High Dynamic Range Imaging Sensor Parasitic Capacitance
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Solution Overview
Problem
Conventional high dynamic range imaging systems struggle to capture scenes with fast-moving objects and require excessive storage due to the need for multiple exposures and additional components like switches and capacitors in each pixel, leading to increased costs and inefficiencies.
Innovation Solution
The proposed system utilizes a high dynamic range image sensor with reset lines having parasitic capacitance to increase the capacitance of floating diffusion nodes, allowing for improved dynamic range capture without additional switches and capacitors, and employs an electronic rolling shutter for efficient image acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple exposure technique is used to capture high dynamic range images, then the dynamic range is improved, but the system cannot capture fast moving objects and requires excessive storage
Solution Approach 1:
The patent implements a dynamic exposure time mechanism where each pixel can independently vary its exposure duration based on local scene brightness. This allows simultaneous capture of both bright and dark regions in a single exposure, achieving high dynamic range without requiring multiple sequential exposures, thereby enabling capture of fast-moving objects.
Solution Approach 2:
The system dynamically adjusts the exposure time parameter for different regions of the image sensor based on detected light intensity. By changing the exposure time parameter adaptively across different pixels, the system captures adequate signal from both bright and dark areas in a single shot, resolving the contradiction between dynamic range and capture speed.
2Illumination intensity
If conventional high dynamic range pixels with additional switches and capacitors are used, then the dynamic range is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent makes the floating diffusion node serve multiple functions: it acts as both the charge storage element during exposure and the charge-to-voltage conversion node during readout. By eliminating dedicated transfer switches and additional capacitors, the system achieves high dynamic range functionality using only the inherent floating diffusion node, thereby reducing device complexity while maintaining dynamic range performance.
Solution Approach 2:
The floating diffusion node automatically performs charge accumulation during exposure and subsequent charge-to-voltage conversion during readout without requiring external control switches or additional components. This self-service mechanism simplifies the pixel structure while maintaining the ability to capture high dynamic range images.
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 capture of high dynamic range images with reduced component costs and improved efficiency, allowing for scenes with varying illumination levels to be captured effectively, including fast-moving objects, while minimizing storage requirements.
Implementation Method 1
Each pixel receives incident photons (light) and converts the photons into electrical signals
Implementation Method 2
reset lines having parasitic capacitance to increase the capacitance of floating diffusion nodes
Data Source
AI summary
An imaging system may include an imager with pixels and with reset lines that can be selectively deactivated and floated. When the reset lines are deactivated and floated, the reset lines may be connected to floating diffusion nodes in the pixels to increase the capacitance of the floating diffusion nodes. The reset lines may have parasitic capacitances that are used to supplement the capacitances of the floating diffusion nodes, when the reset lines are connected to the floating diffusion nodes. The imager may be used to capture high dynamic range images by simultaneously capturing a first image with a long integration time and a second image with a short integration time. The first and second images may be combined into a high dynamic range image.