Shared Pixel Architecture for CMOS Image Sensor Fill Factor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensor pixels face challenges in maintaining high fill factor and readout speed as pixels become smaller, with transistors occupying increasing space, reducing the photosensitive area and complicating fabrication.
Innovation Solution
The implementation of a shared pixel architecture with straight gate transfer transistors and consolidated readout circuits, where multiple pixels share a readout circuit, reduces the space required for transistors and enhances charge transfer efficiency, simplifying fabrication and increasing fill factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixels are made smaller to increase image sensor resolution, then the number of pixels increases, but the photosensor area and fill factor decrease
Solution Approach 1:
Multiple pixels (specifically four pixels) share a common readout circuit including the floating diffusion region, reset transistor, source follower transistor, and row select transistor. This consolidation reduces the per-pixel transistor area, allowing smaller pixels to maintain adequate fill factor while increasing overall sensor resolution
2Productivity
If pixels are made smaller to increase pixel density, then the number of pixels per unit area increases, but the transistors occupy a larger proportion of pixel space
Solution Approach 1:
The readout circuit components (floating diffusion region, reset transistor, source follower transistor, row select transistor) are shared among multiple pixels, reducing the number of transistors that must be contained within each individual pixel structure and reducing overall transistor space requirements
Solution Approach 2:
The shared readout circuit serves multiple pixels simultaneously, with the floating diffusion region accumulating charge from multiple photosensors and the transistors performing readout functions for multiple pixels, thereby reducing redundant circuitry
3Area of stationary object
If pixels are made smaller to maintain small image sensor size, then the overall sensor dimensions remain small, but the fill factor decreases
Solution Approach 1:
By consolidating readout circuitry into shared components served by multiple pixels, the circuit area is amortized across more photosensors, allowing smaller pixel dimensions while maintaining adequate fill factor proportions
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 approach allows for smaller pixels with higher fill factors and improved readout speed, effectively addressing the space and efficiency issues in CMOS image sensor design.
Implementation Method 1
each pixel including a photosensor, which may be a photogate, a photoconductor, a photodiode, or other photosensor having a doped region for accumulating photo-generated charge
Data Source
AI summary
Methods and apparatuses using pixels with shared readout circuits are used to increase pixel fill factor and operation efficiency.