Interferometer Path-Length Control for Laser Focus Stability
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Solution Overview
Problem
Current laser processing systems face challenges in maintaining accurate and reliable continuous distance determination, particularly due to uncontrolled variations in the real optical distance between the deflection system and the work surface, leading to irregularities in laser focus and poor material quality.
Innovation Solution
A measurement module with an optical path length regulator system that adjusts the optical path length difference between the reference and object arms of an interferometer, allowing for real-time compensation of distance variations using a broadband low coherence interferometric measurement system, integrated with a laser processing module for precise distance detection and focus control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an adjustable focusing system is used to overcome the limited work distance range of f-theta-lenses, then the range of available work distances is improved, but the system complexity and difficulty of maintaining accurate distance determination increase due to uncontrolled variations in real optical distance
Solution Approach 1:
The patent implements a feedback mechanism using an interferometric measurement system that continuously monitors the real optical distance between the deflection system and work surface. The measured distance information is fed back to the control unit, which automatically adjusts the focusing system to compensate for distance variations, thereby maintaining accurate focus without increasing manual complexity
Solution Approach 2:
The patent replaces manual or mechanical distance adjustment mechanisms with an optical measurement and automatic control system. The interferometric measurement system and automated feedback control substitute for complex mechanical focusing adjustments, reducing mechanical complexity while improving adaptability
2Ease of operation
If pre-set settings of the adjustable focusing system are stored in a look-up table format, then the focal position can be dynamically adjusted, but the measurement precision deteriorates due to uncontrolled variability in actual distance caused by surface irregularities
Solution Approach 1:
The interferometric measurement system provides real-time feedback on actual distance variations caused by surface irregularities. This feedback enables the control unit to dynamically adjust the focusing system beyond pre-set look-up table values, compensating for uncontrolled variability and maintaining measurement precision
Solution Approach 2:
The patent combines pre-set look-up table settings with real-time interferometric measurement. The look-up table provides preliminary focusing settings for known distances, while the interferometric system performs preliminary detection of actual distance variations, enabling both ease of operation and measurement precision
3Extent of automation
If distance detection systems based on triangulation, time-of-flight, or chromatic-confocal measurement are used, then continuous distance determination is enabled, but the reliability decreases because these systems are not suitable for on-axis configuration and are subject to the same sources of variability
Solution Approach 1:
The patent replaces triangulation, time-of-flight, or chromatic-confocal measurement systems with an interferometric measurement system. The interferometric system enables on-axis configuration that is not suitable for other methods, providing more reliable distance determination by eliminating the limitations of alternative measurement technologies
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 accurate and reliable distance measurements and focus maintenance across a broad range of work distances, improving the quality of laser processing by compensating for variations in the optical path length, thus ensuring consistent material quality.
Implementation Method 1
broadband low coherence interferometric measurement system
Implementation Method 2
broadband low coherence interferometric measurement system configured for measuring distances
Data Source
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AI summary
The invention refers to a measurement module (10) for a laser processing apparatus (1) in which a first optical path (Pi) and a second optical path (P2) are defined for laser light within a housing (11). The first optical path (Pi) has a fixed predefined optical path length. The second optical path (P2) is defined between a connection port (12) of the housing and a coupling port (14) and has a variable optical path length adjustable by an optical path length regulator system (20). The invention further refers to an interferometer system comprising a measurement module with a first optical path (Pi) corresponding to a reference arm of the interferometer system and with a second optical path (P2) corresponding to an object arm of the interferometer system, wherein an optical path length regulator system (20) is configured for adjusting an optical path length of the second optical path (P2), i.e., of the object arm of the interferometer system. The invention further refers to a laser processing apparatus (1) comprising a laser processing module (30) for laser-processing a workpiece (P) on a work field (37) using a work beam (W) and a measurement module (10) according to the invention.