Method for monitoring the energy density of a laser beam by image analysis and corresponding device

Patent metadata

Field	Value
Publication number	US-2016228987-A1
Application number	US-201415022850-A
Country	US
Kind code	A1
Filing date	Sep 17, 2014
Priority date	Sep 18, 2013
Publication date	Aug 11, 2016
Grant date	—

Abstract

A method for monitoring the energy density of a laser beam using parameters of the laser beam including regularly applying the laser beam to a reference substrate and measuring, with each application, the resulting light intensity; identifying a change in the light intensity on the reference substrate between at least two measurements; and, when the change in the light intensity is higher than a predetermined threshold, determining the unstable parameter or parameters of the energy density of the laser beam.

First claim

1 . A method for controlling the energy density of a laser beam from at least two parameters of the laser beam, the method comprising the following steps:
regularly applying the laser beam on a reference support and measuring, at each application, the light intensity obtained on this reference support, identifying a variation in the light intensity on the reference support between at least two measurements, and when the variation in the light intensity is greater than a given threshold, determining the unstable parameter(s) of the energy density of the laser beam.

2 . The control method according to claim 1 , wherein the energy density of the laser beam is controlled from three parameters notably comprising the power, the velocity and the size of the laser beam.

3 . The control method according to claim 1 , wherein the step for applying and regularly measuring the light intensity on the reference support comprises the following sub-steps:
(i) applying the laser beam on a reference support and acquiring an image of the laser beam on said reference support, in order to obtain a reference image, (ii) determining the light intensity at the point of application of the laser beam in the reference image, and (iii) regularly applying the laser beam on the reference support and acquiring an image of the laser beam on said reference support, in order to obtain a control image, and determine the light intensity on the reference support at the point of application of the laser beam in the control image, and the step for identifying a variation in the light intensity comprises the following sub-steps: (iv) comparing the light intensity of the thereby obtained control image with the light intensity of the reference image, and (v) inferring therefrom the variation in the energy density of the laser beam.

4 . The control method according to claim 3 , wherein the light intensity is determined by measuring the grey levels of the reference image and of the control image.

5 . The control method according to claim 4 , wherein the gray levels of the reference image and of the control image are measured in several points, so that the light intensity is determined by averaging the intensity profile in each point of each image.

6 . The control method according to claim 3 , further comprising an initial step, before applying the laser beam on a reference surface in order to acquire the reference image, during which an initial value of the parameters is determined, and in which, when the variation in the light intensity is greater than a given threshold, the method further comprises the following sub-steps:
determining the value of the parameters of the laser beam and comparing it to the initial value of said parameters in order to identify the unstable parameter(s), and modifying the laser in order to re-stabilize said unstable parameter(s).

7 . The control method according to claim 6 , wherein the steps (i) to (iii) are re-iterated with the laser beam once it is modified, in order to define a new reference image.

8 . The control method according to claim 7 , wherein the initial step is also re-iterated.

9 . A device for controlling the energy density of a laser beam from at least two parameters of the laser beam, said parameters comprising a power, a velocity and/or a size of the laser beam, the device controlling the energy density of the laser beam according to claim 1 , and in that it comprises:
an image acquisition system, configured for acquiring images of the laser beam on the reference support, and an image processing system, adapted for comparing the light intensity of the different images acquired by the image acquisition system and identifying a variation in the light intensity on the reference support between at least two measurements, and data processing means, adapted for determining, from the variation in the light intensity, whether at least one of the parameters of the laser beam is unstable.

10 . The control device according to claim 9 , wherein the reference support comprises a homogenous coating.

11 . The control device according to claim 9 , wherein the reference support comprises a plate in aluminium alloy.

12 . The control device according to claim 11 , wherein the plate in aluminium alloy is anodized and comprises an anodization layer.

13 . The control device according to claim 12 , wherein the anodization layer is of a black color.

14 . The control device according to claim 12 , wherein the anodization layer has a thickness comprised between 0.5% and 3% of a thickness of the plate in aluminium alloy, preferably of the order of 1%.

15 . The control device according to claim 14 , wherein the thickness of the plate in aluminum alloy is of the order of 1 mm and the thickness of the anodization layer is of the order of 0.01 mm.

Assignees

• Snecma

Inventors

• Baudimont Cyrille
• Fouquet Julie
• Monnet Didier

Classifications

• B29C64/393

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• B22F12/90

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• B22F10/36

  of energy beam parameters · CPC title

• B22F10/20

  Direct sintering or melting · CPC title