Methods and systems for characterizing laser machining properties by measuring keyhole dynamics using interferometry
Inventors
Assignees
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Publication Number
US-11426816-B2
Publication Date
2022-08-30
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 a material modification process using a focused, scanning material processing beam applied to a sample location. The system includes a beam delivery head that focuses the material processing beam relative to the sample location and scans the material processing beam relative to the sample location. An imaging system is optically coupled to the beam delivery head to produce at least one imaging beam directed toward the sample location and toward a reference reflective surface.
The imaging system is of a spectral domain type or a swept-source type and includes an optical interferometer that produces an interferometry output based on at least one sample optical path length compared to a reference optical path length. The reference optical path length is adjusted in coordination with scanning the material processing beam. The adjustment is in correlation with a changing position of the focus of the material processing beam as the processing beam is scanned, such that the reference arm optical path length correlates with the changing focus position.
Embodiments describe directing a component of the imaging beam on a sample arm path through the beam delivery head to imaging beam positions at the sample location, and directing a component of the imaging beam on at least one reference arm path to the reference reflective surface. In the system, at least a portion of the sample arm path and at least a portion of at least one reference arm path are included in the beam delivery head. In coordination with scanning, the system changes the reference optical path length by adjusting the reference reflective surface, and in some embodiments adjusts a focal lens with an actuator together with the reference reflective surface.
Claims Coverage
Three independent claims are identified: clm-00001, clm-00011, and clm-00017. Across the independent claims, the core inventive theme is using a spectral-domain or swept-source optical interferometer, including OCT for clm-00011, to measure interferometry based on a sample optical path length compared to an adjustable reference optical path length that is coordinated with scanning and correlates with a changing focus position of the processing beam.
Coordinated reference path length adjustment during scanning
An imaging system includes an optical interferometer that produces an interferometry output based on at least one sample optical path length to the sample location compared to a reference optical path length to a reference reflective surface, and the reference optical path length is configured to be adjusted in coordination with scanning the material processing beam and in correlation with a changing position of the focus of the material processing beam as the processing beam is scanned.
Optical coherence tomograph with sample and reference arm paths in the beam delivery head
The beam delivery head includes at least a portion of a sample arm path and at least a portion of at least one reference arm path including at least one reference reflective surface; a reference optical path length is configured to be adjusted by adjusting the at least one reference reflective surface, with the beam delivery head changing the reference optical path length in coordination with scanning the processing beam; and the imaging system is an optical coherence tomograph of a spectral domain type or a swept-source type producing an imaging beam directed on the sample arm path to imaging beam positions at the sample location and on the reference arm path to the reference reflective surface, with interferometry output based on at least one sample optical path length compared to the reference optical path length.
Method coordinating processing-beam scanning with reference arm path length correlation to focus position
A method comprising generating a material processing beam and an imaging beam of a spectral domain type or a swept-source type; focusing and scanning the material processing beam relative to the sample location; directing components of the imaging beam on a sample arm path to the sample location and on at least one reference arm path; and adjusting a reference arm optical path length relative to the sample location in coordination with scanning the material processing beam such that the reference arm optical path length correlates with a changing position of the focus of the material processing laser beam as the processing beam is scanned.
All independent claims require interferometric imaging, spectral domain or swept-source, and OCT in clm-00011, to compare sample optical path length to an adjustable reference optical path length, where the reference optical path length is coordinated with scanning and correlates with the changing focus position of the processing beam.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Not explicitly described in patent.
Interested in licensing this patent?