Methods and Systems for Characterizing Laser Machining Properties by Measuring Keyhole Dynamics Using Interferometry

Patent metadata

Field	Value
Publication number	US-2016039045-A1
Application number	US-201414775136-A
Country	US
Kind code	A1
Filing date	Mar 13, 2014
Priority date	Mar 13, 2013
Publication date	Feb 11, 2016
Grant 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.

First claim

1 . An apparatus comprising:
an imaging optical source that produces imaging light that is applied to a material processing system, wherein the material processing system implements a material modification process and creates a phase change region (PCR) in a material; at least one element that directs the imaging light at a plurality of imaging beam positions proximate the PCR; at least one input-output port that outputs a first component of the imaging light to an optical access port of the material processing system and that receives a reflection component of the imaging light; an optical combiner that combines the reflection component and at least another component of the imaging light to produce an interferometry output, the interferometry output based on a path length taken by the first component and the reflection component compared to a path length taken by the at least another component of the imaging light; and an interferometry output processor that processes the interferometry output to determine at least one characteristic of the PCR.

2 . The apparatus of claim 1 , further comprising a material processing beam source that produces a material processing beam that is applied to the material in the material modification process, wherein the material processing beam creates the PCR in the material.

3 . The apparatus of any preceding claim, wherein the interferometry output processor processes interferometery outputs over a period of time to determine the at least one characteristic of the PCR.

4 . The apparatus of any preceding claim, wherein the at least one characteristic of the PCR comprises at least one of:
keyhole depth; location of maximum keyhole depth; average depth; location; width; length; surface shape; subsurface shape; subsurface keyhole length; subsurface profile; subsurface keyhole width; wall slope; sidewall angle; collapse; instability; dynamics of liquid region of the PCR; location of interface between liquid and solid region; and other physical parameters of the PCR.

5 . The apparatus of any preceding claim, wherein the plurality of imaging beam positions comprise:
a plurality of imaging beam positions normal to the sample location; or a plurality of imaging beam positions having at least two different incident angles that are not normal to the sample location; or at least one imaging beam position normal to the sample location and at least one imaging beam position that is at an angle other than normal to the sample location.

6 . The apparatus of any preceding claim, further comprising:
a feedback controller that controls at least one processing parameter of the material modification process based on at least one of the determined at least one characteristic.

7 . The apparatus of any preceding claim further comprising:
a record generator that generates a record of the material modification process based on at least one of the determined at least one characteristic at a plurality of times.

8 . The apparatus of any preceding claim, further configured to evaluate quality of a weld produced by the material modification process optionally based on the record.

9 . The apparatus of any preceding claim, further comprising:
an acoustic energy source and/or an optical energy source configured to excite waves in a liquid region of the PCR to provide information regarding PCR dynamics.

10 . The apparatus of any preceding claim, wherein:
at least one of the plurality of imaging beam positions is outside the PCR.

11 . The apparatus of any preceding claim, wherein:
light is applied to at least two of the plurality of imaging beam positions simultaneously.

12 . The apparatus of any preceding claim, wherein:
light is applied to at least two of the plurality of imaging beam positions sequentially.

13 . The apparatus of any preceding claim wherein:
the plurality of imaging beam positions are achieved by changing the position and/or angle of at least one imaging beam relative to the material processing beam during the material modification process.

14 . The apparatus of any preceding claim, wherein:
the number of positions where imaging light is applied to the sample is changed during the material modification process.

15 . The apparatus of any preceding claim, wherein:
at least one of the plurality of imaging beam positions does not have an incident position that is on a line formed by the material processing beam.

16 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is used to determine a width or diameter of the keyhole when viewed from the same direction as the material processing beam is applied.

17 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is focused to a diameter that is smaller than a diameter of the material processing beam.

18 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is focused to a diameter that is similar to a diameter of the material processing beam.

19 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is focused to a diameter that is larger than a diameter of the material processing beam.

20 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is focused to a diameter that encompasses the PCR.

21 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of the imaging beam positions is focused to a diameter that is larger than the PCR.

22 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is used to take successive readings at a frequency of approximately 1 kHz or more.

23 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is used to take successive readings at a frequency of approximately 10 kHz or more.

24 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is used to take successive readings at a frequency of approximately 100 kHz or more.

25 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is used to determine a maximum depth achieved by a keyhole in the PCR over a period of time.

26 . The apparatus of claim 25 wherein:
the determination of maximum depth is used to control at least one parameter of the material modification process to reduce a number of instances where material modification fails to penetrate beyond a specified depth and/or into a specified material.

27 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is used to determine a shape and size of a keyhole in the PCR over time.

28 . The apparatus of any preceding claim, wherein:
imaging light applied to at least one of the plurality of imaging beam positions is used to determine if a keyhole collapses or fails to maintain a specified depth.

Assignees

• Univ Kingston

Inventors

• Webster Paul J L

Classifications

• B23K10/02

  Plasma welding · CPC title

• B23K26/14

  using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor (B23K26/12 takes precedence) · CPC title

• B23K15/0046

  Welding · CPC title

• B26F3/004

  by means of a fluid jet (methods for use of abrasive blasting for cutting B24C1/045; guns for abrasive fluid jets B24C5/02; perforating by non-mechanical means, e.g. by fluid jet B26F1/26) · CPC title

• B26F1/26

  Perforating by non-mechanical means, e.g. by fluid jet · CPC title