Local Tone Curve Resampling for Frame Exposure Consistency
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Solution Overview
Problem
Tone mapping algorithms often result in inconsistent tone mapping of the same object across consecutively captured frames due to changes in framing or object motion, leading to artifacts such as flicker, banding, poor contrast, and saturation.
Innovation Solution
Determine the change in exposure times between frames and apply a local tone curve resampled from a previous frame to match the exposure time of the current frame, mitigating artifacts like frame-to-frame flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If local tone mapping is applied to each frame independently, then the dynamic range compression and spatial detail preservation are improved, but frame-to-frame flicker and banding artifacts occur due to exposure time variations
Solution Approach 1:
The patent pre-calculates and stores tone curves for multiple exposure times. When processing a frame, the system retrieves the appropriate pre-computed tone curve based on the current exposure time, avoiding real-time recalculation and ensuring consistency across frames with the same exposure settings.
Solution Approach 2:
The patent interpolates between discrete tone curves when exposure times change, creating smooth transitions. The system adjusts the tone curve parameters continuously based on exposure time variations, preventing abrupt changes that cause flicker while maintaining adaptability to different lighting conditions.
2Adaptability or versatility
If tone curves are adjusted for each frame based on current exposure time, then exposure adaptability is improved, but computational complexity and processing time increase
Solution Approach 1:
The system pre-computes tone curves for a range of exposure times and stores them for rapid retrieval. This eliminates the need for complex real-time tone curve generation, reducing computational complexity during frame processing while maintaining exposure adaptability through the pre-prepared curve library.
Solution Approach 2:
The patent computes tone curves for more exposure times than strictly necessary (excessive action) and stores them in advance. This allows the system to handle any exposure time variation without performing additional computations, trading some memory usage for reduced processing complexity.
3Ease of operation
If the same tone curve is applied across frames with different exposure times, then processing simplicity is maintained, but image quality deteriorates due to inconsistent tone mapping
Solution Approach 1:
The patent changes the tone curve parameters based on exposure time variations. By adjusting the curve characteristics to match the current exposure conditions, the system maintains processing simplicity through automated parameter selection while achieving consistent and accurate tone mapping across frames with different exposure settings.
Data Source
AI summary
Disclosed herein are a system, method, and computer program product embodiments for generating an exposure-adjusted frame based on local tone curve sampling. In some embodiments, a change in exposure times between a first frame captured by an image sensor and a second frame captured by an image sensor subsequent to the first frame may be determined. Different local tone curve resampling techniques may be performed based on whether the change is an increase or decrease in exposure times. Such techniques may resample local tone curves generated for the first frame to match the exposure time of the second frame. The resampled local tone curves, when applied to the second frame, mitigate various artifacts in the second frame, such as frame-to-frame flicker.