Sub-pixel Image Shifting Frequency Correction Electron Microscope
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Solution Overview
Problem
Existing image processing methods for scanning electron microscopes, such as those disclosed in Japanese Unexamined Patent Application Publication No. 2006-308471 and WO2010/070815, fail to maintain accurate length measurement values when shifting images by sub-pixel amounts, leading to image blur and decreased reproducibility due to changes in frequency characteristics caused by pixel interpolation filters.
Innovation Solution
An electron beam device and image processing method that includes a sub-pixel shift process using a pixel interpolation filter and a frequency correction process to maintain the frequency characteristic of the image, preventing changes in length measurement values, even when shifting by sub-pixel amounts, by employing a data processing unit and correction calculation processing unit within the electron microscope system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image shifting is performed using pixel interpolation filter for sub-pixel amounts, then image position accuracy is improved, but frequency characteristic changes causing length measurement value changes
Solution Approach 1:
The patent changes the parameters of the pixel interpolation filter by introducing correction coefficients that adjust the filter's frequency characteristics. By modifying the filter parameters based on the shift amount, the system maintains consistent frequency characteristics across different shift operations, preventing length measurement value changes while achieving accurate sub-pixel positioning.
Solution Approach 2:
The patent implements a feedback mechanism where the actual frequency characteristics of the pixel interpolation filter are measured and used to calculate correction coefficients. These correction coefficients are then applied to adjust the filter in subsequent operations, creating a closed-loop system that maintains measurement consistency.
2Manufacturing precision
If pixel interpolation filter is used for sub-pixel shifting, then image shifting precision is improved, but frequency characteristic degradation occurs
Solution Approach 1:
The patent modifies the parameters of the pixel interpolation filter by introducing correction coefficients that compensate for frequency characteristic degradation. The correction coefficients are calculated based on the relationship between shift amounts and frequency characteristics, allowing the filter to maintain stable frequency characteristics even when performing sub-pixel shifting operations.
3Ease of operation
If image shifting is performed by integer pixel amounts, then processing simplicity is maintained, but sub-pixel positioning accuracy cannot be achieved
Solution Approach 1:
The patent segments the image shifting operation into two distinct stages: first, an integer pixel shift that maintains processing simplicity; second, a sub-pixel shift using a corrected pixel interpolation filter that achieves high positioning accuracy. This segmentation allows the system to benefit from both simplicity and precision without compromising either.
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 ensures accurate and reproducible length measurements by stabilizing the frequency characteristic of images after shifting, thereby preventing changes in length measurement values and enhancing the precision and reliability of measurements, especially at high magnifications.
Implementation Method 1
emits an electron beam which has been finely throttled onto a specimen, detects two-dimensional electrons occurred by electron beam irradiation and reflected electrons
Implementation Method 2
detects two-dimensional electrons occurred by electron beam irradiation
Data Source
AI summary
To acquire a correction image by performing a sub-pixel shift process for shifting an image using a pixel interpolation filter by a pixel shift amount between pixels and a frequency correction process for correcting a frequency characteristic of the image after shifted.