In-Display Fingerprint Sensor Pixel Structure
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Solution Overview
Problem
In-screen fingerprint detection technologies face challenges with low accuracy due to reduced effective photosensitive area and signal-to-noise ratio when integrated into display screens, as existing active pixel sensors require multiple transistors and have limited light transmittance, reducing the range of received reflected light and increasing detection noise.
Innovation Solution
A fingerprint detection module with a simplified structure using two transistors and one photosensitive diode, where the photosensitive unit receives reflected light after voltage switching, outputs electrical signals based on pulse control signals, and the acquisition component acquires fingerprints from voltage differences, eliminating the need for additional selection transistors and increasing the photosensitive area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing active pixel sensors with multiple transistors are used in display screens, then fingerprint detection function is achieved, but the effective photosensitive area is reduced and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent extracts and removes the selection transistor from the active pixel sensor structure, keeping only the essential photosensitive diode and two transistors for charge transfer and readout. This extraction of unnecessary components increases the effective photosensitive area while maintaining fingerprint detection functionality.
Solution Approach 2:
The patent optimizes the local structure of the pixel sensor by creating different functional regions: a larger photosensitive area for light reception, a charge transfer region, and a readout region. This local differentiation allows maximum photosensitive area while maintaining detection capability.
2Reliability
If existing active pixel sensors with multiple transistors are used in display screens, then fingerprint detection function is achieved, but detection noise increases due to limited light transmittance
Solution Approach 1:
By removing the selection transistor that blocked part of the reflected light, the patent allows more light to reach the photosensitive diode, thereby increasing signal strength and improving signal-to-noise ratio for more reliable detection.
Solution Approach 2:
The patent changes the structural parameters of the pixel sensor, specifically reducing the number of transistors and optimizing their arrangement, which improves light transmittance and reduces detection noise while maintaining detection reliability.
3Ease of manufacture
If multiple transistors are used in each pixel sensor, then charge transfer and selection functions are achieved, but device complexity increases and photosensitive area decreases
Solution Approach 1:
The patent extracts the selection transistor function from the pixel sensor structure, simplifying each pixel to contain only the photosensitive diode and two transistors. This reduces device complexity and increases the photosensitive area available for fingerprint detection.
Solution Approach 2:
The two remaining transistors in each pixel are designed to perform multiple functions: charge transfer from the photosensitive diode and signal readout to the acquisition component, eliminating the need for separate selection transistors and reducing overall 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
This solution enhances the signal-to-noise ratio and accuracy of fingerprint detection by increasing the photosensitive area and reducing the occupied space, leading to improved fingerprint recognition capabilities within display screens.
Implementation Method 1
the photosensitive unit receives reflected light of a to-be-detected fingerprint and accumulates charges, and forms a second electrical signal according to the accumulated charges
Data Source
AI summary
The fingerprint detection module having at least one fingerprint identification component and an acquisition component. The fingerprint identification component includes a reset unit, a photosensitive unit, and a follower unit. The reset unit switches a voltage at an output end of the photosensitive unit to an initial voltage according to a reset signal. The photosensitive unit receives reflected light of a to-be-detected fingerprint and accumulates charges, outputs a first electrical signal according to a received pulse control signal at a first level, and outputs a second electrical signal according to a next received pulse control signal at the first level. The follower unit receives the first electrical signal and forms a first voltage, and receives the second electrical signal and forms a second voltage. Further, the acquisition component receives the first voltage and the second voltage, and acquires the fingerprint according to a difference between the second and first voltage.