THORLABS BC207UV, Operating Manual

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BC207 Series Chapter 6: Operation Instructions
Page 107
MTN026962-D02
The Normal Scan pursues an ISO compliant measurements. 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 ap-
proximately half of them shall be distributed beyond two Rayleigh Lengths from the
beam waist
."
The first run of the Normal Scan is executed with respect to the entered number of Data
Points , in other words, like a coarse scan. A preliminary Rayleigh Length is calculated in order
to evaluate if the number of measured data points is sufficient to fulfill the ISO standard require-
ments. If so, a hyperbolic fit is applied. If not, a second run adds additional measurements
within the Rayleigh Length on both sides and/or beyond twice the Rayleigh Length.
For a M
2
measurement, running the Normal Scan is highly advised. The coarse scan is suitable
for a first estimate of the beam waist position or other preliminary measurements.
Reset
Restores the default settings for M² settings:
Parameter Default Setting
Beam Width Beam Width Clip (1/e²)
Wavelength 635 nm
Timeout 15 sec
Start 0 mm
Stop 200 mm
Min. Data Points 10
Scan Method Normal Scan
Calculation Area
The settings for the Calculation Area can be made in the Beam Settings panel . During a
Beam Quality Measurement (M
2
or Divergence), the Automatic Calculation Area is enabled by
default for effective noise reduction. Reflections and artifacts from filters, lenses or other optical
elements can be suppressed as well using the automatic Calculation Area.
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 cases it might be useful to adjust the Clip Level to cover the whole intensity.
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