Vehicle Camera Exposure Control for Motion Blur and Contrast
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Solution Overview
Problem
Existing exposure control methods for vehicle cameras, especially in driver assistance systems, face challenges in reliably detecting objects under varying lighting conditions and high-speed motion, leading to blurring and low-contrast images.
Innovation Solution
A method for exposure control that dynamically adjusts exposure time based on ambient brightness and vehicle speed, using a combination of optimal and short exposure times to maintain image quality for multiple driver assistance functions, such as lane detection and traffic sign recognition, by recording intermediate images with shorter exposure times when optimal times exceed a threshold, and alternating exposure frames to prevent motion blur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a long exposure time is used to improve image brightness and contrast in low-light conditions, then image quality for lane detection is improved, but motion blur increases and traffic sign recognition reliability deteriorates
Solution Approach 1:
The patent divides the single image recording task into two separate recordings: one with long exposure time for lane detection and one with short exposure time for traffic sign recognition. This segmentation allows each function to receive optimized image data without compromise.
Solution Approach 2:
Different parts of the image data are processed with different exposure characteristics. The lane detection function receives data optimized for brightness and contrast (long exposure), while traffic sign recognition receives data optimized for sharpness and detail (short exposure). Each function gets locally optimized quality.
2Reliability
If a short exposure time is used to reduce motion blur and improve traffic sign recognition, then traffic sign detection reliability is improved, but image contrast and brightness deteriorate
Solution Approach 1:
The patent separates the imaging requirements into two distinct recording operations, allowing traffic sign recognition to use short exposure time for sharpness while lane detection uses long exposure time for contrast, eliminating the trade-off.
Solution Approach 2:
The short exposure time is applied specifically to the portion of image data needed for traffic sign recognition, while the long exposure time is applied to the portion needed for lane detection. Each function receives locally optimized image quality.
3Device complexity
If a single optimal exposure time is used for all driver assistance functions, then processing complexity is reduced, but image quality cannot be optimized for different functions simultaneously
Solution Approach 1:
The patent segments the image acquisition process into multiple exposures with different parameters, allowing each driver assistance function to receive optimally exposed image data. This segmentation increases acquisition complexity but reduces processing complexity by providing pre-optimized data.
Solution Approach 2:
The exposure time parameter is changed between different image recordings to optimize for different functions. The system dynamically adjusts the exposure parameter based on the specific driver assistance function being served, improving overall reliability.
Data Source
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AI summary
A method for controlling the exposure of a camera system in a motor vehicle is provided. The camera system is used to record a sequence of images of the surrounding area of the vehicle with an optimal exposure time. The optimal exposure time is specified as a function of the ambient brightness or the brightness of individual objects in the image. At least one interim image is recorded with a short specified exposure time, which is to say an exposure time that is shorter than the optimal exposure time, if the optimal exposure time is longer than a specified threshold value. At least two driver assistance functions are carried out based on the image data of the camera system. For a first driver assistance system, the image data recorded with the optimal exposure time is used, and for a second driver assistance system the image data recorded with the shorter exposure time are used.