Hybrid CMOS Image Sensor Event-Driven Mode Architecture
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Solution Overview
Problem
Conventional image sensors lack ultra-high frame rates and ultra-high speed capture capabilities, which are essential for applications like machine vision, gaming, and artificial intelligence, while attempts to enhance them result in compromised image quality.
Innovation Solution
A hybrid imaging system with a stacked CMOS image sensor architecture that includes a normal image sensing mode and an asynchronous event-driven mode, utilizing a combination of pixel arrays and event-driven sensing arrays with hybrid bonds and mixed-signal circuitry to enable high-speed image capture without compromising image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional image sensors are used, then image quality is maintained, but ultra-high frame rates and ultra-high speed capture capabilities are lacking
Solution Approach 1:
The image sensor is divided into two separate arrays: a first array optimized for normal imaging mode and a second array optimized for event-driven mode. This segmentation allows each array to be independently optimized for its specific function, enabling ultra-high frame rates in event mode without compromising image quality in normal mode.
Solution Approach 2:
The system dynamically switches between two operational modes: normal imaging mode for high-quality image capture and asynchronous event-driven mode for ultra-high speed capture. This dynamic operation allows the sensor to adapt to different application requirements, achieving both image quality and ultra-high frame rates as needed.
2Loss of energy
If normal imaging mode is used, then image quality is maintained, but power consumption is higher
Solution Approach 1:
The event-driven functionality is extracted as a separate second array with dedicated event-driven circuitry, rather than attempting to enhance normal imaging circuitry for event detection. This extraction allows the system to use low-power event detection only when needed, reducing overall power consumption while maintaining event detection capability.
Solution Approach 2:
The system changes operational parameters by switching between two distinct modes: normal imaging mode with higher power consumption for continuous capture, and asynchronous event-driven mode with lower power consumption that only activates when events occur. This parameter change optimizes the balance between power consumption and event detection productivity.
3Adaptability or versatility
If conventional single-array architecture is used, then device complexity is low, but dual-mode operation capability is lacking
Solution Approach 1:
The stacked CMOS image sensor achieves multi-functionality by integrating two arrays with different architectures in a single device. The first array handles normal imaging while the second array handles event-driven sensing, allowing the sensor to perform both functions within one unified package, enhancing adaptability without requiring separate devices.
Solution Approach 2:
The patent employs a stacked three-dimensional architecture where the first and second arrays are positioned at different vertical levels. This dimensional arrangement allows both arrays to coexist without interfering with each other, managing the complexity of dual-mode operation through spatial separation while maintaining a compact form factor.
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
The hybrid system achieves ultra-high frame rates and ultra-high speed capabilities while maintaining great image and video quality, reducing power consumption and bandwidth requirements by asynchronously detecting events, thus enhancing performance in event-driven applications.
Implementation Method 1
The image sensor includes an array of pixels having photosensitive elements (e.g., photodiodes) that absorb a portion of the incident image light and generate image charge upon absorption of the image light
Data Source
AI summary
An image sensor includes a source follower coupled to a photodiode to generate an image signal responsive to photogenerated charge. The image signal is received by image readout circuitry through a row select transistor. A reset transistor resets the photogenerated charge. A first node of mode select circuit is coupled to the reset transistor, a second node is coupled to a pixel supply voltage, and a third node is coupled to an event driven circuit. The mode select circuit couples the first node to the second node during an imaging mode to supply the pixel supply voltage to the reset transistor. The mode select circuit is further configured to couple the first node to the third node during an event driven mode to couple a photocurrent of the photodiode to drive the event driven circuit through the reset transistor to detect changes in the photocurrent.