Rolling Shutter Sensor Pulsed Light Timing
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Solution Overview
Problem
Rolling shutter image sensors face limitations in achieving high frame rates when used with pulsed light, as they can only capture light during sensor blanking time, leading to a compromise between frame rate and pulse duration, and result in a low signal-to-noise ratio due to pulsing only during a fraction of the frame integration time.
Innovation Solution
The system employs pulsed light patterns and algorithmic reconstruction techniques to decouple signals from individual illuminations by timing pulsed illumination differently frame-to-frame, allowing light to be captured by at least two sequential frames, thereby eliminating blanking time and increasing the frame rate and signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rolling shutter captures pulsed light only during blanking time, then frame rate can be maintained, but pulse duration is limited and signal-to-noise ratio decreases
Solution Approach 1:
The patent applies periodic action by implementing a pulsed illumination scheme where light is emitted in periodic pulses during the integration period. Multiple pulses are delivered across different rows of the rolling shutter sensor, with each pulse synchronized to the row integration timing. This periodic pulsed illumination allows the system to maintain high frame rates while accumulating sufficient light signal over the extended integration period, effectively resolving the contradiction between fast frame rate and adequate pulse duration for signal-to-noise ratio.
2Device complexity
If rolling shutter uses sequential row-by-row readout, then device complexity is reduced, but frame rate is limited during pulsed light imaging
Solution Approach 1:
The patent applies dynamics by making the illumination timing adaptive to the rolling shutter readout progression. The pulsed illumination is dynamically synchronized with the sequential row integration process, where pulse timing and duration are adjusted for each row based on its integration window. This dynamic synchronization allows the simple rolling shutter structure to achieve high frame rates in pulsed light imaging by optimizing the illumination pattern to match the temporal characteristics of sequential readout.
3Reliability
If pulsed illumination is used during blanking time only, then clean illumination within frames is achieved, but signal-to-noise ratio is reduced
Solution Approach 1:
The patent applies preliminary action by delivering pulsed illumination during the integration period before the readout of each row begins. The illumination pulses are timed to occur during the integration window, ensuring that the light signal is captured during the sensitive period. This preliminary illumination action, combined with the rolling shutter's natural blanking during readout, achieves both clean illumination within frames and sufficient signal accumulation for high signal-to-noise ratio.
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 enables the highest frame rate operation of rolling shutter image sensors while maintaining clean illumination within frames, enhancing image quality and capturing richer information by combining multiple frames under different illumination conditions.
Implementation Method 1
a photodetector positioned to receive light from the scene; and a controller operatively coupled to the light engine and the photodetector
Data Source
AI summary
An imaging system and method for imaging a scene using a rolling shutter are described. In an embodiment, the method includes illuminating a scene with first and second illumination light; generating frame signals with a photodetector comprising a plurality of pixels arranged in a plurality of rows, wherein the frame signals are based on light received from the scene with sequentially integrated rows of pixels of the plurality of rows, and wherein a frame signal includes signals from pixels of each of the plurality of rows; and generating images of the scene based on an intensity of the frame signals and the proportion of the first illumination light and the second illumination light emitted onto the scene during the first and second frames, wherein a proportion of the first illumination light and the second illumination light in a first frame is different than in a second frame.