What are the different types of fingerprint scanners?

Fingerprint scanners have become a crucial feature in smartphones, even in entry-level smartphones. Beyond unlocking the device, they are used for payment authentication, authorising purchases on app stores, and remembering passwords. Over the past decade, fingerprint scanner technology has evolved significantly. 

Initially, scanners used to be embedded in the home button on the bottom bezel. Today, high-end phones feature ultrasonic or optical in-display scanners, while budget-friendly phones sport side-mounted or rear-mounted scanners. When display sizes started to increase, it led to the elimination of the dedicated buttons on the bottom bezel, and the fingerprint scanner moved to the backside of the device. 

In 2018, Vivo launched the Vivo X21, the world’s first smartphone with an in-display fingerprint scanner. In 2019, Samsung launched the Galaxy S10 series with the world’s first smartphone equipped with an ultrasonic in-display fingerprint scanner. This ultrasonic technology offers enhanced security and accuracy compared to traditional optical scanners. Let’s explore the various types of fingerprint scanners currently available in the smartphone industry.

Optical fingerprint scanners

Various smartphones come equipped with an optical fingerprint scanner embedded beneath the display. It uses light to capture the fingerprint image. When a finger is placed on the scanner, light is projected onto the surface, and the reflections from the ridges and valleys of the fingerprint are captured by a sensor.

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Optical in-display fingerprint scanners offer a cost-effective and straightforward implementation, hence their widespread use in smartphones across different price points. However, they can be deceived by high-quality fingerprint reproductions and may exhibit reduced accuracy when fingers are dirty or wet.

Capacitive fingerprint scanners

Capacitive fingerprint scanners were quite common in the early days of fingerprint scanner technology in smartphones, and often featured in the home button or on the back of the devices. They are still in use, embedded under the power button placed on the right edge of the phone.

Unlike optical in-display fingerprint scanners, capacitive fingerprint scanners use an array of tiny capacitors to generate an electrical image of your fingerprint’s ridges and valleys. When a finger is placed on the scanner, the capacitive sensor measures the electrical differences between the ridges and valleys of the fingerprint. 

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They offer higher accuracy compared to optical scanners and are more difficult to deceive. However, they may face a challenge identifying a fingerprint when the finger is wet or dirty.

Ultrasonic fingerprint scanners

Ultrasonic fingerprint scanners offer superior security and accuracy compared to other methods. A screen embedded with an ultrasonic in-display fingerprint scanner emits high-frequency sound waves that bounce off your finger when it is placed on the sensor. The scanner analyses the pattern of these reflected waves to construct a highly detailed 3D map of your fingerprint. Because this map includes features like blood flow beneath the skin, ultrasonic scanners are incredibly difficult to fool.

Ultrasonic fingerprint scanners are still relatively new and require more sophisticated hardware, making them a more expensive option. They are found on fewer devices compared to the more popular optical or capacitive scanners. Phones from the Samsung Galaxy S23 series, Galaxy S22 series, and Galaxy S21 series are some of the recent handsets equipped with ultrasonic in-display fingerprint scanners.

Which phones come with side-facing, optical, and ultrasonic fingerprint scanners?

Phones with LCD screens typically have side-facing fingerprint scanners because current technology limitations prevent the implementation of in-display fingerprint scanners with LCD panels. On the other hand, phones with OLED panels offer more flexibility, potentially featuring side-facing, optical in-display, or even ultrasonic in-display fingerprint scanners.

At present, phones below Rs 15,000 typically have side-facing fingerprint scanners. Some smartphones with OLED panels, such as the recently announced Poco X6 Neo, feature an OLED screen along with a side-facing fingerprint scanner. OLED display phones above Rs 20,000 are mostly equipped with optical in-display fingerprint scanners, whereas a few premium flagship phones, such as Samsung S-series flagship phones, have ultrasonic in-display fingerprint scanners.

As you read above, each type of fingerprint scanner has its own pros and cons. However, emerging technologies like multispectral and thermal fingerprint scanners are on the horizon, promising to further enhance security and functionality in smartphones. It remains to be seen when these technologies make their way into the world of smartphones.