Color Filter Array Spatial Frequency Design for Moire Reduction
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Solution Overview
Problem
Conventional color image sensors using regular arrays of color filters, such as the Bayer array, face challenges in simultaneously preventing color moire and improving image resolution, often requiring optical low-pass filters that deteriorate image quality and introduce noise components due to non-uniform spatial frequency.
Innovation Solution
A color imaging apparatus with a photoelectric conversion element group and color filters arranged to reduce low-frequency components and increase high-frequency components, utilizing interpolation processing to generate image signals, thereby reducing color moire and noise without the need for optical low-pass filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a regular array of color filters (e.g., Bayer array) is used, then color filter processing can be performed, but color moire is generated and image resolution deteriorates
Solution Approach 1:
The patent applies asymmetry by using a random array instead of a regular periodic array for color filters. This random arrangement breaks the spatial regularity that causes color moire patterns, while still maintaining the ability to perform color filter processing through subsequent interpolation operations.
Solution Approach 2:
The patent introduces dynamic elements by using multiple candidate random arrays and selectively applying different arrays for different color components (R, G, B). This dynamic selection approach optimizes the balance between preventing color moire and maintaining image resolution across different spatial frequencies.
2Object-affected harmful factors
If an optical low-pass filter is added to prevent color moire, then color moire is reduced, but image resolution deteriorates and noise components increase
Solution Approach 1:
The patent extracts and removes the optical low-pass filter from the imaging system entirely. Instead of using physical filtering, the invention achieves color moire prevention through software-based interpolation processing on signals from randomly arranged color filters, thereby avoiding the resolution loss and noise introduction caused by optical filters.
Solution Approach 2:
The patent replaces the mechanical/optical low-pass filter with a digital signal processing approach. By using interpolation algorithms to reconstruct full-color images from the random array sensor data, the system achieves moire prevention without the physical constraints and quality degradation imposed by optical filtering.
3Object-affected harmful factors
If a random array of color filters is used, then color moire is suppressed, but noise components are introduced due to non-uniform spatial frequency
Solution Approach 1:
The patent changes the spatial frequency distribution parameters by carefully designing the random array to achieve uniform spatial frequency characteristics. This parameter optimization ensures that the random arrangement suppresses color moire while maintaining uniform noise distribution across the frequency spectrum, preventing excessive noise in specific frequency regions.
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 effectively reduces color moire and noise in captured images while maintaining or improving image resolution, ensuring high-quality imaging without the drawbacks of conventional optical low-pass filters.
Implementation Method 1
a photoelectric conversion element group having a plurality of photoelectric conversion elements
Implementation Method 2
color filters of at least two colors arranged on respective photoelectric conversion elements
Data Source
AI summary
An image sensor includes a photoelectric conversion element group, and color filters of at least two colors arranged on respective photoelectric conversion elements of the photoelectric conversion element group. The color filters are arranged on the respective photoelectric conversion elements such that a spatial frequency component of array of color filters of each color includes a reduced amount of component in a low-frequency region and a band component in a high-frequency region.