Touch ID: Inside the fingerprint scanner on Apple's iPhone 5s

Apple unveiled the new iPhone 5s and iPhone 5c at a special event held at its headquarters in Cupertino. While the iPhone 5c did not live up to its promise of being a 'low-cost iPhone', the iPhone 5s showed off some promising innovations, like the new Apple A7 chip and, perhaps the highlight of the event, a built-in fingerprint scanner called Touch ID.

Touch ID can be used to unlock the phone, by simply placing a finger on the Home button. It can also be used to confirm purchases made on the App Store, iBookstore or the iTunes Store.

You can scan and add multiple fingerprints (e.g. left and right thumbs, as well as index fingers), including those from multiple people (e.g. your wife or kids), and Touch ID will authenticate based on any of stored prints.

In case you are worried about privacy, Apple assures that fingerprints are encrypted and stored in a secure area inside the new A7 chip. Fingerprints are not accessible to any third-party apps, and nor are they sent to Apple's servers or backed onto iCloud.

So what's the technology behind Apple's latest innovation? The Touch ID capacitive sensor embedded in the Home button scans your finger at 500ppi resolution to get a high resolution image of your finger. The sensor embedded in the Home button is just 170 microns thin.

The new Home button is made out of sapphire crystal, one of the "clearest, hardest" materials out there. The Home button protects the fingerprint sensor and also acts as a lens to precisely beam your fingerprint to the scanner. The Home button is surrounded by a steel ring, that can detect touches and tell Touch ID to start scanning when a finger is placed.

The sensor uses advanced capacitive touch to take high-resolution image of the sub-epidermal layers of your skin. The resultant image is then analysed, and grouped into one of three fingerprint types: Arch, Loop or Whorl. It then analyses ridges and other details too small for the human eye to see, to come up with a match for one of the stored fingerprints.

Here's a video that gives a closer look at Touch ID.

Leaked iPhone 5S user guide reveals 'Touch ID' name for fingerprint sensor

While a number of reports including a recent one by the Wall Street Journal have confirmed the presence of a fingerprint sensor on the new iPhone, a new leaked image of the iPhone 5S' alleged Quick Start Guide also gives a name to the feature.
 
We're just hours away from Apple's special event where it is expected to unveil the new iPhones, and now a new image that claims to feature the documentation accompanying the iPhone 5S, has beenposted by French website Nowhereelse.fr that describes the Home button as 'Home button/ Touch ID sensor.' There also appears to be a silver ring around the Home button in the guide.
 
If the image turns out to be genuine, it would imply that Apple will refer to the fingerprint scanner as the Touch ID sensor, and that the consumer name of the feature would be Touch ID. The authenticity of the image has not been verified, and a report by Apple Insider points out that Apple doesn't use the "Volume buttons" and " Ring/silent switch" terms seen in the leaked guide. It is somewhat of a departure from Apple's usual "Volume Up/Down" and "Ring/Silent" naming conventions seen on the latest iPhone Quick Start Guide, though some of these terms do appear in the iPod and iPad manuals.
 
The exact use case for the fingerprint scanner is still not known but it's being speculated that that it could be a way to authenticate users while unlocking the phone or while buying apps and other content.
 
Earlier today, a Wall Street Journal report had confirmed that Apple will include a fingerprint scanner on the more expensive of two iPhones it is expected to unveil later in the day.
 
Just a few days back, a new leak that claimed to identify a Home button flex cable in the iPhone 5S in a way confirmed that the Home button would integrate a fingerprint scanner. 
 
Purported images of the iPhone 5S casing had also revealed a silver ring around the phone's Home button, indicating the possibility of a fingerprint scanner being present on the button.