Fingerprint reader: characteristics, operation and types

Not way back, if you happen to had been fingerprinted, it was in all probability since you had been being accused of a criminal offense; Now, nonetheless, it is without doubt one of the favourite strategies so as to add a layer of safety to our gadgets as a result of they’re a really dependable, easy and additionally low-cost technique.

Why are fingerprints distinctive?

It is kind of apparent why we now have fingerprints: the small friction ridges on the guidelines of our fingers make it simpler for us to know the objects we wish to grasp with our hand. By making the fingers rougher, these ridges improve the power of friction between our palms and the objects we maintain, making it troublesome for issues to fall off. You have fingerprints even earlier than you’re born, and actually the fingerprints are absolutely shaped when you might have solely been within the womb for 7 months. Unless you might have hand accidents, your fingerprints will stay the identical all through life.


What makes fingerprints such an excellent approach of differentiating folks is that they’re just about distinctive: fingerprints are developed by an primarily random course of along with your DNA code, and as a result of the atmosphere within the womb it additionally has its impact, even two twins have completely different fingerprints. While it’s attainable to seek out two folks with just about an identical fingerprints, the probabilities of this occurring are negligible.

Therefore, when fingerprints are used to manage an individual’s entry to a pc system akin to a laptop computer or smartphone, the probabilities of a random individual having the right fingerprint are typically so slim. that are virtually ridiculous, far lower than an individual can guess your password or can break a bodily block. Therefore, fingerprints are thought of the most effective safety techniques on the market.

How does a fingerprint reader work on a laptop computer?

Taking your fingerprints at a police station includes urgent your fingers on an ink pad and then rolling your fingers throughout a chunk of paper to depart a clear impression on a sheet. The impressions are additionally saved digitally afterwards in order that the police can confirm you probably have dedicated any recognized crimes or if you happen to achieve this sooner or later (this is named “being on file”).

But when fingerprints are used to manage entry to pc techniques like a laptop computer, extra subtle strategies should be used: we should have a fingerprint reader that scans the floor of the finger shortly and then converts the scanned illustration right into a code that may be in contrast. with its database, that’s, to permit entry beforehand it’s vital that the fingerprint is already processed and saved.

Portable fingerprint reader

There are 3 ways to scan the fingers. An optical scanner works by shining vibrant mild onto your fingerprint and actually taking {a photograph} of it. If you have ever photocopied your hand, you may know precisely how this works, however as an alternative of manufacturing a unclean black photocopy, the picture is fed into the PC’s scanner, which makes use of a light-sensitive microchip (be it a CCD, a charge-coupled machine or a CMOS picture sensor) to supply a digital picture. The PC routinely analyzes the picture, choosing simply the fingerprint, and then makes use of subtle pattern-matching software program to transform it into code.

Another sort of scanner, generally known as a capacitive, measures your finger electrically. When the finger rests on a floor, the grooves of the prints contact the floor whereas the gaps between them are barely exterior of it. In different phrases, there are completely different distances between every a part of the finger and the floor under, so the capacitive scanner creates a picture of the fingerprint by measuring these distances; This sort of scanner is a bit just like the contact screens of cell phones, though though they’re quicker than optical ones, they don’t work effectively when the finger isn’t clear or is moist.

Measure Fingerprint

The third sort of fingerprint reader known as an ultrasonic scanner as a result of it makes use of high-frequency sound waves (ultrasound) to “map” your finger as an alternative of utilizing mild just like the earlier two. This sort of scanner could be built-in beneath contact screens, which is why it’s utilized in some smartphone fashions, however its operation is just like that of optical scanners for all functions.

What occurs in the course of the fingerprint scan?

Unlike unusual digital pictures, scans should seize precisely the correct quantity of element (brightness and distinction) in order that particular person ridges and different particulars within the fingerprint can precisely match beforehand taken scans. Remember that fingerprints can be utilized as proof in prison trials, the place a conviction might lead to a protracted jail sentence; For this cause, high quality management is definitely an important a part of the fingerprint scanning course of, and this is applicable equally to a laptop computer fingerprint reader.


This is how the scanning course of works with a easy optical scanner (with the opposite two types it’s comparable however with the variations that we now have defined within the earlier part):

  1. A row of LEDs scans the intense mild onto the glass (or plastic) floor that you simply place your finger on (typically known as a stage).
  2. Image high quality will fluctuate relying on the way you press, how clear or greasy your fingers are, how clear the scanning floor is, the ambient mild degree, and so forth.
  3. The mirrored mild bounces off the finger by the glass in direction of a CCD or CMOS picture sensor.
  4. The longer this picture seize course of takes, the brighter the picture shaped on the sensor will probably be.
  5. If the picture is simply too vibrant, areas of the fingerprint (together with vital particulars) could disappear fully, like a digital picture indoors the place the flash is simply too shut or too sturdy. If it’s too darkish, the picture will seem black and the main points will probably be invisible for the other cause.
  6. An algorithm checks whether or not the picture is simply too mild or too darkish; if that’s the case, an audible beep or LED indicator alerts the operator and the measurement must be repeated.
  7. If the picture is appropriate, one other algorithm checks the extent of element, normally by counting the variety of ridges and ensuring there are alternating zones of sunshine and darkish (as you’d count on from a good footprint picture). If the picture fails this take a look at, return to step 1.
  8. As lengthy because the picture passes these two checks, the scanner accepts the picture, which is saved as a suitable scan on a laptop computer’s inner reminiscence chip for this function. Typically photographs captured this manner are 512 x 512 pixels (the scale utilized by the FBI) ​​and the usual picture is 2.5 cm (1 inch) sq., with 500 dots per inch of decision and 256 shades of grey.
  9. Now the PC can retailer the picture in its database (quickly or indefinitely) and routinely evaluate it with the fingerprints which can be authorised to unlock the gear and permit entry.