Shared Bias Circuit for Pixel Area Reduction in Photodetection
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Solution Overview
Problem
Existing photodetection devices face challenges in reducing pixel size while maintaining effective light detection and event signal generation.
Innovation Solution
A photodetection device comprising a plurality of pixels, each with a light-receiving element, a generation circuit, and a change detection circuit. A selector circuit couples one of the change detection circuits to a coupling node, where a bias circuit is applied, and a comparison circuit generates an event signal by comparing the signal at the coupling node with a predetermined threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each pixel includes a complete set of circuits (light-receiving element, generation circuit, change detection circuit, bias circuit, comparison circuit), then the photodetection device can independently detect light changes and generate event signals, but the pixel size increases
Solution Approach 1:
The patent merges the bias circuits of multiple pixels into a single shared bias circuit. The bias circuit is configured to supply bias signals to multiple light-receiving elements simultaneously, eliminating the need for separate bias circuits in each pixel. This merging approach significantly reduces the area occupied by circuits while maintaining the independent detection capability of each pixel through the selector circuit that selectively connects pixels to the shared bias circuit.
Solution Approach 2:
The shared bias circuit is designed to serve multiple pixels universally. It can supply bias signals to any of the multiple light-receiving elements as needed, making a single circuit perform the function that would otherwise require multiple separate circuits. This multi-functionality approach reduces overall circuit count and pixel area while preserving individual pixel detection capabilities.
2Ease of operation
If multiple change detection circuits are simultaneously connected to separate bias circuits, then each pixel can operate independently, but the device complexity and area increase
Solution Approach 1:
The patent introduces a selector circuit as an intermediary between the multiple change detection circuits and the single shared bias circuit. The selector circuit selectively connects one pixel at a time to the shared bias circuit, enabling independent operation of each pixel while using a single bias circuit. This intermediary component manages the sharing resource efficiently without compromising the independence of individual pixel operations.
3Area of moving object
If the bias circuit is shared among multiple pixels, then the pixel size can be reduced, but the selector circuit is needed to manage the shared resource
Solution Approach 1:
The patent merges multiple bias circuit functions into a single shared bias circuit that serves multiple pixels. By combining the bias supply function for all pixels into one circuit, the overall area is reduced. The selector circuit manages this shared resource by selectively connecting different pixels to the shared bias circuit as needed, enabling area reduction while maintaining functional independence.
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 proposed solution allows for a reduction in pixel size, enabling smaller photodetection devices while maintaining the ability to detect light changes and generate event signals effectively.
Implementation Method 1
a light-receiving element, a generation circuit configured to generate a light-receiving signal corresponding to an amount of light received by the light-receiving element
Data Source
AI summary
A photodetection device of the present disclosure includes: a plurality of pixels each including a light-receiving element, a generation circuit configured to generate a light-receiving signal corresponding to an amount of light received by the light-receiving element, and a change detection circuit configured to detect an amount of a change in the light-receiving signal; a selector circuit configured to couple one of a plurality of the change detection circuits in the plurality of pixels to a coupling node; a bias circuit coupled to the coupling node; and a comparison circuit configured to generate an event signal by comparing a signal in the coupling node and a predetermined threshold with each other.