image processing

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replied on Mon, Apr 2 2012 11:10 AM

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Hi Jonas,

It sounds like what you are seeing is an effect of thermal drift. Thermal drift is slow compared to the tinme it takes for a single line hence you do not see it there. When looking in the slow scan direction, however, you propably see a bow or sometimes even slow "waves".

I do not know the temperature stability of your environement but suggest measuring that and trying to keep that constant if it isn't.

Stefan

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JFP replied on Mon, Apr 2 2012 11:22 AM

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Hi Stefan,

Thanks for your help. I don't think it's thermal drift, because it's not monotone and all images look alike. For example see the attached crosssections. Every image shows exactly this behavior but when it's because of thermal drift they should not, or?

Best regards

Jonas

Scan angle 0° (red: slow, blue fast scan direction):

Scan angle 90° (red: slow, blue fast scan direction):

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Joop de Vries replied on Mon, Apr 2 2012 1:53 PM

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If you increase the setpoint with 1V in contact mode, is it still the same? For me it looks like bad tracking.....

If it is not bad tracking, check with a known sample (callibration grid) if the z sensor is still ok.

Joop 

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JFP replied on Tue, Apr 3 2012 2:57 AM

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Hi Joop,

thanks for your help.

I checked if there is the same behavior on a calibration grid, but there is no bow in slow scan direction.

Wouldn't one expect bad tracking rather in the fast scan direction than in the slow?

best regards

Jonas

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Joop de Vries replied on Wed, Apr 4 2012 5:57 AM

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Oh...... probably I misunderstood what you wrote. So the pictures you show is not one scanline but is perpendicular on the scanlines....... Thats strange, no more idea's

If you increase or decrease the scanarea you still have the same shape?