Biometric Sensor Signal Strength via Intermediate Logic
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Solution Overview
Problem
Capacitive fingerprint sensors, particularly two-dimensional arrays, face challenges with noise reduction and parasitic capacitive coupling, leading to degraded image quality and increased complexity and cost due to the need for in-pixel amplification and high-performance TFT circuitry.
Innovation Solution
A biometric imaging sensor system that incorporates a capacitive gap sensor array with an intermediate logic circuit to control the activation sequence of sensor pixel locations, using a single signal from a controller to individually address transmitter and receiver electrode traces, and employs high dielectric constant materials in the sensor substrate to boost signal strength and reduce noise, allowing for a more compact and cost-effective design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If in-pixel amplification and high-performance TFT circuitry are used, then signal quality is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent moves the amplification function from the pixel plane (2D) to the substrate level (3D/underneath), using interlayer dielectric layers and conductor patterns to route and amplify signals before they reach the readout circuitry. This dimensional shift eliminates the need for complex in-pixel TFT circuitry while maintaining signal quality.
Solution Approach 2:
The patent introduces intermediate signal boosting structures (amplifier circuits) positioned between the capacitive sensor array and the final readout circuitry. These intermediaries amplify the weak sensor signals before further processing, improving signal quality without requiring complex circuitry at each pixel location.
2Measurement precision
If in-pixel amplification and high-performance TFT circuitry are used, then signal quality is improved, but manufacturing cost increases
Solution Approach 1:
The patent relocates amplification circuitry from the expensive pixel plane to the substrate level, where standard semiconductor fabrication processes can be used. This dimensional relocation simplifies manufacturing by eliminating the need for high-performance TFT fabrication at each pixel, significantly reducing manufacturing costs while maintaining signal quality.
Solution Approach 2:
The patent uses standard, low-cost amplifier circuits and interlayer dielectric materials instead of expensive high-performance TFT circuitry. These simpler components are easier and cheaper to manufacture using conventional semiconductor processes, reducing overall device cost while achieving the necessary signal amplification.
3Strength
If glass layer thickness is reduced, then device durability is improved, but signal strength decreases
Solution Approach 1:
The patent introduces intermediate signal boosting structures (amplifier circuits) positioned between the capacitive sensor array and the final readout circuitry. These intermediaries amplify the weak sensor signals before further processing, improving signal quality without requiring complex circuitry at each pixel location.
Solution Approach 2:
The patent changes the electrical parameters (gain, bandwidth) of the intermediate amplifier circuits to optimize signal amplification. By adjusting these parameters, the system compensates for the reduced signal strength from thinner glass layers, maintaining reliable fingerprint sensing while enabling more durable thin-glass construction.
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 enhances signal strength and reduces noise, improving the signal-to-noise ratio and enabling more efficient and cost-effective fingerprint imaging without the need for high-performance TFT circuitry at each pixel, thus addressing the challenges of noise and complexity in existing two-dimensional capacitive fingerprint sensors.
Implementation Method 1
using high dielectric constant materials in the sensor substrate and signal boosting structures to enhance signal strength
Implementation Method 2
a plurality of capacitive gap sensor electrode traces forming an array of biometric sensor imaging pixel locations
Data Source
AI summary
A biometric imager may comprise a plurality of sensor element traces formed in or on a sensor substrate which may comprise at least a portion of a display screen defining a biometric sensing area and forming in-active pixel locations; an auxiliary active circuit formed in or on the sensor substrate on the periphery of the biometric sensing area and in direct or indirect electrical contact with the sensor element traces; and providing a signal processing interface to a remotely located controller integrated circuit. The sensor element traces may form a portion of one dimensional linear sensor array or pixel locations in a two dimensional grid array capacitive gap biometric imaging sensor. The auxiliary circuit may provide pixel location selection or pixel signal amplification. The auxiliary circuit may be mounted on a surface of the display screen. The auxiliary circuit further comprising a separate pixel location selection controller circuit.