Phone fingerprint sensors, particularly those commonly found in smartphones, primarily use capacitive scanners that use electrical current to sense and map the ridges and valleys of a fingerprint. Let's break down how these sensors function.
Capacitive Fingerprint Sensors: A Detailed Look
Capacitive fingerprint sensors are a popular choice for smartphones due to their accuracy and security. Here's how they operate:
- Electrical Current Mapping: These sensors contain an array of tiny capacitors.
- Finger Placement: When a finger is placed on the sensor, the ridges of the fingerprint come into close contact with some of the capacitors, while the valleys are further away.
- Capacitance Variation: The distance between the fingerprint ridges/valleys and the capacitors creates variations in capacitance (the ability to store an electrical charge). Ridges, being closer, result in higher capacitance, and valleys, being farther, result in lower capacitance.
- Data Conversion: The sensor measures these capacitance variations.
- Image Creation: The sensor then converts this capacitance data into a detailed digital map of the fingerprint.
- Authentication: This map is compared to previously stored fingerprint data to authenticate the user.
Advantages of Capacitive Sensors:
- Higher Resolution and Security: Capacitive sensors capture detailed fingerprint data, making them more secure than older optical scanners.
- Accuracy: They provide accurate fingerprint mapping by detecting variations in electrical capacitance.
Disadvantages of Capacitive Sensors:
- Sensitivity: They can be sensitive to temperature and electrostatic discharge.
- Damage Risk: Can be affected by scratches, moisture, or dirt on the finger or sensor.
How Capacitive Sensors Offer Superior Security:
Because capacitive sensors create a detailed map of the fingerprint based on electrical characteristics, they are much more difficult to fool than optical scanners which simply take a 2D image.
