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Z-Scan Height
Z-Scan Height
group box
Focus Offset
Focus
Offset
controls
2004-11
Operating Manual for the LS Series Scanner No. 30001798 Rev. No. 1.5
6. LSServer, Scanner Shell and Download
•
Slide Thickness static edit box
The Slide Thickness static box gives information about the current slide
thickness that has been defined in the Geometry Parameters tab.
The Slide Thickness is considered in displaying the slide scheme and
needs to be defined for searching the focal plane within an appropriate
range.
•
Z-Scan End controls
Use the Z-Scan End controls (µm) to enter the End value of the
autofocus z-scan (= scan in vertical direction). Use the arrows or type in
the value manually.
•
Z-Scan Start controls
Use the Z-Scan Start controls (µm) to enter the Start value of the
autofocus z-scan (= scan in vertical direction). Use the arrows or type in
the value manually.
For a Standard.saf file, the default start and end values for the autofocus
search area are +/- 800 µm. The range considers the tolerance of the
slide thickness, the tolerances of positioning the slide adapter to the
instrument as well as internal tolerances of the instrument itself. However,
it might be necessary to increase the z-scan to guarantee that the
algorithm finds the focal position reliably.
Higher autofocus search areas (increased z-scan distances) prolong the
time for autofocus determination.
•
Focus Offset controls
Use the Focus Offset controls (µm) to measure a certain value below or
above a focal plane. Set the value by spinning the arrows or by typing in
the offset manually.
In certain cases the autofocus plane and the scan plane might differ, for
instance: - slides with cover glasses, slides with membranes or filters. A
certain value can be set as focus offset to perform the scan below (-) or
above (+) the focal plane.
E.g.: For a cover glass with a thickness of 170 µm, the correct focus
offset would be 113 µm, - calculated according to following formula:
Formula for the offset: d-[(n-1)/n]*d
n= refractive index of the cover glass (= 1,5)
d= thickness of cover glass
6-45
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