CMOS Image Sensor Pixel Layout for Dynamic Conversion Gain
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current image sensors, particularly CMOS image sensors, face challenges in optimizing conversion gain for varying operating modes, which affects signal-to-noise ratio and dynamic range in different image capturing conditions.
Innovation Solution
The image sensor design includes a pixel array with multiple floating diffusion regions connected through metal lines, allowing for adjustable conversion gain by varying the size of the floating diffusion region based on operating modes, thereby optimizing signal processing for different imaging scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the floating diffusion region size is fixed, then the device structure is simple, but the conversion gain cannot be optimized for different operating modes
Solution Approach 1:
The patent implements dynamic conversion gain adjustment by enabling the floating diffusion region size to change based on operating mode. Multiple floating diffusion regions with different areas are provided, and through control signals, the effective floating diffusion region size is dynamically adjusted to match different imaging conditions, thereby optimizing conversion gain adaptability without permanently increasing structural complexity.
Solution Approach 2:
The pixel structure is designed with multi-functionality by incorporating multiple floating diffusion regions that can serve different purposes depending on the operating mode. The same pixel structure can adapt to various imaging scenarios (such as different light conditions or resolution requirements) by selectively activating different floating diffusion regions, making the device universally applicable across multiple operating conditions.
2Adaptability or versatility
If multiple floating diffusion regions are provided with different sizes, then conversion gain can be optimized for different modes, but the manufacturing process becomes more complex
Solution Approach 1:
The floating diffusion region is segmented into multiple sub-regions with different areas within each pixel. This segmentation allows the pixel to provide multiple conversion gain levels by activating different segments. The segmented structure is designed to be compatible with standard CMOS fabrication processes, where each segment can be formed using conventional photolithography and doping techniques, thereby managing manufacturing complexity while achieving multi-mode adaptability.
3Measurement precision
If the floating diffusion region size is dynamically adjusted, then signal-to-noise ratio is improved, but the control circuit complexity increases
Solution Approach 1:
The control circuits of multiple pixels are merged and shared. Instead of each pixel having an independent control circuit for adjusting its floating diffusion region, the patent implements a shared control mechanism where a single control signal can simultaneously adjust the effective floating diffusion region size across multiple pixels. This merging approach reduces the overall control circuit complexity while still achieving improved signal-to-noise ratio through dynamic conversion gain optimization.
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 enhances the signal-to-noise ratio and dynamic range by dynamically adjusting the conversion gain according to the operating mode, improving image quality across different imaging conditions.
Implementation Method 1
Each of the plurality of pixels may include at least two photodiodes
Implementation Method 2
controlling a capacitance ratio using junction capacitance or a metal capacitance around the pixel depending on the operating mode
Data Source
AI summary
Provided is an image sensor including a first pixel including a first floating diffusion region and a second floating diffusion region, a second pixel including a first floating diffusion region, a second floating diffusion region, and a third floating diffusion region, a third pixel including a first floating diffusion region and a second floating diffusion region, and a fourth pixel including a first floating diffusion region, a second floating diffusion region, and a third floating diffusion region, wherein the second floating diffusion region of the first pixel and the second floating diffusion region of the second pixel are connected through a first metal line, and wherein the third floating diffusion region of the second pixel and the third floating diffusion region of the third pixel are connected through a second metal.