Organic Light Emitting Display Luminance Deviation Compensation
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Solution Overview
Problem
Active matrix organic light emitting displays experience luminance deviation due to changes in electrical characteristics of driving TFTs, particularly because gate signals and initialization states differ between image display and luminance recovery data, leading to uneven luminance between display lines with and without real-time sensing.
Innovation Solution
The display system includes a gate driving circuit and data driving circuit that supply synchronized gate and data pulses to ensure the same pulse shape for both image display and luminance recovery, minimizing luminance deviation by compensating for changes in TFT characteristics using a timing controller that modulates digital data based on the location of the sensing target display line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If real-time sensing is performed during vertical blank period, then compensation performance for TFT electrical characteristic changes is improved, but luminance deviation between display lines with and without sensing occurs
Solution Approach 1:
The patent applies preliminary action by performing luminance recovery data programming before the next image display period begins. During the vertical blank period, the sensing target display line is programmed with luminance recovery data that compensates for TFT electrical characteristic changes, ensuring that when the line becomes active again, the luminance is already corrected. This prevents luminance deviation while maintaining compensation performance.
Solution Approach 2:
The patent changes parameters by adjusting the gate signal waveform and timing for luminance recovery data programming. Specifically, the gate signal for luminance recovery is designed with different timing characteristics compared to normal image display gate signals, allowing the OLED to receive appropriate drive current during recovery while maintaining uniform luminance across all display lines.
2Ease of operation
If gate signals for image display and luminance recovery differ, then sensing operation can be performed, but luminance deviation occurs between image display data and luminance recovery data
Solution Approach 1:
The patent applies equipotentiality by ensuring that the gate signal timing and waveform for luminance recovery data programming are designed to create equivalent electrical conditions to normal image display. The gate signal for luminance recovery is synchronized and timed such that the OLED experiences similar drive conditions, resulting in consistent luminance output despite the different data being programmed.
3Measurement precision
If sensing operation is performed on one display line, then electrical characteristic changes are detected, but emission duty varies across different display lines
Solution Approach 1:
The patent applies local quality by implementing sensing operations on specific sensing target display lines while other lines perform normal image display. Each sensing target line is selectively programmed with luminance recovery data during vertical blank periods, allowing localized compensation without affecting the overall emission duty uniformity across the entire display panel.
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 approach minimizes luminance deviation between display lines with and without real-time sensing by ensuring equal charge levels and pulse shapes for image display and luminance recovery, maintaining consistent luminance across the panel.
Implementation Method 1
When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the hole transport layer HTL and electrons passing through the electron transport layer ETL move to the light emitting layer EML and form excitons. As a result, the light emitting layer EML generates visible light.
Data Source
AI summary
An organic light emitting display includes a display panel including display lines, on which a plurality of pixels each including an organic light emitting diode and a driving thin film transistor (TFT) are formed. The display lines are sequentially charged to an image display data voltage in response to an image display gate pulse in an image display period of one frame. A sensing target display line among the display lines outputs a sensing voltage corresponding to changes in electrical characteristic of the driving TFT included in each pixel in response to a sensing gate pulse during a vertical blank period excluding the image display period from the one frame and then is charged to a luminance recovery data voltage. The sensing gate pulse is supplied in the same pulse shape as the image display gate pulse in a predetermined period for charging the luminance recovery data voltage.