Pixel Isolation Layout for Combined Imaging and DVS Readout
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Solution Overview
Problem
Current solid-state imaging devices face challenges in achieving high-resolution imaging and event detection simultaneously due to interference between image and event detection functions, and difficulties in readout of dynamic vision sensor (DVS) and active image sensor signals, leading to degraded image quality and dynamic range.
Innovation Solution
The implementation of a solid-state imaging device with a pixel array where each pixel includes a single photoelectric conversion region and separate readout circuits connected by transfer transistors, surrounded by an isolation structure, allowing for improved light-reception efficiency and isolation between pixels, enabling both imaging and event detection modes from a single pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common photodiode is used for both image sensor and DVS functions (DAVIS system), then device complexity is reduced, but interference between image and event detection functions occurs and dynamic range is degraded
Solution Approach 1:
The pixel is divided into distinct functional regions: a photoelectric conversion region for light detection and separate circuit regions for image sensor and DVS functions. This spatial segmentation allows each function to operate independently without interference, resolving the contradiction between structural simplicity and functional isolation.
Solution Approach 2:
Transfer transistors are introduced as intermediary elements to selectively connect the photoelectric conversion region to either the image sensor readout circuit or the DVS readout circuit. These intermediaries enable clean signal routing and prevent cross-talk between the two detection functions while maintaining a single photodiode structure.
2Reliability
If additional photodiodes are provided for time-based readout (ATIS system), then image sensor and DVS signals can be provided separately, but resolution and image quality are degraded
Solution Approach 1:
A single photoelectric conversion region serves dual purposes: it generates signals for both image sensor capture and DVS event detection. This multi-functional approach eliminates the need for additional photodiodes, maintaining high resolution and image quality while still enabling separate signal readout through the transfer transistor switching mechanism.
3Device complexity
If readout circuits are integrated without isolation structures, then device complexity is reduced, but interference between adjacent pixels occurs
Solution Approach 1:
The pixel structure is segmented into isolated regions using dielectric isolation structures that physically separate adjacent pixels. This segmentation prevents electrical interference and crosstalk between neighboring pixels while maintaining a compact overall design, resolving the contradiction between device simplicity and reliable pixel isolation.
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 configuration enhances light-reception efficiency and image quality by allowing simultaneous operation of imaging and DVS modes with improved isolation between pixels, addressing the limitations of existing technologies.
Implementation Method 1
Each pixel includes a single photoelectric conversion region
Data Source
AI summary
An imaging device includes a plurality of unit pixels or pixels, with each pixel separated from every other unit pixel by an isolation structure. Each unit pixel includes a photoelectric conversion unit, a pixel imaging signal readout circuit, and an address event detection readout circuit. A first transfer transistor selectively connects the photoelectric conversion unit to the pixel imaging signal readout circuit, and a second transfer transistor selectively connects the photoelectric conversion unit to the address event detection readout circuit. The photoelectric conversion unit, the pixel imaging signal readout circuit, the address event detection readout circuit, and the first and second transfer transistors for a given pixel are located within a pixel area defined by the isolation structure. The isolation structure may be in the form of a full thickness dielectric trench isolation structure.