Display Controller Gamma Correction via Adaptive Interpolation
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Solution Overview
Problem
As image data size increases, the size of the lookup table for gamma correction also grows, leading to increased errors due to the need for larger reference data storage, especially when using limited bit depth, which results in posterization and discrete brightness changes not appearing smoothly.
Innovation Solution
A display controller with a lookup table and an interpolation circuit that calculates corrected data using either exponential or linear interpolation methods based on reference data, reducing the lookup table size by storing only reference data and interpolating based on a reference value, with exponential interpolation for image data below the reference value and linear interpolation for data at or above it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lookup table size is increased to store more reference data for gamma correction, then the precision of gamma correction is improved, but the device complexity and memory requirements increase
Solution Approach 1:
The patent segments the gamma correction process into two parts: a compact lookup table storing only reference data points, and an interpolation circuit that calculates intermediate values. This segmentation allows the lookup table to remain small while the interpolation circuit provides the necessary precision for gamma correction of any input value.
Solution Approach 2:
The interpolation circuit acts as an intermediary between the compact lookup table and the final gamma-corrected output. It takes reference data from the lookup table and computes precise correction values for any input datum by performing linear interpolation between adjacent reference points, thereby achieving high precision without requiring a large lookup table.
2Device complexity
If only reference data is stored in the lookup table to reduce size, then the device complexity is reduced, but the measurement precision of gamma correction deteriorates due to increased error
Solution Approach 1:
The interpolation circuit serves as an intermediary that recovers precision lost by using a compact lookup table. It computes accurate gamma correction values for any input datum by interpolating between stored reference points, ensuring that the reduced lookup table size does not compromise correction precision.
Solution Approach 2:
The patent changes the approach from storing all possible correction values to storing only reference parameters (key data points). The interpolation circuit then dynamically computes intermediate values based on these parameters, transforming a full-table storage approach into a parameter-based approach that reduces memory usage while maintaining precision.
3Device complexity
If linear interpolation is used for all image data, then the device complexity is reduced, but the manufacturing precision of brightness representation deteriorates in dark portions
Solution Approach 1:
The patent applies different interpolation methods to different regions of the image data range. For dark portions (lower brightness values), it uses exponential interpolation to achieve finer granularity and better match human visual sensitivity. For brighter portions, it uses linear interpolation. This local adaptation of interpolation quality ensures optimal precision where needed while maintaining overall system efficiency.
Solution Approach 2:
The patent changes the interpolation parameter (method type) based on the input datum value. When the input datum is below a reference threshold, exponential interpolation is applied; otherwise, linear interpolation is used. This parameter change allows the system to optimize precision for dark regions without unnecessarily complicating the processing of brighter regions.
Data Source
AI summary
A display controller includes a lookup table configured to store a plurality of reference data and an interpolation circuit configured to calculate a corrected datum by performing correction on an image datum based on the plurality of reference data. The interpolation circuit determines whether the image datum is less than a reference value, calculates the corrected datum using a first interpolation method when the image datum is less than the reference value, and calculates the corrected datum using a second interpolation method different from the first interpolation method when the image datum is equal to or greater than the reference value. When the corrected datum is calculated using the first interpolation method, the interpolation circuit calculates the corrected datum based on a first reference datum, which corresponds to a product of the image datum and the reference value, among the plurality of reference data.