Fingerprint Sensor Row Initialization for Blur and Noise Reduction
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Solution Overview
Problem
Fingerprint sensing devices face challenges in reducing image blur and blocking external noise, leading to inaccurate fingerprint pattern acquisition.
Innovation Solution
A fingerprint sensing device with a matrix configuration of scan lines, initialization lines, and sensing lines, utilizing a scan driver and sensing driver to apply specific signal levels to sensing pixels, including transistors and capacitors, to enhance signal reception and reduce noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fingerprint sensing is used, then fingerprint recognition is provided, but image blur occurs and external noise interferes with accurate pattern acquisition
Solution Approach 1:
The sensing device is divided into multiple sensing pixel rows with selective initialization. The scan driver applies initialization signals to specific rows (a-numbered rows) while excluding others (b-numbered rows), segmenting the sensing area to reduce noise propagation and improve pattern acquisition accuracy for each segment.
Solution Approach 2:
Different initialization strategies are applied to different sensing pixel rows based on their positions. The a-numbered rows receive enable-level initialization signals while b-numbered rows receive disable-level signals, creating local quality differences that optimize signal-to-noise ratio in specific regions and reduce overall image blur.
2Object-affected harmful factors
If selective initialization is applied to reduce noise, then external noise is blocked, but device complexity increases due to additional control circuits
Solution Approach 1:
The scan driver performs multiple functions: it generates scan signals for row selection, produces initialization signals for capacitor initialization, and controls the timing of these signals. This multi-functionality reduces the need for separate dedicated circuits, thereby limiting the increase in device complexity while achieving noise blocking.
Solution Approach 2:
The initialization capacitors are pre-charged to specific voltage levels (enable-level or disable-level) before sensing operations begin. This preliminary action prepares the sensing pixels in advance, allowing them to quickly respond to fingerprint contact and reducing the need for complex real-time noise cancellation circuits.
3Reliability
If initialization signals are applied to all sensing pixel rows, then signal reception is enhanced, but image blur increases due to uniform charging
Solution Approach 1:
The initialization pattern is made asymmetric by applying enable-level signals to a-numbered rows and disable-level signals to b-numbered rows. This asymmetric initialization creates differential charging states that enhance signal reception in specific rows while maintaining image clarity by preventing uniform blur across all rows.
Solution Approach 2:
Initialization signals are applied partially to only certain sensing pixel rows (a-numbered rows) rather than all rows. This partial action enhances signal reception where needed while avoiding the excessive uniform charging that would cause image blur, thereby maintaining measurement precision.
Data Source
AI summary
A fingerprint sensing device includes: a fingerprint sensor including scan lines and initialization lines extending in a first direction and arranged in a second direction, sensing lines extending in the second direction and arranged in the first direction, and sensing pixels connected to the scan lines, the initialization lines, and the sensing lines and disposed in a matrix configuration; a scan driver configured to apply an enable-level initialization signal to a-numbered sensing pixel rows while applying a disable-level initialization signal to b-numbered sensing pixel rows, and applying an enable-level scan signal to one sensing pixel row in the b-numbered sensing pixel rows; and a sensing driver configured to receive a sensing signal from the sensing pixel row to which the scan signal is applied through the sensing lines, wherein the a and b are positive numbers that are greater than 2.