© 2011 Thorlabs
140 Thorlabs Beam 4.0
6.4
Ellipse (fitted)
The beam shape is being fitted to an ellipse using the set clip level (down from the peak).
Diameter (clip level) is given for the minor axis (min), major axis (max) and their
arithmetic mean value.
Ellipticity and Eccentricity of the beam are defined in ISO 11146-1 as
where d
min
denotes the minor and d
max
the major axes of the approximated beam
ellipse, respectively.
Orientation denotes the angle of the major ellipse axis is with respect to the
horizontal x axis and is within the range -90° < ≤ 90°.
6.5
X-Y-Profile Measurement
Beam Width Clip (xx%)
Beam width is the distance between two points on opposed edges of a captured
beam profile in X and Y axis whereas its height is defined by a certain percentage of
the peak power. This percentage is called clip level.
Preferred clip levels are for instance 50 % (Full Width at Half Maximum) and 13.53%
(exactly 1/e²).
Since the Beam Profiler software supports a variable clip level, the beam width is
always displayed with its clip level in brackets.
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