Monitoring material processing using imaging signal density determined from inline coherent imaging (ICI)

A method comprising:

• producing a plurality of A-scans of a workpiece using an inline coherent imaging (ICI) system, wherein the A-scans are spaced by distance or time;
• and
• classifying A-scans as pertaining to at least one aspect of a phase change region or workpiece sub-region, wherein classifying the A-scans is performed using a monitoring system, wherein the A-scans are classified into categories representing the at least one aspect of the phase change region or the workpiece sub-region, and wherein the at least one aspect of the phase change region or workpiece sub-region is at least one of:
• vapor channel, vapor channel bottom, vapor channel sidewall, weld penetration depth, melt pool, workpiece surface, material composition, material phase, and material density.

A system comprising:

• a material processing system configured to generate a process beam and to direct the process beam toward a workpiece;
• an inline coherent imaging (ICI) system configured to generate an imaging beam, to direct the imaging beam toward the workpiece together with the process beam, to produce an interferometer output from a reflection of the imaging beam, and to detect the interferometer output to produce ICI data;
• and
• a monitoring system programmed to
• receive the ICI data and to determine at least an ICI imaging signal density, and
• classify at least one aspect of a phase change region or workpiece sub-region using the imaging signal density.