HDR Imaging via Object-Scene Exposure Segmentation
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Solution Overview
Problem
Conventional CMOS imagers face challenges in capturing high dynamic range images with moving objects, as motion artifacts and edge blurs degrade image quality due to the need for multiple exposures and image registration, which can be time-consuming and prone to errors.
Innovation Solution
The method involves capturing multiple images of a scene over a range of exposure times and a single low dynamic range image of an object, using image processing to merge these images and reduce motion artifacts by generating masked radiance images that isolate the object from the scene, thereby minimizing the impact of object movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple images are captured over a range of exposure times to extend dynamic range, then the dynamic range of the image sensor is extended, but motion artifacts are introduced that degrade image quality
Solution Approach 1:
The patent segments the image capture process into two distinct parts: (1) capturing multiple images of the scene without the object at different exposure times to establish the HDR scene radiance, and (2) capturing a single image of the object at a low exposure time. This segmentation allows the object to be captured with minimal motion artifacts while the scene is captured with extended dynamic range, resolving the contradiction between dynamic range extension and image quality maintenance.
2Illumination intensity
If the sensitivity of the image sensor is adjusted to capture bright areas, then the bright features are captured sufficiently, but the dark features are not captured sufficiently
Solution Approach 1:
The patent performs preliminary action by capturing multiple images of the scene at different exposure times before capturing the object. These pre-captured scene images are used to generate an HDR radiance map that contains information about both bright and dark areas. When the object is later captured at a single low exposure time, the HDR processing can incorporate the pre-acquired scene information to recover dark feature details that would otherwise be lost, thus preventing information loss while optimizing for bright area capture.
3Illumination intensity
If multiple images are captured in rapid succession to extend dynamic range, then the dynamic range is extended, but changes in the scene between captures introduce motion artifacts
Solution Approach 1:
The patent extracts the object from the scene for separate capture. By taking out the object capture from the multi-exposure sequence and performing it separately at a single low exposure time, the method eliminates the need for the object to remain stationary during multiple exposures. This extraction approach reduces the total time the scene must be held static while still achieving HDR extension for the scene portions, thus mitigating motion artifacts without excessive time loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the creation of high dynamic range images with reduced motion artifacts and improved quality by separating object and scene exposures, ensuring accurate representation of both bright and dark areas without the need for extensive motion compensation.
Implementation Method 1
Image sensors typically include an array of optical detectors, such as photodiodes, that generate an electrical response in proportion to the intensity of incident light
Data Source
AI summary
Methods, image processors and imaging devices for capturing a high dynamic range (HDR) image. Multiple images of a scene are captured at respectively different exposure settings. A further image of an object placed in the scene is captured at one exposure setting. A first radiance image is formed from the multiple images. A second radiance image is formed from the further image. The first radiance image and the second radiance image are merged to form the HDR image.