OLED Pixel Compensation via Dynamic Measurement Resistor
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Solution Overview
Problem
Variations in characteristics of driving transistors in active matrix OLEDs lead to moiré patterns and deteriorated image quality due to differences in threshold voltage and mobility, necessitating precise compensation to improve image quality.
Innovation Solution
A display device with a compensator that measures and calculates pixel currents to determine actual threshold voltage and mobility of driving transistors, using a measurement resistor to convert currents into voltages and control resistance values based on voltage differences, and a method to transmit these values to adjust data voltages for image data compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large panel is used to increase display area, then the display area is improved, but variations in characteristics of driving transistors increase causing moiré patterns
Solution Approach 1:
The patent applies preliminary action by measuring the characteristics of driving transistors before normal display operation and pre-calculating compensation values. The compensator measures threshold voltage and mobility of each pixel's driving transistor during a test period, then stores compensation data in advance. This allows the system to correct for transistor variations before they cause visible moiré patterns, enabling large panel displays to maintain uniformity across the entire display area.
2Device complexity
If simple current measurement is used to reduce complexity, then device complexity is reduced, but measurement precision of pixel currents deteriorates
Solution Approach 1:
The patent introduces an intermediary measurement resistor connected between the pixel circuit and ground. This resistor converts the pixel current into a measurable voltage signal without requiring complex current sensing circuitry. The voltage across the measurement resistor is proportional to the pixel current, allowing accurate measurement while keeping the overall system simple. This intermediary approach enables precise current measurement for compensation purposes without adding significant complexity to the display device.
3Device complexity
If measurement resistor resistance value is fixed to simplify control, then control complexity is reduced, but measurement precision across different gray scale levels deteriorates
Solution Approach 1:
The patent implements a dynamic measurement resistor whose resistance value changes based on the gray scale level being measured. The control unit adjusts the measurement resistor's resistance according to the applied data voltage level, ensuring optimal voltage signal strength across different gray scale ranges. This dynamic adjustment allows the system to maintain high measurement precision whether measuring bright or dark pixel states, improving overall compensation accuracy without requiring overly complex fixed-resolution measurement circuits.
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
Accurately compensates for variations in driving transistor characteristics, enhancing image quality by precisely adjusting threshold voltage and mobility, thereby reducing moiré patterns and improving overall display performance.
Implementation Method 1
the measurement resistor to convert the first pixel current corresponding to the first data voltage into a first measured voltage and the second pixel current corresponding to the second data voltage into a second measured voltage
Data Source
AI summary
A display device includes a plurality of pixels, each of said plurality of pixels includes a driving transistor and a light emitting diode, a compensator to receive first and second pixel currents generated by the plurality of pixels according to first and second data voltages respectively applied to the plurality of pixels, the compensator to calculate an image data compensation amount to compensate for variations in characteristics of the driving transistor of each of said plurality of pixels and a data selector to transmit the first and second data voltages to the plurality of pixels and to transmit the first and second pixel currents to the compensator, the compensator to measure the first and second pixel currents generated as a result of the first and second data voltages corresponding to different gray scale levels and to calculate an actual threshold voltage and mobility of the driving transistor of each of the pixels, the compensator including a measurement resistor, the compensator to control a resistance value of the measurement resistor, the measurement resistor to convert the first pixel current corresponding to the first data voltage into a first measured voltage and the second pixel current corresponding to the second data voltage into a second measured voltage.