In-display fingerprint sensors will soon no longer be a feature restricted to smartphones with OLED screens. According to Lu Weibing, the general manager of the Redmi phone brand, the company’s research and development team has solved the problem of fitting these fingerprint sensors to LCD screens, indicating cheaper phones will receive this biometric security feature in the future.
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The primary problem for fitting such sensors to LCD screens was the thickness of the panel and the presence of a backlight, which stopped light from passing through the screen to the fingerprint sensor beneath. While many smartphones use OLED screens that avoid this problem, they are usually expensive upper mid-range or flagship devices. Cheaper smartphones use LCD panels, and therefore usually have rear or side-mounted fingerprint sensors today.
Weibing writes in his Weibo post on the subject that Redmi, which is part of the Xiaomi family, has used a film of, “infrared high transmittance” material to allow light to pass through an LCD screen and onto the fingerprint sensor. By doing so, it has the option of adding an in-display fingerprint sensor to its low-cost phones, which in turn helps it clean up the exterior design, and give the phones a more modern, high-end look.
While Redmi’s innovation is exciting news, it’s likely not to have worked on the project alone. In April 2019, China-based technology firm Fortsense said it had found success with an LCD in-display fingerprint sensor. Goodix Technology has also said it would be able to mass produce an optical in-display fingerprint sensor for LCD screens in 2020. It’s possible Redmi worked with one of these two, or another company, to make the sensor.
The bigger question is, will LCD in-display sensors be any good when they arrive? We don’t know yet; but anyone who used the early optical fingerprint sensors in 2018 will remember they were not very good. They were often slow and unreliable, something a security system should not be, and may have led many to rely on less secure ways of safeguarding their phones out of frustration.
In-display fingerprint sensors soon evolved to use faster and more reliable ultrasonic systems. However, sensors embedded in LCD screens will not use this technology, and may suffer from the same problems we saw when the tech was first introduced. The industry has had time to improve the experience between then and now, and the demo video Weibing including on his Weibo post shows the sensor reacting quickly; but expectations should be get in check before we get to try it out.
Redmi has not commented on when the first phone with its new LCD in-display fingerprint sensor will arrive.