Electron Microscope Noise Cancellation via DC Component Extraction
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Solution Overview
Problem
Conventional electron microscopes face issues with contrast nonuniformity due to noise cancellation methods that multiply the effective value of noise signals, leading to fringe patterns and poor image quality when large amplitude noise is present.
Innovation Solution
An electron microscope configuration that includes a DC component extractor, an arithmetic section for division and multiplication, and a high pass filter to isolate and subtract AC components from the noise signal, allowing for reduced noise effects and improved image clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise cancellation is performed by multiplying the effective value of noise signals, then emission noise is removed from images, but contrast nonuniformity and fringe patterns occur when large amplitude noise is present
Solution Approach 1:
The patent extracts only the DC component from the effective value of the noise signal, separating it from the AC component. This is achieved through a DC component extractor that processes the noise signal to isolate its steady-state portion, which is then used for noise cancellation. This extraction principle resolves the contradiction by using only the stable DC portion for multiplication, avoiding the introduction of AC-induced contrast nonuniformity and fringe patterns while still effectively removing emission noise.
Solution Approach 2:
Instead of directly using the full effective value (which includes both DC and AC components) for noise cancellation multiplication, the patent inverts the approach by first extracting only the DC component and then using this extracted DC component for the multiplication operation. This inversion of the conventional approach eliminates the harmful AC effects while preserving the beneficial noise cancellation function.
2Object-affected harmful factors
If the effective value of noise signals is used for noise cancellation, then emission noise is reduced, but the computation time increases and response speed decreases
Solution Approach 1:
The patent extracts only the necessary DC component from the noise signal, which represents the steady-state emission noise level. This extraction process is computationally simpler than calculating and storing the full effective value over extended periods, thereby reducing computation time while maintaining effective noise cancellation performance.
3Object-affected harmful factors
If noise cancellation processing is applied, then image clarity is improved by removing emission noise, but device complexity increases due to additional processing circuits
Solution Approach 1:
The patent introduces a DC component extractor that isolates only the DC portion of the noise signal. This extraction functionality can be implemented with minimal additional circuitry compared to full effective value processing, thus reducing the overall device complexity while maintaining effective noise cancellation.
Solution Approach 2:
The patent uses a simplified model of the noise signal (only the DC component) instead of the complete complex noise waveform. This copying approach uses a reduced representation that requires less processing power and simpler circuitry while still achieving the primary goal of noise cancellation.
4Measurement precision
If AC components are included in noise signal processing, then complete noise characterization is achieved, but contrast nonuniformity and fringe patterns are introduced
Solution Approach 1:
The patent explicitly extracts and separates the DC component from the AC component of the noise signal. By taking out only the DC component for noise cancellation processing, the method achieves sufficient noise characterization without introducing the contrast nonuniformity and fringe patterns that would result from including AC components in the multiplication operation.
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 configuration effectively reduces contrast nonuniformity and enhances image quality by extracting and removing noise components, providing stable and clear STEM images even with large amplitude noise.
Implementation Method 1
electrons emitted from a field emission electron gun
Implementation Method 2
a lens 113a... focused beam is scanned over the sample A
Data Source
Figure 1
Figure 2
Figure 3(A)~3(J)
AI summary
There is provided an electron microscope capable of producing good images by reducing contrast nonuniformity. The electron microscope (1) includes: an electron beam source (11) for producing an electron beam; a noise cancelling aperture (12) and an amplifier (42) for detecting a part of the electron beam; an effective value computing circuit (44) and a low frequency cut-off circuit (46) for extracting a DC component of an effective value of a detection signal emanating from the amplifier (42); an image detector (15) for detecting a signal produced in response to impingement of the beam on a sample (A); a preamplifier circuit (20) and an amplifier circuit (30); a divider circuit (54) for performing a division of the output signal (X) from the amplifier circuit (30) by the output signal (Y) from the amplifier circuit (42) and producing a quotient signal indicative of the result of the decision (X/Y); and a multiplier circuit (58) for multiplying the quotient signal by a signal (Z) extracted by the low frequency cut-off circuit (46).