TFT Panel Fingerprint Sensor Using Total Reflection
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Solution Overview
Problem
Conventional fingerprint recognition sensors face challenges in miniaturization and contamination issues, particularly when recognizing larger areas like the palm, due to the need for optical lenses and light sources, which increase the device's volume and susceptibility to malfunctions from surface contaminants.
Innovation Solution
A thin film transistor (TFT) panel type fingerprint recognition sensor utilizing a total reflection unit with a glass substrate and photodiode to image fingerprints and palm areas without direct light irradiation, incorporating a dielectric layer and reflective sheet for efficient light management and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical type fingerprint recognition sensors use optical lenses to process optical images, then imaging quality is improved, but device volume increases and manufacturing complexity increases
Solution Approach 1:
The patent merges the optical lens function with the TFT panel by utilizing the panel's own transparent electrode and pixel structure as the imaging element. The transparent electrode serves dual purposes: as an electrode for the display function and as a transparent lens for optical image processing, eliminating the need for separate optical lenses and reducing device volume.
Solution Approach 2:
The TFT panel is designed to perform multiple functions simultaneously: display function through the pixel structure and optical imaging function through the same transparent electrode and pixel array. This multi-functionality allows the device to eliminate separate components for imaging, thereby reducing overall device volume while maintaining imaging quality.
2Volume of stationary object
If capacitance type fingerprint recognition sensors are used to reduce device volume, then device volume is reduced, but reliability decreases due to contamination from direct contact
Solution Approach 1:
The patent introduces an optical field as an intermediary between the finger and the sensor. Light passes through the transparent TFT panel to capture the fingerprint image without requiring direct contact between the finger and the sensing elements. This optical mediation maintains reliability by preventing contaminant adhesion while still enabling fingerprint recognition.
Solution Approach 2:
The patent replaces the mechanical contact-based capacitance sensing system with an optical imaging system. Instead of using direct contact to detect capacitance changes, the system uses light transmission and imaging through the transparent TFT panel, thereby eliminating the contamination issue associated with mechanical contact while maintaining compact device volume.
3Measurement precision
If conventional palm recognition devices use separate light sources and image capturing mechanisms, then imaging capability is improved, but device complexity and volume increase
Solution Approach 1:
The patent combines the light source, optical path, and image capturing functions into a single integrated TFT panel structure. The transparent electrode and pixel array serve both as the light modulation element and the image sensor, eliminating the need for separate light sources and capturing mechanisms while maintaining imaging capability.
Solution Approach 2:
The TFT panel is designed to perform multiple functions simultaneously: the pixel structure serves as both the display element and the image sensor, while the transparent electrode functions as both an electrical conductor and an optical element. This multi-functionality reduces device complexity by eliminating separate components for lighting and imaging.
4Measurement precision
If optical lenses are used in fingerprint recognition sensors, then imaging precision is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent merges the optical lens function with the TFT manufacturing process by utilizing the existing transparent electrode and pixel structure as the imaging element. This integration allows the optical imaging function to be achieved through standard TFT manufacturing techniques without requiring separate precision optical lens manufacturing and assembly processes.
Solution Approach 2:
The patent replaces the mechanical optical lens system with an integrated optical-electronic system based on the TFT panel structure. This substitution enables imaging precision to be achieved through semiconductor manufacturing processes, which are more suitable for mass production and offer better manufacturing ease compared to precision optical lens fabrication and alignment.
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 TFT panel sensor achieves a significantly simplified structure, enabling imaging of both fingerprints and palmar areas with improved image quality and reduced size, minimizing light dispersion and contamination risks, while maintaining durability and resolution.
Implementation Method 1
a total reflection unit configured to totally reflect light emitted from a light source
Implementation Method 2
a photodiode configured to sense light reflected from the total reflection unit
Data Source
AI summary
The present invention relates to a TFT panel type fingerprint recognition sensor comprising: a total reflection unit for totally reflecting light emitted from a light source; a photodiode for detecting light reflected through the total reflection unit; and a TFT panel for processing voltage output from the photodiode so as to perform imaging.