Every smartphone now comes with fingerprint scanners, even on budget phones, due to falling costs. Biometrics not only enhances security but also makes it easier to unlock the device compared to a PIN or password. It has become quite mature since it was first introduced and is now available on mobile phones and laptops. Classic PIN and password unlock methods have been replaced by fingerprint and face unlocking features.

Have you ever wondered how this works? Smartphones with bezel-less designs and the demand for tougher security have led to the development of Optical Fingerprint Under Display technology, which can operate under 1 mm of glass and even with wet fingers.

How fingerprint scanners work

They are embedded under the display and detect the light reflected by the fingerprint through the gaps in the OLED display panel. With advancements in technology, there are now different types of sensors.

Optical Fingerprint Under Display Sensor Work: Biometric Technology

There are three different types of fingerprint scanner. Here is how they work:

Optical fingerprint scanner

This is one of the oldest techniques used to increase security. It relies on higher-contrast images than regular 2D images of the finger and uses algorithms to detect unique patterns of fingerprints. Similar to a camera, it incorporates arrays of LEDs or display flash and typically has a higher number of diodes per inch to capture up-close, fine-tuned resolution and analyze the lightest and darkest areas of the photo.

  • It is easier to bypass with a high-quality image that captures the most sensitive details.
  • It uses optical fingerprint data combined with a capacitive sensor to differentiate between a real and fake finger.
  • This type of scanner needs to be more secure when dealing with sensitive details.

Capacitive Scanners

This kind of fingerprint scanner is normally found on rear-mounted and side-mounted fingerprint scanners on the device. It offers additional security benefits.

It uses tiny capacitors to store electrical charge in a circuit to collect data, connected through conductive plates on the surface to detect movement and track the details of the fingerprint.

  • It is more difficult to fool than an optical scanner because it is capable of identifying even slight changes in charge.
  • It can only be hacked either by hardware or software hackers, increasing the level of security enough to handle data.
  • It also has gesture functionality and a default “press-and-hold” design for reliable unlock.

Ultrasonic fingerprint scanner

This has a faster processing speed and a larger finger-reading area that captures the details of the fingerprint.

It consists of both an ultrasonic transmitter and a receiver. It creates a fingerprint through ultrasonic pulses transmitted to the finger over the scanner. Then, depending on the ridges, pores, and other characteristics, it creates a unique 3D fingerprint for a secure alternative to capacitive scanners.

  • It is the most secure fingerprint scanner.
  • It is slower than other scanners due to complex processing, and it conflicts with screen protectors, limiting fingerprint scanning.

Apart from this, there are some other fingerprint biometric technologies, including thermal fingerprint sensors.

Fingerprint scanner processing

The software of the device also plays a vital role alongside the hardware. OEMs process the data using slightly different algorithms to find patterns in order to identify fingerprint characteristics. All of the data is stored on the device to keep information secure in the Trusted Execution Environment (TEE) based on TrustZone technology.

Optical Fingerprint Under Display Sensor Work: Biometric Technology

The TEE cannot be accessed through apps. Some apps and websites also allow users to use a fingerprint scanner. Furthermore, in the near future, fingerprint scanning will move towards a passwordless future. The FIDO (Fast IDentity and Online) alliance has developed cryptographic protocols to use protected hardware zones to enable passwordless authentication, increasing speed, providing a high level of security, and allowing for hidden in-display designs.


A fingerprint reader that’s hidden behind the smartphone’s glass. To achieve a completely bezel-less smartphone, we require much innovation. For this, we can manufacture smartphones using a hidden camera that pops up or a sliding mechanism.

Nevertheless, today, we have the in-display fingerprint sensor. Many people refer to it as a screen fingerprint reader, but technically, the sensor is placed under the screen. So, the fingerprint scanner in a smartphone needs much space, where it has to be bonded to the screen.

At the top, there is glass, then an AMOLED display panel, and then a fingerprint reader. Screen reader technology has not been developed yet, where the reader is on the display panel, which allows the entire area to read your fingerprint.

Mostly, smartphones use an optical scanner through a green light to scan your finger and then reflect the light that reaches the fingerprint sensor to generate an image. OLED screens, aluminum, and specific kinds of materials support it. Manufacturers use the bottom area of the device, where the sensor is placed.

Optical Fingerprint Under Display Sensor Work: Biometric Technology

OLED screens, aluminum, and specific kinds of materials support it. The Huawei Porsche Design Mate RS is the first commercially available smartphone on the market that features Goodix’s in-display fingerprint sensor. It is the fastest fingerprint sensor that unlocks in just 0.002 seconds.

There is no effect when using a screen protector. It is a good idea to use a fingerprint scanner on the front of the device. With time, it has definitely improved and is a quality of life improvement. It also works smoothly on wet and dry hands or cold hands.

If we look at security, we should remember that an optical sensor will not sense a pulse, while a capacitive sensor can. The capacitive sensor can be unlocked with the use of fake scans.