Imaging Pixel With Dual Storage Nodes For Wide Dynamic Range
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Solution Overview
Problem
Conventional image sensors face challenges in achieving a wide dynamic range (WDR) and capturing moving objects without distortion, particularly due to limitations in dynamic range and image distortion caused by rolling shutter methods.
Innovation Solution
The imaging device employs a pixel structure with multiple storage nodes and distinct timing controls for charge shifting and integration, allowing for simultaneous wide dynamic range and global shutter capabilities by differentiating integration times and reading operations across multiple storage nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a rolling shutter method is used to sequentially shift charges by row or line, then device complexity is reduced, but image distortion occurs when capturing moving objects
Solution Approach 1:
The pixel array is divided into multiple groups, with each group containing multiple pixels that can be processed independently. This segmentation allows different parts of the image to be captured at different times while maintaining global synchronization, resolving the contradiction between simplified control and accurate moving object capture
Solution Approach 2:
The charge shifting timing is made dynamic rather than fixed. Different groups of pixels are shifted at different times based on their positions, allowing the system to adapt the timing to capture moving objects accurately while maintaining manageable control complexity through programmable timing adjustments
2Measurement precision
If well capacity of photoelectric conversion area is increased to increase dynamic range, then measurement precision improves, but device complexity increases
Solution Approach 1:
Each pixel is divided into multiple sub-pixels with different well capacities. The first photoelectric conversion area has smaller well capacity for high-luminance regions, while the second photoelectric conversion area has larger well capacity for low-luminance regions. This segmentation enables wide dynamic range without requiring the entire pixel to have increased capacity, thus managing device complexity
Solution Approach 2:
Different regions of the pixel array are assigned different local qualities in terms of well capacity. The patent applies different integration times and well capacity characteristics to different pixel groups based on their luminance requirements, allowing each region to be optimized for its specific imaging needs while maintaining overall system efficiency
3Adaptability or versatility
If separate methods are used for global shutter and WDR pixels, then adaptability improves, but device complexity increases
Solution Approach 1:
The pixel structure is designed to be universal and multi-functional. Each pixel can operate in both global shutter mode and WDR mode by configuring different photoelectric conversion areas and integration times. This multi-functionality eliminates the need for separate pixel types for different imaging modes, reducing device complexity while maintaining high adaptability to various imaging environments
Solution Approach 2:
The imaging device uses dynamic timing control to switch between different operating modes. The control circuit adjusts integration times and charge shifting timing based on the imaging requirements, allowing a single pixel structure to adapt to both global shutter and WDR modes dynamically rather than requiring separate hardware configurations
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 enables the imaging device to capture images with a wide dynamic range and moving objects without distortion, improving both low-luminance and high-luminance image quality.
Implementation Method 1
one parameter indicating a performance of a complementary metal oxide semiconductor (CMOS) image sensor is a dynamic range (DR), which is indicated as a ratio of minimum input signals detectable by the CMOS image sensor to maximum input signals that may not saturate the CMOS image sensor
Data Source
AI summary
An imaging device and a method of driving the imaging device including a plurality of pixels and a control circuit to apply a signal to the pixels, wherein the pixels include a photodiode, a floating diffusion node, a first storage node and a second storage node connected in parallel between the photodiode and the floating diffusion node, a first shift switching unit to selectively shift charges integrated in the photodiode to the first storage node, a second shift switching node to selectively shift the charges integrated in the photodiode to the second storage node, a first transfer switching unit to selectively transfer charges integrated in the first storage node to the floating diffusion node, a second transfer switching unit to selectively transfer charges integrated in the second storage node to the floating diffusion node, and a reset switching unit.