AMOLED Reference Pixel Aging Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Active matrix organic light emitting device (AMOLED) displays face challenges in accurately measuring pixel characteristics for aging compensation, leading to issues like image sticking due to color shifts and uneven luminance, as existing compensation techniques fail to account for temporal and spatial variations in OLED materials with low stability.
Innovation Solution
A system is introduced that includes reference pixels to measure and compensate for aging effects, adjusting the energization levels of subpixels to maintain a constant display white point by measuring voltage and current inputs to OLEDs, and using tables to store compensation factors for non-uniformity, aging, and dynamic effects, allowing for simultaneous compensation of multiple degradation phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pixel calibration is performed during each video frame by changing grayscale values, then compensation for aging effects can be achieved, but visual artifacts occur and OLED aging is accelerated
Solution Approach 1:
The patent applies preliminary action by performing pixel calibration during blanking intervals before the video frame is displayed, rather than during the active display period. This allows compensation data to be prepared in advance without causing visual artifacts or accelerating OLED aging during normal operation.
Solution Approach 2:
The patent introduces an intermediary mechanism by using a separate calibration mode that operates independently from normal video display. This intermediary calibration process allows measurement and compensation without interfering with the primary display function, avoiding visual artifacts and reducing stress on OLEDs.
2Productivity
If OLEDs are constantly driven at full brightness for testing, then pixel functionality can be verified, but accelerated aging occurs and electrical faults may not be detected
Solution Approach 1:
The patent applies parameter changes by varying the drive current and grayscale levels during calibration instead of constantly operating at full brightness. This allows comprehensive pixel characterization across different operating conditions while reducing overall stress and extending OLED lifespan.
Solution Approach 2:
The patent implements periodic action by performing calibration at specific intervals (e.g., during blanking intervals or at scheduled times) rather than continuous full-brightness operation. This periodic calibration approach maintains testing effectiveness while significantly reducing cumulative stress on OLEDs.
3Measurement precision
If reference pixels are added to measure aging effects, then compensation accuracy improves, but device complexity increases
Solution Approach 1:
The patent applies universality by designing reference pixels that share the same drive transistor and OLED structure as active pixels, allowing them to be controlled and measured using the existing pixel circuitry and control infrastructure. This multi-functional approach enables aging measurement without requiring entirely separate measurement systems.
Solution Approach 2:
The patent uses copying by creating reference pixels that are identical copies of active pixel structures, placed in known-good locations that are not subjected to aging stress. These copied reference structures provide a stable baseline for comparing aging effects in active pixels without adding fundamentally new device elements.
4Reliability
If multiple compensation factors are stored in tables, then comprehensive degradation compensation is achieved, but memory requirements and processing complexity increase
Solution Approach 1:
The patent applies segmentation by dividing compensation into separate factors stored in different tables (e.g., gamma correction table, aging compensation table, color shift table). This segmentation allows each compensation aspect to be independently calculated and applied, improving comprehensiveness while enabling modular processing that manages complexity.
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 provides accurate and efficient compensation for aging effects, reducing image sticking and maintaining display quality by dynamically adjusting subpixel brightness to counteract color shifts and luminance variations, thereby extending the lifespan of AMOLED displays.
Implementation Method 1
The OLEDs emit light based on current supplied through a drive transistor
Data Source
AI summary
A voltage-programmed display system allows measurement of effects on pixels in a panel that includes both active pixels and reference pixels coupled to a supply line and a programming line. The reference pixels are controlled so that they are not subject to substantial changes due to aging and operating conditions over time. A readout circuit is coupled to the active pixels and the reference pixels for reading at least one of current, voltage or charge from the pixels when they are supplied with known input signals. The readout circuit is subject to changes due to aging and operating conditions over time, but the readout values from the reference pixels are used to adjust the readout values from the active pixels to compensate for the unwanted effects.