Cellphone theft would be pointless if the devices cut out as soon as they fell into the wrong hands. But adding a fingerprint recognition system and another window to press your finger on makes phones too bulky. Now US company Identix says an all-purpose phone screen made from glass with a very low refractive index will do the trick (WO 03/012729).
The owner of the phone places a fingertip on the window, and red light from an LED underneath reflects from the bright ridges of the finger. Through total internal reflection, the fingerprint pattern 鈥渂ounces鈥� out through the glass onto an image sensor.
