Line-Interleaved Image Sensor Dynamic Exposure Control
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Solution Overview
Problem
Line-interleaved image sensors face challenges in capturing high dynamic range images due to noise in short exposure frames, which can result in motion-induced artifacts and noisy bright regions, as it is difficult to distinguish scene motion from noise.
Innovation Solution
The pixel array is logically split into two or more spatial subarrays, with a long exposure subarray exposed for the entirety of a frame interval and a short exposure subarray exposed in multiple subframes, allowing for conditional readout based on charge threshold, dynamically adjusting exposure time to reduce noise in low-light regions without compromising dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If short exposure is used to capture bright regions, then dynamic range is improved, but noise increases causing motion-induced artifacts
Solution Approach 1:
The pixel array is divided into multiple subarrays (first subarray and second subarray) that are exposed at different time intervals. The first subarray is exposed during a first time interval while the second subarray is exposed during a second time interval, allowing each subarray to be optimized for different exposure durations to capture both dark and bright regions without noise artifacts.
Solution Approach 2:
The patent implements dynamic exposure control where different portions of the pixel array are exposed for different durations. The first subarray uses a first exposure duration while the second subarray uses a second exposure duration, enabling adaptive exposure timing that optimizes both dynamic range and image quality by matching exposure time to local scene requirements.
2Reliability
If long exposure is used to reduce noise, then image quality improves, but bright regions become saturated
Solution Approach 1:
The pixel array is segmented into multiple subarrays with different exposure characteristics. The first subarray is exposed for a longer duration to capture dark regions with low noise, while the second subarray is exposed for a shorter duration to prevent saturation in bright regions, thereby maintaining both image quality and dynamic range.
Solution Approach 2:
Different portions of the pixel array are assigned different exposure durations based on their specific imaging requirements. The first subarray uses longer exposure for regions needing noise reduction, while the second subarray uses shorter exposure for regions prone to saturation, achieving local optimization of both image quality and dynamic range.
3Illumination intensity
If line-interleaved pattern is used to expose different rows at different intervals, then dynamic range is improved, but processing complexity increases
Solution Approach 1:
The pixel array is divided into multiple subarrays that can be independently exposed and processed. This segmentation allows for simplified processing of each subarray while maintaining the overall dynamic range benefit of line-interleaved exposure, reducing the complexity compared to processing the entire array uniformly.
Solution Approach 2:
The patent implements dynamic exposure control where different portions of the pixel array are exposed for different durations. The first subarray uses a first exposure duration while the second subarray uses a second exposure duration, enabling adaptive exposure timing that optimizes both dynamic range and image quality by matching exposure time to local scene requirements.
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 reduces low-light noise and extends dynamic range by varying the effective duration of short exposure subframes, maintaining image quality and reducing artifacts.
Implementation Method 1
Each pixel element includes a photodiode
Data Source
AI summary
Photocharge is integrated within a first plurality of pixels of an integrated-circuit image sensor during a first exposure interval. A read-out signal is output from each pixel of the first plurality of pixels upon conclusion of the first exposure interval, each read-out signal indicating a respective level of photocharge integrated within the corresponding pixel during the first exposure interval. Photocharge is also integrated within a second plurality of pixels during a second exposure interval that transpires concurrently with the first exposure interval and has a duration not more than half the duration of the first exposure interval. A read-out signal is output from each pixel of the second plurality of pixels at least twice with respect to the second exposure interval, with each such read-out signal indicating a respective level of photocharge integrated within the corresponding pixel during at least a portion of the second exposure interval.