Here at CES 2018, I had a chance to look at what some of us probably considered mere fantasy a few short years ago: a fingerprint scanner that can see through a smartphone display. It sounds like something that must be so complex it would be beyond explanation, but really, the basic principles aren't terribly difficult to grasp.

The short of it is this: smartphone screens are light-permeable, because they are porous. The thinner the display, the more light-permeable it probably is, and OLED screens are the thinnest currently being manufactured. By shining a bright enough light through the porous display, a sensor can observe the reflection of your fingerprint against the display components and use that to create a computer-readable image.

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