THORLABS WFS150, Operation Manual

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70 WFS150 / WFS150C Manual
© <2007> ... Thorlabs GmbH
It is required to define a Zernike radius because the Zernike functions fitted to the
measured wavefront are normalized to a Unity Radius = 1. Calculated Zernike
coefficients refer to the here defined pupil radius (see
Zernike Fit Setup ).
Pupil Diameter (mm)
The here defined Pupil Diameter is twice normalized radius (= 1) of the Zernike
functions. This Pupil Diameter in mm can be set manually or automatically.
If ' Use Beam Width' is enabled the pupil diameter is automatically adapted to the
measured beam width. The beam width is measured using the second moment
method and corresponds to the 1/e
2
diameter in case of a Gaussian beam shape.
Note: The second moment method will calculate accurate beam widths only
when ambient light is shielded from the Wavefront Sensor and the ' Black Level '
of the camera is properly aligned (see Camera Settings Setup ) . A positive offset
to the beam's intensity distribution will lead to beam diameters larger than real. A
manual defined '
Noise Cut Level ' in the Camera Settings will help to reject an
increased dark level.
Let ' Use Beam Width ' unchecked to define the pupil size manually. You may
define an elliptical pupil by entering different values for X and Y diameter. Here,
the mean diameter defines the Zernike circle.