Camera Exposure Control for Video Stability
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Solution Overview
Problem
Existing methods for setting exposure in image capturing devices are inadequate for capturing motion video, as they are designed for single still images and do not address the challenges of varying lighting conditions over extended periods, leading to oscillating exposure settings.
Innovation Solution
A method that calculates exposure settings by determining a temporary exposure value based on signal levels and cost functions, adjusting for saturated pixels to maintain stable exposure across a series of images, using a histogram to reduce processing capacity and prioritize relevant areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exposure settings are automatically calculated based on image data from the image sensor for single still images, then the exposure can be optimized for individual images, but the method causes oscillating exposure settings when capturing motion video or series of images
Solution Approach 1:
The patent segments the exposure control process into two distinct phases: a first exposure value determined by histogram and cost function analysis for optimal image quality, and a second exposure value adjusted specifically for video stability. This segmentation allows each phase to optimize for its specific goal without interfering with the other, resolving the oscillation problem while maintaining exposure optimization.
Solution Approach 2:
The patent implements dynamic adjustment of exposure values based on the capture mode (still image vs. motion video). The system dynamically switches between optimization-driven exposure control for still images and stability-driven exposure control for video sequences, adapting the control strategy to the specific application requirements.
2Measurement precision
If detailed histogram and cost function calculations are performed for every image frame, then accurate exposure determination is achieved, but processing capacity and time consumption increase
Solution Approach 1:
The patent applies partial action by performing complete histogram and cost function calculations only for the first exposure value determination, then using a simplified adjustment process for the second exposure value. This partial application of the full calculation process maintains accuracy where needed while reducing processing burden in subsequent steps.
Solution Approach 2:
The patent performs preliminary histogram analysis and cost function evaluation to determine the first exposure value before capturing the actual image. This preliminary action allows the system to pre-calculate optimal exposure settings based on scene analysis, reducing the need for repeated calculations during actual image capture and processing.
Data Source
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Figure 2
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AI summary
The present invention relates to a device and a method for determining exposure settings in a camera. The method comprises the acts of capturing an image frame by means of an image sensor, the exposure of the capturing is based on an initial exposure value setting, determining a temporary exposure value by finding an exposure value that results in a substantially optimum value when applied to a total cost calculation, wherein the calculating of said total cost from a specific exposure value is based on signal levels at the specific exposure value of image pixels in the captured image frame combined with a cost function, calculating a saturated pixels cost related to the saturated pixels for the captured image at the temporary exposure value, determining a next exposure value by finding a decrease in exposure value, in relation to the temporary exposure value, for which decrease a change in total cost for non-saturated pixels, in relation to the total cost for non-saturated pixels at the temporary exposure value, is substantially equal to the saturated pixel cost calculated at the temporary exposure value, using this determined next exposure value for capturing a new image frame.