Elliptical Gain Lens Shading Correction for Image Uniformity
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Solution Overview
Problem
Existing imaging systems suffer from lens shading or vignetting, which causes a brightness decrease towards the periphery of an image due to optical characteristics of the lens, necessitating effective correction methods to enhance image quality.
Innovation Solution
A lens shading correction circuit and method that adjusts the color of each pixel by considering all pixels, using elliptical gain values generated from bi-quadratic functions based on pixel positions, and applies these gains through a series of multipliers and adders to correct for vignetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lens shading correction is applied using traditional methods, then image quality is improved, but power consumption increases and memory requirements increase
Solution Approach 1:
The patent changes the mathematical model parameters from traditional circular or polynomial models to elliptical gain parameters, allowing more accurate representation of lens shading characteristics with fewer parameters. This enables effective correction while reducing computational complexity and power consumption
Solution Approach 2:
The patent extracts only the essential elliptical gain parameters needed for correction, storing them in a compact form. This extraction of critical parameters reduces memory requirements while maintaining correction effectiveness, avoiding storage of large correction tables
2Manufacturing precision
If lens shading correction is applied using traditional methods, then image quality is improved, but device complexity increases
Solution Approach 1:
The patent simplifies the correction model by using elliptical gain parameters instead of complex polynomial or lookup table approaches. This parameter change reduces the number of computational operations required while maintaining correction accuracy, thereby reducing circuit complexity
Solution Approach 2:
The patent replaces complex mechanical or hardware-based correction mechanisms with a simplified mathematical model implemented in software or firmware. This substitution reduces hardware circuit complexity while achieving the same correction effect
3Illumination intensity
If lens shading correction is applied, then brightness uniformity is improved, but processing time increases
Solution Approach 1:
The patent uses elliptical gain parameters that can be computed with simpler mathematical operations compared to traditional methods. This parameter choice enables faster computation of correction values for each pixel, reducing processing time while maintaining brightness uniformity
Solution Approach 2:
The patent pre-calculates and stores elliptical gain parameters offline, so that during actual image processing, only simple parameter application is needed. This preliminary action separates the complex calculation phase from the real-time processing phase, reducing processing time for live imaging
Data Source
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AI summary
A lens shading correction circuit includes an elliptical gain generation circuit configured to extract a position of a pixel and generate an elliptical gain value using elliptical gain parameters and the extracted position and a multiplier configured to output an output value by multiplying the elliptical gain value by a weight for the pixel. The lens shading correction circuit corrects the lens shading based on the first output value and a gain increment value.