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7.6 Software limits via Range Flag
The range flag can be used to switch off the autofocus servo outside of a certain Z-position range.
This is a useful safety feature for all users, but can also be used to maintain focus on certain focal
planes at high magnification without refocusing onto other planes, and to enable rapid exchange of
samples.
Switch the controller into MAN FOC mode. Bring the sample into focus. Open the Range
dialogue box which can be found on the main GUI taskbar.
Tick the box to turn on the range flag.
Enter positive and negative movement limits. The values entered relate to the maximum
allowed positive and negative change in Z-position from the Z-position at which the PureFocus
850 servo was switched on. Limits can either be narrow to ensure fidelity to a small depth of
field, or wide to simply protect the objective.
Click Set.
Switch the controller into MAN SRV mode. The range flag should appear green.
Take note of the Z-position shown in the main GUI. If this value moves outside the range limits
set, the range flag will deactivate (turn grey) and the autofocus servo will also deactivate.
Note that the servo will reactivate if the error signal dictates that the PF850 drive the focus back
into the defined range.
To turn off the range limits, untick the box in the range dialogue box
and click set.
Section 8: OEM features
The PureFocus850 GUI has a number of features which can be used by customers who are writing
their own software to initiate specific behaviours. These features are not intended for use outside of
this context.
8.1 Interface selection via interface flag
Samples such as cell culture dishes or LCD screens may contain multiple reflective interfaces.
Similarly, immersion objectives may produce complex signals with multiple interfaces. Any of these
interfaces can be used by the PureFocus850 assuming the error value is zero at a given offset value.
The signal reflected at each of these interfaces can be used, via the interface flag, by software
developers to trigger unique scanning behaviour in the PureFocus850.
In the following example two interfaces will be shown, and whilst further interfaces may be present in
practise, the principles remain the same.
Click setup to open the setup graph. Switch the controller into MAN FOC mode.
