Scanner compensates for distance from surface, by a weird morph effect, that's why I've had problems matching some drawings to previous scans, hard to "fix" even in Photoshop, depending on microscopic distance of parts of a sheet if not 100% flat, which often it isn't once it is touched and drawn on, even though not visible to the naked eye, how the scanner sees.

If you look at it from a distance, it looks almost holographic to me, do you see it? What if it could be algorithmically reverse engineered back to looking right, in 3D?! Using some reference item scanned first and then calculated for distance/3D adjustment, using your scanner as a "3D" / holographic scanner. A silly idea?  I stumbled over this: http://en.wikipedia.org/wiki/Scanography.