How the fingerprint scanner works on Xiaomi: technology and setup

Xiaomi’s modern smartphones offer users a wide range of biometric security technologies, among which fingerprint scanning remains one of the most popular and popular methods. Unlike simple passwords or graphic keys, biometric data is unique to each person, which ensures a high level of security for personal data. However, few people think about what exactly happens inside the device when the finger touches the surface of the screen or the side button.

The principle of operation of the sensor depends on the type of installed matrix, which can be optical or ultrasonic. In budget and medium-budget models of the brand, optical scanners are most often used, working on the principle of photography, while flagship devices can be equipped with more advanced ultrasonic modules. Understanding these differences helps the user not only to correctly configure the gadget, but also effectively eliminate possible problems in the unlock system.

In this article, we will discuss in detail the physical and software aspects of the work of biometrics in the shell of MIUI and HyperOS. You will learn how the process of reading a skin pattern occurs, why recognition errors sometimes occur and what hidden functions are available to advanced users.

The principle of operation of optical scanners in Xiaomi screens

The optical fingerprint scanner, which is installed in most Xiaomi mid-range smartphones, is a miniature camera placed directly under the display. When you click on the selected area of the screen, the system commands you to turn on the bright backlight of the pixels in the touch zone. OLED-Matrix, illuminates the crests and troughs of your finger, then reflected back to the sensor.

The resulting image is converted into a digital code that is compared to a reference sample stored in a protected area of the processor memory. The key advantage of this technology is the ease of implementation and relatively low cost of production, which allows Xiaomi to offer the unlock function by fingerprint even in available models. However, the speed and accuracy are directly dependent on the quality of the backlight and the cleanness of the screen surface.

Importantly, optical sensors require direct contact with the surface of the display. Unlike capacitive buttons that respond to the body's electrical current, physical transmission of light is required, which is why high-density protective glass or contamination can make identification difficult.

⚠️ Attention: Using cheap protective glasses with opaque edging or matte coating can completely block the work of the built-in scanner, since the light will not be able to pass to the sensor and back.

💡

If the scanner is unstable, try reconfiguring the fingerprint by adding the same finger twice at different angles, which will increase the likelihood of successful unlocking.

Technology of ultrasonic scanning in flagships

Xiaomi’s flagship devices, such as the Mi Ultra series or the top-end Redmi models, are often equipped with ultrasonic scanners developed in collaboration with Qualcomm. Their principle of operation is radically different from optical analogues: instead of light, a high-frequency sound wave is used. The sensor generates an ultrasonic pulse that bounces off the surface of the finger and returns back, creating an accurate pulse. 3D-skin-mapping.

Ultrasound technology has a number of undeniable advantages, most notably its ability to work through pollution, water and fat. Even if your hands are wet or stained, your smartphone has no problem counting the fingerprint, because the sound wave easily passes through these obstacles. In addition, this method of scanning is considered safer, since it is much more difficult to recreate a three-dimensional model of a finger than forging a two-dimensional image.

The response speed of ultrasonic scanners in Xiaomi devices is traditionally higher, and activation does not require a bright flash of the screen, which is especially convenient in the dark. However, the cost of such modules is much higher, which limits their use to only the premium segment of the market. In the software part, these sensors integrate with the security system at a deeper level, ensuring data protection even when trying to physically open the device.

Physical scanners: side and back buttons

Despite the ubiquity of screen solutions, many users still prefer the classic physical scanners built into the body of a smartphone. In modern Xiaomi models, they are most often located in the side button on the on, combining unlock and activate power, such modules work on a capacitive principle, reading the electrical properties of the skin.

Capacitive sensors form an electrical charge map, where the finger crests close the circuit and the troughs do not. This allows you to create a high-precision image of the fingerprint without the need for light or sound. The lateral arrangement is considered ergonomically the most convenient, since the finger naturally falls on the end of the device when it is captured.

The rear scanners that have been seen in older Xiaomi models are gradually becoming a thing of the past, giving way to more compact solutions. However, their reliability remains the benchmark: they are almost unaffected by external factors, such as scratches on the screen or thick protective glass. The mechanical button provides haptic returns, helping the user to accurately find the scanning area.

• 👍 High reaction speed and instant unlocking of the device in any conditions.
• 💧 Independence of screen state: works even when the display is broken or in the always-on screen mode.
• 🔋 Minimum power consumption compared to optical analogues built into the matrix.
• 🛡️ Resistance to software interface failures, as the module has a separate communication channel with the processor.

Software processing and MIUI algorithms

Iron is only half of the success, and software is the other half. In Xiaomi smartphones, a dedicated secure TEE (Trusted Execution Environment) module is responsible for processing biometric data. Fingerprint data never leaves this secure perimeter and is not transferred to the company's servers or cloud storage.

The MIUI shell algorithms are constantly analyzing the quality of the image being read. If the system notices that the finger is not applied correctly or the pressure is too weak, it ignores the input attempt, preventing false positives. When you first set up, the user undergoes a calibration process, during which several dozen digital casts of the same finger are created at different angles.

With the release of the HyperOS update, biometrics algorithms have improved to speed up response in games and applications. The scanner can now be used as a priority if an application is running from a trusted list, and it learns user habits by remembering which finger and angle you most often unlock your phone.

Comparison of biometric protection technologies

To determine which type of scanner is best for your use case, you need to conduct a comparative analysis of the characteristics. Each technology has its strengths and weaknesses, which become noticeable only during long-term use.

Optical scanners are better off in price and prevalence, but they are less likely to work in bright sun or pollution. Ultra-block models are free of these disadvantages, but only available in expensive devices. Physical buttons remain the most reliable, but they take up useful space on the case, which contradicts the trend for framelessness.

💡

The choice of scanner type affects not only the convenience, but also the autonomy of the device: optical sensors consume more battery power due to the need to illuminate the scanning area.

Fingerprint setting and calibration

The scanner is properly configured to work well. Many users make the mistake of adding a fingerprint in only one position, leading to unlock problems when the phone is on the table or in a case. The Settings menu → Passwords and security → Fingerprints has full functionality for managing biometrics.

It's recommended that you add the same finger twice, but apply it the same way you hold your phone in your pocket or when it's on the table, and this creates an extended pattern that the system can recognize in an unusual situation, and it's also worth periodically removing old, irrelevant fingerprints and adding new ones, because the condition of the fingers' skin can change over time.

To increase sensitivity, some Xiaomi models have a hidden engineering option available through the developer menu or special codes. However, standard settings are usually enough for comfortable use. If the phone no longer recognizes the finger, try to wipe the screen and finger itself, and check if the protective glass is too thick.

⚠️ Warning: Do not use chemical solvents or aggressive liquids to clean the scanner area, this may damage the oleophobic screen covering or the sensor itself.

Frequently Asked Questions (FAQ)