Xiaomi subsidiary Redmi also plans to use a fingerprint reader installed directly under the display surface on its affordable smartphones, even if the device is equipped with an LCD. So far, under-screen sensors were only possible with OLEDs.
Redmi's general manager Lu Weibing recently published a video on the Chinese Twitter counterpart Weibo, in which a smartphone prototype of Xiaomi's own brand can be seen, which is equipped with a new type of fingerprint reader, also reported by GadgetsNDTV. Thanks to infrared technology, it is able to capture the user's fingerprint even when the backlighting that is usual with LCDs is actually in the way. Xiaomi wants to use the new infrared technology to install fingerprint readers under LCDsNormally, the previously available under-screen sensors use the fact that OLED panels are translucent and so you can use the optical sensors to detect the surface of the finger when it is illuminated by the display when the finger is placed on it. This is possible because OLED panels do not need the additional level for the backlight required for LCDs - after all, the pixels themselves light up with OLEDs.
The technology was now shown by Xiaomi and Redmi now uses a special material that is transparent to infrared light. Therefore, you can now install an infrared transmitter at the bottom of the screen, whose light reflects off the surface of your fingers and can then be detected by an IR sensor. Despite the use of an LCD panel, you get a fingerprint that can be used to identify the user.
It is still unclear whether the new infrared-based solution is as secure as the optical sensors previously used in connection with OLED panels. One limitation of the design of the new infrared-based under-display sensors is the fact that the position for placing your finger is very close to the bottom of the screen. This can lead to reduced ergonomics, depending on the size of the user's hands or fingers.
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