How the scanner works on Xiaomi phones: from fingerprints to document scanning

The scanner on Xiaomi smartphones is not just a button to unlock the screen. Behind the external simplicity hides a complex system of optical and ultrasonic sensors, software algorithms and integrations with the Internet. MIUI. Depending on the model of the device (be it a budget Redmi or flagship Xiaomi 14), the scanner can work in different ways: somewhere uses a classic capacitive sensor, and somewhere – an innovative sensor. 3D-face scanner with infrared backlight.

But how do these technologies interact with hardware and software? Why is the fingerprint scanner hidden under the screen on some models and put on the back of the screen on others? And most importantly, how do you set up the scanner so it works quickly, accurately and without failure? In this guide, we will look at all the types of scanners that are installed in Xiaomi phones, their working principles, and give practical tips for optimization and troubleshooting.

Types of scanners on Xiaomi phones: how they differ

Xiaomi uses three main types of scanners, each with its own pros and cons. The choice of technology depends on the price segment of the device and the year of release. For example, budget models still have capacitive scanners on the back, while flagships get ultrasonic or optical sensors under the display.

Let’s look at the key differences:

• 📱 Capacitive scanner is the simplest and cheapest option, it works by measuring the electrical capacity of the finger skin, it is installed on the back or in the power button (for example, in the Redmi Note 10.
• 🔍 The optical scanner under the screen uses LED backlight to create a fingerprint image, more accurate than the capacitive one, but requires special attention. OLED-Screen (found in Xiaomi) 12T or POCO F5).
• 🌊 The ultrasonic scanner is the most advanced option (for example, in Xiaomi 13 Ultra). 3D-finger scanning, works even with wet hands and through protective glass.

Interestingly, Xiaomi is also experimenting with facial scanners, but they haven't yet gained mass adoption due to security concerns.For example, the Xiaomi Mi 11 was implemented. 3D-Face scanner with infrared camera, but it was replaced by a simpler one. 2D-variant.

How a fingerprint scanner works: technical details

If we talk about the most common type of fingerprint scanner, its work is based on three key components:

1. Sensor – captures a unique pattern of papillary lines.
2. Microcontroller – processes the data and converts it into a digital template.
3. Secure chip – stores encrypted fingerprint data in an isolated memory area (for example, in Qualcomm Secure Processing Unit on Snapdragon chips).

The scanning process takes less than a second:

1. The finger touches the sensor and the sensor reads the pattern.
2. The algorithm compares the resulting imprint with the stored patterns.
3. When matched, access to the system is unlocked.

It's important to understand that Xiaomi doesn't store the full image of the fingerprint, just its mathematical model (hash), which makes the system more secure from hacking, but if the sensor is damaged or contaminated, the accuracy of recognition can fall.

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If the fingerprint scanner gets worse, try re-registering your finger in the settings, sometimes just wipe the sensor with an alcohol napkin.

Scanner. QR-Codes and Documents: How it Works MIUI

In addition to biometric data, Xiaomi phones can scan QR-codes, barcodes, and even documents (passports, driver's license) through the Scanner app or the camera, which runs on computer vision and machine learning.

The recognition algorithm includes several stages:

• 📸 Image capture – the camera captures the object in high resolution.
• 🔎 Processing – the system highlights contours, removes distortion and improves contrast.
• 📊 Recognition – the neural network analyzes the data and converts it into readable text (for documents) or a link (for documents) QR).

For example, in scanning QR-The phone not only opens the link, but also checks it for security through the Xiaomi Security database. If the code leads to a phishing site, the system will show a warning.

To scan documents, MIUI uses OCR (Optical Character Recognition) technology, which supports more than 20 languages, including Russian, to save scanned passports or receipts as editable text, rather than just pictures.

Fingerprint scanner setup in MIUI

To make the fingerprint scanner work as efficiently as possible, you need to set it up correctly. In MIUI, this is done through the Settings menu → Passwords and security → fingerprints. Here is a step-by-step instruction:

Add the main finger (preferably the index right hand)|Register a backup finger (such as a thumb)|Activate the Unlock option when the screen is off|Turn off vibration when recognizing (if annoying)-->

A few important nuances:

• 🔄 Re-registration of the fingerprint – if the finger is damaged (cut, callus), it is better to remove the old print and add a new one.
• 🔒 Security - in MIUI You can only link the print to unlock, but not to payments (for this you need to do it). PIN).
• ⚡ Recognition speed – on flagships (for example, Xiaomi 14 Pro) the scanner works in 0.2 seconds, on public sector – up to 0.8 seconds.

If the scanner refuses to recognize the finger, check:

• Sensor cleanliness (wipe with a napkin).
• MIUI updates (sometimes bugs are fixed in new versions)
• No protective film or cover covering the sensor.

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On some models (such as the POCO X5), you can use the fingerprint scanner to quickly open applications, by tying your finger to a specific gesture setting.

Problems with the scanner and their solutions

Even the most reliable scanners sometimes fail, and let's look at the typical problems and how to fix them:

Especially often, users encounter a problem when the scanner stops working after the MIUI update, in which case resetting the security settings will help:

1. Go to Settings. → Passwords and security.
2. Select Reset fingerprint settings.
3. Remove all the saved prints and add them again.

On models with ultrasonic scanner (for example, Xiaomi 13T Pro) it is strictly impossible to use metal protective rings - they block sound waves and make the scanner inoperable.

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If the fingerprint scanner stopped working after the phone fell, the sensor plume may have gone, and only the service center will help.

Hidden scanner features you didn’t know about

The scanner on Xiaomi phones has a lot more to do than unlock the screen. Here are some little-known features:

• 🔐 Fast Payment – In some banking applications (e.g. SberPay) you can link a fingerprint to confirm payments.
• 📁 Hidden folders -- in MIUI There is a function of a protected folder, access to which can be limited to a fingerprint.
• 🎮 Game mode – on some models, the scanner can be used to quickly start games (for example, touching the sensor opens the game). PUBG Mobile).
• 📱 Multiplayer mode – if there are multiple profiles on the phone, everyone can link their fingerprint.

Another interesting feature is scanning fingerprints in apps, for example, in Xiaomi Home you can protect access to smart devices with a fingerprint, and in the Gallery you can hide individual photos.

On flagship models (such as the Xiaomi 14 Ultra), the face scanner can work even in complete darkness thanks to infrared illumination, which allows you to unlock the phone at night without turning on the main screen.

Security: How reliable is Xiaomi’s scanner

Many users question the reliability of biometric scanners for fear that their data could be stolen, and Xiaomi actually uses several layers of protection:

• 🔒 Hardware encryption – fingerprints are stored in a secure area of the processor (for example, Qualcomm Secure Processing Unit), which is not accessible even by the most secure processor. MIUI.
• 🛡️ Two-factor authentication – payments are always required PIN, even if the print is attached.
• 🔄 Limitation of attempts – after 5 failed attempts to unlock the scanner is turned off for 30 seconds.

But there are vulnerabilities, such as capacitive scanners that can be fooled with a high-quality print copy (although this requires special equipment), and ultrasonic and optical sensors are more secure, but they are not perfect either.

⚠️ Warning: If you sell or transfer a phone, be sure to delete all fingerprints in the settings. PIN-Biometric data cannot be reset remotely.

For maximum safety, it is recommended:

• Use the hard stuff. PIN-code as a backup method of unlocking.
• Do not register other people’s fingerprints on your phone.
• Update MIUI regularly as new versions close vulnerabilities.

FAQ: answers to frequent questions about the Xiaomi scanner