Image Sensor Dual Conversion Gain High Dynamic Range
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Solution Overview
Problem
Current CMOS image sensors face challenges in implementing high-dynamic range (HDR) images without causing image distortion, such as motion artifacts, especially when exposure times of pixels differ.
Innovation Solution
The implementation of an image sensor with a dual conversion gain mechanism, where pixels share floating diffusion regions and are processed by multiple analog-to-digital converters (ADCs) in different modes, allowing for selective connection of column lines to process signals with varying conversion gains, thereby extending the dynamic range and reducing motion artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple ADCs with different conversion gains are used to extend dynamic range, then HDR capability is improved, but device complexity increases
Solution Approach 1:
The pixel array is divided into first pixels and second pixels, where first pixels use a first conversion gain and second pixels use a second conversion gain. This segmentation allows different regions to operate at different conversion gains simultaneously, extending the overall dynamic range without requiring complex switching mechanisms for each pixel.
Solution Approach 2:
The image sensor is designed to operate in multiple modes (first mode with first conversion gain, second mode with second conversion gain) by selectively connecting column lines to different ADCs. This multi-functionality allows the same hardware to adapt to different dynamic range requirements without adding dedicated hardware for each mode.
2Adaptability or versatility
If different exposure times are used for pixels to achieve HDR, then dynamic range is improved, but motion artifacts increase
Solution Approach 1:
Different regions (first pixels and second pixels) are assigned different conversion gains locally within the same exposure time. This allows HDR capability to be achieved without varying exposure times across pixels, thereby avoiding motion artifacts while maintaining the ability to capture both bright and dark regions effectively.
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 generation of HDR images with improved dynamic range and reduced motion artifacts, even when exposure times of pixels are identical, enhancing image quality and reducing distortion.
Implementation Method 1
converting light energy into an electrical signal by using a photoelectric conversion element included within each pixel
Data Source
AI summary
Disclosed is an image sensor that includes a pixel array including first pixels sharing a first floating diffusion region and second pixels sharing a second floating diffusion region, a first analog-to-digital converter, a second analog-to-digital converter, and a switch circuit. In a first mode, the first analog-to-digital converter processes the first pixels, and the second analog-to-digital converter processes the second pixels. In the second mode, the first analog-to-digital converter processes a first image component of a pixel signal of the first pixels, and the second analog-to-digital converter processes a second image component of the pixel signal of the first pixels. An HDR image is implemented based on processing results of the first analog-to-digital converter and the second analog-to-digital converter.