THORLABS M2MS, Operating Manual

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BP209 Series 10 Application Note
Rev: 8.1, 14-Feb-2022 © 2022 Thorlabs Page 141
10 Application Note
This chapter contains some background information about the measurement methods of beam
profiles.
Beam profiles can be characterized by a number of different parameters. We aim to offer a
software that allows to measure all usual beam parameters based on ISO11146-1 standard.
In the following sections detailed explanations are given to the measured parameters.
10.1 Coordinate Systems
Lab System
The lab system (AKA reference system) of coordinates is based on the true X and Y coordinate
orientation of the drum in accordance with the marking on the front panel.
Transformed System
The transformed system of coordinates is based on the calculated beam axes (minor and major
axes for elliptical fit or for 4
s beam diameter).
10.2 Raw Data Measurements
Lab (or Reference or Sensor) Coordinate System
4 s Beam Width is the width of a beam in X and Y axes (centroids), derived from the second
moment calculation:
where s
x
and s
y
are the standard deviation of the horizontal or vertical marginal distribution, re-
spectively:
and
Note
The 4 s Beam Width measurement is not in conformity with ISO11146! Displayed results are
for information only!
In accordance with ISO11146-3, beam diameters shall be defined at a 1/e² clip level for Slit
Beam Profilers, while for Camera Beam Profilers the 4
s X' and 4 s Y' beam widths apply.
Peak Position
X, Y : position of the pixel with highest intensity (AD value) which is found first with respect to
reference position.