Nowadays, in-display fingerprint readers are becoming a popular choice for smartphone manufacturers. Let’s take a look at how they work and the differences between optical and ultrasonic readers.
The tech behind under-display fingerprint readers
In-display fingerprint readers were first introduced in 2017 with the launch of the Vivo X20 Plus UD. However, the technology didn't take off until the release of the iPhone X in late 2017. The main reason for this was that Apple had been using a different biometric authentication method since the launch of the iPhone 5S - Touch ID - which used a capacitive sensor embedded in the home button. Android phone manufacturers, on the other hand, largely opted for an ultrasonic in-display fingerprint scanner. This guide will explain how both of these technologies work, and the pros and cons of each.
Optical vs ultrasonic
There are two main types of fingerprint readers: optical and ultrasonic. Most of the scanners we've seen so far are optical scanners – these use light to illuminate your finger. A tiny camera under the screen takes an image of your finger which is then compared to the stored image. The downside? It can be difficult to get a good image if your fingers are wet or dirty. Ultrasonic fingerprint readers use sound waves to create a 3D image of your fingerprint. This means they can work even if your fingers are wet or dirty, and they're also more accurate than optical scanners. However, they're not as common as optical scanners yet, so you're likely to find them in more high-end devices like the iPhone Xs and Xr.
Is ultrasonic better?
The biggest difference between the two technologies is how well they work under different types of displays. Ultrasonic readers are better suited for OLED displays, since they emit their own light and don't rely on the backlight of an LCD. Optical readers, on the other hand, are better for LCDs since they use the existing backlight to see your fingerprint. So which one is better? It really depends on your handset. If your phone has an OLED display, go for ultrasonic. If it has an LCD display, go for optical. But ultimately, it'll come down to whether or not more handset manufacturers adopt in-display fingerprint readers—if they don't, ultrasonic may lose out to optical because of the extra cost.
Wider zone optical sensors
We're expecting plenty more phones to launch with optical sensors—the tech certainly isn't going away. In fact, it's likely that Apple will switch to an optical sensor in its 2020 iPhones. So why are phone makers moving away from ultrasonic sensors? For one, ultrasonic sensors require more precise finger placement than optical sensors. They also don't work as well through materials like glass or metal. That said, they're still more secure than optical sensors. With an ultrasonic sensor, you need to be very precise in where you place your finger on the sensor. If your finger is even slightly off, the sensor will fail to read your fingerprint. Optical sensors, on the other hand, have a wider zone in which they can read fingerprints. This means you could literally put your thumb down anywhere on the screen and it would unlock the phone. While this may not be as secure as an ultrasonic sensor, it's definitely more convenient.
In-display fingerprint readers are the next step in smartphone security and authentication. By 2020, it's estimated that over 1.5 billion smartphones will have an in-display fingerprint reader. There are two main types of in-display fingerprint readers: optical and ultrasonic. Optical readers use a wider zone sensor to image your fingerprint, while ultrasonic readers use a more precise ultrasound signal to image your fingerprint. Ultrasonic readers are often seen as being more accurate and secure, but optical readers are catching up fast.
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