Next in this series we’ll examine the different types of fingerprint scanners.
Types of Fingerprint Scanners
There are four types of fingerprint scanners used for security and data protection: optical, thermal, capacitive, and ultrasonic.
Optical scanners are the oldest and simplest form of this technology. A photograph of the fingerprint is taken with a digital camera. While algorithms are used to distinguish unique patterns on the surface, the resulting image is only a 2D picture. A high-quality image of a fingerprint can be used to “trick” an optical scanner.
Thermal sensors use the same material from infrared cameras to detect temperature differences between the contact surface and fingerprint ridges and valleys to make a fingerprint image. The ridges of the fingerprint are measured and the valleys are not. One of the biggest issues with this type is typical ambient temperature is roughly the same as finger temperature so differences in temperature are not detected.
Capacitive scanners send electrical currents to record the complex pattern of ridges and valleys found on a person’s fingerprint. The resulting image records the depth of the valleys and height of the ridges so even a high-quality print image won’t trick the capacitive scanner because it’s flat. The capacitive scanner requires the person’s finger to actually be present in order to generate the image again for verification. Capacitive scanners are the most common kind of fingerprint scanner today.
Ultrasonic scanning is the latest in fingerprint scanning technology. High frequency sound waves are used to penetrate the finger’s epidermal layer, enabling it to “see” beneath the outer layer of skin. Both an ultrasonic transmitter and receiver are used to produce an extremely detailed 3D image of the fingerprint.
Currently ultrasonic scanning is expensive and slow - such highly detailed scans take time to capture. Prototypes are currently being tested for use in mobile devices.