I've used fiber optic cable for that exact purpose. You can use it for
both illumination and sensing. It's neat because it reduces the mass you
need to zip around. Back when I did it (1985?) you could just use a
fiber emitter and detector pair. Nowadays they probably integrate
electronics into them, which might get in the way of what you want to
do. But you could always hack together some way to couple fiber to an
led and a photodiode.

Cheerful regards,

Bob

On Tue, Oct 23, 2012, at 03:28 PM, IVP wrote:
> Hi all,
>=20
> I'm working on a project which involves scanning line drawings into
> memory (a large SRAM). Ideally the images will be laser printed on
> white paper, so the contrast will be good and lines should be sharp.
> But other users may not adhere to recommendations, for a variety
> of reasons, so I'm looking for components or techniques that will
> reasonably cover all eventualities
>=20
> My aim is to be able to resolve to 0.5mm or better. I've made an
> X-Y bed, 600mm x 600mm (but I may well go bigger), with a
> couple of steppers and threaded rod that has good positional
> resolution, now I need a read head
>=20
> Some things I hope to try ASAP -
>=20
> Illuminate from the back with an LED with a opto sensor above the
> paper. This would involve an extra mechanism for the LED to follow
> the read head. No big deal
>=20
> A reflective or proximity opto, which would bounce IR off the paper
>=20
> Some lens system to enlarge the detection area
>=20
> I've used these techniques for other projects but not with resolution
> as the primary goal. Mostly for event detection. I expect I may have
> to restrict a sensor's field of view (eg pinhole mask)
>=20
> Any other ideas or experiences ? I keep daydreaming about cameras
> but I don't think that's necessary, and I want to use components that
> are cheap and repeatedly available. Even something like an optical
> mouse sensor perhaps. Cheap enough to scavenge from a bought one
> or pick up as broken
>=20
> TIA
>=20
> Joe
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