A fingerprint scanner is a device that reads the image of a finger with all its features in the form of a papillary pattern and transmits the scan result to the software. A specialized application compares the resulting image with a sample created at the stage of forming a biometric password.
Types of fingerprint scanners
All currently used fingerprint scanners can be classified into three groups based on the physical principle of operation:
semiconductor (silicon);
optical;
ultrasound.
Semiconductor scanner
This type of scanner receives an image based on the properties of the semiconductors, which vary in the contact area of the papillary model and the scanner. The technology of this type of scanning device can be based on several technologies:
Capacitive scanners: The operation of such scanners are based on the effect when the capacitance of the PN junction in a semiconductor device changes when the crests of the papillary pattern and the elements of the semiconductor matrix are touched.
Pressure-sensitive scanners: The fingerprint scanner of this type uses a unique matrix of piezoelectric elements in his work. When a finger touches the matrix, the ridges put pressure on it and the depression, respectively, does not. Based on the pressure exerted on the matrix, an image is created.
Thermal scanners: Scanning devices of this type use sensor consisting of pyroelectric elements. These sensors record the temperature difference and then convert it into voltage.
Radiofrequency scanner: Scanners of this type consist of micro-antenna, which generate a weak signal. The resulting image is obtained in response to the papillary pattern of the electromotive force. Which works to produces a graphic picture of the fingerprint.
Long thermal scanners: Like thermo scanners. The only difference is that the finger must be held across the glass and not connected.
Capacitive broaching scanners: The technology for obtaining images of the papillary pattern is the same as the capacitive one, but getting is different. The finger is held on the scanning surface.
Radiofrequency broaching scanner: The working principle of these devices are the same as radiofrequency. The way to remove the image is not to put the finger on the device but to run a finger on its surface.
Optical scanners
A fingerprint scanner of this type receives the image of a finger by the optical method. The basis of the operation of devices of this type is various technologies.
FTIR scanner: These devices use the effect of an altered internal reflection.
Fibre optic scanner: The fingerprint scanner is a fibre optic matrix, each containing a photocell.
Electro-optical scanners: Obtaining an image comes from an electro-optical polymer containing a layer that emits light.
Optical broaching scanner: This type of equipment is a refinement of fibre optic devices in which to obtain an image, it is necessary to slide a finger on the surface and not connect it.
Roller scanner: To get an image, you need to keep your finger on the roller, where you take photos of the finger with papillary patterns.
Contactless scanner: Finger scanning is done without contact. The finger is applied to the hole, where it is highlighted from different sources, and the built-in camera captures the image of the finger.
Ultrasound scanner
This type of device scans the surface of the finger with ultrasonic waves and, based on the measured distance of the reflected waves from the depressions and protrusions; an image is created. This type of device differs from the above in that the scan result is of higher quality.
Fingerprint scanners aren’t just reserved for the top tier of smartphones these days. Even your reasonably priced mid-ranger can come securely packing additional hardware. Technology has moved on from the early days too, here’s a look at how the latest fingerprint scanners work and the differences.
How does a capacitive scanner work?
Capacitive scanners are the most common ones because the most dated and therefore tested. However, many smartphones use optical sensors that arrived later, more precise, and easily overcome, much more than capacitive ones.
Virtually all fingerprint sensors not integrated into the screen are capacitive. The name is due to how it is made; they use electric current to read a fingerprint using a series of tiny capacitors (also called capacitors), each with a minimal electrical charge.
Think of the sensor made up of squares (capacitors) on a checkerboard, only on a microscopic level where each of the capacitors are smaller than the width of a fingerprint ridge.
Each capacitor includes two conductive plates that come into contact when a crest of the footprint contacts the sensor. Connecting the two plates changes the amount of charge that a particular capacitor has. And wherever there is a valley in print, the demand in that specific capacitor remains the same.
This system allows you to create a footprint map based on which capacitors have a specific amount of charge and which do not. The touchscreen of the displays works similarly, but the sensors work on a much more detailed level.
How does an optical scanner work?
Optical scanners are much easier to understand because they use a more straightforward method of enrolling the smartphone owner’s fingerprints: they take pictures of the fingerprints.
The sensor illuminates the fingerprint with a small LED light. Then a camera takes a quick snapshot capturing the light and dark areas that denote the ridges and valleys of the fingerprint, respectively.
Optical sensors are less secure than capacitive ones (a photo is enough to deceive them) can be integrated under a smartphone’s display, allowing you to create full-screen smartphones.
But there are other disadvantages too, for example, a scratched touch surface or a dirty finger can cause the fingerprint not to be recognized.
How does an ultrasound scanner work?
The latest fingerprint scanning technology to enter smartphone space is an ultrasonic sensor announced before being inside the Pro smartphone le Max. Qualcomm and its Senso ID technology are also an essential part of the design. In this particular phone.
The hardware made up of both an ultrasonic transmitter and a receiver to capture the details of a fingerprint. So first, an ultrasonic pulse is transmitted against the finger, which is placed over the scanner. Then, some of this pulse is absorbed, and some of it is bounced back towards the sensor. And it happens depending on the ridges, pores and other details that are unique to each fingerprint.
There is no microphone listening out for these return signals. Instead, a sensor capable of detecting mechanical stress is used to calculate the intensity of the ultrasonic pulse returning at different points on the scanner. Scanning for extended periods allows for additional depth data to be captured, resulting in a highly detailed 3D reproduction of the scanned fingerprint. The 3D nature of this acquisition technique makes it an even safer alternative to capacitive scanners.