An in-depth look at fingerprint sensor technology amid ‘iPhone 5S’ rumors

Motorola Atrix Fingerprint Sensor (via DigitalTrends)

As this fall approaches, both rumors and actual evidence have pointed to the next iPhone’s marquee feature being a fingerprint sensor for authentication purposes. We previously provided iOS 7-based evidence and information regarding Apple’s work on implementing a fingerprint sensor in future products.
While we reported that Apple is actively developing fingerprint solutions that sit within a display for products a few years into the future, it seems that this year’s iPhone fingerprint sensor could be integrated into the iconic home button.
In light of these rumors, Geppy Parziale, a biometric authentication expert from InvasiveCode, has compiled in-depth look at the technology that powers miniature fingerprint sensors:

The article provides in-depth detail behind the science of fingerprint sensors. Specifically, the post shares why biometrics are a viable authentication solution. The article also defines some of the critical terminology in the field, explaining which terms and technologies are relevant to an iPhone-embedded-solution. The article also presents interesting detail behind how the sensors actually function:

Let’s take a look at the most critical component of the entire fingerprint recognition process: the sensor. Recognition is highly dependent on the quality of the captured fingerprint image as in less noise, and better image. The core technology used to manufacture the sensors can introduce noise and errors on the captured fingerprint image, influencing the recognition to such a negative extreme that you could be continuously rejected by the system (false rejection) or somebody else could be granted access to the system instead of you (false acceptance).

The rest of the sensor section is worth a read: it includes in-depth technical details about how the tech functions. Parziale also shares some concern about fingerprint technology, noting that some sensors do not have a long lifespan. Perhaps this is why Apple will not trust such a sensor with payments, as we previously noted.

In everyday life, things are even worst. You usually use your hands for different tasks and you usually touch different types of materials. Small portions of the objects you touch accumulate on the skin of your finger. When you touch the fingerprint sensor,  you deposit these material on its surface. Additionally, your skin produces sweat (a combination of water and different types of salts) and the sebum (a oily/waxy substance our body produces). When you touch the surface of a fingerprint sensor, the mix of the sweat, sebum and any substance accumulate during your daily activities become a killer combination for the sensor surface that speeds up the destruction of its surface… If you search for the specifications of a CMOS fingerprint device, you will find a number representing the lifetime of a device. That number is expressed in number of touches (before it completely dies). That number is provided in ideal conditions of usage and in a normal operating environment of temperature and humidity. But remember where you normally use your iPhone. You keep it in your “dirty” pockets, you leave it on different surfaces, and in humid and hot or cold and dry environments. Sometimes water drops on it or you forget it in your car under the sun. All these factors stress the working conditions of the sensor surface and contribute to speeding up its decay process.

Of course, sensor performance will vary and with Apple’s expertise in hardware, perhaps they will implement a well-built sensor in the rumored upcoming iPhone. Apple-owned Authentec has worked on numerous types of sensor designs, so time will tell which specific technology Apple uses to bring fingerprint scanning mainstream.
Past history indicates that Apple introduces an “S” iPhone following a major redesign. In line with this was an iPhone 4S to follow the iPhone 4. The 4S added a faster chip, better camera, and Siri as the main selling point. With last year’s Authentec acquisition and the recent rumors and evidence, it seems likely that a fingerprint sensor will be this year’s “Siri.”
Besides a fingerprint sensor, the next iPhone will likely sport the same design as the iPhone 5 (with the phone likely to be dubbed “iPhone 5S”), an improved camera system, and a faster, A7 processing chip. Speculation has pointed to a launch toward the end of September.