Methods and systems for characterizing laser machining properties by measuring keyhole dynamics using interferometry
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Publication Number
US-12257644-B2
Publication Date
2025-03-25
Expiration Date
Abstract
A method, apparatus, and system are provided to monitor and characterize the dynamics of a phase change region (PCR) created during laser welding, specifically keyhole welding, and other material modification processes, using low-coherence interferometry. By directing a measurement beam to multiple locations within and overlapping with the PCR, the system, apparatus, and method are used to determine, in real time, spatial and temporal characteristics of the weld such as keyhole depth, length, width, shape and whether the keyhole is unstable, closes or collapses. This information is important in determining the quality and material properties of a completed finished weld. It can also be used with feedback to modify the material modification process in real time.
Core Innovation
The invention relates to systems and methods for keyhole welding that create a phase change region (PCR) in a material of a sample, where the PCR includes a keyhole. An imaging system produces an imaging beam and an interferometer forms an interferometry output and an interferogram from the interferometer output. The interferometer includes a reference arm and a sample arm, and the sample arm output signal includes reflections from the sample location.
A deflection element controls the direction of the imaging beam, and a controller controls the deflection element to maintain alignment of the imaging beam relative to a feature of the PCR. The feature of the PCR is substantially a bottom surface of the keyhole of the PCR. The center of the imaging beam is directed to lag behind the material processing beam in a direction related to a velocity direction of the material processing beam relative to the sample location.
In the method embodiment, a material processing beam is applied to a sample location to create the PCR that includes a keyhole, then an imaging beam is applied to the sample location. The imaging beam is deflected such that it maintains alignment relative to the bottom surface of the keyhole, while the imaging beam center lags behind the material processing beam in a direction related to the relative velocity direction. The document further supports controlling or determining alignment behavior using the interferometer output and detecting misalignment relative to the PCR feature.
Claims Coverage
Two independent claims are identified: one system claim and one method claim. Across the independent claims, the main inventive features involve keyhole welding PCR imaging using an interferometer, maintaining alignment to a bottom-surface feature of the PCR, and directing the imaging beam center to lag behind the material processing beam based on relative velocity direction.
Keyhole welding with imaging interferometer and lag-aligned imaging beam
A system includes a material processing laser source configured to generate a material processing beam that is applied to a sample location in a material modification process creating a phase change region (PCR) including a keyhole; an imaging system producing an imaging beam; an interferometer with a reference arm and a sample arm whose outputs are combined by a combiner to produce an interferometry output; and a signal detector configured to produce an interferogram from the interferometry output. The system includes a deflection element controlling the direction of the imaging beam and a controller that controls the deflection element to maintain alignment of the imaging beam relative to a feature of the PCR, where the feature is substantially a bottom surface of the keyhole, and directs a center of the imaging beam to lag behind the material processing beam in a direction related to a velocity direction of the material processing beam relative to the sample location.
Deflected imaging beam aligned to keyhole bottom surface with velocity-related lag
A method applying a material processing beam to a sample location in a material modification process including a keyhole welding process to create a phase change region (PCR) with a keyhole; applying an imaging beam to the sample location; and deflecting the imaging beam such that it maintains alignment relative to a feature of the PCR, where the feature is substantially a bottom surface of a keyhole of the PCR, and directing a center of the imaging beam to lag behind the material processing beam in a direction related to a velocity direction of the material processing beam relative to the sample location.
Overall claim coverage centers on imaging and interferometry for keyhole welding PCR, where alignment is maintained to substantially the bottom surface of the keyhole and the imaging beam center lags behind the processing beam according to the processing velocity direction relative to the sample location.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Not explicitly described in patent.
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