Shared-Floating-Diffusion Pixel Readout for Rolling and Global Shutter
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Solution Overview
Problem
Existing imaging devices face challenges in achieving high-quality imaging without complex hardware, particularly in portable devices, where image resolution and dynamic range are limited by the inability to simultaneously read multiple subpixels effectively under different light conditions.
Innovation Solution
The proposed imaging device and pixel structure incorporate a pixel array with multiple subpixels sharing a floating diffusion region, allowing for simultaneous reading under a global shutter state and sequential reading under a rolling shutter state, utilizing independent transfer signals and capacitors to enhance image capture and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple subpixels share one floating diffusion region, then imaging resolution is improved, but the complexity of signal reading and control increases
Solution Approach 1:
The pixel is divided into multiple subpixels (e.g., four subpixels) that share a common floating diffusion region. Each subpixel has its own photodiode and transfer transistor, but they all transfer signals to the shared floating diffusion region for processing. This segmentation allows higher resolution without proportionally increasing the complexity of the floating diffusion region itself.
Solution Approach 2:
The patent implements dynamic switching between rolling shutter mode and global shutter mode through control circuits. In rolling shutter mode, subpixels are read sequentially one by one. In global shutter mode, all subpixels are read simultaneously. This dynamic operation allows the system to adapt to different imaging requirements and resolve the contradiction between resolution and reading complexity.
2Device complexity
If rolling shutter state is used to read subpixels one by one, then device complexity is reduced, but imaging quality and dynamic range deteriorate
Solution Approach 1:
The control circuit is designed to dynamically switch between rolling shutter mode (sequential reading) and global shutter mode (simultaneous reading) based on imaging requirements. This allows the system to use simpler sequential reading for normal conditions while achieving high imaging quality when needed through global shutter operation.
Solution Approach 2:
The system changes the reading mode parameter between sequential and simultaneous based on the imaging task. By adjusting this parameter, the system can optimize between device complexity and imaging quality, using global shutter mode when high imaging quality is required and rolling shutter mode when complexity reduction is prioritized.
3Measurement precision
If global shutter state is used to read subpixels simultaneously, then imaging quality is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Multiple subpixels share a common floating diffusion region and common control structures. The reset transistor, source following transistor, and output transistor are shared among all subpixels. This merging reduces the overall device complexity compared to having separate circuits for each subpixel, while still enabling simultaneous reading capability.
Solution Approach 2:
The shared floating diffusion region and common transistors serve multiple functions: they can receive signals from any subpixel, perform reset operations, amplify signals, and output to the readout circuit. This multi-functionality reduces the total number of components needed while maintaining global shutter capability.
4Measurement precision
If pixel concentration is increased, then resolution is improved, but other imaging performance aspects become more important
Solution Approach 1:
The ability to switch between rolling shutter and global shutter modes provides adaptability to varying imaging conditions. Global shutter mode is beneficial for capturing high-speed objects and maintaining dynamic range in varying light conditions, while rolling shutter mode provides sufficient performance for static or slow-moving scenes.
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 increases image resolution and dynamic range, enabling high-speed object capture and reducing the 'tailing phenomenon' in images, while maintaining a compact and efficient design without sacrificing photosensitive area.
Implementation Method 1
a sensing layer, which comprises a photodiode, a transfer gate, and a floating diffusion region
Data Source
AI summary
The present disclosure relates to an imaging device, a pixel and a method thereof The imaging device comprises: a pixel array, which comprises multiple pixels arranged in rows and columns, wherein at least one pixel comprises multiple subpixels, and the multiple subpixels share one floating diffusion region; and a control circuit, which controls the pixel array; wherein the control circuit reads the multiple subpixels one by one under the rolling shutter state, and reads the multiple subpixels simultaneously under the global shutter state.