This is the web address for information on MidiScan software, which
can be used to produce a MIDI file from a scanned image of sheet music:

    http://www.musitek.com/midiscan.html

I haven't tried it myself, and I've heard both enthusiastic and
lukewarm comments from users.

Here is a link for PianoScan, a scaled down version of MidiScan,
and much cheaper ($99):

    http://www.musitek.com/piano.html

Meta Brown