Thank you Yeti, in the Fourier domain (FFT, filtering, inverse FFT) what kind of filtering is used? There should be two different filters used, one highpass filter for the roughness and a lowpass filter for the waviness, which seperates the profiles. There are several possible filters for this and I need to know which one is used in Gwyddion, to be able to compare the waviness and roughness parameters with parameters calculated with another program for Laser Scanning Microscope Measurements.
Regards, Lena -----Ursprüngliche Nachricht----- Von: David Nečas (Yeti) [mailto:[email protected]] Gesendet: Montag, 18. Juni 2012 16:40 An: Gwyddion use discussion Betreff: Re: [Gwyddion-users] Filtering in roughness and waviness profile On Mon, Jun 18, 2012 at 03:53:08PM +0200, Mandl, Magdalena wrote: > i´m calculating the roughness and waviness in Gwyddion with the ISO > button. I guess as low-pass filter an Gaussian filter is used, is > this right? No, the high/low separation is done directly in the Fourier domain (i.e. FFT, filtering, and inverse FFT). I am not an expert at norms I recall there are several possible separation methods. > Furthermore, i´m wondering that I just chose one cut-off frequency > "fc", which cuts the roughness off from the waviness and the other way > round for the roughness. In ISO 4287 they talk about three cutoff > frequencies (see picture). What about the Cut-off frequency "fs" in > gwyddion, which cuts off the noise and makes the primary profile? > Also what about the Cut-off frequency "ff" in gwyddion, which cuts off > the coarse shape and makes together with the cut off fc the waviness > Profile. "fs" always infinity and "ff" is always zero. I.e. anything above "fc" goes to roughness, anything below goes to waviness. Regards, Yeti ------------------------------------------------------------------------------ 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 [email protected] 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 [email protected] https://lists.sourceforge.net/lists/listinfo/gwyddion-users
