Laser Head Optics Position Sensing Using Low-Coherence Interferometry
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Solution Overview
Problem
Existing laser processing machines lack precise and real-time control over the position of optical elements and operating parameters such as assist gas pressure and temperature, leading to potential inaccuracies in laser cutting, drilling, welding, and additive manufacturing processes.
Innovation Solution
The implementation of a low coherence interferometry technique for real-time monitoring of optical element positions and operating parameters, allowing for precise determination of optical path lengths and refractive index variations, thereby ensuring accurate control of laser processing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional laser processing machines are used without advanced monitoring systems, then the device complexity is low, but the manufacturing precision and reliability of laser processing operations deteriorate
Solution Approach 1:
The patent replaces complex mechanical measurement systems with optical interferometry. The interferometric system uses light waves to measure the position of optical elements with high precision, substituting mechanical sensors and actuators with an optical-based measurement approach that achieves sub-micrometer resolution without complex mechanical structures
Solution Approach 2:
The patent introduces an interferometric measurement system as an intermediary between the optical elements and the control system. This intermediary uses reference beams and measurement beams that interfere to produce fringe patterns, providing precise position information without requiring direct mechanical contact or complex sensing mechanisms
2Measurement precision
If real-time monitoring of optical element positions is implemented using low coherence interferometry, then the manufacturing precision improves, but the device complexity increases
Solution Approach 1:
The patent extracts only the essential measurement function from complex sensor systems. By using low coherence interferometry, it isolates the position measurement task to specific optical paths with beam splitters and detectors, removing unnecessary complexity from the overall system while maintaining high measurement precision
Solution Approach 2:
The patent changes the measurement parameter from mechanical displacement to optical path difference. By measuring the interference fringe patterns resulting from optical path length differences, the system achieves high precision measurement without requiring complex mechanical measurement mechanisms
3Reliability
If precise control of optical element positions is achieved through interferometry, then the reliability of laser processing improves, but the ease of operation deteriorates
Solution Approach 1:
The patent implements a feedback system where the interferometric measurement of optical element positions is continuously monitored and fed back to the control system. This feedback enables automatic correction of position deviations, maintaining reliable laser processing control while reducing the need for manual intervention and calibration
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 enables precise and repeatable control of laser beam direction and power distribution, improving the accuracy and consistency of laser processing operations, including cutting, drilling, welding, and additive manufacturing.
Implementation Method 1
generating a measurement optical beam (M) from a low coherence optical radiation source, said measurement optical beam being reflected or scattered by at least one back-reflective surface of an optical element interposed along an optical transport path of a processing laser beam; generating a reference optical beam (R) from said low coherence optical radiation source; superimposing said measurement optical beam (M) and said reference optical beam (R) to form a pattern of interference fringes
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.