Image Sensor Flicker Mitigation via Phase-Offset Control Signals
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Solution Overview
Problem
Image sensors in electronic devices face inefficiencies in light flickering mitigation due to unnecessarily long integration time periods, which can affect the effectiveness of light flickering mitigation and lead to overflow effects in the floating diffusion region.
Innovation Solution
Implementing control signal generation circuitry that generates control signals with phase offsets between different control signals, allowing for shorter and more resolved integration times by asserting and deasserting control signals during specific phases, thereby enhancing light flickering mitigation capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If image pixels use long integration time periods for light flickering mitigation, then light flickering mitigation capability is improved, but overflow effects occur in the floating diffusion region and charge accumulation efficiency decreases
Solution Approach 1:
The patent segments the integration time period into multiple shorter sub-intervals by using multiple control signals (first control signal and second control signal) that are asserted and deasserted at different phases. This segmentation allows the pixel to perform multiple integration cycles within the total exposure period, preventing overflow in the floating diffusion region while maintaining effective light flickering mitigation through the accumulated charge from multiple cycles.
2Reliability
If image pixels use long integration time periods, then light flickering mitigation is enhanced, but the number of integration cycles within exposure period is reduced
Solution Approach 1:
The patent implements dynamic control of the integration process by using multiple control signals with phase offsets. The first control signal and second control signal are asserted and deasserted at different phases, creating a dynamic integration pattern where multiple shorter integration cycles are performed within the total exposure period. This dynamic approach increases the number of integration cycles while maintaining mitigation effectiveness through cumulative charge accumulation.
3Device complexity
If control signals are asserted and deasserted at the same phase, then control is simplified, but integration time cannot be optimized for flickering mitigation
Solution Approach 1:
The patent employs periodic action by using control signals that are asserted and deasserted in repeated cycles with phase offsets. The first control signal and second control signal operate in periodic patterns where they are asserted during specific phases and deasserted during other phases. This periodic control mechanism enables multiple integration cycles within the exposure period, optimizing light flickering mitigation performance while maintaining systematic control through the repetitive nature of the operation.
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 allows for a larger number of integration times within the same exposure period, reducing the likelihood of overflow effects and improving the capture of flickering light, while maintaining effective charge accumulation and image signal generation.
Implementation Method 1
The rows of image pixels each contain a photodiode for generating charge in response to image light
Data Source
AI summary
An image sensor may include image pixels arranged in rows and columns. The image pixels may include an anti-blooming transistor controlled by a first control signal and a transfer transistor controlled by a second control signal. The first and second control signals are generated based on different sets of phases. The different sets of phases are offset from each other. By having a delayed or offset set of phases, the first and second control signals may be asserted independently from each other thereby providing shorter integration time periods during a light flicker mitigation mode of operation. An additional set of phases may be added before readout operations to account for the delay and ensure proper readout operations.