Methods and Systems for Coherent Imaging and Feedback Control for Modification of Materials

Patent metadata

Field	Value
Publication number	US-2018290235-A1
Application number	US-201816007377-A
Country	US
Kind code	A1
Filing date	Jun 13, 2018
Priority date	Sep 25, 2010
Publication date	Oct 11, 2018
Grant 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.

First claim

We claim:

1 . An apparatus comprising:
a laser beam source that produces a laser beam that is applied to a sample location in a material modification process, wherein the material modification process is a welding process; an imaging optical source that produces imaging light; an optical interferometer that produces an interferometry output using at least a component of the imaging light that is delivered into a phase change region created in the material during the welding process, the interferometry output based on at least one optical path length to at least one point in the phase change region compared to another optical path length; a detector that receives the interferometry output and produces a detector output that is indicative of a characteristic of the phase change region during the welding process; and a feedback controller that controls at least one processing parameter of the material modification process based on the detector output.

2 . The apparatus of claim 1 , wherein the feedback controller processes multiple instances of the detector output to identify a change in the detector output in respect of a material being processed, and wherein feedback control is a function of such change.

3 . The apparatus of claim 2 , wherein the feedback controller provides an indication of a modification rate, sample motion, or a rate of change, based on the change in the detector output.

4 . The apparatus of claim 1 , wherein the feedback controller is a real-time controller that controls the at least one processing parameter of the material modification process during the process.

5 . The apparatus of claim 1 , wherein the at least one processing parameter includes power of the laser beam.

6 . The apparatus of claim 1 , wherein the feedback controller controls at least one processing parameter based on a depth measurement.

7 . The apparatus of claim 1 , wherein the feedback controller controls power of the laser beam based on a depth measurement.

8 . The apparatus of claim 1 , further comprising:
an interferogram processor that performs an analysis based on the interferometry output to produce a depth measurement reflecting how deep the laser beam has penetrated in the phase change region.

9 . The apparatus of claim 8 , wherein the feedback controller controls at least one processing parameter based on the depth measurement.

10 . The apparatus of claim 8 , wherein the interferogram processor produces a depth measurement relative to a surface of the material.

11 . The apparatus of claim 1 , wherein the optical interferometer further produces an output based on a component of the imaging light that is delivered to a different location on the material being processed.

12 . The apparatus of claim 1 , wherein the interferometer is a Michelson interferometer.

13 . A method comprising:
applying a laser beam to a sample location as part of a material modification process, wherein the material modification process is a welding process; generating imaging light with an imaging optical source; producing an interferometry output using at least a component of the imaging light that is delivered into a phase change region created in the material during the welding process, the interferometry output based on at least one optical path length to at least one point in the phase change region compared to another optical path length; detecting the interferometry output producing a detector output that is indicative of a characteristic of the phase change region during the welding process; and controlling at least one processing parameter of the material modification process based on the detector output.

14 . The method of claim 13 further comprising:
producing a depth measurement reflecting how deep the laser beam has penetrated in the phase change region, wherein the at least one processing parameter of the material modification process is controlled based on the depth measurement.

15 . The method of claim 14 , wherein the at least one processing parameter includes power of the laser beam.

16 . The method of claim 13 , wherein the at least one processing parameter includes power of the laser beam.

17 . The method of claim 13 further comprising: producing an interferometry output using a component of the imaging light that is delivered to a different location on the material being processed.

18 . The method of claim 17 wherein the detector output for the component of the imaging light that is delivered into the phase change region is indicative of depth of a keyhole formed in the phase change region.

19 . The method of claim 14 wherein the depth measurement is relative to a surface of the material.

20 . The method of claim 14 wherein the at least one processing parameter is controlled in real-time during the material modification process.

Assignees

• Ipg Photonics Corp

Inventors

• Webster Paul J L
• Fraser James M
• Yang Victor X D

Classifications

• B29C64/393

  for controlling or regulating additive manufacturing processes · CPC title

• B22F10/30

  Process control · CPC title

• B22F10/10

  Formation of a green body · CPC title

• B22F10/36

  of energy beam parameters · CPC title

• B22F10/66

  by mechanical means · CPC title