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)... best regards julian > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers -- Mit freundlichen Grüßen aus Pinneberg Julian Wingert Hellenkamp 8 25421 Pinneberg Phone: 0170/4516094 Mail: julian.wing...@web.de USt-IdNr.: DE272503212 ------------------------------------------------------------------------------ _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
