Variable Sensitivity Pixels for Extended Dynamic Range
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current image sensors have a limited dynamic range, which can result in an incomplete representation of scenes that exceed their capture capabilities, leading to a need for increased dynamic range without degrading noise, responsivity, or linearity.
Innovation Solution
The method involves multiple transfer and sample operations to increase the floating diffusion capacitance by connecting additional floating diffusions, allowing for variable sensitivity in converting photoelectron charge to voltage through a shared floating diffusion network in the image sensor pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the dynamic range of image sensors is increased by adding additional floating diffusions and performing multiple transfer operations, then the ability to capture high-contrast scenes is improved, but the device complexity increases
Solution Approach 1:
The image sensor divides the capture process into multiple segments, performing separate transfers to different floating diffusions for different brightness levels. This segmentation allows the sensor to handle high-contrast scenes by processing bright and dark regions independently, then combining the results to achieve extended dynamic range without requiring a complete redesign of the entire sensor architecture.
Solution Approach 2:
The invention dynamically switches between different floating diffusions based on the brightness of the captured scene. By making the capacitance value variable rather than fixed, the sensor can adapt to different lighting conditions in real-time, selecting appropriate floating diffusions during the transfer process to optimize the dynamic range for each specific scene requirement.
2Adaptability or versatility
If additional floating diffusions are connected to increase capacitance, then the dynamic range is extended, but the area occupied by pixel components increases
Solution Approach 1:
Multiple floating diffusions are merged into a shared network that serves multiple pixels. Instead of dedicating separate floating diffusions to each pixel, the invention combines several floating diffusions into a shared resource pool that can be dynamically allocated to different pixels based on scene requirements, thereby extending dynamic range while minimizing the area increase per pixel.
Solution Approach 2:
The additional floating diffusions serve multiple functions: they act as storage nodes for different brightness levels, serve as transfer destinations for multiple photodiodes, and can be selectively connected based on scene requirements. This multi-functionality allows the same hardware components to contribute to extended dynamic range without proportionally increasing the pixel area.
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 extends the dynamic range of image sensors by altering the capacitance of floating diffusions, enabling more accurate representation of high-contrast scenes while maintaining noise and linearity performance.
Implementation Method 1
each of which comprises a photodiode for receiving light and generating photoelectric charges
Implementation Method 2
a charge-to-voltage conversion mechanism (50), preferably a floating diffusion
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method for reading out an image sensor, the method includes the steps of integrating charge in a photodetector with the photodetector at a first capacitance; reading the resulting signal level at a first time with the photodetector at the first capacitance; changing the photodetector capacitance to a second capacitance; and reading the signal level associated with the photodetector at the second capacitance.