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So, what are these 'under-glass' finger scanners that may be on the Galaxy S8 and iPhone 8?

By Daniel P.

Updated: Dec 22, 2016, 3:18 AM

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TL;DR

The "under-glass" finger scanning solutions already announced aren't really "in-screen authentication," but they may still lead to the rumored nearly edge-to-edge displays of the Galaxy S8 and OLED iPhone 8.

Home key begone!

By now every geek worth their mettle, and everybody remotely interested in the grand rivalry between Apple and Samsung may have heard that their 2017 flagships - the Galaxy S8 and the iPhone 8 - may ditch the home key. This would bring them one step firther to their rumored "edge-to-edge" design, as they may get thinner, uninterrupted bezels.

Especially in the case of the iPhone and its signature circular home button, removing the key may increase the screen-to-body ratio significantly. The talk of the tape is that only the rumored OLED iPhone 8 model, allegedly codenamed "Ferrari," is going to dispense of the home button, which is only logical considering the millions of iPhone fans that can't imagine their favorite handset without it.

Dude, where's my finger scanner?

So far so good, Apple is rumored to be working a new form of touch controls that may be employed in the curved OLED iPhone 8, and may be the equivalent of on-screen buttons in Android, which in their turn are likely to be used on the Galaxy S8 if it also ships without the legacy physical home key of Samsung. What about the fingerprint reader, though, where's that puppy planning to hide, given that it is now embedded in the home keys?

Phase 3 presents the most difficult challenge: enabling fingerprint scanning anywhere within the display.

Well, if various leaks and rumors may be any indication, it might go deeper under the cover glass that will inevitably be at the front of the S8 and iPhone 8. In fact, Synaptics, the maker of all things 3D touch-y and biometric-y, has already introduced such optical finger scanners. The 6x6mm Natural ID FS4500 fingerprint sensor was outed in August, and can be used under a 0.3mm glass or ceramics layer, while the latest FS9100 optical scanner was announced last week, and it raised the stakes threefold, being able to hide under 1mm of cover glass, and still perform its finger reading functions.

Under-glass in-screen is not, said Yoda

So, these "under-glass" sensors aren't actually embedded in the display itself? Sorry to disappoint, but yes, they "are designed for placement under the cover glass, including 2.5D glass, located in the front, bottom bezel of devices." Synaptics, however, is looking forward to the so-called Phase 2 of in-display fingerprint authentication, which "will involve moving the sensor to a fixed location within the display area,"and using the display photo diodes as lighting source for the optical finger scanner.

Initially the sensor will be located in the bezel area of the cover glass where the button was located. The next step is placing the sensor in the lighted display area, likely in a fixed location at the lower edge just above where the bezel is today... Phase 3 is the ultimate goal of fingerprint scanning on mobile devices. Full in-cell integration of the display with touch navigation and fingerprint scanning will enable persistent authentication that is performed continuously in the background, and in a way that is totally transparent and unobtrusive to the user.

Moral of the fingerprint reader

Thus, we may still have some minimal width non-screen area at the bottoms of the S8 and iPhone 8, unless they have come up with a screen and cover glass package that is less than 1mm thick, or have mastered Phase 2 of in-screen authentication. We actually don't mind a bit of bezel as a natural palm rejection barrier to keep us from inadvertent touches, otherwise perusing a truly "edge-to-edge" phone might turn into an ergonomics nightmare.

That's not to say that there aren't Apple patents where the finger scanner is in the display package itself, it's just that the "under-glass" products already announced and sampling to customers, don't seem to be such solutions. If anybody can pull this off, though, it's Apple and Samsung, so we are really looking forward to their potentially disruptive iPhone 8 and Galaxy S8 next year.

source: Synaptics