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Subject: Re: linear optical encoder - reflective
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Date: Tue, 17 Sep 2002 21:52:41 GMT
NNTP-Posting-Date: Wed, 18 Sep 2002 07:52:41 EST
Organization: BigPond Internet Services (http://www.bigpond.net.au)
I've seen a fellow do this with a laser printer and transparency - to
produce a fine linear graticule.
This was then 'scanned' with an IR pair to act s a linear transducer.
"Bill Sloman" wrote in message
> email@example.com wrote in message
> > hi all,
> > i'm trying to build an optical encoder. i've done it many times before,
> > this one is giving me trouble....
> > it needs to be reflective, and linear.
> > that is, it's a straight steel rod with a series of black stripes on it
> > (about 0.5mm spacing) that i want to use to detect linear displacement.
> > i've been playing around with lenses and photodetectors and the guts of
> > old optical mice, but it's just so fiddly and I cant make it work.
> > I have some small cylindrical pieces of some clear acrylic stuff (about
> > 3mm diameter) to use as cylindrical lenses, and some HLC2701 optical
> > detector modules, but I cant make it work.
> > does anyone have any tips on this sort of thing? or some off the shelf
> > parts that can do it directly?
> There are quite a few other suppliers of optical linear sensors in the
> market, but Heidenhain seemd to be the market leader when I last know
> much about the subject.
> All but one of the lathes at Cambridge Instruments used Heidenhain
> reflective scales and optical sensors.
> The one exception used a Sony system which had magnetic sensors
> looking a rod magnetised with an alternating sequence of north and
> south poles at very precise intervals.
> The (shrouded) Heidenhain sensor assemblies had to be flushed with
> compressed air from time to time. The Sony system was a fit and
> Bill Sloman, Nijmegen
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