Especially the really small ones on the side.
In: 316
They work by bouncing ultrasonic waves off your finger to an internal receiver to create a map of your fingerprint, similar to how an ultrasound scan looks during a medical procedure. It can then compare this scanned finger with anyone’s finger using the scanner.
Edit: it’d be much easier to imagine it as a kind of camera that takes a picture of the fingerprint.
There are 3 major technologies: optical, ultrasonic and capacitive.
This is an incredibly huge simplification, but opticals basically take a picture of your fingerprint, but of course the sensor is modified so that it’s not actually a picture and better suited for fingerprints, detecting the pattern better.
Ultrasonic fingerprint sensors send mechanical waves to your finger, the waves bounce back in a way that’s unique to each finger print, and then the sensor proceeds to detect and analyze the mechanical waves. If you wanna try it for yourself, place your hand on the side of a solid object, and slap the other side of the object (not too hard, don’t break anything!). If your first hand felt a vibration, congratulations, you just sent and received a mechanical wave!
Finally, capacitative sensors are like mine fields. The sensor has tons of tiny little “mines” that when the sensor is turned on, any part of skin that is currently on a mine has that mine blow up, and those that don’t have their mines intact. This then allows for the image of the fingerprint to be recreated from what mines are blown up and which aren’t.
In this analogy, the mines can detect skin because skin can somewhat conduct electricity, and without getting to complicated, each individual mine checks if electricity can flow (because skin is conductive) and blows up, while those that don’t blow up couldn’t conduct electricity because they were touching air instead of skin.
Essentially, the scanner takes a “photograph” of your finger print with a lot of detail (which is why you have to move your finger around a bunch before it will be accepted) and keeps it to compare to future attempts to unlock your phone. When you press your finger against the sensor after that, it looks for unique characteristics like bends and curves in specific places in what it is seeing to confirm a match to the original it has stored in order to grant access.
Even though others gave a good explanation I will try it too but more ELI5 way.
Traditionally lets start with some metaphor.
Think of a flute. When you blow air into it, the air flows through and makes a sound. Now imagine you put your finger on one of the holes of the flute. What happens? The air can’t pass through that hole anymore, so it bounces back, creating a different sound.
Now, let’s shrink down the flute to the size of a small button on your phone. Boom, you have a fingerprint sensor.
Instead of air, the sensor uses a special technology to feel the tiny electrical signals from your skin. When you place your finger on the sensor, it measures the way the electricity moves through your skin
Your fingerprint has unique patterns, like the lines and swirls on your fingertips. These patterns affect how the electrical signals reflect back to the sensor.
The sensor can pick up those differences and create a digital version of your fingerprint.
In a nutshell, the fingerprint sensor is like a tiny flute with just one hole that feels the unique patterns of your finger, and if it matches the right tune, it lets you in.
Why feel like a criminal when unlocking your phone? Let these fingerprint sensors give you that FBI agent feeling!
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