Laser Head Optical Position Sensing Using Low-Coherence Interferometry
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Solution Overview
Problem
Existing laser processing machines face challenges in precisely controlling the position of optical elements and monitoring operating parameters such as pressure and temperature, which can lead to inaccuracies in laser cutting, drilling, welding, and additive manufacturing processes.
Innovation Solution
The implementation of a low coherence interferometry technique allows for the precise determination of the local position of optical elements and monitoring of operating parameters by using a measurement optical path and a reference optical path, enabling real-time adjustments and improving process accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement methods are used for optical element positioning, then the device complexity is low, but the measurement precision is insufficient
Solution Approach 1:
The patent introduces a low-coherence light source as an intermediary measurement tool that does not interfere with the high-power processing laser beam. This intermediary light source enables precise optical path length measurements through interferometry without affecting the primary laser processing function, thereby achieving high measurement precision while maintaining operational simplicity
Solution Approach 2:
The patent replaces traditional mechanical measurement systems with an optical interferometry-based measurement system. By using optical path length differences and interference patterns, the system achieves sub-micrometer positioning precision without complex mechanical sensors or actuators, reducing mechanical complexity while improving measurement accuracy
2Manufacturing precision
If real-time monitoring of optical element positions is implemented, then the manufacturing precision is improved, but the loss of time for measurements increases
Solution Approach 1:
The patent implements continuous real-time monitoring of optical element positions during laser processing operations. The low-coherence interferometry system operates continuously alongside the laser processing, providing uninterrupted position data without stopping or pausing the manufacturing process, thereby maintaining high manufacturing precision without time loss
Solution Approach 2:
The system performs preliminary calibration and establishes reference optical path lengths before actual processing begins. This preliminary setup enables rapid continuous monitoring during operation without requiring repeated calibration or measurement cycles, reducing time loss while maintaining precision throughout the manufacturing process
3Reliability
If multiple optical elements are monitored simultaneously, then the reliability of laser processing is improved, but the device complexity increases
Solution Approach 1:
The patent employs a universal low-coherence interferometry platform that can monitor multiple optical elements simultaneously using a single measurement system. By utilizing the same light source and detection infrastructure for multiple measurement paths, the system achieves high process reliability through comprehensive monitoring without proportionally increasing device complexity
Solution Approach 2:
The patent divides the monitoring system into independent measurement channels, each dedicated to monitoring a specific optical element. This segmentation allows parallel monitoring of multiple elements without interference between channels, maintaining system reliability while managing complexity through modular architecture where each channel can be independently optimized and maintained
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 method enables accurate and real-time monitoring of optical element positions and operating parameters, enhancing the precision and reliability of laser processing operations, such as cutting, drilling, and welding, and improving the quality of three-dimensional structures produced via additive manufacturing.
Implementation Method 1
generating a measurement optical beam of optical radiation M from said source (100), said measurement optical beam (M) being led along a measurement optical path (PM) to a sensor arrangement (S)... generating a reference optical beam of optical radiation R from said source (100), said reference optical beam (R) being led along a reference optical path (PR) to said sensor arrangement (S)... superimposing said measurement optical beam (M) and said reference optical beam (R)... detecting a pattern of interference fringes (F) between said measurement optical beam (M) and said reference optical beam (R)
Data Source
AI summary
A method for determining local position of an optical element associated with an optical path for transporting a laser beam in a working head of a machine for laser processing a material, includes generating a measurement beam of low coherence optical radiation traveling a measurement optical path, leading the measurement beam towards the optical element and the reflected or diffused measurement beam towards an optical interferometric sensor arrangement, generating a reference beam of low coherence optical radiation traveling a reference optical path and leading the reference beam towards the interferometric optical sensor arrangement, superimposing the measurement and reference beams on a common region of incidence, detecting a position of a pattern of interference fringes between the measurement and reference beams, and determining a difference in optical length between the measurement and reference optical paths as a function of the position of the interference pattern along an illumination axis, or of the frequency of the interference pattern in the frequency domain.