Coupled Gate Imaging Pixels Routing Overflow Charge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional imaging systems suffer from image artifacts due to moving objects, flickering lighting, and objects with changing illumination, leading to issues like object distortion, ghosting, and color artifacts, especially in high dynamic range scenarios where exposure times are shorter than frame duration.
Innovation Solution
The implementation of image sensors with coupled gate structures that allow for the routing of overflow charge from photodiodes to storage nodes or a pixel voltage supply, enabling separate readout of overflow and non-overflow charges, thereby increasing the dynamic range and minimizing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional imaging systems use standard exposure times, then normal imaging is achieved, but image artifacts occur in high dynamic range scenes due to overexposure or underexposure
Solution Approach 1:
The pixel is segmented into multiple independent charge storage regions: a first charge storage region coupled to a first floating diffusion node and a second charge storage region coupled to a second floating diffusion node. This segmentation allows simultaneous capture of different charge levels, enabling the system to handle both bright and dark portions of high dynamic range scenes without artifacts.
2Speed
If integration times are shortened to capture fast-changing scenery, then motion artifacts are reduced, but portions of the image frame are not fully exposed leading to distortion and ghosting effects
Solution Approach 1:
The pixel performs preliminary charge accumulation in separate storage regions during the integration period. By pre-capturing charge from different portions of the scene in parallel, the system ensures complete exposure of all image portions even during fast-changing scenarios, preventing distortion and ghosting effects.
3Device complexity
If conventional pixels use single charge storage, then circuit complexity is low, but dynamic range is limited causing overexposure or underexposure in high contrast scenes
Solution Approach 1:
Each pixel functions as a multi-functional unit capable of simultaneous charge accumulation in multiple regions, overflow charge routing to different floating diffusion nodes, and independent readout paths. This universality allows the same pixel structure to handle various lighting conditions and dynamic range requirements without requiring different pixel types.
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 enhances the dynamic range of imaging systems, reducing artifacts caused by moving objects and flickering lighting, and improves image quality in scenes with varying illumination by allowing for more accurate charge handling and readout.
Implementation Method 1
Each image pixel includes a photodiode
Data Source
AI summary
An image sensor may include one or more pixels having a coupled gate structure that may selectively route overflow charge from a photodiode to increase the dynamic range of the pixel. The coupled gate structure may include two, three or four transistors. During charge accumulation in the pixel, overflow charge may pass from a photodiode to the coupled gate structure to be selectively routed to one of a plurality of paths. Timing of control signals for a subset of the transistors in the coupled gate structure may alternate such that only one transistor is active to pass charge to one of the plurality of paths at any given time. Depending on the selected path, overflow charge may be routed to a pixel voltage supply or to one or more storage nodes in the pixel. Pixels may also include a dual-gain structure, which may provide additional charge storage capacity.