Methods and systems for coherent imaging and feedback control for modification of materials
Inventors
WEBSTER, Paul J. L. • Fraser, James M. • YANG, Victor X. D.
Assignees
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Publication Number
US-9457428-B2
Publication Date
2016-10-04
Expiration Date
Abstract
Methods and systems are provided for using optical interferometry in the context of material modification processes such as surgical laser or welding applications. An imaging optical source that produces imaging light. A feedback controller controls at least one processing parameter of the material modification process based on an interferometry output generated using the imaging light. A method of processing interferograms is provided based on homodyne filtering. A method of generating a record of a material modification process using an interferometry output is provided.
Core Innovation
The invention describes an apparatus for a welding process or a sintering process that uses a material processing beam source and an imaging optical source to perform inline coherent imaging of a phase change region created in material during processing. The apparatus includes an optical interferometer that produces an interferometry output using at least a component of the imaging light delivered to the phase change region, where the interferometry output is based on optical path length to at least one point in the phase change region compared to another optical path length. The optical path length is substantially matched to the optical path length to the phase change region.
A detector receives the interferometry output and produces a detector output indicative of a characteristic of the phase change region during the material modification process. The apparatus generates at least one record based on the detector output at a plurality of times and/or controls at least one processing parameter of the material modification process based on the detector output. This enables monitoring and automated control tied to the characteristic of the phase change region detected by the interferometry output.
The described embodiments further support depth-related monitoring by using interferometry processing to produce a depth measurement reflecting how deep the material processing beam has penetrated the phase change region at a sample location. They also include sensing subsurface-level changes, such as temperature change, state change, change in fluid flow, and change in a pressure wave, with at least one embodiment observing changes in a speckle pattern. Additional embodiments refine optical path-length matching relative to an imaging system field of view, and use record generation and feedback control to monitor process characteristics over time.
Claims Coverage
Independent claim clm-00001 covers an apparatus that combines inline coherent imaging interferometry with a welding or sintering process and either records interferometry-derived detector output over time, performs feedback control of processing parameters from detector output, or performs both. The independent claim includes five core functional blocks: material processing beam, imaging interferometer with matched optical path lengths to the phase change region, detector-derived phase-characteristic output, and record generation and/or feedback control.
Material modification beam apparatus for welding or sintering
A material processing beam source produces a material processing beam applied to a sample location in a material modification process, wherein the material modification process is a welding process or a sintering process.
Inline coherent imaging interferometer with matched optical path lengths
An imaging optical source produces imaging light; an optical interferometer produces an interferometry output using at least a component of the imaging light delivered to a phase change region created in the material, wherein the interferometry output is based on at least one optical path length to at least one point in the phase change region compared to another optical path length, substantially matched to an optical path length to the phase change region.
Detector output indicative of phase change region characteristic
A detector receives the interferometry output and produces a detector output indicative of a characteristic of the phase change region during the material modification process.
Record generation and/or feedback control from detector output
A record generator generates at least one record based on the detector output at a plurality of times; or a feedback controller controls at least one processing parameter of the material modification process based on the detector output; or both (i) and (ii).
Across the independent claim, the inventive concept is an apparatus that monitors a phase change region in welding or sintering using interferometry output derived from imaging light with optical path length comparison, converts interferometry output into a detector output indicative of the phase region characteristic, and either records that detector output over time, uses it for feedback control of processing parameters, or performs both.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Inline coherent imaging monitoring of an optical phase change region during material modification, including welding process monitoring and sintering process monitoring.
Depth-related monitoring based on interferometry-derived depth measurement reflecting how deep the material processing beam penetrates the phase change region at a sample location.
Subsurface change monitoring using detector output indicative of subsurface-level changes including temperature change, state change, change in fluid flow, and change in a pressure wave, including speckle-pattern-based sensing.
Monitoring and control logic that records process-related indicators and/or applies feedback control based on interferometry-derived detector output.
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