Global Shutter Sensor Motion Artifact Reduction
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Solution Overview
Problem
Advanced image sensors with wide dynamic range (WDR) suffer from motion and flicker artifacts due to differences in exposure times, which are difficult to eliminate without compromising spatial resolution or introducing additional image artifacts.
Innovation Solution
Implementing a global shutter sensor that divides short exposure periods into multiple intervals aligned with long exposure times, allowing for simultaneous charge transfer and accumulation on sampling capacitors, thereby synchronizing both integration periods and canceling out flicker by positioning short exposure intervals at opposite phases of the flicker cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If different pixels are associated with one of a plurality of exposure times to achieve wide dynamic range, then the dynamic range is enhanced, but motion artifacts and flicker artifacts occur due to motion in the scene and short exposures
Solution Approach 1:
The pixel array is divided into first pixels with first exposure times and second pixels with second exposure times, where the exposure times differ by an integer multiple of a reference time. This segmentation allows different pixels to capture different exposure durations simultaneously, enabling WDR while maintaining temporal consistency within each pixel group to reduce motion and flicker artifacts.
Solution Approach 2:
The exposure time parameter is varied across different pixel groups, with first pixels having exposure times of T, 3T, 5T... and second pixels having exposure times of 2T, 4T, 6T..., where T is a reference time. This parameter change strategy enables the sensor to capture both bright and dark regions while the integer multiple relationship ensures that corresponding pixels in different rows complete their exposure cycles synchronously, eliminating motion artifacts and flicker.
2Illumination intensity
If long exposure pixels are combined with short exposure pixels to enhance dynamic range, then the dynamic range is improved, but spatial resolution is reduced
Solution Approach 1:
The pixel array is segmented into different pixel groups with different exposure times, where each group maintains its own complete set of exposure measurements. This segmentation allows the system to preserve spatial resolution by having corresponding pixels in different rows capture the same spatial location with different exposure durations, rather than averaging or downsampling across the entire array.
Solution Approach 2:
Each pixel in the array serves multiple functions: it acts as both a long exposure pixel and a short exposure pixel depending on its group assignment, capturing both bright and dark scene information. This multi-functionality allows the entire pixel array to contribute to both dynamic range enhancement and spatial resolution preservation simultaneously.
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 effectively reduces motion artifacts and eliminates flicker, ensuring that both short and long exposure integrations cover the same scene duration and cancel out flicker signals, resulting in improved image quality without sacrificing spatial resolution.
Implementation Method 1
accumulating a first plurality of charges during a first exposure time from a first plurality of pixels, accumulating a second plurality of charges during a plurality of second exposure times from a second plurality of pixels
Implementation Method 2
Each short integration interval is followed by a transfer of charge, in the short exposure pixels, from a photodiode to a sampling capacitor within the pixel, while long exposure pixels are still under integration
Data Source
AI summary
At least one example embodiment discloses a method of generating an image using a global shutter image sensor. The method includes accumulating a first plurality of charges during a first exposure time from a first plurality of pixels, accumulating a second plurality of charges during a plurality of second exposure times from a second plurality of pixels, the plurality of second exposure times occurring during the first exposure time and being shorter than the first exposure time and generating the image based on the first plurality of charges and the second plurality of charges.