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Beamage-M² User Manual Revision 6 37
6.1. PROCEDURE FOR MANUAL MEASUREMENT
This procedure explains how to execute an M² measurement with a Beamage camera without the need to
use a Beamage-M² system. It requires the use of a lens, a Beamage camera, some hardware to align and
keep them on
the laser beam’s optical axis, and a ruler.
1) Start the image capture.
2) Ensure that the following conditions are met to maximize the accuracy of the M
2
measurement:
a. Set the Beam Diameter Definition at 4 sigma (ISO)
b. Set the Crosshair position at:
i. Centre: Centroid
ii. Orientation: Auto Orient
c. Execute Subtract Background to minimize the noise
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3) Click the M
2
button in the main menu.
Figure 6-2: M
2
button
4) Go to the M
2
SETUP panel and enter the parameters of your setup:
a. Enter the laser wavelength
b. Enter the focal length of the lens chosen for the installation
Figure 6-3: M
2
Fixed Values window
5) Measure the distance between the lens and the sensor of the Beamage. The sensor is positioned
at 7.8 mm from the front of the casing. Enter the distance in Manual Settings (see 5.3.4)
6) Click on the
Add button. The measured X and Y widths, the exposure time and the image will
automatically be saved.
7) Move the Beamage and repeat steps 5 and 6 as you go along the Z-axis. You will notice that, as
you get closer to the waist, the diameters and exposure times will decrease.
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Note that, in theory, the background subtraction is only valid for one exposure time. For rigorous
measurements, the subtraction should be performed for every measurement as they will be executed at
different exposure times. However, making a background subtraction at the highest exposure time and then
using the
Auto Exposure will greatly minimize the error. It is thus a very acceptable method in standard
environments.