Periodic Noise Filtering With Aliasing-Aware Harmonic Suppression
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Solution Overview
Problem
Existing methods for filtering periodic noise in images often result in the removal of high-frequency information or introduce ringing effects, failing to effectively suppress periodic noise while preserving image details.
Innovation Solution
A method and filter system that detects the fundamental, harmonic, and aliasing frequencies of periodic noise, filtering these frequencies based on their energy levels to generate a filtered spectrum, and restoring the input signal to reduce noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low-pass filter is used to remove high frequency noise, then periodic noise is filtered, but high-frequency information of the image is removed simultaneously
Solution Approach 1:
The patent segments the frequency spectrum into multiple bands and processes different frequency components separately. By dividing the spectrum, the filter can selectively remove periodic noise at specific frequencies while preserving other frequency information, thus resolving the contradiction between noise removal and information retention.
Solution Approach 2:
The patent applies different filtering strengths to different frequency bands. Instead of uniform filtering across all frequencies, the filter adapts its response locally to each frequency band, allowing aggressive filtering of periodic noise frequencies while maintaining gentle filtering for frequency bands containing important image information.
2Object-affected harmful factors
If a band-pass filter is used to remove narrow bandwidth noise, then periodic noise is filtered, but ringing effect is introduced affecting sharp edges
Solution Approach 1:
The patent employs dynamic filtering where the filter characteristics adapt based on the local signal properties. The filtering strength and bandwidth are adjusted dynamically for different frequency bands and signal regions, allowing effective periodic noise removal while minimizing the introduction of ringing artifacts that would affect sharp edges.
3Object-affected harmful factors
If a median filter or two-dimensional Gaussian band-stop filter is used to suppress periodic noise interference, then noise suppression is achieved, but non-noise information in the specific frequency band is filtered
Solution Approach 1:
The patent divides the frequency spectrum into multiple bands and identifies periodic noise frequencies specifically. By segmenting the spectrum, the filter can target only the problematic periodic noise frequencies for suppression while leaving other frequency bands containing non-noise information intact, thus avoiding the collateral filtering of useful signal content.
Solution Approach 2:
The patent changes filtering parameters adaptively based on the detected periodic noise characteristics. The filter selectively modifies its response parameters (such as filtering strength and frequency targeting) to match the specific periodic noise frequencies present, ensuring that only noise components are suppressed while preserving non-noise information in other frequency regions.
Data Source
AI summary
A method for filtering periodic noise and a filter using the method are provided. The method includes: obtaining an input signal; detecting a fundamental frequency corresponding to a maximum peak in a spectrum of the input signal, detecting a harmonic frequency according to the fundamental frequency, and detecting an aliasing frequency corresponding to the harmonic frequency in response to the harmonic frequency corresponding to the fundamental frequency being greater than a Nyquist frequency of the input signal; filtering the fundamental frequency and at least one of the harmonic frequency and the aliasing frequency of the spectrum to generate a first filtered spectrum, and restoring the input signal according to the first filtered spectrum to generate an output signal; and outputting the output signal. The method for filtering the periodic noise and the filter using the method may filter the periodic noise in the input signal affected by an aliasing effect.