In-Display Ultrasonic Fingerprint Sensors for Smartphones Provide Improved Authentication and User Experience

In-display fingerprint sensors technologies are starting to find their way into smartphones and are currently using optical scanners with a more advanced ultrasonic technology expected to be released next year. Ultrasonic fingerprint scanners can allow an entire device’s screen display, or a large portion of it (even a dirty one), to work as a fingerprint reader. This allows a user to unlock a phone, open a secure app, or authenticate a payment just by placing their finger on the display.

Ultrasonic sensors make use of ultrasonic sound to create a 3D image of a fingerprint. The sensors determine a fingerprint’s unique ridges along with other details. In contrast, standard capacitive and optical fingerprint scanners create easy-to-replicate two-dimensional (2D) images of a user’s fingerprint that provides a less secure authentication technique. Optical fingerprint scanners also require the user to press their finger in a specific, predefined portion of the screen while ultrasonic sensors allow for a larger portion of the screen to function as a reader. All types of in-display fingerprint sensors allow for a more discreet form factor that takes up less space than a normal fingerprint sensor and is often being embedded under the case or glass, which also provides a safer environment from damage and water. This allows smartphones to be designed with improved bezel-less displays to offer a larger screen size on a smaller device—although there is an obvious extra cost associated with this technology as compared to current fingerprint sensors.

A number of companies currently offer devices with in-display fingerprint scanners using the optical 2D image recognition technology. Smartphone models using this feature include Huawei’s Porsche Design Mate RS and Mate 20 Pro; Vivo’s V11 Pro, X21, and NEX S; OnePlus’s 6T; Xiaomi’s Mi 8 Explorer Edition; and Oppo’s R17.

Leading smartphone vendor Samsung does not yet have a model in the market with an in-screen fingerprint sensor. Samsung has announced recently that it will be offering an ultrasonic fingerprint sensor on the Galaxy S10 (expected for release in Q1 2019) and has said that the technology is faster and more secure than optical fingerprint sensors. The Galaxy S10 is expected to be the first smartphone in market with an ultrasonic fingerprint sensor embedded in the display. The company has also said that the same sensors would be used in its Galaxy Note 10 and Galaxy A series smartphones, which are due for release later in 2019. The technology is based on Qualcomm’s three-dimensional (3D) Sonic Sensors that read and authenticate fingerprints alongside its Snapdragon 855 platform. The ultrasonic sensor does not compare the scanned image to a stored 2D pattern; instead, it creates a 3D mold of the print by bouncing soundwaves off the skin through the smartphone’s display, making it a more accurate method of authentication.

Apple is also currently refining its own in-display fingerprint technology, despite having removed Touch ID from its iPhone X devices in favor of Face ID. Apple continues to deny rumors that have suggested it wanted to build an in-display fingerprint sensor in the 2017 iPhone X device but was unable to ready the technology in time. The company is now working on a patent for a new technology that would allow it to add fingerprint-reading capabilities to Apple device displays without requiring a home button, enabling it to restore fingerprint authentication technology to its devices.

Apple’s new technology differs from Samsung’s ultrasonic fingerprint sensor and the optical fingerprint readers used in smartphones from China-based manufacturers. It uses several cameras and lights that are positioned beneath a layer of the display and not visible to the user. The cameras capture 3D image data of the fingerprint by measuring the slope of the skin surface to provide authentication. It must be noted that Apple often designs technologies that do not always find their way onto devices, and that could be the case here; however, it does highlight that smartphone manufacturers are investigating new ways in which to provide more secure and user-friendly fingerprint authentication technologies that only require the user to touch any part the screen.

With these new developments in the technology, ABI Research expects roughly 30 million smartphones with in-display fingerprint scanners to ship in 2018, increasing to nearly 230 million in 2023 and to over 550 million in 2027 at a compound annual growth rate of 40% to become standard in many flagship devices from companies such as Huawei, Samsung, and Apple. More companies are likely to look to ultrasonic fingerprint scanning, or other 3D technologies such as Apple’s, to provide in-display fingerprint authentication as it is a more secure option that is less likely to be fooled by an image of a person’s fingerprint. This new technology is likely to replace standard fingerprint scanning technologies by offering a smaller form factor that allows the screen to become bezel-less and by offering a more secure authentication technique that takes a 3D—rather than a 2D—image. They also can read fingerprints in difficult conditions, such as when a user’s fingers are wet. Many devices are also likely to continue to offer a facial recognition option, making use of a smartphone’s in-built camera and allowing people to decide on their own authentication method.

An important consideration for companies looking to add the technology to their devices is cost. Adding in-display fingerprint sensors can be expensive due to the components that are required and the process of adding the scanner to the screen. This pushes up the price of the overall device. For flagship smartphones, this is often not a problem, as companies aim to add the newest and best technologies to such devices; however, for lower-end smartphones, it is unlikely that in-display fingerprint scanners will become the norm as it will push the price of the device out of the budget market.

When adding an in-display fingerprint scanner to a smartphone, considerations must be made about whether a screen protector will affect its ability to provide accurate readings. Many people are now turning to hard-wearing tempered glass screen protectors that offer a higher level of protection to their devices. If the fingerprint sensor does not work with such a product, it will become frustrating for the user and could ultimately be dropped as a feature.

The technology must also be compatible with apps (especially in banking and payment apps) that would normally be unlocked using a fingerprint sensor. There have been some issues with current smartphones’ optical in-display fingerprint sensors that are not working with apps; it is likely that ultrasonic fingerprint scanners will have the same problem due to the way in which the technology works and instead require the user to also enter a Personal Identification Number (PIN) code. This is likely to be frustrating for users, so a solution needs to be found to overcome this problem. Offering a secondary authentication method, such as facial recognition, will likely aid here until a solution has been found that will allow users to require one method of authentication.

As in-display fingerprint sensing continues to be developed, a number of other applications will become available. The technology will likely allow for continuous authentication to take place in the background and detect at all times whether the person using the phone is the registered user. This will be particularly useful with an ultrasonic authentication that can be utilized by a larger portion of the screen—meaning that the user could be authenticated when they tap on an app’s icon on the screen.