© 2007-2012 Thorlabs GmbH
35Operating Instruction
The max. wavefront dynamic range is considerably lower because spot shifts
are limited to the fixed calculation windows.
Therefore, there is an increased risk of mismeasurement due to camera
saturation!
Besides that, centroid position results become extremely sensitive to the
cameras black level and ambient light because all pixel intensities within the
entire spot window (width x height pixels) contribute to the final centroid result.
Also low black level intensities will shift the result towards the window center.
In order to assure correct measurements in Highspeed Mode you need to take care
especially for the following setup parameters:
Exposure Time and Master Gain
Black level of the camera
Noise cut level for centroid interrogation
Please refer to chapter Camera Settings Setup for a detailed explanation of
these settings.
NOTE
Measurement speed is limited by the camera's exposure time. You need to apply a
sufficient high power level so that exposure time can be set much shorter than 1 /
required speed in fps!
Keep an eye on the status window!
Because the camera saturation remains unknown in Highseed Mode in case the
auto exposure option is disabled the camera image may suffer from over- or under
exposure which is leading to wavefront mismeasurement.
In order to reach the highest possible measurement speed, all 'power too high' or
'power too low' warnings are disabled in Highspeed Mode when the auto exposure
feature is also disabled. As a consequence, Highspeed Mode with disabled auto
exposure feature is only applicable when working at a quite constant power level.
But, a measurement error due to violation of the spot windows by the detected
centroids can be displayed.
NOTE
If this warning occurs, the wavefront measurement is most likely disturbed by spots
which are truncated by its detection window.
Achivable Speed
The following table shows the speed enhancement in Highspeed Mode for a typical
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