TFT Fingerprint Sensor Reference Signal Correction
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Solution Overview
Problem
Fingerprint sensing systems, especially those implemented for large areas using cost-efficient technologies, face challenges with signal variations due to interference and temperature-dependent properties, leading to reduced signal quality and a limited usable temperature range.
Innovation Solution
Incorporating a reference signal source to provide a reference signal that corrects read-out signals in the fingerprint sensing system, utilizing CMOS technology for more controlled and less temperature-sensitive circuitry, and employing semiconductor circuitry with adaptive leakage current management to enhance signal-to-noise ratio and expand the temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If TFT technology is used for large area fingerprint sensing, then manufacturing cost is reduced and area is increased, but signal quality deteriorates due to interference and temperature variations
Solution Approach 1:
A reference signal source is introduced as an intermediary element to provide a reference signal that compensates for interference and temperature variations. The reference signal source acts as a mediator between the pixel elements and the read-out circuitry, allowing the system to maintain signal quality while using cost-efficient TFT technology for large area coverage.
Solution Approach 2:
The system implements feedback by using the reference signal to correct read-out signals from pixel elements. The reference signal provides information about environmental conditions (interference and temperature), which is then used to adjust and correct the fingerprint sensing signals, maintaining measurement precision despite using economical TFT technology.
2Area of stationary object
If TFT technology is used for large area fingerprint sensing, then sensing area is increased, but signal stability deteriorates due to temperature-dependent properties
Solution Approach 1:
The reference signal source serves as an intermediary that monitors temperature variations across the large sensing area and provides correction signals. This allows the system to maintain signal stability throughout the extended sensing area by compensating for temperature-dependent properties of the TFT technology.
3Measurement precision
If reference signal correction is applied, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
The reference signal source is designed as a relatively simple intermediary component that provides correction signals without requiring complex processing circuitry. The correction mechanism leverages the reference signal to improve signal-to-noise ratio while keeping the additional hardware complexity minimal.
Data Source
Figure 1~2
Figure 3
Figure 4A~4C
AI summary
A fingerprint sensing system comprising a plurality of conductive selection lines; a plurality of conductive read-out lines crossing the selection lines; selection circuitry controllable to provide a selection signal on at least one selected selection line in the plurality of selection lines; a plurality of pixel elements formed at intersections between the selection lines and the read-out lines; a reference signal source configured to provide a reference signal; and read-out circuitry coupled to each read-out line in the plurality of read-out lines and to the reference signal source, the read-out circuitry being configured to acquire a read-out signal via a read-out line connected to a selected pixel element, when the selected pixel element provides the sensing signal; acquire a reference signal from the reference signal source; form a corrected read-out signal for the selected pixel element based on the read-out signal and the reference signal; and provide corrected read-out signals.