THORLABS WFS20-14AR, Operation Manual

Page: 31 / 153

© 2007 - 2018 Thorlabs
5 Operating Instruction
29
High-Speed Mode (WFS20 only)
For a detailed description of the differences between Normal and Highspeed Mode please refer
to section
WFS20 High Speed Mode .
Pupil Definintion Tab
The pupil defines a circular area within the spot field and wavefront display. It is the physical
representation of a mathematical unit circle (radius = 1).
ated within the pupil are used for fitting the measured wavefront distortions to Zernike functions.
This is accomplished by normalizing the physical centroid positions (in mm or camera pixels) to
the dimensionless positions within the unit circle.
Consequently, a wavefront reconstructed from selected Zernike functions can be calculated
and displayed only within the pupil area.
The Zernike calculations, which require a circular pupil, can also be adapted to elliptical beams.
Set the pupil to an elliptical shape, and the software scales the x and y axes to fit a unit circle.
After completing the calculations, the software scales the results back to the elliptical pupil.
For a measurement, the pupil size and shape are selected to match the diameter of the beam
that is tested. The measured Zernike coefficients are related to this selected area only. For a
Gaussian beam shape the pupil diameter is often set to its 1/e² diameter.
To define the pupil, Select the Pupil Definition tab in the Setup Wavefront Sensor panel:
57