Again - 1RPD... My application is easy here... Thats why I said additional sensing for calibration.
If you go for the real speed, you simple have to scan faster than noise can be. The real world has the niceness to be slow, compared to what a fpga can do... Best regards Julian On 8. August 2015 10:02:00 MESZ, Nicholas Mc Guire <der.h...@hofr.at> wrote: >On Sat, 08 Aug 2015, Julian WIngert wrote: > >> Am 08.08.2015 um 04:00 schrieb EBo: >> > On Aug 7 2015 5:32 PM, Peter C. Wallace wrote: >> >> On Fri, 7 Aug 2015, EBo wrote: >> >> >> >>> Date: Fri, 07 Aug 2015 17:13:25 -0600 >> >>> From: EBo <e...@sandien.com> >> >>> Reply-To: EMC developers <emc-developers@lists.sourceforge.net> >> >>> To: emc-developers@lists.sourceforge.net >> >>> Subject: Re: [Emc-developers] research on optical encoders >> >>> >> >>> On Aug 7 2015 4:16 PM, andy pugh wrote: >> >>>> On 7 August 2015 at 12:23, EBo <e...@sandien.com> wrote: >> >>>>> Possibly, but I cannot tell from the information Renishaw >> >>>>> published >> >>>>> in >> >>>>> that brochure. >> >>>> I think that the target is a barcode. The head can see enough >> >>>> barcode >> >>>> to tell exactly where it is on the code sequence to within one >bar, >> >>>> then looks at the absolute position of the bars in the viewing >area >> >>>> to work out the rest of the bits of data. >> >>> I think it is following on the same idea roughly. Looking at the >> >>> renshaw they claim it can give you 1nm (1e-9m) or 3.9e-8 inches >> >>> precision. I have no idea how they are pulling that off besides >> >>> laser >> >>> interferometry and ring counting. Can you suggest another method >> >>> that >> >>> would work? >> >> AFAIK they dont use a laser, just a bright LED thats pulsed to >take a >> >> snapshot >> >> of the barcode, probably with a rather high resolution linear >sensor >> >> array (or >> >> multiple arrays with pixel interleaving) >> >> >> >> Quite high-sub pixel interpolation should possible with such a >setup >> >> because >> >> of all the duplicated edges >> > agreed with the laser/LED. I would have to study sub pixel >> > interpolation to see how much additional interpolation you could >get. >> >> You can get really fine results on a theoretical perfect black/white >> change and the imaging sensor mounted 45deg. of an almost unlimited >> degree of subsampling. >> Even with a cheap camera and optics there should be no problem to >> resolve down to the uM scale. Problem is the speed of such a >construct. >> Even with high performance camera systems you have a delay that makes >it >> imho unusable in realtime positioning. >> >> If you are able to interface the sensor with an FPGA doing the >realtime >> analysis - well then you have what renishaw probably has build... >> >> What should "relatively" easy to be doable is to add such a slow >scale >> to recalibrate the machine position regularly. >> >> My first idea was to use a laser mouse sensor, which is easily >> interfaceable even with MESA cards - there are ones with SPI >interface - >> but my application is the calibration of my astronomic mount - which >> hardly moves more than 1RPD (Rounds per DAY)... >> > >maybe a somewhat naive question - but how would you deal with vibration > >of the cameras/sensors ? gut feeling - if you try to deduce 10E-9 m >then >even just environment noise would become a problem or is there some way >to eliminate that in practice ? > >thx! >hofrat > >------------------------------------------------------------------------------ >_______________________________________________ >Emc-developers mailing list >Emc-developers@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/emc-developers -- Diese Nachricht wurde von meinem Mobiltelefon mit Kaiten Mail gesendet. ------------------------------------------------------------------------------ _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
