Different Types of Fingerprint Scanners – Optical, Capacitive and Ultrasonic
This article goes on to explain the basic differences among the different fingerprint scanners in terms of the technology used and how they work.
Optical fingerprint scanners are the oldest to come by of capturing the fingerprints and then comparing them. Firstly an image is captured as in a photograph, unique algorithms are then used to detect patterns on the finger’s surface to mark off any marks and ridges. This is done by differentiating the dark and light areas of the captured image. The sensors are designed to have a specific resolution. If the resolution is higher, the sensor can capture finer details of your finger. They essentially capture a two-dimensional picture. The Suprema Realscan G10 is a portable scanner that employs advanced optical technology to capture the patterns and ridges in dry and wet fingers.
This technology is commonly found in scanners these days. This technology uses many arrays of small capacitor circuits to collect differentiating data about fingerprints. Capacitors can store charge and therefore if they are connected to conducting plates on the surface, they and track the fingerprint details. The presence of an air gap will not bring about any change in the stored charge. The changes are tracked using an op-amp integrator which is further converted using an analog-to-digital converter. The data can be saved for later comparisons. For higher resolution pictures, more capacitors have to be connected.
This is the latest technology to be used in fingerprint scanners. The hardware used in these scanners consists of an ultrasonic transmitter and a receiver. An ultrasonic pulse is transmitted against the finger placed on the scanner panel. Whereas some of it is absorbed, the rest is echoed back. This is dependent on the valleys, ridges, pores and other marks found on the finger. These are unique to every finger.
The mechanical stress measured by a sensor is used to calculate the intensity of the reflected ultrasonic pulse. This happens at different points on the scanner. If the time period of scanning is longer, the depth of data that is captured is more and enables a 3D rendering of the surface.