I thought, based on anandtech review, that this scanner is not optical but electrical, hence "sub epidermal scanning", so why does a printed finger work?
- the capacitance of the ridges and crests of one's fingerprint dominates any differences in subcutaneous capacitance (possibly because they are closer to the scanner, or because there simply is too little variance in capacitance between flesh and hair veins)
- subcutaneous structures resembles fingerprints too much (seems quite possible, as there must be a reason that it is hard to permanently change one's fingerprints by using sand paper)
Aside: a Google found this procedure: http://www.zoklet.net/bbs/archive/index.php/t-202956.html I don't have the faintest idea whether that is real, but regardless, I don't recommend it.
Yes, it could also be Johnny Appleseed's fingerprint, used as an image users are familiar with, but http://en.wikipedia.org/wiki/Friction_ridge seems to confirm it, too ("The pattern of ridges they produce in hands and feet". I'm not sure whether they refers to the epidermal cells or to the blood vessels (less likely), but that doesn't matter)