Stacked DVS Pixel Readout Layout for Low-Noise High-Speed Imaging
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Solution Overview
Problem
Dynamic vision sensors (DVS) face bottlenecks due to wiring congestion, reduced design flexibility, increased dark noise, and limited sensitivity and speed, primarily because the circuit configurations for address event detection and pixel signal readout occupy a significant portion of the light-receiving element's substrate, leading to reduced performance in high-speed applications.
Innovation Solution
The proposed imaging device includes a first pixel with a photoelectric conversion region and a readout circuit that converts electric charges into a logarithmic voltage signal, utilizing bonding pads for electrical contact and transistor configurations that allow for efficient power and signal distribution across substrates, enabling improved noise reduction and sensitivity while maintaining design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If both address event detection circuit and pixel signal readout circuit are formed in the same substrate as the light-receiving element, then dynamic vision sensor functionality is achieved, but wiring congestion occurs causing reduced design flexibility, increased dark noise, and limited sensitivity and speed
Solution Approach 1:
The patent divides the imaging device into separate substrates: a first substrate containing the light-receiving element and a second substrate containing the readout circuit. This segmentation physically separates the detection function from the readout function, eliminating wiring congestion on a single substrate while reducing dark noise and improving sensitivity and speed.
Solution Approach 2:
The patent transitions from a planar 2-D architecture to a 3-D stacked architecture by bonding the readout circuit substrate to the light-receiving element substrate. This vertical stacking allows both functions to coexist without wiring congestion, as connections are made through vertical vias rather than horizontal routing on the same plane.
2Adaptability or versatility
If both address event detection circuit and pixel signal readout circuit are formed in the same substrate as the light-receiving element, then dynamic vision sensor functionality is achieved, but design flexibility is reduced
Solution Approach 1:
By separating the light-receiving element and readout circuit onto different substrates, the patent simplifies the design of each individual component. The light-receiving element substrate can be optimized for sensitivity with minimal wiring, while the readout circuit substrate can be independently designed and configured, greatly enhancing design flexibility.
Solution Approach 2:
The patent introduces bonding pads and bonding wires as intermediary connection elements between the two substrates. These intermediaries provide flexible connection options that can be configured according to different design requirements, allowing for easier routing and connection strategies without the constraints of on-substrate wiring.
3Adaptability or versatility
If both address event detection circuit and pixel signal readout circuit are formed in the same substrate as the light-receiving element, then dynamic vision sensor functionality is achieved, but sensitivity and speed are limited
Solution Approach 1:
The patent separates the light-receiving element from the readout circuit onto different substrates, eliminating the wiring congestion that occurs when both are on the same substrate. This reduction in wiring complexity decreases signal transmission delays and allows for faster readout speeds, directly improving processing speed for high-speed applications.
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 noise reduction, design flexibility, and sensitivity, enabling the imaging device to operate effectively in high-speed applications by optimizing the use of substrate space and improving signal processing efficiency.
Implementation Method 1
a first photoelectric conversion region disposed in a first substrate and that converts incident light into first electric charges
Data Source
AI summary
An imaging device includes a first pixel. The first pixel includes a first photoelectric conversion region disposed in a first substrate and that converts incident light into first electric charges. The first pixel includes a first readout circuit including a first converter that converts the first electric charges into a first logarithmic voltage signal. The imaging device includes at least one bonding pad on the first substrate and in electrical contact with the first converter. The at least one bonding pad overlaps at least part of the first pixel.