EL Display Uniformity Compensation via Gamma Correction
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Solution Overview
Problem
Electroluminescent displays face non-uniformity issues due to variability in light-emitting materials and thin-film transistors, leading to suboptimal brightness and bit depth, with existing solutions requiring extensive memory, computational resources, or reducing dynamic range.
Innovation Solution
A method that measures light-emitting element performance at multiple code values, forms groups to calculate linear transformations, selects the transformation with the preferred difference, and applies it to compensate input signals for improved uniformity, reducing memory and computational requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If linear scaling method is used to correct brightness variations, then display uniformity is improved, but dynamic range and brightness are reduced
Solution Approach 1:
The patent applies gamma correction to transform the display characteristics, changing the parameter of brightness response from linear to power-law relationship. This allows the display to achieve uniformity correction while preserving the full dynamic range and brightness capabilities through the gamma transformation function.
Solution Approach 2:
The patent performs preliminary measurement of each pixel's brightness characteristics during manufacturing, storing these measurements in a lookup table. This preliminary characterization enables the system to apply pre-calculated correction factors during operation, achieving uniformity without reducing overall brightness.
2Manufacturing precision
If complete lookup table is used to characterize each pixel, then uniformity correction is improved, but memory cost increases
Solution Approach 1:
The patent reduces the characterization data from complete lookup tables to simple gamma parameters (gamma value and offset) for each pixel. This parameter reduction maintains uniformity correction capability while dramatically reducing memory requirements from storing thousands of lookup table entries to storing only two parameters per pixel.
Solution Approach 2:
The patent uses a simplified gamma correction model that captures the essential non-linear behavior of OLED pixels without requiring complete characterization at all brightness levels. This partial characterization approach provides sufficient uniformity correction while minimizing memory usage.
3Manufacturing precision
If extensive computational circuitry is used within device controller, then uniformity correction is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex computational circuitry with a simplified digital processing approach using gamma correction formulas. Instead of implementing hardware-based lookup tables or complex algorithms, the system uses straightforward power-law calculations that can be performed with minimal computational resources.
Solution Approach 2:
The patent transforms the uniformity correction problem from requiring extensive computational resources to using simple gamma parameter adjustments. By changing the correction approach to rely on pre-calculated gamma values rather than real-time complex computations, the device complexity is significantly reduced.
4Device complexity
If linear approximation is used to correct pixel response, then computational complexity is reduced, but errors increase at various light levels
Solution Approach 1:
The patent replaces linear approximation with gamma correction, changing the mathematical model from linear to power-law relationship. This parameter change in the correction function accurately models the non-linear response characteristics of OLED pixels across all light levels, eliminating the errors that plague linear approximation methods.
Data Source
AI summary
A method of compensating uniformity of an EL device, having a plurality of light-emitting elements, including providing the EL display; and measuring the performance of one or more light-emitting elements at three or more different code values. At least two different groups of code values are formed from the three or more code values, while calculating a linear transformation for converting an input signal to a compensated signal from the performance measurements for each of the groups. Subsequently, the difference between the measured performance and compensated signal is calculated over the range of code values for each of the groups; while the linear transformation, having a preferred difference, is selected. Additionally an input signal is received and employed with the selected linear transformation to calculate a compensated signal to drive the EL display.