Shared Floating Diffusion Regions in Image Sensor Circuits
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Solution Overview
Problem
As the integration density of pixels increases in image sensors to achieve high resolution, the area of photoelectric conversion elements per unit pixel decreases, leading to reduced sensitivity and saturated signal amount, making it difficult to maximize light-receiving efficiency due to the need for multiple charge-transmission transistors and lines.
Innovation Solution
The implementation of shared floating diffusion regions in image sensor circuits, where pairs of adjacent photoelectric conversion elements share a floating diffusion region and charge-transmission transistors, with charge-transmission lines connected to the gates of adjacent rows of transistors, allowing for reduced number of charge-transmission lines and improved light-receiving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the integration density of pixels is increased to achieve high resolution, then the number of pixels per unit area is improved, but the area of photoelectric conversion elements per unit pixel decreases, leading to reduced sensitivity and saturated signal amount
Solution Approach 1:
Adjacent photoelectric conversion elements share common floating diffusion regions and charge-transmission transistors, merging previously separate components. This reduces the total number of individual components per pixel, thereby increasing the photoelectric conversion element area while maintaining high integration density
Solution Approach 2:
A single floating diffusion region serves multiple photoelectric conversion elements simultaneously, and a single charge-transmission transistor handles charge from multiple photoelectric conversion elements. This multi-functional approach reduces component count and increases light-receiving area per pixel
2Ease of operation
If multiple charge-transmission transistors and lines are used to read charge from each photoelectric conversion element, then the readout capability is improved, but the number of required charge-transmission lines increases, making it difficult to secure maximum light-receiving efficiency
Solution Approach 1:
Multiple charge-transmission transistors share common charge-transmission lines by controlling transistors in adjacent rows simultaneously. This merging of signal paths reduces the total number of charge-transmission lines required while maintaining the ability to readout from individual photoelectric conversion elements
Solution Approach 2:
Charge-transmission signals are applied periodically to adjacent rows of charge-transmission transistors, enabling sequential readout of multiple rows through shared lines. This time-division approach allows full readout capability with fewer physical lines
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 light-receiving efficiency, sensitivity, and saturated signal amount by reducing the number of charge-transmission lines and amplification, reset, and selection transistors, while maintaining high resolution.
Implementation Method 1
a first photoelectric conversion element and a second photoelectric conversion element respectively receive first incident light and second incident light and generate first charge and second charge
Data Source
AI summary
An image sensor can include a plurality of photoelectric conversion elements arranged in a matrix. A plurality of floating diffusion regions can be shared by respective corresponding pairs of adjacent photoelectric conversion elements. A plurality of charge-transmission transistors can respectively correspond to the photoelectric conversion elements, where each of the charge-transmission transistors are connected between a corresponding one of the plurality of photoelectric conversion elements and a corresponding one of the plurality of floating diffusion regions. A plurality of charge-transmission lines can be commonly connected to gates of respective corresponding pairs of adjacent rows of charge-transmission transistors, where each of the respective corresponding pairs of adjacent rows of charge-transmission transistors can be connected to respective ones of the plurality of photoelectric conversion elements in different adjacent rows of floating diffusion regions.