Methods and systems for coherent imaging and feedback control for modification of materials
Inventors
Kanko, Jordan • WEBSTER, Paul J. L. • Fraser, James M.
Assignees
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Publication Number
US-10898969-B2
Publication Date
2021-01-26
Expiration Date
Abstract
Methods and systems are provided for using optical interferometry in the context of material modification processes such as surgical laser, sintering, and 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 is an apparatus and method for monitoring and/or controlling a material modification process that includes a coherent imaging system integrated with a material processing beam. An optical interferometer produces an interferometry output based on optical path length to points in a phase change region and/or a surrounding region created in the material before, during, and/or after the material modification process, and the detector output is indicative of a characteristic of the phase change region and/or surrounding region during the material modification process.
The apparatus further includes one or more auxiliary optical sensors that collect light in a plurality of wavelength bands to measure at least one intrinsic optical emission from the phase change region, the surrounding region, or both. The intrinsic optical emission is intrinsic to the material modification process, and the auxiliary sensor output is connected to a signal processor, a quality assurance signal generator, a feedback processor/controller, and/or a record generator.
The disclosed monitoring and control architecture addresses closed-loop additive manufacturing monitoring by providing in situ morphology/interferometry-based assessment and intrinsic-emission sensing. The coherent imaging system and auxiliary optical sensing are combined to support detecting and differentiating characteristics associated with failure modes and process-condition related variations during material modification processes such as sintering, welding, brazing, and combinations thereof, including additive manufacturing variants and hybrid additive/subtractive manufacturing contexts.
Claims Coverage
The document provides two independent claims: an apparatus claim and a method claim. Across these independent claims, the main inventive features are centered on coherent interferometry of a phase change region with auxiliary multi-wavelength intrinsic optical emission sensing, coupled to record generation and quality assurance/feedback outputs that enable monitoring and/or controlling process parameters.
Coherent interferometry of phase change and/or surrounding region
A coherent imaging system including an optical interferometer produces an interferometry output using imaging light delivered to a phase change region and/or a surrounding region created in the material before, during, and/or after the material modification process, wherein the interferometry output is based on at least one optical path length to at least one point in the phase change region and/or the surrounding region compared to another optical path length, and the detector receives the interferometry output to produce a detector output indicative of a characteristic of the phase change region and/or the surrounding region during the material modification process.
Detector output indicative of region characteristics during processing and record generation over time
The detector output is indicative of a characteristic of the phase change region and/or the surrounding region during the material modification process, and a record generator generates at least one record based on the detector output at a plurality of times.
Auxiliary multi-wavelength intrinsic optical emission sensing and integration with QA/feedback/records
One or more auxiliary optical sensors collect light in a plurality of wavelength bands that measure at least one intrinsic optical emission from the phase change region, or the surrounding region, or both, producing one or more auxiliary sensor output, wherein the intrinsic optical emission is intrinsic to the material modification process, and wherein the one or more auxiliary sensor output is connected to at least one of a signal processor, a quality assurance signal generator, a feedback processor/controller, and a record generator such that at least one of the signal processor, quality assurance signal generator, feedback processor/controller, and record generator generates at least one of a record, annunciation, and feedback output.
Using interferometry output for controlling at least one processing parameter
Interferometry output indicative of a characteristic of the phase change region and/or the surrounding region during the material modification process is used to control at least one processing parameter of the material modification process.
Auxiliary sensing output connected to QA/feedback/records used for monitoring/adjusting
Auxiliary optical sensors collect light in a plurality of wavelength bands to measure intrinsic optical emission from the phase change region, or the surrounding region, or both, producing one or more output connected to at least one of a signal processor, a quality assurance signal generator, a feedback controller, and a record generator, wherein at least one of the signal processor, quality assurance signal generator, feedback controller, and record generator generates at least one of a record, annunciation, and feedback output, and wherein at least one of the record, annunciation, and feedback output is used for one or more of controlling, monitoring, and adjusting the material modification process.
Both independent claims share a core architecture: a coherent interferometer-based imaging system produces interferometry output correlated to characteristics of a phase change region and/or surrounding region during processing, while one or more auxiliary optical sensors measure intrinsic optical emission across multiple wavelength bands. The resulting interferometry and auxiliary sensor outputs are tied to detector output, record generation over a plurality of times, and outputs including quality assurance, annunciation, and feedback for monitoring and/or controlling at least one processing parameter.
Stated Advantages
Enables quality assurance, annunciation, and feedback outputs based on detector output and auxiliary intrinsic optical emission sensing.
Supports closed-loop monitoring by providing interferometry-based in situ indication of phase change region characteristics and integrating intrinsic emission measurements across multiple wavelength bands.
Generates records based on detector output at a plurality of times.
Uses interferometry output to control at least one processing parameter of the material modification process.
Provides record, annunciation, and feedback outputs used for controlling, monitoring, and adjusting the material modification process.
Documented Applications
In situ monitoring and/or controlling of a material modification process using a material processing beam with a phase change region and/or surrounding region assessment via coherent imaging interferometry and auxiliary intrinsic optical emission sensing.
Additive manufacturing monitoring and closed-loop additive manufacturing monitoring using coherent interferometry and multi-wavelength intrinsic emission sensing during, before, and/or after material modification processes.
Material modification processes including sintering, welding, brazing, and combinations thereof, and contexts including hybrid additive/subtractive manufacturing.
Laser surgery for hard tissue drilling/cutting.
Welding with keyhole monitoring and keyhole stability.
Breakthrough/refill detection.
Additive manufacturing quality assurance and control, including powder bed and melt pool-related monitoring.
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