Electron Microscope Noise Cancellation Offset Adjustment
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Solution Overview
Problem
Existing electron microscopes face challenges in effectively performing noise cancellation due to insufficient information about the detector offset, especially when temperature variations affect the output signals, leading to increased noise in images.
Innovation Solution
An electron microscope configuration and method that allows for easy offset adjustment by measuring the output signal from the image detecting portion while blocking the electron beam, calculating and setting the offset signal into the noise canceling portion, which can be done synchronously with image acquisition, thereby maintaining optimal offset information and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offset signal is calculated based on detector output signal without blocking electron beam, then offset information can be obtained, but temperature variations cause signal drift leading to inaccurate offset calculation
Solution Approach 1:
The patent applies preliminary action by measuring the detector output signal before the electron beam is introduced to the sample. Specifically, the offset signal is measured during a period when the electron beam is blocked or before sample irradiation begins, ensuring that temperature drift during beam operation does not affect the offset measurement accuracy. This timing separation allows accurate baseline offset characterization independent of thermal effects.
2Reliability
If detector offset information is not available, then noise canceling function cannot be performed effectively, but obtaining offset information requires additional measurement steps
Solution Approach 1:
The patent implements self-service by enabling the system to automatically measure and determine its own detector offset signal without requiring external calibration equipment or manual intervention. The microcontroller automatically controls the beam blocking mechanism, measures the detector output during the blocked period, calculates the offset signal, and stores it for noise cancellation operations. This self-calibration capability makes the noise canceling function effective while maintaining ease of operation.
Solution Approach 2:
The system performs preliminary offset measurement and calibration before normal imaging operations begin. The offset signal is determined in advance during system initialization or between imaging sessions, so that when imaging starts, the noise canceling function is already configured with accurate offset information. This preliminary setup eliminates the need for complex real-time adjustments during operation.
3Reliability
If offset signal is not updated regularly, then noise cancellation performance degrades due to temperature drift, but frequent updates increase measurement time
Solution Approach 1:
The patent applies periodic action by implementing a time-based update mechanism where the offset signal is remeasured at predetermined intervals during imaging operations. The microcontroller is configured to automatically trigger offset measurements at regular time intervals or after specific conditions are met, ensuring that temperature drift is compensated without requiring continuous measurement. This periodic updating maintains noise cancellation accuracy while minimizing time loss compared to continuous monitoring.
Data Source
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AI summary
An electron microscope is offered which has a detector and a noise canceling circuit whose offset can be easily adjusted if any information about the offset of the detector is not available. Also, a method of adjusting this microscope is offered. The method of adjusting the electron microscope (1) starts with measuring the output voltage from a preamplifier (20) at given timing while blocking the electron beam transmitted through a sample (14) from hitting the detector (15) (step S 140). An offset voltage to be set into the noise canceling circuit (30) is calculated based on the measured output voltage from the preamplifier (20) (step S150). The calculated offset voltage is set into the noise canceling circuit (30) (step S160).