Fourier Transform Moire Pattern Correction in Radiographic Apparatus
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Solution Overview
Problem
Conventional radiographic apparatuses face challenges in accurately correcting line deficiencies due to errors in X-ray grid density, leading to moire patterns that cannot be accurately corrected, especially when the grid density differs from the detector's resolution.
Innovation Solution
A radiographic apparatus that includes a Fourier transform element, a peak frequency detection element, a pixel cycle conversion element, and a line deficiency correction element, which conducts one-dimensional Fourier transforms on moire patterns, detects peak frequencies, converts them to pixel cycles, and corrects line deficiencies using pixel values, even with grids having errors or different densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an X-ray grid is used to eliminate scattered radiation, then scattered rays are eliminated and clear X-ray images can be obtained, but a moire pattern appears in the obtained X-ray image due to the difference between the resolution of the X-ray detector and the density of the X-ray grid
Solution Approach 1:
The patent applies Fourier transform to the detected X-ray image data to analyze the moire pattern frequency characteristics. By detecting the peak frequency in the Fourier transform result, the system identifies the moire pattern's spatial frequency. This allows the system to calculate the actual number of pixels per moire pattern cycle and use this information to correct line deficiencies, thereby converting the harmful moire pattern into useful frequency information for image correction.
2Ease of operation
If conventional line deficiency correction is conducted by using pixel values of every 4 adjacent pixels, then correction can be performed when moire pattern lines are in vertical direction, but correction is not accurate when X-ray grid density has errors or differs from detector resolution
Solution Approach 1:
The patent implements a feedback mechanism where the Fourier transform of the detected image is analyzed to detect the peak frequency corresponding to the moire pattern. This detected frequency information is fed back to calculate the actual number of pixels per moire cycle, which then adjusts the line deficiency correction strategy. Instead of using a fixed correction method, the system adapts the correction based on the actual moire pattern characteristics, thereby improving correction accuracy even when grid density has manufacturing errors.
3Device complexity
If fixed correction methods are used for line deficiency, then correction process is simple, but correction accuracy deteriorates when moire pattern frequency varies due to grid density errors
Solution Approach 1:
The patent transitions from a static, fixed correction method to a dynamic correction approach. The system performs Fourier transform on the detected image to dynamically determine the moire pattern's peak frequency, then calculates the actual number of pixels per cycle based on this detected frequency. This dynamic adaptation allows the correction process to adjust to variations in grid density and moire pattern frequency, maintaining high correction accuracy without requiring complex manual intervention.
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 solution enables precise correction of line deficiencies and moire pattern elimination, ensuring clear X-ray images by accurately determining the number of pixels in a cycle of the moire pattern, thereby addressing the inaccuracies caused by grid density errors.
Implementation Method 1
The X-ray grid is composed of an absorbent (e.g. lead) that absorbs X-ray and a transmission material (e.g. aluminum or air) that transmits X-rays
Implementation Method 2
a Fourier transform element that conducts one-dimensional Fourier transform on a line orthogonal to a line of a moire pattern appearing in the X-ray image
Data Source
AI summary
An apparatus, system, and method corrects line deficiency in radiographic systems. A Fourier transform element provides a one-dimensional Fourier transform on a line orthogonal to a line of a moire patterns appearing in an X-ray image during a use. A peak frequency detection element detects the peak frequency indicating the spatial frequency of the moire pattern on the basis of the results of one-dimensional Fourier transform. The detected peak frequency is transformed to a number of pixels in 1 cycle of the moire pattern by a pixel cycle conversion element. The line deficiency correction element obtains pixels of the same phase as the line deficiency pixel in the moire pattern from the number of pixels, and then corrects the line deficiency pixel by using the pixel value thereof. Since the number of pixels in 1-cycle is acquired from the moire pattern in the X-ray image, the line deficiency can be corrected.