Event Imaging Pixel Circuit for Low-Light Dynamic Range
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Solution Overview
Problem
Asynchronous solid-state imaging devices face challenges in low illuminance due to decreased photocurrent per pixel from miniaturization and high resolution, leading to reduced signal-to-noise ratio and dynamic range, affecting event detection sensitivity and accuracy.
Innovation Solution
A solid-state imaging device with detection pixels that include a photoelectric conversion element, a logarithmic conversion circuit, and transistors connected to a common line, which converts photocurrent into a voltage signal and outputs luminance changes, enhancing dynamic range through shared detection circuits and transistor configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pixel microfabrication is performed along with miniaturization and high resolution trends, then imaging resolution is improved, but photocurrent per pixel decreases resulting in deteriorated SN ratio and narrower dynamic range at low illuminance
Solution Approach 1:
Multiple detection pixels share a common first common line and common detection circuit, merging their signal paths. This allows the system to maintain high resolution by keeping individual pixel structures small while improving the SN ratio by combining photocurrent signals from multiple pixels through the shared common line and detection circuit, thereby expanding dynamic range at low illuminance without sacrificing imaging resolution
Solution Approach 2:
The detection circuit serves multiple functions: it processes signals from individual pixels for high-resolution imaging and simultaneously aggregates signals from multiple pixels through the common line for enhanced low-illuminance performance. This multi-functional design allows the same hardware structure to support both high resolution and improved SN ratio requirements
2Adaptability or versatility
If transistors operate in subthreshold region to detect address events, then event detection capability is achieved, but dynamic range at low illuminance becomes limited due to dependence on SN ratio
Solution Approach 1:
The patent combines multiple pixel signals through a shared common line and detection circuit, allowing the system to maintain event detection capability while improving dynamic range at low illuminance by aggregating signals from multiple pixels, thereby reducing the impact of thermal noise on individual pixel detections
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 solution improves event detection sensitivity and accuracy at low illuminance by expanding the dynamic range and reducing errors, facilitating microfabrication and high-resolution imaging.
Implementation Method 1
a photoelectric conversion element; a first circuit that outputs a luminance change of incident light incident on the photoelectric conversion element
Data Source
AI summary
Solid-state imaging devices are disclosed. In one example, a solid-state imaging device includes detection pixels that each output a luminance change of incident light, a detection circuit that outputs an event signal based on the luminance change, and a first common line connecting the detection pixels to each other. Each of the detection pixels may include a photoelectric conversion element, a logarithmic conversion circuit that outputs a voltage signal corresponding to a logarithmic value of photocurrent from the photoelectric conversion element, a first circuit that outputs a luminance change of incident light based on the voltage signal, a first transistor connected between the photoelectric conversion element and the logarithmic conversion circuit, and a second transistor connected between the photoelectric conversion element and the first common line. The detection circuit includes a second circuit that outputs the event signal based on the luminance change output from each of the detection pixels.