Color Filter Array Pattern Reduces Color Aliasing
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Solution Overview
Problem
Conventional CMOS image sensors with color filter arrays, especially those including clear pixels, suffer from color aliasing due to the alignment of clear filters, leading to incorrect color representation in images.
Innovation Solution
The design of a color filter array pattern that minimizes color aliasing by arranging filters in a specific pattern where all spectral photoresponses are present in at least two directions within a minimal repeating unit, ensuring that every row, column, major diagonal, and minor diagonal include all required photoresponses, thereby reducing misinterpretation of colors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If clear pixels are included in the color filter array to increase sensitivity, then the sensitivity of the image sensor is improved, but color aliasing occurs due to alignment of clear filters
Solution Approach 1:
The patent applies asymmetry by breaking the conventional symmetric Bayer pattern arrangement. Clear pixels are positioned at specific asymmetric locations within the color filter array, particularly in the corners and center, rather than following a regular symmetric pattern. This asymmetric distribution ensures that clear pixels are not aligned in ways that cause color aliasing, while still maintaining their sensitivity-enhancing function across the entire array.
2Ease of manufacture
If clear pixels are aligned in conventional patterns, then manufacturing is simplified, but color aliasing increases due to misinterpretation of colors
Solution Approach 1:
The patent applies local quality by assigning different functions to different regions of the color filter array. Clear pixels are strategically positioned in specific local areas (corners and center) rather than uniformly distributed. This allows each region to serve its optimal function: clear pixels in corners and center provide reference points for color accuracy, while other regions maintain conventional color filter patterns for standard imaging. This localized approach maintains manufacturing simplicity while improving color accuracy.
3Device complexity
If conventional Bayer pattern is used, then device complexity is low, but color aliasing occurs at high resolution
Solution Approach 1:
The patent applies segmentation by dividing the color filter array into distinct functional regions. The array is segmented into corner regions, center region, and intermediate regions, each with different filter assignments. Clear pixels are concentrated in corner and center segments, while conventional color filters dominate the intermediate segments. This segmentation allows the system to maintain overall pattern simplicity while introducing localized modifications that prevent color aliasing at high resolutions.
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
Embodiments are disclosed of a color filter array including a plurality of tiled minimal repeating units. Each minimal repeating unit comprises a set of individual filters grouped into an array of M rows by N columns, wherein each set of individual filters includes a plurality of individual filters having at least first, second, third, and fourth spectral photoresponses. If M equals N, at least two directions within each minimal repeating unit include individual filters having all the spectral photoresponses, the at least two directions being selected from a set of directions consisting of row, column, major diagonal and minor diagonal. And if M ≠ N at least two directions within each of one or more N x N or M x M cells within the minimal repeating unit include individual filters having all the spectral photoresponses, the at least two directions being selected from a set of directions consisting of row, column, major diagonal and minor diagonal of each cell.