Synchronized Pulsed Illumination for Rolling Shutter Temporal Shear
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Solution Overview
Problem
Low-cost CMOS image sensors with rolling shutters introduce temporal shear in image frames, causing artifacts in imaging of moving objects due to asynchronous light capture across the frame.
Innovation Solution
An illumination system with a controller that actuates radiation sources in a pulsed mode to synchronize with the rolling shutter of CMOS image sensors, ensuring each area of the scene is illuminated only during the exposure period of corresponding sensor elements, enhancing the signal-to-background ratio without increasing average power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a rolling shutter is used to capture images sequentially across sensor rows, then the device complexity is reduced and cost is lowered, but temporal shear artifacts appear in images of moving objects
Solution Approach 1:
The illumination system uses periodic pulsed illumination synchronized with the rolling shutter exposure timing. Each row of sensor elements receives illumination only during its specific exposure period, creating a periodic illumination pattern that matches the periodic scanning of the rolling shutter. This synchronized periodic action eliminates temporal shear artifacts while maintaining the simple rolling shutter structure.
2Measurement precision
If continuous illumination is used during exposure periods, then the signal-to-background ratio is improved, but the average power consumption increases
Solution Approach 1:
Instead of continuous illumination, the system uses periodic pulsed illumination that is synchronized with the rolling shutter exposure periods. The illumination is turned on only during the brief exposure windows when each row of sensor elements is actively capturing light, and turned off during the readout periods. This periodic illumination maintains high signal-to-background ratio during exposure while dramatically reducing average power consumption compared to continuous illumination.
Solution Approach 2:
The illumination timing is pre-synchronized with the rolling shutter exposure schedule. Each illumination pulse is activated in advance of or exactly during the exposure period of its corresponding sensor row, ensuring that illumination is present only when needed for signal capture. This preliminary timing coordination optimizes the signal-to-background ratio without requiring continuous power delivery to the illumination sources.
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
The solution effectively reduces ambient radiation collection during exposure periods, improving the signal-to-background ratio and minimizing artifacts in images captured with rolling shutter CMOS image sensors.
Implementation Method 1
an illumination assembly, including a plurality of radiation sources and projection optics, which are configured to project radiation from the radiation sources onto different, respective regions of a scene
Implementation Method 2
An imaging assembly includes an image sensor and objective optics configured to form an optical image of the scene on the image sensor
Data Source
AI summary
Imaging apparatus includes an illumination assembly, including a plurality of radiation sources and projection optics, which are configured to project radiation from the radiation sources onto different, respective regions of a scene. An imaging assembly includes an image sensor and objective optics configured to form an optical image of the scene on the image sensor, which includes an array of sensor elements arranged in multiple groups, which are triggered by a rolling shutter to capture the radiation from the scene in successive, respective exposure periods from different, respective areas of the scene so as to form an electronic image of the scene. A controller is coupled to actuate the radiation sources sequentially in a pulsed mode so that the illumination assembly illuminates the different, respective areas of the scene in synchronization with the rolling shutter.