How is it possible to “read” fingerprints using sound?
The real value of ultrasound in the field of biometrics lies in the particular characteristics of sound waves to both reflect and pass through objects. Where a light in a closed room is blocked from escaping by the solid walls, sound can easily be heard both inside the room and, to a lesser degree, outside the room. This unique ability makes it possible for high-frequency sound waves to pass through foreign substances and accurately measure the ridges and valleys of a fingerprint without regard for dirt, grease, ink, moisture, grime, or other substances routinely found on our fingers. This capability makes ultrasonic fingerprint identification extremely accurate since it eliminates the many variables that cause most false readings in traditional optical scanners.
