Finger Sensor Pixel Circuitry Shielding Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fingerprint sensors operating in display regions of portable electronic devices face challenges in capturing high-quality images due to noise and interference from thick protective covers, leading to unacceptable biometric performance.
Innovation Solution
A fingerprint sensor design with pixel sensing circuitry that operates in measurement and shielding modes, using a plurality of pixels, pixel sensing traces, and electrodes, where active pixels are coupled to a drive signal and inactive pixels to a voltage reference, reducing interference and noise by shielding the sensing area from external influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the finger sensing area is separated from the integrated circuit to improve device integration and allow placement over display regions, then device adaptability and integration are improved, but noise and interference from thick protective covers increase, degrading measurement precision
Solution Approach 1:
The sensing system is divided into separate functional components: the integrated circuit remains separated from the finger sensing area, allowing independent optimization of each component. The sensing area can be placed over display regions while the IC is positioned in non-display regions, resolving the contradiction between device integration and measurement precision.
Solution Approach 2:
A shielding electrode is introduced as an intermediary element between the finger sensing area and external interference sources. This shielding electrode, connected to ground or reference potential, blocks noise and interference from thick protective covers, maintaining measurement precision while allowing device integration.
2Ease of operation
If the finger sensing area is placed over display regions to improve device integration, then ease of operation and device functionality are improved, but noise from thick protective covers increases, worsening measurement precision
Solution Approach 1:
The shielding electrode acts as a mediator that enables the finger sensing area to be placed over display regions while protecting against noise from thick protective covers. This allows the device to maintain both ease of operation through integrated display functionality and measurement precision through noise shielding.
Solution Approach 2:
The shielding electrode is positioned in advance to preemptively block noise and interference before they can affect the sensing process. By placing the shielding electrode between the sensing area and external interference sources, the system prevents degradation of measurement precision while maintaining device functionality.
3Measurement precision
If shielding electrodes are added to reduce noise and interference, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The shielding electrode is implemented as a thin conductive layer or film that can be integrated into the existing sensor structure without adding significant bulk or complexity. This thin-film approach maintains measurement precision while minimizing the impact on device complexity.
Solution Approach 2:
The shielding electrode serves multiple functions: it shields against noise and interference, provides an additional sensing element, and can be integrated with existing device layers. This multi-functionality improves measurement precision while minimizing the increase in device complexity.
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 effectively reduces noise and interference, enabling high-quality fingerprint measurements even when the sensor is positioned at a distance from the integrated circuit, improving biometric performance and durability.
Implementation Method 1
A fingerprint sensing circuit for reducing noise and parasitic capacitive coupling
Implementation Method 2
A fingerprint sensing circuit for reducing noise and parasitic capacitive coupling
Data Source
AI summary
A finger sensor may include pixels, pixel sensing traces each associated with a respective pixel, and electrodes overlying the pixel sensing traces. The finger sensor may also include pixel sensing circuitry coupled to the pixel sensing traces and the electrodes. The pixel sensing circuitry may be capable of operating in a measurement mode by operating the pixels so that at least some of the pixels are active, and at least some other of the pixels are inactive and coupling pixel sensing traces associated with the inactive pixels to a voltage reference. The pixel sensing circuitry may also be capable of operating in the measurement mode by coupling electrodes associated with the active pixels to the voltage reference and coupling electrodes associated with the inactive pixels to a drive signal.