Fingerprint unlocking technology is widely used in current mobile phones, but this function relies on the accuracy of the screen's recognition of fingerprints. However, when a screen protector is installed, will the screen protector affect the fingerprint recognition capability?
There are two main types of fingerprint unlocking: "Optical Fingerprint Recognition" and "Ultrasonic Fingerprint Recognition." The way they work affects how well they can work with screen protectors.
Optical Fingerprint Recognition
This type uses light from the screen (usually OLED) to light up your fingerprint. The sensor then reads the reflected light to make a 2D image for matching. It relies on the screen being bright and clear, so if the screen protector blocks too much light (like privacy films or poor-quality protectors), it can cause problems with recognition.
Ultrasonic Fingerprint Recognition
This type uses sound waves to scan your fingerprint’s 3D details. It works by sending out sound waves and measuring how they bounce back. This technology is more sensitive to the thickness of the protector. If the protector is too thick, it can block the sound waves, making recognition slower or causing it to fail.
How Protector Thickness Affects Fingerprint Sensitivity
The thickness of the screen protector is very important for fingerprint recognition. Different technologies can handle thickness differently.
For optical recognition, the main concern is how much light can pass through. If the protector allows enough light (usually over 90% transparency), the thickness doesn't matter much. A protector that is about 0.3mm thick usually works fine.
Privacy screen protector may cause issues because they block light from the side. This can make it harder for the optical sensor to recognize your fingerprint, but it can usually be fixed by re-registering the fingerprint or changing the pressing angle.
Ultrasonic recognition is more sensitive to thickness. If the protector is too thick (more than 0.3mm), the sound waves won’t pass through easily, which may cause the system to fail or need extra presses. For example, Xiaomi 15 suggests a protector thickness of 0.16mm, and anything above 0.26mm may reduce sensitivity.
Other Factors That Affect Fingerprint Recognition
Besides thickness, the following things can also affect how well the protector works with fingerprint sensors:
Full adhesive protectors are better because they stick tightly and reduce air bubbles and signal interference, which is especially good for ultrasonic sensors.
The oil-repellent layer on the protector can affect how well fingerprints show up and how much oil or dirt sticks to it. Dirty protectors can block light or sound, so it’s important to clean them regularly.
Finger condition matters too. Ultrasonic sensors work well with wet or dry fingers, but optical sensors might have trouble if your finger is wet because it can change how light reflects.
How to Choose the Right Protector
For optical fingerprint models: Choose a protector with at least 90% light transparency and a thickness of no more than 0.3mm. Avoid privacy or matte films.
For ultrasonic fingerprint models: Choose a protector with a thickness of 0.2mm or less, and make sure it’s labeled “for ultrasonic use.”
In short, optical sensors care more about light passing through, while ultrasonic sensors care more about how thick the protector is. If fingerprint unlocking is important to you, pick a protector that matches your phone’s fingerprint technology and pay attention to thickness, transparency, and fit. As technology improves, screen protectors will work better with fingerprint sensors, but choosing the right protector is still the best way to ensure good performance.
