Frequency-Based Color Shading Profile for Lens Correction
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Solution Overview
Problem
Existing lens shading correction methods are inefficient in adapting to variations in image sensor units and light sources, leading to inconsistent image quality, particularly in live video systems, due to sensor and lens variations, and are often complex to implement.
Innovation Solution
The implementation of a frequency-based color shading profile that uses amplitude and phase parameters from hue distributions to correct for brightness and color shading, allowing for adaptive lens shading correction by analyzing low-frequency signals and filtering out high-frequency noise, enabling efficient and cost-effective image enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dynamic lens shading correction is employed using auto white balance mechanism for color temperature prediction, then color temperature prediction is achieved, but accuracy is insufficient and same color of different wavelength issues remain unresolved
Solution Approach 1:
The patent changes the parameter basis for correction from auto white balance color temperature prediction to frequency-based chrominance shading profile parameters (amplitude and phase). By transforming the correction approach to use frequency domain parameters derived from chrominance shading analysis, the system achieves more accurate color correction that addresses both color temperature and wavelength differentiation issues simultaneously.
2Reliability
If adaptive lens shading correction techniques are used to predict color temperature according to image content, then high performance in removing lens shading is achieved, but implementation complexity increases
Solution Approach 1:
The patent extracts only the essential frequency-based chrominance shading profile parameters (amplitude and phase) from the complex adaptive correction techniques. By taking out only the critical frequency domain parameters needed for correction and discarding unnecessary complex image content analysis steps, the system maintains high lens shading removal performance while significantly reducing implementation complexity.
3Ease of manufacture
If lookup tables with correction values for each pixel are used, then lens shading correction is applied, but adaptability to sensor and lens variations is poor
Solution Approach 1:
The patent transitions from static lookup tables to dynamic frequency-based chrominance shading profile parameters. The amplitude and phase parameters are derived adaptively from actual image chrominance shading characteristics, allowing the correction system to dynamically adjust to different sensor and lens variations while maintaining implementation simplicity through parameter-based correction.
Data Source
AI summary
Methods and apparatus for providing adaptive lens shading correction in at least a portion of a shaded image frame perform luminance lens shading correction for a portion of the shaded image frame and detect a color flat area in the shaded image. The methods and apparatus generate a frequency-based color shading profile that includes color shading parameters including an amplitude parameter and phase parameter corresponding to hue distributions from experimental shading data and generate an unshaded image by performing color shading correction on the detected color flat areas of the shaded image frame using the color shading parameters.