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78 WFS Series

an elliptical pupil by entering different values for X and Y diameter. Here, the mean

diameter defines the Zernike circle.

NOTE

This option 'Use Beam Width' must be switched off when entering Highspeed Mode

of WFS10 instruments because the beam width cannot be measured with a

sufficient accuracy in Highspeed Mode.

NOTE

The pupil diameter cannot be defined larger than the active camera area defined

with Camera Image Size in the Camera Settings . In this case the warning "Pupil

is larger than selected camera area" (see chapter Measurement Warnings and

Errors ) will occur. This limitation prevents Zernike calculations with increased

uncertainties because the measurement points (spots of the lenslets) are no more

equally distributed across the pupil area.

See chapter Minimal Beam and Pupil Diameter for the minimal pupil diameter

required for calculation of Zernike modes up to a desired order.

It is recommended to use a 'Circular Pupil' by selecting the appropriate option.

Here, only the diameter in X needs to be entered and the Y diameter is set to the

same value.

Pupil Center (mm)

The pupil center in mm can also be set manually or automatically.

It is recommended to enable 'Use Beam Centroid' in order to automatically adapt

the pupil center to the measured beam centroid coordinates. In case of fluctuations

of the beam position during the measurement, the Wavefront Sensor will

automatically follow the wandered spot. If you switch to manual input you can use the

' 0.0' button to set the pupil centroid to the center of the Wavefront Sensor.

NOTE

Manual definition of the pupil center requires a careful and stable beam adjustment,

otherwise the measurement results will suffer from increasing errors.

It is recommended to review the pupil size and position using the appropriate

functions in the 'Spot Field' and 'Beam View' displays. The 'Show Pupil' option

must be enabled in the appropriate configuration panels.

NOTE

This option 'Use Beam Centroid' must be switched off when entering Highspeed

Mode of WFS10 instruments because the beam centroid cannot be measured with

a sufficient accuracy in Highspeed Mode.

127

THORLABS WFS Series User Manual

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