OLED Display Calibration via Lookup Tables for Mura Reduction
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Solution Overview
Problem
OLED displays suffer from non-linear brightness response and color shift issues due to manufacturing variations, leading to mura and color artifacts, especially at low brightness levels, caused by uneven current response between red, green, and blue subpixels and parasitic capacitances in the OLED driver circuits.
Innovation Solution
The implementation of a method to calibrate lookup tables (LUTs) for correcting pixel values and brightness levels, using a calibration device to measure and generate LUTs that account for variations in OLED panels, ensuring more linear brightness response and reduced color shift by adjusting the current through each subpixel, thereby improving display uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If OLED displays use current control for brightness, then brightness control precision is improved, but manufacturing variations cause non-linear response and color shift
Solution Approach 1:
The patent applies preliminary calibration during manufacturing to measure and store correction values for each OLED panel's non-linear characteristics. By pre-characterizing each panel's response curve and storing lookup tables (LUTs) with correction data, the system compensates for manufacturing variations before the product reaches the customer, enabling precise brightness control despite panel-to-panel variations.
Solution Approach 2:
The patent transforms the raw non-linear current-to-brightness relationship into a linear controlled parameter by applying correction curves and lookup tables. The system measures actual panel characteristics and creates customized parameter transformations (correction LUTs) that map desired brightness values to actual required current values, effectively linearizing the control response across different panels.
2Use of energy by moving object
If OLED driver circuits operate at low brightness levels, then energy consumption is reduced, but mura and color artifacts become more visible
Solution Approach 1:
The patent implements feedback-based calibration where the actual light output of each OLED panel is measured and used to generate correction data. By continuously monitoring and adjusting for panel-specific non-linearities through stored correction LUTs, the system maintains uniform brightness and color accuracy even at low drive levels where mura and color artifacts would normally be most visible.
3Manufacturing precision
If calibration measurements are performed on all OLED panels, then display uniformity is improved, but calibration time and complexity increase
Solution Approach 1:
The patent segments the calibration process into efficient measurement steps and organizes correction data into lookup tables structured by brightness levels and color channels. By dividing the calibration into discrete measurable parameters (red, green, blue subpixel responses at multiple brightness levels) and storing results in optimized LUT structures, the system achieves comprehensive panel characterization without requiring excessive measurement time.
Data Source
AI summary
A method is provided for controlling display of an image on a display panel of a display device, the method comprising determining a commanded brightness level for the display panel, generating an index look-up table (LUT) and a mura LUT based on the brightness level and a relationship between pixel output and pixel value for each pixel of the display panel for each of a plurality of brightness levels, the relationship determined during a calibration phase and stored in memory of the display device, determining an index value for each pixel of the display panel based on the index LUT, determining a corrected pixel value for each pixel based on the mura LUT and the index value, and sending the corrected pixel value to that pixel within the display device.