Lens Shading Correction Modulation for Image Sensors
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Solution Overview
Problem
Digital image sensors in personal electronic devices face challenges in capturing images with high dynamic range and low noise, as they often experience signal clipping and noise issues due to limited dynamic range and small sensor size, leading to loss of image detail and noise suppression that affects rendering quality.
Innovation Solution
The implementation of adaptive auto-exposure strategies and dynamic range compensation techniques that adjust exposure targets and lens shading corrections based on scene illuminance and focus distance, allowing for extended dynamic range capture without multiple exposures, and employing noise filtering to balance signal-to-noise ratio and prevent clipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional auto exposure algorithms adjust exposure parameters to capture the scene, then the exposure is balanced, but signal clipping occurs causing loss of image detail
Solution Approach 1:
The patent applies dynamics by making the lens shading correction gains adjustable and scene-dependent rather than fixed. The system dynamically modulates the gains based on detected scene lux levels and lens focus distance, allowing the correction strength to adapt to different lighting conditions and prevent clipping in various scene configurations
Solution Approach 2:
The patent changes the parameters of lens shading correction by modulating gains as a function of scene illuminance (lux level) and focus distance. Instead of applying fixed correction values, the system adjusts the correction strength based on these varying parameters to optimize image quality and prevent clipping across different shooting conditions
2Reliability
If longer sensor integration time is used to enhance image signal and reduce noise, then signal-to-noise ratio improves, but signal clipping occurs in brightly-lit scenes
Solution Approach 1:
The system dynamically adjusts lens shading correction gains based on real-time scene lux detection, allowing longer integration times in dimly-lit scenes to improve signal-to-noise ratio while preventing clipping in brightly-lit scenes through reduced correction strength when needed
Solution Approach 2:
The patent implements feedback by detecting scene lux levels and using this information to modulate the lens shading correction gains. This closed-loop approach allows the system to respond to actual lighting conditions and adjust correction strength accordingly, optimizing both noise performance and clipping prevention
3Measurement precision
If lens shading correction is applied to correct vignetting and color shading, then image uniformity improves, but noise is amplified in low-light conditions
Solution Approach 1:
The patent makes lens shading correction gains dynamic and scene-dependent, reducing correction strength in low-light conditions to prevent noise amplification while maintaining adequate correction in well-lit scenes where uniformity is more critical
Solution Approach 2:
The system changes the correction parameters (gains) based on scene lux levels, applying stronger correction in bright conditions for uniformity and weaker correction in dim conditions to minimize noise amplification, thus adapting to lighting conditions
4Stability of the object's composition
If fixed lens shading correction gains are used, then correction is consistent, but it does not adapt to different scene lux levels and focus distances
Solution Approach 1:
The patent transforms fixed lens shading correction into a dynamic system that adapts to different scene conditions by modulating gains based on detected lux levels and focus distance, maintaining correction consistency within each condition while adapting across conditions
Solution Approach 2:
The system creates a universal lens shading correction approach that works across multiple scene conditions by making gains dependent on lux level and focus distance, allowing a single correction mechanism to serve multiple lighting and focusing scenarios
Data Source
AI summary
This disclosure pertains to systems, methods, and computer readable media for performing lens shading correction (LSC) operations that modulate gains based on scene lux level and lens focus distance. These gains compensate for both color lens shading (i.e., the deviation between R, G, and B channels) and vignetting (i.e., the drop off in pixel intensity around the edges of an image). As scene illuminance increases, the sensor captures more signal from the actual scene, and the lens shading effects begin to appear. To deal with the situation, the lens shading gains are configured to adaptively ‘scale down’ when scene lux approaches zero and ‘scale up’ when scene lux changes from near zero to become larger. The lens shading gain may also be modulated based on the focus distance. For optical systems without zoom, the inventors have discovered that the amount of lens shading fall off changes as focus distance changes.