1:
A transparent protective film with optimized optical properties serves as an intermediary between the collimated light source and the fingerprint ridges. This film maintains structural simplicity while enabling accurate optical sensing by properly transmitting and directing light through the protective layer to capture fingerprint patterns.
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
Enables accurate recognition of fine fingerprints without thickness reduction and improves connectivity between PCBs in display devices, enhancing security and usability in portable devices.
Implementation Method 1
a directional light unit for progressing a light from the light source through a total reflection, and for converging light deviated from the total reflection by an object having biometric information
Implementation Method 2
an optical film between the cover substrate and the low refractive layer having a light-incident element for refracting the light supplied from the light source so as to progress the light into the cover substrate
Data Source
AI summary
Disclosed herein is an optical image sensor device comprising a light source; a first printed circuit board (PCB) having a first through hole for accommodating the light source; a directional light unit configured to progress a light from the light source through a total refraction, and configured to converge light deviated from the total reflection by an object having biometric information when the object is placed to be adjacent to the directional light unit in a predetermined area, and emit it outside thereof; and an optical sensor between the first PCB and the directional light unit to receive the light emitted from the directional light unit.