Electron Microscope Deflector Control for Orthogonal Scanning
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Solution Overview
Problem
Manufacture tolerance and assembly errors in electron microscopes complicate the achievement of orthogonal scanning directions for electron beams, leading to image distortion.
Innovation Solution
A control unit processes scanning directions using predetermined equations to adjust the electron beam's path, ensuring orthogonality between scanning directions, with the control unit providing a signal to the deflector coils to regulate current and align the beam within a required orthogonality limit, typically around 90 degrees.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manufacture tolerance and assembly error are present in the deflector, then the deflector can be manufactured and assembled, but the orthogonality between scanning directions deteriorates leading to image distortion
Solution Approach 1:
The control unit performs preliminary measurement of the actual scanning directions before normal operation, determines the deviation from orthogonality, and pre-calculates the corrected drive signals. This preliminary action compensates for manufacturing tolerances and assembly errors, ensuring orthogonal scanning directions without requiring precision manufacturing.
2Reliability
If the control unit adjusts scanning directions using predetermined equations, then image distortion is minimized, but the system complexity increases
Solution Approach 1:
Instead of using complex mechanical adjustment mechanisms to achieve orthogonal scanning directions, the patent substitutes a control unit that uses predetermined mathematical equations to calculate and adjust the drive signals. This replaces potential mechanical complexity with computational processing, maintaining reliability while avoiding additional mechanical components.
3Manufacturing precision
If the control unit processes scanning directions based on predetermined equations, then the orthogonality is improved, but the processing time increases
Solution Approach 1:
The control unit performs the measurement and calculation of corrected drive signals as a preliminary action before normal imaging operation begins. Once calculated, these corrections can be applied continuously without requiring repeated real-time calculations during imaging, thus minimizing time loss while maintaining precision.
Solution Approach 2:
The control unit creates a corrected model of the drive signals based on the measured deviations. Instead of continuously measuring and recalculating during operation, it uses the copied corrected signal patterns to maintain orthogonal scanning directions throughout the imaging process, reducing processing time.
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 effectively minimizes image distortion by ensuring precise alignment of scanning directions, improving image quality without requiring specific calibration with each specimen sample.
Implementation Method 1
The deflector may comprise one or more deflector coils. The current running through the coils is regulated to control the scanning directions of the deflector.
Data Source
AI summary
A control unit for controlling a deflector in an imaging apparatus. The imaging apparatus includes an electron gun arranged to provide electron beam to scan a specimen, and the deflector. The deflector is arranged to move the electron beam in a first scanning direction and a second scanning direction that are in the same plane for scanning the specimen. The control unit is configured to determine the first scanning direction and the second scanning direction, and process the determined first scanning direction and the determined second scanning direction based on predetermined equations. The control unit is further configured to provide, based on the processing, a control signal to the deflector to adjust one or both of the first scanning direction and the second scanning direction such that they become substantially orthogonal.