Asymmetric Color Filter Array for Luminance Signal-to-Noise Ratio
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Solution Overview
Problem
Existing color filter arrays in electronic imaging sensors face challenges in achieving optimal signal-to-noise ratio while maintaining compatibility with standard image processing electronics, leading to suboptimal color integrity and resolution, especially in luminance and chrominance representation.
Innovation Solution
An optimized color filter array pattern with larger green filters relative to red and blue filters, maintaining a 4:2:2 ratio, and corresponding micro-lens sizing to enhance luminance signal-to-noise ratio without compromising chrominance information, ensuring compatibility with standard Bayer CFA processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard Bayer CFA pattern with equal-sized red, green, and blue filters is used, then color information is captured uniformly across all channels, but the luminance signal-to-noise ratio is suboptimal because green filters (which contribute most to luminance) do not occupy sufficient area
Solution Approach 1:
The patent applies asymmetry by making green filters larger than red and blue filters in the CFA pattern. Specifically, green filters occupy approximately 50% of the total filter area while red and blue filters each occupy about 25%, creating an asymmetric distribution that optimizes luminance capture since green light contributes most to perceived brightness. This asymmetric design directly improves luminance signal-to-noise ratio while maintaining compatibility with standard Bayer processing through appropriate pattern arrangement.
2Measurement precision
If the green filter area is increased to improve luminance signal-to-noise ratio, then luminance quality improves, but the area available for red and blue filters is reduced, potentially compromising chrominance information
Solution Approach 1:
The patent applies local quality by assigning different filter sizes to different color channels based on their specific functional requirements. Green filters are enlarged locally to capture more luminance information, while red and blue filters maintain smaller sizes sufficient for chrominance capture. This localized differentiation optimizes each color channel's performance according to its role in the overall image quality, with green contributing primarily to luminance and red/blue contributing primarily to color information.
Solution Approach 2:
The patent applies parameter changes by modifying the relative areas of different colored filters from the traditional equal-area Bayer pattern. The green filter area parameter is increased to approximately 50% of total filter area, while red and blue filter area parameters are reduced to approximately 25% each. This parameter adjustment optimizes the balance between luminance and chrominance information capture, improving luminance signal-to-noise ratio while preserving sufficient chrominance data through the optimized area distribution.
3Measurement precision
If a non-standard CFA pattern is used to optimize luminance signal-to-noise ratio, then imaging performance improves, but compatibility with standard image processing electronics is lost
Solution Approach 1:
The patent applies universality by designing a CFA pattern that serves multiple functions: it optimizes luminance signal-to-noise ratio through asymmetric green filter sizing while simultaneously maintaining compatibility with standard Bayer CFA processing pipelines. The pattern preserves the characteristic 2:1 ratio of green to (red+blue) filters that standard processors expect, allowing the optimized pattern to be processed using existing demosaicing and color processing algorithms without requiring specialized hardware or software modifications.
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
The solution improves the luminance signal-to-noise ratio by approximately 3.5 dB and maintains color integrity with standard image processing, supporting higher resolution and reduced noise in imaging applications while adhering to existing standards.
Implementation Method 1
green, red and blue color filters are respectively positioned at first, second and third locations of each picture element
Implementation Method 2
Each pixel element has a microlens formed over the pixel element
Data Source
AI summary
A color filter array (CFA) and image processing system wherein a color filter overlaying an image sensor has a luminance element (i.e. green filter in RGB space, or yellow in CMY space) that is made larger than the other two chrominance elements (i.e. red, blue or cyan, magenta). Additionally, overlaying micro-lenses may be sized to correspond to the relative sizes of the underlying color filters. The optimized filter array is compatible with existing de-mosaic image processing.