Pixel Isolation Structure for Combined Imaging and Event Sensing
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Solution Overview
Problem
Existing solid-state imaging devices face challenges in achieving high light-reception efficiency and effective isolation between imaging and event detection functions, leading to degraded resolution and dynamic range, particularly in high-speed applications like autonomous vehicles and robotics.
Innovation Solution
The proposed imaging device incorporates a pixel array with a single photoelectric conversion region and separate readout circuits for imaging and event detection, utilizing transfer transistors of different types to enable simultaneous imaging and dynamic vision sensing modes with enhanced isolation between pixels through a dielectric isolation structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single photodiode is shared between image sensor and DVS functions (DAVIS system), then device complexity is reduced, but interference between imaging and event detection functions occurs and dynamic range degrades
Solution Approach 1:
The pixel is divided into distinct functional regions: a photoelectric conversion region for generating charges and separate readout circuit regions for imaging and DVS functions. This spatial segmentation allows independent optimization of each function while maintaining signal isolation through physical separation and dielectric structures.
Solution Approach 2:
Dielectric structures are introduced as intermediary elements between the photoelectric conversion region and readout circuits, and between adjacent pixels. These dielectric layers act as mediators that electrically isolate different functional regions while allowing the device to maintain a unified structure without requiring separate photodiodes for each function.
2Reliability
If additional photodiodes are added for time-based readout (ATIS system), then imaging and DVS functions are isolated, but resolution and image quality degrade
Solution Approach 1:
A single photoelectric conversion region serves multiple functions: it generates charges for both imaging operations and DVS event detection. The universal photoelectric conversion region eliminates the need for additional photodiodes, maintaining high resolution and image quality while enabling dual functionality through shared charge generation.
Solution Approach 2:
While the photoelectric conversion region is unified, the readout circuits are segmented into separate imaging readout and DVS readout paths. This segmentation allows independent signal processing for each function, achieving effective isolation without requiring separate photodiodes, thus preserving image quality.
3Device complexity
If readout circuits are integrated closely with photoelectric conversion regions, then device complexity is reduced, but interference between adjacent pixels increases
Solution Approach 1:
Dielectric structures are positioned between adjacent pixels and between the photoelectric conversion region and readout circuits. These dielectric intermediaries provide electrical isolation that prevents crosstalk and interference between neighboring pixels while allowing the readout circuits to remain integrated with the photoelectric conversion regions, maintaining low device complexity.
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 improves light-reception efficiency and reduces interference between imaging and event detection signals, enabling improved resolution and dynamic range, particularly suitable for high-speed applications.
Implementation Method 1
Each pixel includes a single photoelectric conversion region, a first readout circuit selectively connected to the photoelectric conversion region by a first transfer gate or transfer transistor
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.