Optical, Capacitive, and 3D Ultrasonic Fingerprint Sensors: Which Is Best for Biometric Authentication?

I picked up a new smartphone to review the other day. As is my practice, I dived into fishing out every little bit of info about it and in the process stumbled on the fact that it has a 3D ultrasonic fingerprint sensor for biometric authentication. That inspired me to write an article explaining the different types of fingerprint scanners found in phones today.

The first thing to point out is that while all fingerprint sensors provide your phone with security, the level of accuracy, detail, and security they provide differs from one type to another. How fast they work aslo differed from one type to the other. Some types of fingerprint scanners also work well with under certain conditions that others perform poorly in.

Pixel 5a 5G fingerprint scanner

Types of Fingerprint Scanners

Regardless of the location of the fingerprint scanner on a phone – In-display, rear, or side, there are three types of fingerprint sensors in use in cell phones today. They are: Optical, Capacitive, and Ultrasonic. Which type is used in a particular smartphone depends on a number of factors, including cost.

Optical Fingerprint Sensors

These sensors use light to scan the fingerprint and create a 2D image of the fingerprint. They are generally less expensive than other types of sensors but may not be as accurate and can be fooled by fake fingerprints.

Optical sensors are the most common type of fingerprint sensors found in a wide range of smartphones, from entry-level models all the way to premium flagships. The list of cell phones with an optical scanner include older flagships like the Samsung Galaxy S21 and Pixel 6 Pro, as well as more budget models like Pixel 4a, Motorola Moto G Power (2021), and LG Stylo 6.

Capacitive Fingerprint Sensors

These sensors use electronic capacitors to scan the fingerprint. They can detect the ridges of the fingerprint and are more accurate than optical sensors. They are commonly used in smartphones and are fast and reliable.

A capacitive sensor is much more difficult to fool than an optical scanner, because the results can’t be replicated with an image, and even are difficult to fool with a prosthetic, as different materials will record slightly different changes in charge at the capacitor. This makes capacitive fingerprint scanners much more secure than optical ones.

Capacitive fingerprint sensors are popular among budget and mid-range smartphones. Some examples of popular smartphones with a capacitive fingerprint sensor include: iPhone 5s through to iPhone 8, Google Pixel phones all the way to Pixel 5, OnePlus 8 and 9 models, and Nokia 5.4.

Ultrasonic Fingerprint Sensors

These sensors use ultrasonic waves to create a 3D image of the fingerprint. They are more accurate than optical sensors and can work even if the finger is dirty, oily, or wet. They are also more expensive than other types of sensors. Ultrasonic fingerprint scanners are the most secure. They are also the ones used in premium flagship smartphones.

Examples of phones with ultrasonic fingerprint sensors include Samsung Galaxy S23, S23+, and S23 Ultra, Samsung Galaxy Z Fold4, Samsung Galaxy Z Flip4, and Motorola Edge+.

Samsung S23, S23 Plus, and S23 Ultra all use an ultrasonic fingerprint sensor.
Samsung’s S23 range use ultrasonic fingerprint sensors

Ultrasonic vs Capacitive vs Optical Fingerprint Sensors, on Summary

The main differences between an Ultrasonic fingerprint sensor, a capacitive fingerprint sensor, and an optical fingerprint sensor are:

  • Accuracy and Security: Ultrasonic fingerprint sensors are more accurate, and thus more secure, than optical sensors because they create a 3D image of the fingerprint, while optical sensors can only create a 2D image. Capacitive fingerprint scanners sit in the middle, in terms of accuracy.
  • Speed: Traditionally, capacitive and optical sensors were initially much faster than ultrasonic fingerprint sensors. But the technology keeps maturing and the speed difference has been reduced to the barest minimum, if at all it still exists. On the Samsung Galaxy S23 which we reviewed, the 3D ultrasonic fingerprint scanner is very fast.
  • Environmental conditions: Ultrasonic sensors can work even if the finger is dirty, oily, or wet, as well as in low-temperature conditions and strong sunlight. Optical sensors may have difficulty reading fingerprints in these conditions.
  • Cost: Implementing an optical fingerprint scanning technology is generally less costly than implementing a capacitive or an ultrasonic fingerprint scanner. As such, optical scanners tend to be found in low-cost smartphones, capacitive in mid-range and budget smartphones, while ultrasonic scanners are found only in the most premium smartphones.

Which type of fingerprint scanner is best for biometric authentication?

The answer is obvious: 3D ultrasonic fingerprint sensors are the best type for for biometric authentication in smartphones and other mobile gadgets. They offer the best accuracy, security, and have become really fast. If you can afford a premium smartphone that has one, buy it. If not, a budget device with a capacitive scanner will do just fine.

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