Why the iPhone 8 needs to ship with Apple’s new fingerprint sensor

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Apple was recently awarded a patent for what looks like an fingerprint scanner embedded into the display assembly. Interestingly, the patent had been filed with the United States Patent and Trademark Office in June 2014 and has just been made public. If Apple was to pursue developing this technology, we could see the iPhone and the iPad have a higher percentage of the screen make up the body. There would be some significant advantages with such a system, but before we get into the details of those, let’s examine how a fingerprint scanner works.

Traditional Scanner vs. Capacitive Scanner
A fingerprint scanner essentially works by scanning unique patterns on your finger. The traditional optical sensors would take a photo of your print for the record and then every time you scan your finger, match what its reading against the print that is stores. Since this is a photo-bsaed method, it is easy to fool using a well replicated photo of a print. Capacitive scanners, which are found on almost all mobile phone, work very differently. They create an image of your print by measuring the variance in electrical conduction across your finger’s ridges. The “hills and valleys” in your fingerprint register varying amounts of electrical conductance. The sensor measures this, converts it into a digital signal and stores it securely on a separate chip. This system is harder to fool because in order to by-pass this system,  you’d need not only an intricately accurate replica of the fingerprint, but also it has to be made on a material that has the exact same conductance as human skin. Not impossible to achieve, but hard enough to keep more notorious elements out.

What does a Capacitive scanner scan
it wouldn’t be incorrect to assume that a fingerprint scanner reads the entire structure of your print. However, what it is looking for are unique patterns. Typically, the data coming from the fingerprint reader is scanned for where ridges and lines end, or where a ridge splits in two. Collectively, these and other distinctive features are called minutiae. If a scanned fingerprint matches several of these minutiae then it will be considered a match. Algorithms look for a certain number of correct matches of these minutiae, instead of working on matching the whole print. This is why you’re still able to unlock your phone with a partially cut finger, or even using just a small portion of your finger.

What’s wrong with capacitive scanners today
Capacitive fingerprint scanners have become very accurate and fast over the last few years. By design, the technology should not work if your finger is wet or has hand lotion on it, but we’ve seen manufacturers overcome those hurdles, with some phones even being able to pick up the print from pruned fingers. Unfortunately, the capacitive assembly takes up quite a bit of space inside the phone, and given the amount of components involved it making it, also ends up costing more than an ideal price. Plus they’re the reason there’s dead space on your iPhone at the base of the screen.

Apple’s Solution: Be Different, but stay the same
Apple’s patent indicates that they will be clubbing infrared light emitting diodes and infrared sensors right into the display, amidst all those tiny RGB pixels. They’re going to use light to generate a scan of your fingerprint, but this isn’t merely a photograph like that of an optical sensor. Apple’s plan is to use infrared emissions instead of electricity to generate a map of your fingerprint. The variance between the ridges would absorb and reflect this infrared light in different ways, which will be picked up by the infrared sensors on the display assembly, creating a similar “image” of your finger. This is the same process used by capacitive sensors, only here, Apple will use infrared light instead of electricity.

IR LED and Sensor diodes create the fingerprint map

The Advantages of Apple’s potential new sensor
The most obvious advantage of using this new method of fingerprint authentication is that Apple could get rid of the entire TouchID assembly, utilizing the real estate to increase screen size. We wouldn’t go as far as to say it would have cost benefits, as we already have seen that Apple’s new OLED panels will cost them a whole $30 more than the IPS LCD panels they had been using so far. Best case scenario, these OLED panels being made by Samsung for Apple already have these IR-LEDs and Sensors built in, which is why they cost so much. Worst case scenario, Apple has no intention of implementing this technology in the upcoming iPhone 8/iPhone X and when it does plan to do so, the display assembly could possibly cost even more to manufacture. The second advantage of eliminating TouchID would be the fact that the iPhone would be able to shed some weight. Who doesn’t love a light phone?

Apple’s method of accounting for ambient light while scanning your finger

Potential challenges to the new technology
While it is widely known that Apple does not implement a feature till they know it “just works”, there are some potential challenges to the new fingerprint sensor. The most obvious being the battery life. With the display pushing more components in the running, there is a possibility of the battery life taking a hit. However in the patent filing, Apple does say that infrared light was chosen so that the sensor could work even with the display turned off so as to conserve battery. Then there’s the issue of LED failure. What happens if an infrared LED or a sensor fails? While modern day LEDs have become very reliable, there is always the possibility that something might go wrong. In such an event, its possible the entire display might need to be changed, unless Apple plans to make the entire screen one giant fingerprint reader. From the patent filing, it appears that Apple should be able to make the entire display capable of reading a fingerprint, which would be a good idea so that a failed infra-red LED doesn’t break the fingerprint reader, warranting changing the whole display.

IR LEDs and Sensors could be spread across the entire display assembly

Ever since its debut in 2015, the capacitive method of fingerprint authentication has certainly gotten better, however, the system as a whole hasn’t evolved much. Apple’s patent reveals what could be the next phase of fingerprint authentication and it is something worth being excited about. With the upcoming iPhone 8, we can only hope that part of the reason the company went with OLED panels was in order to incorporate this technology. Unfortunately, it happens all too often that companies file for and win patents for new technologies, but nothing really comes off it. We hope that this wont be the case with Apple’s new fingerprint technology.