Image Sensor Photodetector Local Saturation Optimization
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Solution Overview
Problem
Image sensors face a trade-off between full well capacity and defect pixel density, where increasing voltage for higher full well capacity can lead to increased defect pixels, and existing solutions do not effectively optimize signal saturation across the image sensor plane, particularly affecting dynamic range and low-light performance.
Innovation Solution
The use of locally optimized saturation signals for image sensor photodetectors, allowing pixel-wise optimization of full well capacity and switching between local and global saturation modes based on image capturing conditions, such as illumination, to improve signal-to-noise ratio and reduce vignetting/shading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If higher voltage is applied to pixels to increase full well capacity, then full well capacity is improved, but defect density of pixels increases
Solution Approach 1:
The patent applies local quality by dividing the image sensor into multiple regions with different saturation signal characteristics. Different regions are assigned different saturation signal values optimized for their specific function: some regions use higher saturation signals to maximize full well capacity for bright areas, while other regions use lower saturation signals to minimize defect density for low-light areas. This spatial variation in saturation signal quality allows simultaneous optimization of both full well capacity and defect density across different regions of the sensor.
2Quantity of substance
If global saturation signal optimization is used to maximize full well capacity, then full well capacity is improved, but signal-to-noise ratio in image corners deteriorates
Solution Approach 1:
The patent implements local quality by creating region-specific saturation signal optimizations rather than using a single global value. The image sensor is divided into multiple regions where each region's saturation signal is independently optimized based on local requirements. This allows corner regions to have saturation signals tuned for maximum signal-to-noise ratio while center regions can use higher saturation signals for maximum full well capacity, thereby resolving the contradiction between global full well capacity optimization and local signal-to-noise ratio performance.
3Measurement precision
If pixel-wise optimization of saturation signal is implemented, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the image sensor into a finite number of discrete regions rather than implementing truly pixel-wise independent control. Each region is assigned a specific saturation signal value, creating a manageable set of control parameters. This segmentation approach maintains the benefits of localized optimization for signal-to-noise ratio while avoiding the prohibitive complexity of completely independent pixel-wise control, as the number of control parameters is reduced from pixel-count levels to region-count levels.
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 image quality by improving signal-to-noise ratio in image corners, achieving a better trade-off between dark current and full well capacity, and optimizing exposure levels across the image plane, while reducing defect pixels in low-light conditions.
Implementation Method 1
a plurality of photodetectors configured to convert the light to which they are exposed to into signals for image generation
Data Source
AI summary
An apparatus including: a plurality of photodetectors for converting the light to which they are exposed to into signals for image generation, wherein the photodetectors use locally optimized saturation signal. The apparatus is, for example, an image sensor or an electronic communication device.