WDR Image Merging With LED Flicker-Aware Exposure Weighting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current flicker mitigation methods for wide dynamic range (WDR) imaging, particularly in CMOS image sensors, fail to effectively address LED-induced flicker, leading to a permanent loss of dynamic range and image quality issues such as artifacts and inability to differentiate between flicker and actual scene oscillations.
Innovation Solution
A method for WDR image merging that detects flicker based on signal levels across different exposure frames, adjusts pixel data weighting to reduce flicker impact, and sets exposure times to mitigate LED-induced flicker, enabling effective flicker correction even with multiple flickering LED sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If exposure time is constrained to avoid saturation in bright regions, then flicker mitigation is achieved, but dynamic range is permanently lost
Solution Approach 1:
The patent applies dynamics by making the exposure time adaptive rather than fixed. The system dynamically adjusts exposure time based on scene analysis - using longer exposure times when LED flicker is detected and shorter exposure times when it is not present, allowing the camera to optimize between flicker mitigation and dynamic range preservation in real-time
Solution Approach 2:
The patent changes the exposure time parameter dynamically based on detected LED flicker conditions. When flicker is detected, the system increases exposure time beyond the conventional minimum to capture sufficient light during the LED's ON phase, thereby mitigating flicker effects while maintaining image quality
2Object-affected harmful factors
If post-merge image processing is used to remove flicker, then flicker artifacts are reduced, but image quality deteriorates due to artifacts and inability to differentiate flicker from scene oscillations
Solution Approach 1:
The patent performs preliminary flicker mitigation during the WDR merge process rather than as a post-processing step. By detecting LED flicker and adjusting pixel weighting before final image merging, the system prevents flicker artifacts from being embedded in the final image, thereby maintaining image quality while eliminating flicker
Solution Approach 2:
The patent extracts and separates flicker detection and mitigation as distinct functions from the general image processing pipeline. By specifically identifying flicker patterns and handling them separately during the merge process, the system can针对性地 address flicker without applying blanket processing that would degrade overall image quality
3Productivity
If shorter exposure time is used to capture LED light, then WDR imaging is achieved, but LED flicker becomes more prominent
Solution Approach 1:
The patent makes exposure time dynamic based on LED flicker detection. When LED light sources are detected and flicker is present, the system extends exposure time beyond the minimum required for WDR imaging, allowing sufficient light capture during the LED's ON phase while still maintaining WDR capability through the multi-exposure merge process
Data Source
AI summary
A method of WDR imaging. Exposure times (ETs) are set for first and second frames for an image sensor to avoid second frame saturating by setting a second ET>1/a PWM frequency applied to an LED illuminating a scene to generate second longer ET pixel data (PD). The first frame has first PD and a first ET<the second ET. A high and low intensity threshold are calculated from a full well capacity. Raw image signals are obtained originating from the image sensor of the scene. Flicker is detected by comparing the first and second frame intensity values to the high and low threshold to determine whether the first PD is flickering data. A WDR merge is performed by selecting weightings from the first and second PD for each pixel including increasing weighting of the second PD for flicker. A final image is formed from the weighted WDR merge.