Had a bit more thought about this -
because you are dealing with very small objects
then depth of field for scanning may not be such an issue.
As mentioned I have a cheapo (and I mean cheap @$32 from WalMart) Canon Pixma MP250 all-in-one printer/scanner -
that uses the cheapest CIS technology with LED lighting -
as far as I am concerned the worst of both worlds -
BUT I scanned a couple of needles at the full 600dpi scanning resolution -
without any concerns about the usual focus, lighting, exposure, apertures, tripods -
I just scanned at default settings (literally as I was composing this post) and got:
This is at the very bottom end of the budget for scanners.
As I have mentioned there are scanners that can do 4800dpi
which is 8x higher linear magnification than this result I got.
The DoF is narrow, note the backing paper is OOF -
but the DoF seems adequate for the needle.......