Pixel Circuit Optical Fingerprint Sensing Noise Reduction
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Solution Overview
Problem
Integrated pixel circuits face challenges in accurately identifying fingerprints due to interference from direct light not reflected by the fingerprint, which reduces the fingerprint identification rate, especially when the pixel circuit and fingerprint identification circuit are closely integrated.
Innovation Solution
A pixel circuit with a self-light emitting element, two light-receiving elements, and a pixel control circuit that generates an output signal by differentiating the signals from both light-receiving elements, using transistors and capacitors to remove noise and maintain output voltage around VREF/2, thereby reducing the impact of direct light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pixel circuit and fingerprint identification circuit are integrated, then the device complexity is reduced and manufacturing is simplified, but the fingerprint identification accuracy deteriorates due to direct light interference
Solution Approach 1:
The light-receiving element is divided into multiple sub-elements (first light-receiving element and second light-receiving element) that separately detect different light components. This segmentation allows the circuit to distinguish between direct light and fingerprint-reflected light, maintaining identification accuracy while keeping the integrated structure.
Solution Approach 2:
The patent introduces intermediate signal processing components (transistors and capacitors) that act as mediators to separate and process signals from different light-receiving elements. These intermediaries enable the differentiation of direct light and fingerprint light signals, resolving the accuracy issue while maintaining integration.
2Area of stationary object
If the pixel circuit and fingerprint identification circuit are integrated, then the area is reduced, but the fingerprint identification rate deteriorates due to light interference from glass and electrodes
Solution Approach 1:
By segmenting the light-receiving element into multiple sub-elements positioned to receive different light paths, the patent enables the compact integrated structure to differentiate between light reflected from glass/electrodes and light reflected from the fingerprint, maintaining high identification rate in reduced area.
Solution Approach 2:
Different regions of the light-receiving element are assigned different functions: some regions detect direct light and interference light, while others detect fingerprint-reflected light. This local differentiation allows the compact structure to maintain high identification accuracy despite the reduced area and integrated design.
3Illumination intensity
If the light-receiving element receives direct light from outside or self-emitting element, then the illumination intensity increases, but the fingerprint identification accuracy deteriorates due to noise signal
Solution Approach 1:
The patent extracts and separates the noise signal component (direct light) from the useful signal component (fingerprint-reflected light) by using multiple light-receiving elements with different reception characteristics. This extraction allows the circuit to eliminate the harmful direct light signal while preserving the fingerprint identification signal, maintaining accuracy despite high illumination intensity.
Solution Approach 2:
The circuit uses feedback mechanisms through transistors and capacitors to dynamically adjust and subtract the direct light signal component from the total received signal. This feedback process enables the system to maintain accurate fingerprint identification even when direct light intensity is high, by continuously compensating for the noise signal.
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 effectively prevents output voltage clipping and enhances fingerprint identification accuracy by using differential signals to distinguish between light reflected from the fingerprint and external light, improving the fingerprint identification rate.
Implementation Method 1
a light-receiving element which receives light emitted from the self-light emitting element and reflected from a fingerprint of a user and converts it into a photocurrent
Data Source
AI summary
Disclosed are a pixel circuit comprising an optical fingerprint sensing circuit, a method of driving a pixel circuit comprising an optical fingerprint sensing circuit, and a display device comprising a pixel circuit comprising an optical fingerprint sensing circuit. According to the present disclosure, the pixel circuit comprising an optical fingerprint sensing circuit comprises a pixel control circuit, the pixel control circuit comprising: a first photodetector which receives a light and generates a first signal; a second photodetector which receives a light and generates a second signal; and a self-illuminator which receives differential signals of the first signal and second signal and outputs an output signal, includes at least one transistor component and at least one capacitor component, and outputs a light on the basis of a data signal.