Scanning Unit Control Function for Position Error Compensation
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Solution Overview
Problem
In scanning image capture, particularly in laser scanning microscopes, the limited reaction speed of scanning units leads to position errors and image distortions due to the inability to follow intended nominal movements at higher scanning speeds, resulting in distorted images with defects such as line interlaces and undersampling issues.
Innovation Solution
A method is developed to generate a control function by summing a low-frequency linear function and a periodic function, where the increases in both functions are opposite and equal in magnitude, allowing for mutual compensation to maintain coordinate stability, and the control signals are used to control the scanning unit, decomposing movement into slow and periodic components to achieve desired movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the scanning speed is increased, then the productivity is improved, but the manufacturing precision deteriorates due to position errors and image distortions
Solution Approach 1:
The patent applies preliminary action by pre-calculating and applying correction values to the control signal before the scanning operation. The system determines correction values based on the relationship between scanning speed and position error, then applies these corrections in advance to the control function, allowing the scanning unit to compensate for expected position errors during high-speed operation without requiring real-time feedback adjustments
2Productivity
If the turnaround area is enlarged to increase scanning speed, then the productivity is improved, but the useful area becomes smaller reducing the effective scanning region
Solution Approach 1:
The patent applies parameter changes by modifying the control function parameters to account for position errors that occur during turnaround phases. Instead of physically enlarging the turnaround area, the system changes the control signal parameters (amplitude, phase, timing) to compensate for the position deviations, allowing the scanning unit to maintain accuracy without sacrificing useful scanning area
3Productivity
If the scanning unit is moved rapidly in the line feed direction, then the productivity is improved, but the position error increases due to limited reaction speed
Solution Approach 1:
The patent applies feedback by continuously monitoring the actual position of the scanning unit during line feed movements and comparing it with the intended nominal position. The system uses this position information to determine appropriate correction values that are applied to subsequent control signals, creating a closed-loop control system that maintains accuracy during rapid line feed operations
Data Source
AI summary
A method for generating a control signal is provided. The method includes the steps of decomposing a desired movement into two partial movements which are separately equalized, and the desired control signal is obtained by summing up the corrected components. The first movement is a slowly (mostly linear) changing long-period (period T1) movement, and the second movement is a short-period (period T2) movement, wherein the period T1 is substantially longer than the period T2. The movements have to a large extent opposing temporal derivations which are nevertheless equal in magnitude so that their sum has a time derivative that is zero. In addition, a method is provided for operating a scanning unit periodically displaceable in an infeed direction by an infeed distance.