Published on 28 August, 2014
Zwipe has brought security to your fingertips. The technology behind fingerprint scanners can be categorised into two types: optical and capacitive.
An optical sensor, using an internal light source, illuminates your finger allowing the scanner to turn the light signals into digital pixels like a digital camera. A processor then converts that image into a fingerprint template.
A capacitive sensor, like those on an iPhone 5S and Galaxy S5, also uses images of a fingerprint, but creates that image with a different technology. The capacitive sensor contains an array of small capacitive plates, ranging from a few hundred to many 1000s, and each plate has its own electrical circuit. The sensor often looks like a raised bar (or stripe) and contains a single row of sensors. After swiping your finger over the sensor, the processor then “stitches” together each line of scans to create the image.
One of the more “user-friendly” capacitive sensors is an area sensor, which allows the user to place their finger on the sensor, rather than swiping across, which allows for capturing a larger area in a shorter amount of time.
When a finger is placed on the area sensor, extremely weak electrical charges are created, creating a transfer of energy (called capacitive coupling).
The electrical charge varies depending the distance between the finger’s ridges and valleys and the sensor’s plates. Using these electrical charges, the sensor measures the capacitance pattern across the surface at one time, and sends this digital information to the processor to create a detailed fingerprint template image.
Area sensors are becoming more popular due to their intuitive use, extended lifespan and compact size making them popular choices for laptops, smartphones, credit cards and even company ID badges.