CMOS Rolling Shutter Global Image Capture via Strobed Illumination
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Solution Overview
Problem
CMOS pixel arrays using electrical rolling shutters face image distortion issues due to relative movement between the pixel array and stationary objects during image acquisition, as different rows integrate at different times, leading to artifacts in the image.
Innovation Solution
Implementing a method to acquire global shutter-type video images by using an electrical rolling shutter with strobed light, where all rows of the CMOS pixel array integrate concurrently by controlling the light source to be on during vertical blanking periods and off during image frame readout, effectively mimicking a global shutter operation without the need for additional transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electrical rolling shutter is used to control image acquisition, then image data can be read out sequentially from multiple rows, but image distortion occurs due to relative movement between pixel array and object during integration
Solution Approach 1:
The patent applies preliminary action by using a global shutter mechanism to capture all rows of pixels simultaneously at the start of the integration period, before any relative movement occurs. This ensures that all pixels integrate over the same time window, eliminating distortion caused by movement during sequential row integration in rolling shutter mode.
Solution Approach 2:
The patent segments the pixel array into multiple rows that can be independently controlled, then uses a global shutter to activate all segments simultaneously for integration. After simultaneous capture, the data from different rows are read out sequentially, combining the benefits of global capture with the efficiency of sequential readout.
2Manufacturing precision
If global shutter is implemented to eliminate image distortion, then all pixels integrate simultaneously, but device complexity increases due to additional control circuitry
Solution Approach 1:
The patent makes the control circuitry universal by using a single global shutter control signal that simultaneously activates all rows of pixels. This multi-functional approach allows one control mechanism to manage the entire pixel array, reducing the need for separate control circuits for each row while still achieving simultaneous integration.
Solution Approach 2:
The patent merges the control functions for multiple rows into a single global control signal. Instead of having independent control circuits for each row, the design combines them into one unified shutter control mechanism that activates all pixels simultaneously, thereby reducing overall device complexity while maintaining image quality.
3Productivity
If sequential row-by-row integration is used, then readout circuitry can process data efficiently, but relative movement during integration causes distortion artifacts
Solution Approach 1:
The patent applies preliminary action by capturing all row data simultaneously at the beginning of the integration period using a global shutter, before any relative movement occurs. This ensures that the data reflects the object's state at a single moment in time, eliminating distortion artifacts that would occur if rows were integrated sequentially during movement.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that all pixels are actively integrating simultaneously throughout the entire integration period. This continuous simultaneous capture ensures that no part of the pixel array misses any temporal information, maintaining complete and accurate object representation without distortion.
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 image distortion caused by relative movement, allowing for high-quality video images with minimal artifacts, while maintaining the efficiency of electrical rolling shutter systems and avoiding the size and cost increases associated with traditional global shutters.
Implementation Method 1
Each pixel includes a photodiode PD... the photodiode PD is operable to generate charges (e.g., photogenerated electrons or holes) in response to such light
Data Source
AI summary
A multiple image sensor image acquisition system includes a clock control unit to generate a synchronization clock signal. The synchronization clock signal has a prolonged constant cycle during which the synchronization clock signal is held at a constant level for a period of time corresponding to multiple clock cycles. A first image sensor is coupled with the clock control unit to receive the synchronization clock signal and has a first synchronization unit that is operable to synchronize operation for the first image sensor based on detection of an end of the prolonged constant cycle. A second image sensor is coupled with the clock control unit to receive the synchronization clock signal and has a second synchronization unit that is operable to synchronize operation for the second image sensor based on detection of the end of the prolonged constant cycle. The image sensors are synchronized operationally.