Laser Machining Head Distance Measurement with Pressure Compensation
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Solution Overview
Problem
Laser machining apparatus face challenges in precisely measuring the distance between the machining head and workpiece due to pressure fluctuations affecting optical path lengths, leading to inaccurate measurements, especially when using optical coherence tomography.
Innovation Solution
Incorporating a measuring beam that passes through the interior of the machining head alongside the object beam to compensate for pressure fluctuations, using optical coherence tomography to superimpose and determine interference signals, ensuring accurate distance measurement by matching pressure distributions between the object and measuring beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical coherence tomography is used to measure distance through the machining head interior, then measurement precision is improved, but reliability deteriorates due to pressure fluctuations affecting optical path length
Solution Approach 1:
The patent implements feedback control by continuously monitoring pressure fluctuations within the machining head interior and dynamically adjusting the optical path length compensation. The system measures the actual pressure conditions and uses this information to correct the optical path length calculations in real-time, ensuring reliable distance measurements despite varying pressure conditions during laser machining operations
Solution Approach 2:
The patent compensates for pressure-induced optical path length changes by dynamically adjusting measurement parameters based on detected pressure fluctuations. By changing the reference optical path length parameter according to actual pressure conditions, the system maintains measurement accuracy and reliability across varying operational pressures
2Ease of operation
If a camera is used to observe the machining location, then ease of operation is improved, but measurement precision deteriorates because only lateral offset can be measured, not distance in Z direction
Solution Approach 1:
The patent merges the advantages of camera-based observation with optical coherence tomography by integrating both systems. The camera provides easy operational monitoring of the machining location, while the OCT system simultaneously performs precise Z-direction distance measurements through the same machining head interior, combining the ease of operation with high measurement precision
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 approach provides highly precise distance measurements, enabling effective feedback control to maintain the optimal position of the machining head relative to the workpiece, improving process quality and accuracy in laser machining operations.
Implementation Method 1
generating an object beam by means of a light source of an optical coherence tomograph, and directing the object beam on to the workpiece in such a manner that the object beam passes through the interior and the opening before being incident upon the workpiece; capturing the reflection of the object beam reflected from the workpiece
Implementation Method 2
a measuring beam passes through the interior, which measuring beam is used to compensate falsifications of the measured distance that have been caused by pressure fluctuations in the interior
Implementation Method 3
superimposition the reflection of the object beam with a reference beam generated by the light source of the coherence tomograph; determining the distance between the machining head and the workpiece from an interference signal obtained by the superimposition
Data Source
AI summary
According to a method for measuring the distance between a workpiece and a machining head of a laser machining apparatus, a machining head is provided, which has a housing that has an interior and an opening for emergence of the laser radiation from the machining head. The laser radiation is directed on to the workpiece, after it has passed through the interior and the opening. An object beam is directed on to the workpiece by a light source of an optical coherence tomograph in such a manner that the object beam passes through the interior and the opening before being incident upon the workpiece. In addition to the object beam, a measuring beam passes through the interior. The measuring beam is used to compensate falsifications of the measured distance that have been caused by pressure fluctuations in the interior. The measuring beam in this case may be reflected at a reflective face that is formed on an inner face of an outlet nozzle that comprises the opening, which inner face delimits the interior.