OLED Display Multipixel Sensing for Low Gray Level Compensation
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Solution Overview
Problem
Existing OLED displays face challenges in accurately sensing and compensating for variations in driving properties of pixels, particularly at low gray levels, due to low sensing currents, which limits the ability to compensate for changes in driving properties over time, affecting image quality.
Innovation Solution
The implementation of a multipixel sensing method that simultaneously senses subpixels sharing a common sensing path, allowing for the detection of driving properties at low gray levels by increasing the sensing current through shared REF lines, and storing compensation values to modulate data for each block, thereby stabilizing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single pixel sensing method is used, then the sensing circuit is simple, but the sensing current is too low to accurately detect driving properties at low gray levels
Solution Approach 1:
The patent combines multiple subpixels (e.g., 2×2=4 subpixels) into a sensing unit that shares common sensing paths (REF lines). By merging the sensing currents from multiple subpixels, the total sensing current is increased, enabling accurate detection of driving properties even at low gray levels where individual subpixel currents would be too small.
2Measurement precision
If multiple sensing paths are provided for each subpixel, then sensing accuracy is improved, but circuit complexity and memory capacity increase
Solution Approach 1:
Instead of providing separate sensing paths for each subpixel, the patent merges multiple subpixels to share common sensing paths (REF lines). This reduces the total number of sensing paths required, thereby decreasing circuit complexity and memory capacity while still achieving accurate sensing through combined current measurement.
Solution Approach 2:
The common REF lines serve multiple functions: they are used as sensing paths for multiple subpixels simultaneously, and can be shared between sensing operations and normal display operations. This multi-functionality reduces the need for dedicated separate circuits for each subpixel.
3Measurement precision
If sensing period is extended to increase capacitor charge, then sensing precision is improved, but frame rate and productivity decrease
Solution Approach 1:
By combining sensing currents from multiple subpixels, the patent achieves sufficient charge in the capacitor within the original sampling period. The increased current density from multiple subpixels compensates for the limited sampling time, eliminating the need to extend the sensing period and thus preserving frame rate.
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 enables stable sensing of driving properties at low gray levels and compensates for changes in driving properties over time, improving image quality without significantly increasing memory capacity or circuit complexity.
Implementation Method 1
Each OLED includes an anode, a cathode, and an organic compound layer formed between the anode and the cathode... When a driving voltage is applied to the anode and the cathode, holes passing through the hole transport layer HTL and electrons passing through the electron transport layer ETL move to the emission layer EML and form excitons. As a result, the emission layer EML generates visible light.
Data Source
Figure 1
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Figure 3A~3B
AI summary
An organic light emitting diode display and a method for driving the same are disclosed. The organic light emitting diode display includes a display panel having data lines and gate lines crossing each other, pairs of subpixels having left-right symmetrical structures (P11, P12; P21; P22) each including one or more thin film transistors (TFTs), and sensing paths (16) connected to each pixel of a pair of subpixels, the sensing paths being connected to a sensing circuit (SW2; ADC). The subpixels of the display panel are also arranged in blocks wherein a first block includes a plurality of subpixels having a first TFT structure, and a second block includes a plurality of subpixels having a second TFT structure. Furthermore, the sensing circuit simultaneously senses the plurality of subpixels of the first block through the sensing path and simultaneously senses the plurality of subpixels of the second block through the sensing path.