Constant Bracket HDR Imaging for Ghosting Reduction
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Solution Overview
Problem
Conventional digital cameras with small dynamic ranges struggle to capture a wide range of light levels, leading to pixel clipping and ghosting issues when using exposure bracketing for high dynamic range imaging, especially with subject motion.
Innovation Solution
A novel HDR capture sequence involving capturing multiple images at a single under-exposure value, applying local tone mapping, and generating noise-amplification masks to fuse images, reducing ghosting and improving noise characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If exposure bracketing is used to capture multiple images with different exposure values, then high dynamic range imaging is achieved, but ghosting artifacts increase when subject motion is present
Solution Approach 1:
The patent changes the exposure parameter from varying across multiple images to being constant across all captured images. By capturing multiple images at the same exposure value (constant bracket mode) rather than different exposure values, the system eliminates the fundamental cause of ghosting artifacts while still enabling high dynamic range processing through tone mapping and fusion of the constant exposure images
2Illumination intensity
If multiple images are captured with different exposure values, then dynamic range is extended, but frame-to-frame blur increases due to subject motion
Solution Approach 1:
The patent changes the exposure parameter from varying to constant across all captured images. This parameter change ensures that all images are captured with identical exposure settings, eliminating exposure-induced blur variations and enabling consistent frame-to-frame comparison for effective de-ghosting while maintaining extended dynamic range through computational fusion
3Illumination intensity
If conventional HDR techniques are applied, then high dynamic range images are produced, but processing time and power consumption increase
Solution Approach 1:
The patent captures more images than traditionally required for HDR (using constant bracket mode with multiple images at the same exposure) to enable more aggressive de-ghosting and tone mapping operations. This excessive capture of images at constant exposure allows for more effective noise reduction and detail recovery in shadow regions, achieving high dynamic range with improved efficiency despite the additional capture steps
Data Source
AI summary
Systems, methods, and computer readable media to capture and process high dynamic range (HDR) images when appropriate for a scene are disclosed. When appropriate, multiple images at a single—slightly underexposed—exposure value are captured (making a constant bracket HDR capture sequence) and local tone mapping (LTM) applied to each image. Local tone map and histogram information can be used to generate a noise-amplification mask which can be used during fusion operations. Images obtained and fused in the disclosed manner provide high dynamic range with improved noise and de-ghosting characteristics.