The Nanoscale World

Tip is not in focus when we do Focus Surface

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Vinnie Gupta posted on Fri, Aug 12 2011 11:08 AM

We have a NSIIIa Dimension 3000 system. We use v5.3 software. About a year ago, we got a "Get Size Failure" error, and we copied the "Par" directory and "System. Par" file from the backup. And the error went away.

We have noticed lately that after "Locate Tip" the tip is in focus; when we go to "Focus Surface", the tip gets out of focus immediately.

I cant remember if it was always like that or some parameter is in conflict.

Everything works fine though.

If anybody has a suggestion, I will appreciate that.

Thank you.


Vinnie Gupta

Rochester Institute of Technology



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replied on Fri, Aug 12 2011 3:36 PM

Hi Vinnie,

I am not sure I understand your question. If your tip is away from the surface and the optics are aked to focus onto the surface ('focus surface") the tip has to go out of focus. It should be back in focus, however, once engaged of course. Nanoscope uses the difference in the two focal points to calculate its approach.


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Dear Vinnie,

What you are seeing is normal.  During the "Locate Tip" command, the focusing objective position is adjusted to focus on the cantilever.  When you switch to the "Focus Surface" command, the focusing objective is automatically advanced by a pre-set distance (typically 1 mm) so that you are looking at a focal plane 1 mm below the tip location.  When you bring the surface into focus, you do so by lowering the AFM scanner toward the surface.  When the surface is in focus, the tip position is then known to be 1 mm above the surface.  Therefore, when you engage, the AFM knows how far it needs to lower the tip to find the surface.

Best regards,

Eric Rufe

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Thank you very much Eric for your very clear explanation. --Vinnie Gupta

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mops replied on Tue, Nov 1 2011 6:23 AM

Dear Vennie,

That is normal, I guess all AFMs do the same, mine is like that.

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