Imaging Device Color Filter Array Quantum Efficiency
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Solution Overview
Problem
Conventional digital image sensors face reduced quantum efficiency and color signal-to-noise ratio due to miniaturization, particularly affecting edge pixels, as existing color filter patterns prioritize luminance over color accuracy.
Innovation Solution
A novel color filter configuration with varying sizes and transmission characteristics, where larger 'parent' filters cover multiple pixels and smaller 'child' filters cover fewer pixels, optimizing light capture and balancing color absorption based on silicon absorption coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to increase resolution, then image sensor resolution is improved, but quantum efficiency and color signal-to-noise ratio deteriorate
Solution Approach 1:
The color filter array is segmented into different types (first, second, and third color filters) with varying transmission characteristics. Each type is assigned to different photo detectors based on their position and function, allowing the system to optimize both resolution and quantum efficiency through differentiated filter configurations rather than a uniform approach
Solution Approach 2:
Different color filters are applied to different locations within the pixel array. Edge pixels receive different filter configurations compared to center pixels, with specific filters assigned to maximize light capture in regions where quantum efficiency naturally decreases due to microlens and color filter geometry
2Illumination intensity
If conventional Bayer pattern with 50% green filters is used to improve luminance signal-to-noise ratio, then luminance S/N ratio is improved, but color signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies different color filter transmission characteristics to different photo detectors based on their position in the array. Center pixels use conventional patterns optimized for luminance, while edge pixels receive customized filter configurations that balance luminance and color performance according to local quantum efficiency requirements
Solution Approach 2:
The color filters are designed with varying transmission characteristics (first, second, and third types) that modify the conventional Bayer pattern parameters. This allows adjustment of the color-to-luminance filter ratio dynamically across different regions, optimizing both color and luminance signal-to-noise ratios simultaneously
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 configuration enhances quantum efficiency and color signal-to-noise ratio, particularly at the edges of the image sensor, while maintaining acceptable luminance, by strategically sizing and placing color filters to match the absorption characteristics of silicon.
Implementation Method 1
The photo detector generates an output electrical signal in response to received light
Implementation Method 2
Each of the color filters has a color transmission characteristic... based on the absorption coefficients of colors in silicon
Data Source
AI summary
An imaging device that includes an array of photo detectors each configured to generate an electrical signal in response to received light, and an array of color filters disposed over the array of photo detectors such that the photo detectors receive light passing through the color filters. Each of the color filters has a color transmission characteristic, which vary. To even out color balance, some of the color filters are disposed over a plurality of the photo detectors while others are disposed over only one of the photo detectors. Additional color balance can be achieved by varying the relative area sizes of the color filters and underlying photo detectors based on color transmission characteristics, to compensate for the varying absorption coefficient of the photo detectors at different colors.