Exposure Controller for Artifact-Free High Dynamic Range Imaging
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Solution Overview
Problem
High dynamic range image capture systems face low quality merged images due to artifacts caused by independent exposure settings of dark and bright pixels, which worsen with increasing differences in exposure times between images.
Innovation Solution
The exposure controller sets the first exposure based on pixel intensities and determines a factor to interdependently set the second exposure, ensuring a smooth evolution of exposures as the dynamic range increases, thereby reducing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If independent exposure settings are applied to dark and bright pixels in high dynamic range capture systems, then the dynamic range of the merged image is increased, but artifacts increase and image quality deteriorates
Solution Approach 1:
The patent applies dynamics by making the exposure settings adaptive rather than fixed. The exposure controller dynamically adjusts the exposure of dark and bright pixels based on the actual dynamic range of the scene being captured. This allows the system to maintain optimal image quality across varying scene conditions while still achieving high dynamic range capability when needed.
Solution Approach 2:
The patent changes the exposure parameter dynamically based on scene analysis. The exposure controller modifies exposure times for different pixel groups according to the measured dynamic range, rather than using fixed independent exposure settings. This parameter adaptation reduces artifacts while preserving dynamic range extension benefits.
2Adaptability or versatility
If the difference between first and second exposure times is increased to capture higher dynamic range, then more scene detail is captured, but motion artifacts increase
Solution Approach 1:
The patent dynamically adjusts exposure time parameters based on the measured dynamic range of the scene. When the dynamic range is moderate, the exposure difference between first and second images is reduced to minimize motion artifacts. When the dynamic range is very high, the exposure difference is increased to capture sufficient detail, accepting some artifact risk. This adaptive parameter adjustment resolves the contradiction between dynamic range capture and artifact reduction.
Solution Approach 2:
The system dynamically adapts the exposure time difference based on real-time scene assessment. The exposure controller continuously evaluates the scene's dynamic range requirements and adjusts the exposure parameters accordingly, making the system flexible enough to minimize motion artifacts in low-motion scenarios while maintaining high dynamic range capability when needed.
3Measurement precision
If independent exposure control is used for multiple pixels, then each pixel can be optimized for its intensity range, but the device complexity increases
Solution Approach 1:
The patent segments the pixel array into different groups (dark pixels and bright pixels) that can be exposed independently. This segmentation allows optimization for different intensity ranges while keeping the control mechanism relatively simple by grouping pixels rather than controlling each pixel individually. The exposure controller manages these segments based on scene requirements.
Solution Approach 2:
The exposure controller is designed to universally manage multiple pixel groups with different exposure requirements. Rather than requiring separate control mechanisms for each pixel or group, a single exposure controller handles all pixel groups, adapting its behavior based on the scene's dynamic range characteristics. This multi-functional approach reduces overall system complexity while maintaining optimization capability.
Data Source
AI summary
An image sensor provides a first image with a first exposure and a second image with a second exposure. An exposure controller sets the first exposure in dependence on pixel intensities of at least one of the images. It sets the second exposure in dependence on a factor and the first exposure. The factor is determined in dependence on pixel intensities of at least one of the images.