Optimal autofocus settings

[Anette von der Handt]

Hi,

not sure if this forum section or the JEOL one is the better place.

I have been noticing that my JEOL autofocus (JEOL 8900; unknown autofocus type - I guess maximum intensity) and the PFE autofocus (maximum intensity) results do not match and that the PFE autofocus has a constant slight offset, enough to screw with the Si and Al intensities.

Playing around with the settings has not produced the results I am looking for. Therefore, I wondered if anyone could weigh in with their preferred PFE autofocus settings.
 
Things I have tried so far:
Meddled with the actual brightness settings on the JEOL (OM-AFD) - no effect
Added an automatic offset to the probewin.ini file - no effect, maybe I did it wrong??
Change autofocustype to gaussian - better but results in an error message of 'not enough data points' relatively often.

I would love to play around with it in much more detail and run the debugger but I would rather avoid this now (paying customers). The fact that the JEOL focus does a better job, lets me think that some values in the probewin.ini should be tweaked.

Current settings:
AutoFocusPresent=1
AutoFocusType=1
AutoFocusOffset=0.0
AutoFocusMaxDeviation=30
AutoFocusThresholdFraction=0.33
AutoFocusMinimumPtoB=1.4
AutoFocusRangeFineScan=100
AutoFocusRangeCoarseScan=600
AutoFocusPointsFineScan=200
AutoFocusPointsCoarseScan=100
AutoFocusTimeFineScan=20   ; 1-500 msec
AutoFocusTimeCoarseScan=20

Any input is welcome. Thank you!

Anette

[John Donovan]

I would love to play around with it in much more detail and run the debugger but I would rather avoid this now (paying customers). The fact that the JEOL focus does a better job, lets me think that some values in the probewin.ini should be tweaked.

Right you are!

It's this setting you want to tweak:

AutoFocusOffset=0.0

so enter the value in plus or minus microns.
john

[Anette von der Handt]

Thanks for the quick reply! You know I tried that but in the rush missed the <micron bit, so only moved it an indiscernible 0.002 microns.

So just to be on the safe side, does it matter if I write:

AutoFocusOffset=+20
    or
AutoFocusOffset=20

Much obliged.

[John Donovan]

Thanks for the quick reply! You know I tried that but in the rush missed the <micron bit, so only moved it an indiscernible 0.002 microns.

So just to be on the safe side, does it matter if I write:

AutoFocusOffset=+20
    or
AutoFocusOffset=20

Much obliged.

Well, I never tried that but it should "resolve" OK. Try it!
john