Digital Image Sensor Read-Out Control for Exposure Management
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Solution Overview
Problem
Digital image sensors with rolling shutters and global resets face issues with overexposure and underexposure due to varying ambient light conditions, particularly in applications like face recognition and eye tracking, where cost and complexity need to be minimized.
Innovation Solution
A method that dynamically adjusts the read-out scheme by increasing pixel binning and/or skipping based on exposure values, allowing for adaptive exposure control to prevent saturation and underexposure, using a processor to set read-out schemes that optimize pixel binning and skipping levels in response to ambient light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a rolling shutter with global reset is used to reduce sensor complexity and cost, then device complexity is reduced, but overexposure and underexposure occur due to varying exposure times across pixels
Solution Approach 1:
The patent applies dynamics by making the read-out scheme adaptive and changeable based on real-time exposure conditions. The system dynamically adjusts pixel binning levels and read-out patterns according to detected exposure values, transforming a static rolling shutter configuration into a dynamic system that can respond to varying light conditions and prevent overexposure/underexposure issues
Solution Approach 2:
The patent changes the parameter of pixel binning level from a fixed state to a variable state. By adjusting the binning level (combining different numbers of pixels) based on exposure feedback, the system modifies the effective read-out parameters to maintain exposure uniformity across the sensor array while using a simpler rolling shutter architecture
2Reliability
If pixel binning and skipping are increased to prevent overexposure in bright conditions, then overexposure is avoided, but image quality and resolution deteriorate
Solution Approach 1:
The system dynamically adjusts the binning level based on real-time exposure detection. When exposure values indicate overexposure risk, the system increases binning to reduce individual pixel exposure; when lighting conditions improve, it reduces binning to restore image quality. This dynamic adaptation allows the system to maintain both exposure reliability and image quality across varying conditions
Solution Approach 2:
The patent implements feedback control by continuously monitoring exposure values from the sensor and using this information to adjust subsequent read-out parameters. The exposure value calculated from intensity values feeds back into the control logic that determines the next binning level, creating a closed-loop system that balances exposure reliability with image quality preservation
3Manufacturing precision
If read-out time is increased to improve image quality, then image quality improves, but saturation occurs in bright ambient light conditions
Solution Approach 1:
The system performs preliminary exposure assessment by calculating exposure values from intensity data before committing to a full read-out at a given binning level. This preliminary action allows the system to predict potential saturation and adjust the read-out parameters in advance, preventing saturation before it occurs while preserving image quality through appropriate binning selection
Data Source
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AI summary
A computer implemented method for controlling read-out from a digital image sensor device (1), comprising a plurality of pixels (2), the method comprising the steps of setting a first read-out scheme, based on a first level of pixel binning and/or pixel skipping, reading, based on the first read-out scheme, from the digital image sensor device (1), a first image, determining an exposure value for the first image, based on the intensity value of each one of the first plurality of regions (6, 7, 8) of the first image and comparing the exposure value with a predetermined maximum value. A second read-out scheme based on a second level of pixel binning and/or pixel skipping is set. The level of pixel binning and/or pixel skipping in the second read-out scheme is increased compared to the first read-out scheme, if the exposure value is higher than the predetermined maximum value. Based on the second read-out scheme, a subsequent second image is read. A system configured to perform the method is also described.