Charged Particle Beam Signal Correction via Inverse Filtering
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Solution Overview
Problem
Charged particle beam devices face blurring issues due to frequency band limitations in electrical signal paths, leading to distorted images during high-speed scanning, as the detector and amplifier circuit responses cannot keep pace with signal changes, resulting in convolved output signals.
Innovation Solution
A charged particle beam device that acquires secondary signals at different speeds, calculates a degradation function, and uses an inverse filter for correction, with parameters updated as needed to maintain optimal image restoration over time, addressing the blurring phenomenon by compensating for changes in the transfer function of the electrical signal path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed scanning is performed to increase productivity, then scanning speed increases, but image quality deteriorates due to blurring caused by frequency band limitation
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values in a lookup table before high-speed scanning occurs. The correction values, which compensate for the detector's transient response characteristics, are prepared in advance based on the relationship between scanning speed and signal degradation. During high-speed scanning, these pre-computed correction values are directly applied to restore image quality without real-time calculation delays.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the correction values based on the scanning speed parameter. The lookup table stores correction values corresponding to different scanning speeds, allowing the system to select appropriate correction parameters dynamically. This enables the system to maintain image quality across various scanning speeds by changing the correction parameters rather than the fundamental detection mechanism.
2Manufacturing precision
If slow scanning is performed to maintain image quality, then image clarity is preserved, but productivity decreases due to reduced scanning speed
Solution Approach 1:
The patent introduces an intermediary element - the lookup table containing pre-calculated correction values - that mediates between the detector's limited response speed and the scanning speed requirements. This intermediary allows the system to operate at high scanning speeds while still achieving image quality comparable to slow scanning, as the lookup table effectively decouples the relationship between scanning speed and image degradation.
3Measurement precision
If detector response speed is increased to follow fast signal changes, then signal accuracy improves, but device complexity increases due to hardware requirements
Solution Approach 1:
The patent replaces the mechanical/electrical solution (faster detector hardware) with a computational solution. Instead of increasing the detector's physical response speed, the system uses software-based correction through the lookup table to compensate for the detector's limited response characteristics. This substitution of computational processing for hardware enhancement reduces device complexity while maintaining signal accuracy.
Data Source
AI summary
A charged particle beam device of the present invention has a signal processing function of acquiring a secondary signal obtained when a charged particle beam is caused to scan at a low speed not subjected to a band limitation of an electrical signal path, and a secondary signal obtained when a charged particle beam is caused to scan at a high speed subjected to the band limitation of the electrical signal path, calculating a degradation function (H−1(s)) between the plurality of secondary signals, and using an inverse function thereof as a correction filter; and a function of updating a parameter of the correction filter to an optimal value as needed or at given timing. Accordingly, the charged particle beam device can perform optimum image restoration even when a detector or an amplifier circuit that constitutes the electrical signal path degrades with time.