Electron Microscope Pixel Calibration Using Poisson Mode Values
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Solution Overview
Problem
Existing electron microscopes with direct detection cameras face issues due to varying pixel sensitivities in the image sensor, leading to inaccuracies in image formation and electron counting, which are not effectively addressed by existing correction methods.
Innovation Solution
An electron microscope and calibration method that utilize a correction coefficient calculation unit to determine mode values for each sensor pixel under a Poisson process, calculating correction coefficients to adjust pixel sensitivities based on these values, thereby correcting the sensitivity differences among pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct detection camera is used to capture electron images, then image capture capability is improved, but pixel sensitivity uniformity deteriorates due to manufacturing errors
Solution Approach 1:
The patent applies preliminary action by performing sensitivity correction before actual image acquisition. A correction coefficient calculation unit calculates correction coefficients based on Poisson-distributed electron incident counts, and these coefficients are stored for subsequent application to correct pixel sensitivity variations in captured images, ensuring uniform sensitivity across all pixels.
Solution Approach 2:
The patent changes the parameter of pixel sensitivity by introducing correction coefficients that adjust the output values of individual pixels. By calculating mode values from histograms of electron incident counts and deriving correction coefficients, the system transforms pixels with non-uniform sensitivity into pixels with uniform effective sensitivity, resolving the manufacturing precision issue.
2Measurement precision
If correction coefficients are calculated using Poisson process statistics, then pixel sensitivity correction accuracy is improved, but calculation complexity increases
Solution Approach 1:
The patent replaces complex iterative optimization methods with a direct statistical approach based on Poisson process theory. By utilizing the mathematical property that the mode of a Poisson distribution equals its mean, the system directly calculates correction coefficients from histogram mode values, avoiding the need for complex mechanical or computational optimization processes while maintaining high accuracy.
3Measurement precision
If mode value is determined from histogram of output values, then correction coefficient accuracy is improved, but processing time increases
Solution Approach 1:
The patent creates a statistical model (histogram) that copies the distribution of electron incident counts, then identifies the mode value from this copied distribution. This approach allows accurate determination of the most probable electron count without processing every individual pixel value, significantly reducing processing time while maintaining correction accuracy.
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 accurate correction of pixel sensitivities, improving the accuracy of image formation and electron counting in electron microscopes, enhancing the quality of images produced by direct detection cameras.
Implementation Method 1
a direct detector (image sensor) in which a semiconductor layer that detects an electron beam is thinned
Data Source
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AI summary
An electron microscope (100) includes an electron optical system (10) that irradiates a sample (S) with an electron beam to form an image with electrons transmitted through the sample (S), a camera (30) that includes an image sensor (32) having sensor pixels and captures frame images that are based on output values output from each of the sensor pixels by incidence of the electrons on the image sensor (32), and a correction coefficient calculation unit (504) that calculates correction coefficients for correcting sensitivities of the sensor pixels, wherein the correction coefficient calculation unit (504) determines, from the frame images captured under a condition under which the electrons incident on the image sensor (32) follow a Poisson process, a mode value of the output values for each of the sensor pixels, and calculates the correction coefficients based on the mode value determined for each of the sensor pixels.