Laser Welding Beam Alignment for Accurate Keyhole Depth Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Laser welding devices face inaccuracies in measuring keyhole penetration depth due to optical axis misalignment caused by beam splitter warping, leading to shallower measurements than actual depths.
Innovation Solution
A method that emits a laser beam and a measurement beam coaxially, with the measurement beam having a different wavelength, to determine optical axis deviation and correct its irradiation position to ensure accurate alignment, allowing for precise penetration depth measurement by moving the irradiation position into a predetermined area centered at the laser beam's axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a beam splitter is used to separate the laser beam and measurement beam, then the measurement system can be configured, but the beam splitter may warp due to heat or vibration causing optical axis misalignment
Solution Approach 1:
The patent introduces a beam combiner as an intermediary optical element that merges the laser beam and measurement beam into a single optical path. This mediator allows both beams to travel coaxially through the same optical components, eliminating the need for separate optical paths that would require multiple beam splitters. The beam combiner ensures stable optical axis alignment by providing a single integration point for both beams, thereby preventing misalignment issues caused by beam splitter warping due to heat or vibration.
2Ease of operation
If the optical axis of the measurement beam deviates from the laser beam, then the measurement beam can be emitted to a shallower portion, but the penetration depth measurement becomes inaccurate
Solution Approach 1:
The patent merges the optical paths of the laser beam and measurement beam into a single coaxial path using a beam combiner. This combining ensures that both beams share the same optical axis and focus at the same location on the workpiece. By merging the beams, the system guarantees that the measurement beam always targets the deepest portion of the keyhole where the laser beam is most intense, thereby ensuring accurate penetration depth measurements regardless of external disturbances.
3Device complexity
If the beam splitter warps due to heat or vibration, then the optical axes become misaligned, but the system structure remains simple
Solution Approach 1:
The patent extracts the beam splitter from the optical system and replaces it with a beam combiner configuration. This extraction eliminates the problematic component that warps under thermal or vibrational stress. The beam combiner design allows both the laser beam and measurement beam to be integrated into a single stable optical path without requiring a beam splitter, thereby removing the source of optical axis instability while maintaining structural simplicity.
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 ensures accurate determination of the penetration depth by correcting optical axis deviations, reducing the likelihood of measuring shallower depths than the actual keyhole penetration, thereby enhancing the reliability of weld quality assessment.
Implementation Method 1
The measurement beam is reflected from the bottom of the keyhole and received by an optical interferometer via a beam splitter. Since the optical interferometer can measure the optical path length of the measurement beam, the depth of the keyhole is detected from the measured optical path length
Implementation Method 2
The laser welding device is configured to coaxially align a laser beam with a measurement beam and emit the coaxially aligned beams into a keyhole of a weld portion. The measurement beam has a wavelength different from a wavelength of the laser beam
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A plurality of values measured are relatively compared to determine an optical axis deviation direction in which an optical axis of a measurement beam S deviates from a laser beam L. Then, a first parallel plate 26 and a second parallel plate 27 are rotated to move an irradiation position of the measurement beam S so that an optical axis of the measurement beam S is substantially coaxial with an optical axis of the laser beam L.