Going by the definition of Biometrics from Wikipedia, Biometrics is a technical term used for body measurements and calculations or metrics related to human characteristics. It is formed as Bio + metrics, bio is related to beings and metric means measurement. First, we are going to discuss ways that are used in smartphones.
The first one that we are going to discuss is the Fingerprint scanners. Fingerprint scanners have been quite popular and are being a necessity in the phones, just to follow the “trend”, and are the least expensive hardware feature that can be used in a smartphone. Let’s take look at the type of fingerprint scanners.
  1. Optical Fingerprint scanners: These type of fingerprint scanners produce a virtual image of the fingertips or the pattern of the fingerprint. These type of scanners just match the image of the fingerprint with the pre-set fingerprint. These type of fingerprints aren’t used in phones. Most common use of these type of scanners can be seen in banks for the authentication of the bank employees and you shall probably have seen them. And if you have done re-verification of your mobile numbers using e-KYC you have used these type of scanners. However, you can now link Adhaar card, with your phone number at home using OTP.
  2. Capacitive Fingerprint scanners: These are the scanners that are used in all the phone. There are several capacitors in the scanner and when the ridges (or the humps) of the fingerprint touch the scanner, there is a change in the electrical conductivity of the scanner. The electrical conductivity of the scanner changes in the same pattern as the ridges of the fingerprint. Simply we can say that it actually detects the pattern of the fingerprint rather than just clicking an image of the fingerprint hence are more reliable than the optical ones and so are more expensive.
  3. Ultrasonic Fingerprint scanner: These type of scanners use ultrasonic waves for the detection of the fingerprint. These waves penetrate the epidermal or outer layer of the skin and get reflected by the dermal layer of the skin. This process overcomes the basic drawback of the above two type of scanners, that is dirty hands. If the fingers have dirt and smudges, then these scanners can go bonkers. The ultrasonic waves get reflected by the ridges and valleys of the fingerprint and are read by the receiver. These type of scanner are the upcoming type of scanners that would be used. Qualcomm is testing these scanners in the phones. Vivo V20 Plus UD is leaked to launch with the Under Display fingerprint scanner which is nothing but the Ultrasonic fingerprint scanner. Although have been used some phones as normal ones.
There is some other classification of scanners that are based on the type of working of the scanners.
  • Active type: These scanners are active all the time even if the screen is off. Just touch it and the phone is unlocked or if some other gestures are assigned to it.
  • Passive type: These scanners are not active if the screen is locked. You have to wake the screen up only after then the scanner will be active and you can perform the required action.
Next, we are going to talk about the one which is popularized by Samsung to be used in the phones and is used by Samsung in their flagships, that is Iris Scanner. The scanner captures the picture of the person’s iris as iris, in fact, the whole eye does not change with age, and is not obstructed by spectacles or contact lens. Every person has individual unique iris, thus forms the basis of authentication. The Iris scanner is also more accurate as there are 200 reference points for authentication than 70 points in case of fingerprint scanners.
Minimalistic Illustration of an Eye
The iris scanner works when placed at 3-10 inches from the eye. This is a very simple technique and uses visible light and near-infrared light. Using the near-infrared light pupil gets black and the phone can differentiate between pupil and iris. Then the camera takes a picture of the iris and then locates there 4 parts of the eye – the center of the pupil, edge of the pupil, edge of iris and eyelids and eyelashes. After that, it analyzes the patterns in the iris and then forms a code out of it which then is used for authentication.
The next one is using you Face. Two techniques are used which are the 3D scan and 2D. If we talk about 2D then this is a very simple technique which was present in Android previously till 4.3 or 4.4 and was dead after but has been resurrected recently by some companies. It just captures a photo of you using front camera and then matches it to unlock the device just as in the case with the optical fingerprint scanners.
Talking about the 3D scan. The most popular example of this technique is Apple’s Face ID. The equipment used has an assembly as shown below. The proximity and ambient light sensor help in estimating the light needed to recognize the face. Then the Flood Illuminator is used to illuminate the face.
Face Unlock Mechanism of iPhone X or iPhone 10
The Dot Projector creates a 3D map of depth and area of the face using 30,000 dots. Then the infrared camera captures the dots reflected from the face and along with a thermal signature of the face. Thus, a 3D scan and analyzing of the face is done. Other companies like Huawei are also coming up with their system of 3D scanning of the face and will use in their future smartphones.


The technology keeps on advancing and thus it will be worth seeing what other methods or implementation of the methods of security comes up in the future.

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