Display Panel Luminance Uniformity via Hierarchical Curve Fitting
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Solution Overview
Problem
Traditional methods for enhancing luminance uniformity in display panels, such as polynomial approximation and demura operations performed by source driver ICs, often fail to achieve satisfactory results due to limited memory capacity and computation ability, leading to poor mura correction outcomes.
Innovation Solution
A method involving an automated optical inspection system to measure luminance of sub-pixels using predetermined AOI luminance codes, generating reference curves, and performing two-stage curve fitting to create data-points fitting functions, followed by demura operation using demura lookup tables to adjust luminance codes for improved uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polynomial approximation is used to fit the relationship between grayscale code and luminance, then the demura operation can be performed, but the fitting accuracy is poor leading to uns satisfactory demura outcome
Solution Approach 1:
The patent changes the parameter representation from direct polynomial coefficients to a hierarchical parameter system consisting of global polynomial parameters and local offset parameters. This allows the system to maintain the simplicity of polynomial approximation while adding local adjustments to improve fitting accuracy for each sub-pixel group, thereby resolving the contradiction between computational simplicity and fitting precision.
Solution Approach 2:
The patent segments the display panel into multiple sub-pixel groups and performs curve fitting separately for each group. By dividing the overall fitting task into smaller segments, the system can capture local luminance variations more accurately while still using efficient polynomial approximation methods, thus improving demura outcomes without excessive computational complexity.
2Ease of operation
If demura operation is performed by source driver ICs with limited memory and computation ability, then the operation can be implemented on-device, but the computation ability is insufficient leading to poor demura result
Solution Approach 1:
The patent segments the demura computation into two distinct phases: an offline fitting phase that generates the hierarchical parameters (which can be performed on a powerful external system), and an online compensation phase that applies the pre-computed parameters using simple polynomial evaluation and offset addition (which can be efficiently executed by source driver ICs). This segmentation resolves the contradiction by moving heavy computation externally while maintaining on-device functionality.
Solution Approach 2:
The patent performs the computationally intensive curve fitting and parameter generation as a preliminary offline action before the actual display operation. By pre-computing the global polynomial parameters and local offset values, the system reduces the online computational burden to simple parameter application, enabling source driver ICs with limited computation ability to perform demura operations effectively.
3Quantity of substance
If simple demura algorithm is implemented due to limited memory capacity of source driver ICs, then the hardware requirements are met, but the demura result is not satisfactory
Solution Approach 1:
The patent extracts the computationally intensive curve fitting and parameter generation processes from the source driver ICs and performs them externally. This extraction allows the source driver ICs to store only the essential hierarchical parameters (global polynomial coefficients and local offsets) rather than storing complex algorithms or large lookup tables, thus reducing memory requirements while maintaining high demura quality through the efficient hierarchical parameter application.
Data Source
AI summary
A method for enhancing luminance uniformity of a display panel that includes multiple sub-pixels for a same color element is proposed to include: measuring, for each of the sub-pixels, luminance at multiple predetermined luminance codes, so as to obtain a plurality of data points; performing a two-stage curve fitting to obtain a fitting function that describes a curve fitting the data points; and performing demura operation on an image to be displayed by the display panel based on the fitting function.