Integrated Pixel Circuit for Parallel Display and Fingerprint Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing organic EL display devices face challenges in simultaneously performing display and sensing operations due to variations in thin-film transistor characteristics, leading to luminance variations and the need for complex circuits that hinder high-definition fingerprint detection and simultaneous display-sensing operations.
Innovation Solution
A pixel circuit with a sensor circuit comprising three or less circuit elements and a read transistor, allowing sensing and display operations to be performed in parallel by maintaining the read transistor in an on state during a predetermined period after the sensing process, using a simplified configuration with seven transistors and one capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pixel circuit with sensing function includes ten transistors, two capacitors, and one photodiode to achieve both display and sensing functions, then sensing function is provided, but the circuit complexity increases and it becomes difficult to achieve high definition display
Solution Approach 1:
The patent merges the display function and sensing function into a single integrated pixel circuit. The sensor circuit shares the control node with the display element, and the read transistor serves dual purposes by reading both display data and sensing signals. This integration reduces the total number of circuit elements from ten transistors and two capacitors to seven transistors and one capacitor, resolving the contradiction between versatility and complexity.
Solution Approach 2:
The read transistor is designed to perform multiple functions: it reads the display data during normal operation and also serves as the sensing transistor during fingerprint detection. The sensor circuit uses the same control node and scanning signal lines as the display circuit, allowing a single circuit structure to fulfill both display and sensing roles without requiring separate dedicated circuits for each function.
2Adaptability or versatility
If display operation and sensing operation are performed in separate frame periods, then sensing function is achieved, but simultaneous display and sensing operations cannot be performed
Solution Approach 1:
The patent employs periodic switching between display mode and sensing mode within each frame period. During the first period, the pixel circuit performs display operation with the drive transistor active. During the second period, the same circuit switches to sensing operation with the read transistor active. This periodic alternation allows both functions to be achieved using the same hardware resources without requiring separate frame periods, thereby enabling simultaneous operation capability while maintaining sensing functionality.
3Ease of manufacture
If thin-film transistors are used as drive transistors in pixel circuits, then the display device can be manufactured, but variations in threshold voltage occur causing luminance variations
Solution Approach 1:
The patent implements a threshold voltage compensation mechanism using a capacitor connected to the control node. During the initialization phase, the capacitor stores the threshold voltage information of the drive transistor. During the display phase, this stored information compensates for threshold voltage variations, ensuring uniform luminance across all pixels. This feedback-based compensation resolves the contradiction between ease of manufacture using thin-film transistors and reliability in terms of luminance uniformity.
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
Enables simultaneous display and sensing operations using a reduced number of elements, improving display quality and enabling high-definition fingerprint detection.
Implementation Method 1
a sensor circuit connected to the control node, including three or less circuit elements, and configured to perform a sensing process
Data Source
AI summary
A pixel circuit with sensing function that can perform sensing operation and display operation in a simultaneous and parallel manner is implemented using a small number of elements. For each pixel circuit (20) there are provided a sensor circuit (22) connected to a control node (NG) and including three or less circuit elements; and a read circuit (24) connected to a second conductive terminal of a drive transistor (T4) and including one read transistor (T9). A sensing process is performed during a period during which a drive current is supplied to an organic EL element (21) depending on a potential at the control node (NG). A sensing result reading process is performed by maintaining the read transistor (T9) in on state during a predetermined period after ending the sensing process.