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The Autofocus calibration moves the stage approximately 5 microns out of ideal
focus and collects focus error scores from 100 SpeedBeads. The stage then moves
one micron toward focus and collects focus error scores again. The process is
repeated until the stage reaches a position 5 microns beyond best focus. The data
are then fit to a 3rd order polynomial and the slope of the curve at the inflection point
is determined. This value determines the signal error corresponding to a given focus
error through the typical operating region of the autofocus system. It is used to
determine each move the focus motor makes to correct focus errors. The result and
the limits for the calibration are shown below the list when the calibration is selected.
If the Multimag option is installed the instrument automatically multiplies the S curve
slope by the appropriate factors to compensate for the changes in slope that result
from the additional 60X and 20X magnification.
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