Laser Machining Head With OCT Focus Tracking for Remote Welding
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Solution Overview
Problem
Existing laser processing devices face challenges in precisely positioning the focal spot on workpieces, especially for remote laser welding and cutting, due to shape deviations and positioning tolerances, which limits the ability to produce accurate fillet weld seams on galvanized steel plates and increases material consumption.
Innovation Solution
A processing head with adjustable focusing optics and an optical coherence tomograph that synchronously tracks the optical path length in the reference arm, allowing for precise measurement and positioning of the focal spot over varying distances, using a path length modulator to enhance the axial measuring range of the coherence tomograph.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the processing head is positioned far from the workpiece for remote laser welding, then processing speed increases and spatter contamination is reduced, but the focal spot cannot be positioned accurately on the workpiece surface
Solution Approach 1:
The patent implements an optical coherence tomograph (OCT) that continuously measures the actual distance between the processing head and workpiece surface, providing real-time feedback. This feedback is used by a control device to dynamically adjust the focal length of the focusing optics, ensuring the focal spot remains precisely positioned on the workpiece surface even during remote processing operations.
Solution Approach 2:
The patent dynamically changes the focal length parameter of the focusing optics based on real-time distance measurements from the OCT. By adjusting the focal length in response to measured distance variations, the system maintains accurate focal spot positioning despite the increased head-to-workpiece distance required for remote processing.
2Length of moving object
If the focal length of focusing optics is changed to adjust focal spot distance, then remote processing capability is improved, but the optical path length in the coherence tomograph reference arm becomes mismatched
Solution Approach 1:
The control device receives real-time feedback from the OCT about the current optical path length difference between the object arm and reference arm. When the focal length changes, the control device uses this feedback to calculate and apply the necessary adjustment to the reference arm optical path length, maintaining precise matching.
Solution Approach 2:
The patent implements a dynamic adjustment mechanism where the optical path length in the reference arm is continuously adapted to match changes in the object arm. This dynamic adjustment, controlled by the control device, ensures that the OCT maintains optimal interference conditions despite focal length variations required for remote processing.
3Measurement precision
If a path length modulator is added to track optical path length changes, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The control device serves multiple functions: it processes OCT measurement data, calculates required focal length adjustments, controls the focusing optics, and manages the path length modulator. This multi-functionality reduces overall system complexity by consolidating control functions into a single device rather than requiring separate control systems for each function.
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
Enables precise positioning and tracking of the focal spot, allowing for accurate fillet welds on galvanized steel plates and reducing material consumption by maintaining high processing quality and efficiency in remote laser processing.
Implementation Method 1
Measuring light which has been generated by a measuring light source and reflected by the workpiece, interferes in the coherence tomograph with measuring light which has travelled an optical path length in a reference arm
Implementation Method 2
there is arranged in the reference arm a path length modulator which tracks the optical path length in the reference arm synchronously with and dependent on a change of the focal length of the focusing optics
Implementation Method 3
adjustable focusing optics, which are adapted to focus the laser radiation in a focal spot, the distance between the focal spot and a processing head being changeable by changing the focal length of the focusing optics
Data Source
AI summary
A processing head for a laser processing device adapted for processing a workpiece using laser radiation has: adjustable focusing optics to focus laser radiation in a focal spot having an adjustable distance from the processing head; an optical coherence tomograph to measure a distance between the processing head and the workpiece by measuring an optical interference between measuring light reflected by the workpiece and measuring light not reflected by the workpiece; a path length modulator that can change, synchronously with and dependent on a change of the focal spot distance from the processing head, an optical path length in an optical path along which measuring light propagates; a scanning device, which deflects the laser radiation in different directions; and a control device, which i) controls a focal length of the focusing optics in such a way that the focal spot is situated at a desired location on the workpiece, ii) receives, from the coherence tomograph, information representing the distance between the processing head and the workpiece, and iii) uses information received from the coherence tomograph for a continuous correction of a positioning of the focal spot on the workpiece.