Image Signal Processor for HDR Noise Reduction Before Merging
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Solution Overview
Problem
Existing image processing systems struggle to capture high dynamic range (HDR) images effectively, as they often result in a signal-to-noise ratio (SNR) dip due to noise heterogeneity, leading to a deterioration in image quality.
Innovation Solution
An image signal processor with a noise reduction circuit, HDR circuit, and post-processing circuit that operates in two modes: one for multiple exposure images and another for a single exposure image, reducing noise before merging to generate an HDR image, thereby minimizing SNR dip and enhancing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple exposure images are merged to generate HDR image, then dynamic range is widened, but signal-to-noise ratio deteriorates due to noise heterogeneity
Solution Approach 1:
The patent applies preliminary noise reduction to individual exposure images before merging them into HDR image. The noise reduction circuit processes each exposure image (first, second, and third exposure images) separately to remove noise, and only then are the cleaned images merged. This preliminary action prevents noise heterogeneity from degrading the final HDR image quality while maintaining the widened dynamic range benefit.
2Reliability
If noise reduction is performed on multiple exposure images before merging, then HDR image quality is improved, but processing time and complexity increase
Solution Approach 1:
The patent segments the noise reduction process by applying it independently to each exposure image (first exposure image, second exposure image, third exposure image) rather than processing them as a single combined operation. This segmentation allows parallel processing of multiple images through dedicated noise reduction circuits, improving HDR image quality while managing processing time through concurrent operations.
Solution Approach 2:
The patent applies noise reduction to all three exposure images (first, second, and third) rather than selecting only one or two. This excessive action ensures that noise is removed from every image contributing to the HDR output, maximizing image quality. The processing time increase is offset by the fact that all images are processed simultaneously through parallel circuits rather than sequentially.
3Reliability
If noise reduction circuit and processing steps are added, then image quality is enhanced, but device complexity and hardware cost increase
Solution Approach 1:
The patent merges multiple noise reduction circuits into a unified HDR processing system. The first, second, and third noise reduction circuits are integrated with the HDR circuit that combines the cleaned exposure images. This merging approach enhances image quality through comprehensive noise reduction while avoiding the complexity of completely separate processing systems, as the circuits work together in an integrated fashion.
Data Source
AI summary
An image signal processor includes a noise reduction circuit, a high dynamic range (HDR) circuit and post-processing circuit. The noise reduction circuit performs noise reduction operation on a plurality of exposure noise images each respectively corresponding to one of a plurality of brightness levels to generate a plurality of exposure clean images in a first operation mode and performs the noise reduction operation on a single noise image corresponding to one brightness level to generate a single clean image in a second operation mode. The HDR circuit merges the plurality of exposure clean images to generate an HDR image in the first operation mode. The post-processing circuit generates an output image by processing the HDR image or the single clean image.