Image Signal Interpolation for False Color and Moire Suppression
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Solution Overview
Problem
Conventional image processing methods fail to correctly obtain correlations in high-frequency regions, leading to residual false colors and moire in images, especially near the Nyquist frequency or with aliasing noise.
Innovation Solution
An image processing apparatus that separates image signals from a Bayer pattern into color-specific signals and performs interpolation by determining the correlation between slopes and differences of image signals from G1 and G2 filters, identifying high-frequency regions and adjusting cutoff frequencies to suppress false colors and moire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If color interpolation is performed using surrounding pixels to suppress false color, then false color suppression is improved, but residual false colors and moire remain in high-frequency regions
Solution Approach 1:
The patent segments the image signal into multiple frequency components using band-pass filters, separating high-frequency regions from low-frequency regions. This allows different processing strategies to be applied to different frequency bands, with the high-frequency segment being processed to reduce false colors and moire while preserving detail.
Solution Approach 2:
The patent applies different correlation detection methods to different spatial regions based on their frequency characteristics. In high-frequency regions, a different correlation detection approach is used compared to low-frequency regions, optimizing the false color suppression for each local characteristic.
2Object-affected harmful factors
If adaptive pixel selection is used for luminance signal generation to suppress moire, then moire suppression is improved, but false color and moire remain in high-frequency regions near Nyquist frequency
Solution Approach 1:
The patent segments the signal processing into separate pathways for luminance and color signals, with further segmentation by frequency band. This allows the luminance signal generation to use adaptive pixel selection for moire suppression while the color signal processing handles false color correction in high-frequency regions independently.
Solution Approach 2:
The patent dynamically adjusts the correlation detection method based on the detected frequency characteristics of the input signal. When high-frequency components are detected, the system switches to a different correlation detection approach that is more reliable for that frequency range.
3Device complexity
If conventional correlation methods are used for color interpolation, then processing simplicity is maintained, but false colors and moire cannot be sufficiently reduced in high-frequency regions
Solution Approach 1:
The patent introduces frequency-based segmentation that divides the image processing into multiple stages: low-pass filtering for base signal extraction, band-pass filtering for high-frequency component extraction, and separate correlation detection for each band. This segmented approach reduces false colors and moire while keeping each processing stage relatively simple.
Solution Approach 2:
The patent performs preliminary low-pass filtering to extract the base signal before performing correlation detection. This preliminary action removes high-frequency noise and aliasing components that would otherwise interfere with accurate correlation measurement, simplifying the subsequent processing.
Data Source
AI summary
An object is to suppress a false color and moire that occur in a high-frequency region. Color interpolation circuits of a color-difference signal generating circuit separate an image signal obtained from an image pickup device, in which a plurality of color filters are arranged in a predetermined pattern and in which pixels corresponding to the respective color filters are provided, into image signals of the respective color filters (R, G1, G2, and B), and perform an interpolation process on the image signals of the respective color filters. Then, a false color determining circuit determines whether a target region is a high-frequency region on the basis of at least any of slopes of image signals of the G1 filter and the G2 filter and a difference between the image signals of the G1 filter and the G2 filter in the target region.