X-ray Apparatus Grid Moiré Removal via Line Profile FFT
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Solution Overview
Problem
Conventional X-ray apparatuses face challenges in removing grid moiré patterns in real-time fluoroscopy due to high computational requirements for Fast Fourier Transform (FFT) processing, especially when dealing with large image resolutions, which hinders real-time image processing.
Innovation Solution
The X-ray apparatus employs a pixel extracting section to isolate specific pixels, followed by one-dimensional FFT and peak frequency detection, then uses FIR filtering with calculated coefficients to reduce computational load, allowing for efficient extraction and removal of grid moiré patterns, thereby reducing the necessary calculation amount and logic/computation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fast Fourier Transform processing is applied to the entire image to remove grid moiré patterns, then the grid moiré pattern removal effectiveness is improved, but the computational load and processing time increase significantly
Solution Approach 1:
The patent divides the image processing task into two parts: first, extract a representative line profile from the image; second, perform FFT on this reduced data to obtain filter coefficients, then apply the filter to the full image. This segmentation reduces computational complexity from O(N log N) on the entire image to O(M log N) where M << N is the number of pixels in the representative line, enabling real-time processing while maintaining moiré removal effectiveness.
Solution Approach 2:
The patent extracts only the essential information needed for moiré pattern removal by taking a representative line profile from the image. This extracted line contains sufficient frequency information about the moiré pattern, allowing FFT-based filter design without processing the entire image, thus reducing computational load while preserving removal effectiveness.
2Measurement precision
If Fast Fourier Transform is performed with powers-of-two data points to handle large image resolutions, then the frequency analysis accuracy is improved, but the calculation amount and logic requirements increase
Solution Approach 1:
The patent segments the frequency analysis task to be performed only on a representative line profile rather than the entire high-resolution image. This maintains the ability to use powers-of-two FFT sizes for accurate frequency analysis while dramatically reducing the total number of computations required, making the hardware implementation more feasible.
Solution Approach 2:
The patent changes the approach from direct full-image FFT to an indirect method: extract line profile → perform FFT on line → obtain filter coefficients → apply filter to full image. This parameter change in processing strategy maintains frequency analysis accuracy through proper FFT application while reducing computational burden by operating on reduced data dimensions.
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
This approach enables the efficient extraction and removal of grid moiré patterns with reduced computational requirements, facilitating real-time image processing and maintaining image quality by performing calculations only on a subset of pixels, thus optimizing hardware performance.
Implementation Method 1
a pixel extracting section for extracting pixels determined in advance in each line perpendicular to a grid moiré pattern of an image
Implementation Method 2
a Fast Fourier Transform processing section for performing one-dimensional Fast Fourier Transform to the pixels extracted by the pixel extracting section
Implementation Method 3
a peak-frequency detecting section for detecting a peak frequency from a frequency characteristic for each line calculated by the Fast Fourier Transform processing section
Implementation Method 4
an inverse Fast Fourier Transform processing section for performing inverse Fast Fourier Transform to the frequency characteristic prepared by the frequency-characteristic preparing section
Implementation Method 5
an FIR filtering section for performing FIR filtering on the image with use of a value calculated by the inverse Fast Fourier Transform processing section as an FIR filter coefficient
Data Source
AI summary
An X-ray apparatus includes a pixel-extracting section for extracting pixels determined in advance in each line of an image containing a grid moiré pattern, a FFT processing section for performing one-dimensional FFT to the extracted pixels, a peak-frequency detecting section for detecting a peak frequency from a frequency characteristic for each line having undergone FTT, a frequency-characteristic preparing section for preparing a frequency characteristic for extracting the grid moiré pattern in accordance with the detected peak-frequency, an inverse FFT processing section for performing inverse FFT to the frequency characteristic prepared by the frequency-characteristic preparing section, and an FIR filtering section for performing FIR filtering on the image with use of a value calculated by the inverse FFT processing section as an FIR filter coefficient.