© 2011 Thorlabs
110 Thorlabs Beam 4.0
measurement). The number of recorded beam widths equates exactly to entered
number of Data Points.
The Normal Scan is in the first instance equal to the Coarse Scan but can add a
series of further data points if some conditions for an ISO compliant measurement
are not yet given. The ISO standard requires that
"at least 10 measurements shall be taken. Approximately half of the measurements
shall be distributed within one Rayleigh length on either side of the beam waist, and
approximately half of them shall be distributed beyond two Rayleigh lengths from the
beam waist."
This means the first run of the Normal Scan calculates a temporary Rayleigh length
and evaluates if enough data points are already measured. If yes a hyperbolic fit is
applied. If not a second run adds additional measurements within the Rayleigh length
on both sides and/or beyond two Rayleigh lengths.
For a M
2
measurement the Normal Scan is highly advised. Only, for example, for a
first estimation position of the beam waist position or other simple applications the
Coarse Scan should be used.
Reset
Restores the default settings for M² settings:
4-Sigma Diameter (ISO-Standard)
150 / 300 mm (depending on the stage length)
Calculation Area
The settings for the Calculation Area can be made in the Application Settings .
During a Beam Quality Measurement (M
2
or Divergence) the Automatic Calculation
Area is enabled by default for effective noise reduction. Reflections and artefacts
from filters, lenses or other optical elements can be suppressed as well using the
automatic Calculation Area which is close to the beam profile.
This setting can be changed to manual, but this may affect the measurement.
By default the Clip Level of the Calculation Area is set to 1%. This is a reasonable
value for most applications and measurements. Lowering the clip level leads to
increased calculation area and noise level, this way increasing the measured the
beam width.
For some beams it might be useful to adjust the Clip Level to cover the whole
intensity.
Initial settings
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