Digital Current Adder for Electron Beam Deflection Control
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Solution Overview
Problem
Existing electron beam systems for material processing face challenges in accurately and quickly driving deflection coils and generating images of backscattered electrons due to limitations in data rate and oscillation tendencies of conventional analog amplifiers.
Innovation Solution
A digital current adder arrangement that sums constant, unregulated currents to drive deflection coils, utilizing a binary code-like ratio for current magnitudes and a control circuit to compensate for resistance tolerances and temperature fluctuations, enabling fast and accurate control of electron beams for both processing and image generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional analog amplifiers are used to drive deflection coils, then the electron beam can be controlled with up to 100 kHz control frequency, but the amplifiers tend to oscillate and overshoot, and the response is slow to level off
Solution Approach 1:
The patent replaces the conventional analog amplifier system with a digital system consisting of a microprocessor, digital-to-analog converter, and power amplifier. This substitution eliminates the oscillation and overshoot problems inherent in analog amplifiers while maintaining fast response capability through digital control at 100 kHz update rates.
Solution Approach 2:
The patent implements a feedback mechanism where the actual electron beam position is measured and compared with the desired position, and the error signal is used to adjust the deflection coil currents. This feedback loop ensures stable and accurate beam positioning without the oscillation problems of conventional analog systems.
2Speed
If the control frequency of deflection coils is increased beyond 100 kHz, then faster electron beam control is achieved, but conventional analog amplifiers become too complex and expensive
Solution Approach 1:
The patent replaces complex high-frequency analog amplifiers with a digital control system that operates at 100 kHz. The microprocessor generates control signals that are converted to analog voltages by a DAC, which then drive the deflection coils through a simple power amplifier stage. This digital approach achieves the required control speed without the complexity and cost of conventional high-frequency analog amplifiers.
3Productivity
If data is read from memory at high data rates (30 Mbit/s), then fast processing is achieved, but this data rate cannot be implemented when deflecting an electron beam with conventional amplifiers
Solution Approach 1:
The patent replaces the bottleneck of conventional amplifier bandwidth with a digital control system. The microprocessor can read data from memory at high rates (up to 30 Mbit/s) and process it at 100 kHz update rates, converting this digital data into precise deflection coil control signals. This allows the system to utilize high-speed data processing capabilities that were previously unusable for electron beam control.
4Measurement precision
If analog amplifiers are used for displaying backscattered electrons, then synchronous display is achieved, but the accuracy and resolution are limited by amplifier oscillations
Solution Approach 1:
The patent replaces analog display and detection systems with a digital imaging system. Backscattered electrons are detected by a detector that generates digital signals, which are then processed by a microprocessor to create images displayed on a screen. This digital approach eliminates the oscillation and accuracy problems of analog systems while providing stable, high-resolution imaging of the electron beam position and workpiece surface.
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 allows for rapid and precise control of electron beams, achieving high data rates and generating accurate images of workpiece surfaces, overcoming the limitations of analog amplifiers by preventing oscillations and maintaining high resolution.
Implementation Method 1
A digital current adder arrangement that sums constant, unregulated currents to drive deflection coils
Implementation Method 2
it is also possible to generate an image of the workpiece to be processed, in that the electron beam 'quasi' simultaneously processes the workpiece and, while maintaining the welding capillary or capillaries, the electron beam in Intervals is guided over the surface areas of interest of the workpiece being processed, with a color image being able to be generated from the registered backscattered electrons
Data Source
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AI summary
A current adder arrangement for the rapid control of an inductor, in particular a deflection coil of an electron beam gun, is described, comprising a first voltage strip adapted to be connected to a voltage-stabilized power supply, a second voltage strip adapted to be connected to a first output for powering the inductor, and a plurality of first switchable bridges, each comprising a resistor switchable in series between the first and second voltage strips, with a resistance value such that a first resistor has a first resistance value WR11 = Rmin, a second resistor has a second resistance value WR12 ≥ WR11, and the nth resistor has an nth resistance value WR1n ≥ WR1n-1.