Dear Palma, I´ve red an older input from you and it seems you´ve had kind of the same questions. I don´t understand the filtering:
So first my data is digitalized with an DFT. How can I imagine that? What happens with my data? Before DFT I have a line with measuring points equating hights. Then the DFT is done. What do I have then? The graph of the texture in the ISO button, is it already with DFT? What are the axes in those graphs in the ISO button? After the DFT I select a Cut-off frequency. How can I calculate from it the cut-off wavelength, which is used in other programs and in the ISO Norm? How does the thickness of the measuring line affect the DFT respectively the Cut-off frequency? With the Cut-off frequency a Gaussian filter is used. How can I imagine that? What happens with my data? And last but not least: what interpolation should I choose? -----Ursprüngliche Nachricht----- Von: Palma D'Antonio [mailto:p.danto...@unifg.it] Gesendet: Donnerstag, 17. Mai 2012 11:29 An: Gwyddion use discussion Betreff: Re: [Gwyddion-users] roughness parameters Dear Lena, excuse for my delay in answering, I think that the only way to compare different roughness values is to use the same cut-off frequency, indeed if the samples are similar they will require the same cut-off... if they are so deeply different, maybe it sould not be the case to compare them... anyway remember that the filtering operation is a selection of the surface features you want to characterize and you can roughly control it by looking at the variation of the gwyddion roughness profile while changing the cut-off value. I have a more accurate method to selct the cut-off value but I'm still working on it. I hope to have been helpful Palma. 2012/5/9 Mandl, Magdalena <magdalena.ma...@isc.fraunhofer.de>: > Dear Palma, > > thank you for your help! I tried a bit to calculate the roughness with > gwyddion and so far it works good. I have one more question: > Do I have to select always the same Cut-off to compare the results of > different samples? Or do I select one cut-off per sample? Or can I change the > cut-off in every line-scan? > > Best regards > Lena > > -----Ursprüngliche Nachricht----- > Von: Palma D'Antonio [mailto:p.danto...@unifg.it] > Gesendet: Dienstag, 14. Februar 2012 09:50 > An: Gwyddion use discussion > Betreff: Re: [Gwyddion-users] roughness parameters > > Dear Lena and Luis, I'd like to add something about the issue. > If I'll wrong about, someone will gently correct me. > > 1- when you use the 'ISO' button e select a cut-off, Gwyddion automatically > filter your data (I think it digitalizes the data, makes a > DiscreteFourierTransform and applies a gaussian filter ... or something > similar). Larger the cut-off selected more data are filtered. > The first two or three cut-off values just correct your data for the main > profile shape (plane, circular, etc..). So I don't think you have to do > anything before. You can verify it directly, selecting different cut-off > values and looking at the 'texture' and 'waviness' profiles, that have been > eliminating, and the roughness profile, on which gwyddion compute the > roughness parameters. > > 2- I agree with Luis: it depends on the features size. In order to > characterize some surface features you have to be sure to select a scan step > suitable to make a good sampling of your object (Nyquist problem). At the > same time you have to select a scan area that includes a lot of singular > features (that is, it should be 20 or 30 times the linear dimension of the > features you are interested to). If your roughness and waviness features have > very different sizes, maybe you have to make two different scannings. Those > consideration are deeply handled in metrology handbooks. Besides, the > size-dependence of your roughness parameters is nearly eliminated through > this filtering procedure. > > I hope to have been helpful, > regards > Palma. > > > 2012/2/13 luis vazquez <l...@icmm.csic.es>: >> Dear Lena, >> >> I am a Gwyddion and AFM user, I will try to answer as far as I know: >> >> >> >> >>> >>>1. I read: to calculate the rougness and waviness data I need >>>to filter the AFM-Data first. So my question: In gwyddion when I use >>>the roughness parameters application, do I first have to filter the >>>data, or does gwyddion filter the data automatically in this application? >> >> I think you should first filter (whatever: plane fit, flatten, etc) >> the image and then calculate the roughness data (for instance if you >> do not correct the plane, the image may have very different roughness >> values) >> >> >> >>>2. Does it make sense, to calculate the roughness in smaller >>>areas of the sample, and the waviness in a greater areas? Because of >>>the different structural size which matters. I thought about that, >>>because I realized that when I change the thickness of the Scan line >>>the roughness value drops with expanded lines, the waviness as well. >>>So how should I use the application of the roughness parameters to >>>describe my topographies best? >> >> From my point of view, the roughness does depend on the area sampled >> compared to the typical wavelength (or lateral extension) of the >> surface features. If you have a characteristic surface feature with >> an average size of L, once your scan size is larger (2 or 3 times, >> for >> instance) than L your roughness should more or less saturate (there >> are papers on this issue). >> Perhaps the roughness could drop as you see because your scan size is >> so large that you do not have enough resolution to image properly >> each characteristic surface feature. Regarding waviness I do not work >> with this parameter, so I cannot tell you. >> >> >> >> >>>3. I have a glass substrate covered. But the coating doesn´t >>>cover the glass everywhere. >>>Has gwyddion any way to calculate the coverage factor? >> >> I think Philipp has answered this question already. >> >> regards, >> >> Luis >> >> >>> >>>Thanks Lena >>> >>>--------------------------------------------------------------------- >>>- >>>-------- Try before you buy = See our experts in action! >>>The most comprehensive online learning library for Microsoft >>>developers is just $99.99! Visual Studio, SharePoint, SQL - plus >>>HTML5, CSS3, MVC3, Metro Style Apps, more. 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Free future releases when you >> subscribe now! >> http://p.sf.net/sfu/learndevnow-dev2 >> _______________________________________________ >> Gwyddion-users mailing list >> Gwyddion-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/gwyddion-users > > > > -- > Palma D'Antonio > Laboratorio di Fisica Applicata > Dipartimento di scienze biomediche- Facoltà di Medicina e Chirurgia > Università degli studi di Foggia > email: p.danto...@unifg.it > tel. 0881 732086 > > ---------------------------------------------------------------------- > -------- Keep Your Developer Skills Current with LearnDevNow! > The most comprehensive online learning library for Microsoft developers is > just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro > Style Apps, more. Free future releases when you subscribe now! > http://p.sf.net/sfu/learndevnow-d2d > _______________________________________________ > Gwyddion-users mailing list > Gwyddion-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/gwyddion-users > > ---------------------------------------------------------------------- > -------- > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. > Discussions will include endpoint security, mobile security and the > latest in malware threats. > http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Gwyddion-users mailing list > Gwyddion-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/gwyddion-users -- Palma D'Antonio Laboratorio di Fisica Applicata Dipartimento di scienze biomediche- Facoltà di Medicina e Chirurgia Università degli studi di Foggia email: p.danto...@unifg.it tel. 0881 732086 ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Gwyddion-users mailing list Gwyddion-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gwyddion-users ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Gwyddion-users mailing list Gwyddion-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gwyddion-users
