Fingerprint Imaging With Crossing Electrodes and Drive-Sense Circuits
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fingerprint scanners, particularly optical and capacitive scanners, face issues such as sensitivity to ambient light, surface contamination, and limited imaging area, leading to lower resolution and vulnerability to deception by latent prints or images.
Innovation Solution
A fingerprint scanning device incorporating electrodes and drive-sense circuits that utilize self-capacitance and mutual capacitance to generate a capacitive image, enabling accurate detection of fingerprint ridges and valleys by measuring changes in impedance and capacitance, and integrating this technology into touch screens and edge surfaces for enhanced security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If optical scanners are used for fingerprint imaging, then imaging area is large, but quality is affected by ambient light and surface contamination
Solution Approach 1:
The patent replaces optical scanning mechanisms with capacitive sensing technology. Capacitive sensors detect fingerprint ridges and valleys through electrical field interactions, eliminating dependence on ambient light and optical pathways. This substitution maintains large imaging area while improving reliability by removing sensitivity to environmental factors like light and contamination that plague optical systems.
2Reliability
If capacitive scanners are used for fingerprint imaging, then sensitivity to ambient light is reduced, but imaging area is smaller resulting in lower resolution
Solution Approach 1:
The patent divides the capacitive sensing surface into multiple sensor elements arranged in a grid pattern. Each sensor element independently detects capacitance changes, and the combined data from all elements reconstructs the complete fingerprint image. This segmentation enables the system to achieve both large imaging area and high resolution simultaneously, overcoming the traditional trade-off between sensor size and image quality.
3Reliability
If capacitive scanners are used for fingerprint imaging, then resistance to deception by latent prints is improved, but manufacturing complexity increases
Solution Approach 1:
The patent integrates capacitive sensing functionality into existing touch screen display structures. The same capacitive sensors used for touch input detection also serve fingerprint authentication, eliminating the need for separate dedicated fingerprint scanner components. This multi-functionality approach maintains security accuracy while significantly simplifying manufacturing by leveraging existing display assembly processes.
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 provides high-resolution fingerprint imaging with improved accuracy and resistance to deception, enabling reliable identity verification through capacitive sensing.
Implementation Method 1
Capacitive scanners use an array of capacitor plates (e.g., in a semiconductor sensor chip) to capture an image. In particular, human skin is conductive enough to provide capacitive coupling to an individual capacitive plate of the array.
Implementation Method 2
The drive-sense circuits generate a sensor signal on the electrode and interpret the received signal to produce a representation of an impedance on the electrode. The processing module senses an electrical characteristic of the electrode based on the sensor signal.
Data Source
AI summary
A fingerprint imaging device incorporating a first plurality of electrodes, a second plurality of electrodes and drive-sense circuitry. The first plurality of electrodes and the second plurality of electrodes are separated by a dielectric material and arranged in a crossing pattern in a sensing area. In an embodiment, each of the drive-sense circuits is configured to drive a sensor signal on an electrode of the first plurality or second plurality of electrodes, the sensor signal including a drive signal component and a receive signal component. Each of the drive-sense circuits is further configured to generate, based on the receive signal component, a sensed signal representative of at least a first impedance of the electrode. For at least some of the drive-sense circuits, the sensed signal further represents a second impedance of the electrode in accordance with a drive signal component from a differing electrode. A processing module of the device is configured to process the sensed signals to detect a finger touch to the sensing area and generate a digital representation/capacitive image of a fingerprint corresponding to the finger touch.