Imaging Array Photodiodes with Different Light Sensitivities
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Solution Overview
Problem
Existing image sensors suffer from saturation issues in bright image regions, leading to blooming artifacts and limited dynamic range, which affects the quality of captured images.
Innovation Solution
Incorporating photodiodes with different light sensitivities, including normal and lower light sensitivity photodiodes, where the latter are achieved through light shielding or capacitance adjustment, allowing for highlight pixel gains to be applied to restore image information in saturated regions using neighboring pixel values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional image sensors with uniform photodiodes are used, then manufacturing is simple and consistent, but saturation occurs in bright regions causing blooming artifacts and limited dynamic range
Solution Approach 1:
The patent applies local quality by creating two distinct types of photodiodes with different light sensitivities: normal photodiodes for standard lighting conditions and reduced-sensitivity photodiodes for bright highlight regions. Each photodiode type is optimized for its specific function, allowing the sensor to handle both normal and bright regions without saturation artifacts while maintaining manufacturing feasibility through standardized fabrication processes.
2Adaptability or versatility
If photodiodes with reduced light sensitivity are added to handle bright regions, then dynamic range and highlight capture improve, but device complexity increases
Solution Approach 1:
The patent segments the pixel array into distinct regions with different photodiode characteristics. Normal photodiodes capture standard luminance ranges while reduced-sensitivity photodiodes specifically target highlight regions. This segmentation allows the sensor to expand its dynamic range and adaptability without requiring a complete redesign of the entire sensor structure, as each segment can be integrated using existing fabrication techniques.
3Loss of information
If all photodiodes have the same light sensitivity, then the sensor structure is simple and manufacturing is consistent, but saturation occurs in highlight regions losing image information
Solution Approach 1:
The patent changes the sensitivity parameter of specific photodiodes by adjusting their capacitance values. Reduced-sensitivity photodiodes have higher capacitance (e.g., 2f to 8f) compared to normal photodiodes (e.g., 0.5f to 2f), which prevents saturation in bright regions and preserves highlight information. This parameter change can be implemented during standard CMOS fabrication processes, maintaining manufacturing consistency while preventing information loss in highlights.
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
Enhances image quality and dynamic range by preventing saturation in bright areas, allowing for high-quality image restoration through appropriate gain application and interpolation methods.
Implementation Method 1
An imaging array according to one aspect of the present invention includes a first plurality of pixel sensors... a second plurality of pixel sensors having a second capacitance greater than the first capacitance
Data Source
AI summary
A pixel sensor array includes a plurality of pixel sensors having a first gain and a plurality of pixel sensors having a second gain less than the first gain.