Shulou(Shulou.com)11/24 Report--

1. Your fingerprints my fingerprints are all different. The German philosopher Leibniz said, "there are no two identical leaves in the world."

Our fingerprints are like unique veins on every leaf, everyone has them, they remain the same for life, and they are different from each other.

It is precisely because of the inherent convenience of fingerprints and the ultra-low repetition rate of about 15 billion, fingerprint identification technology has become one of the most widely used biometric technologies, and is closely related to our lives.

For example, did you unlock your phone with your fingerprints a few minutes before you clicked on this article?

2. How do mobile phones identify fingerprints? The mobile phone needs to be equipped with fingerprint identification module, and its working process is usually divided into three steps: acquisition, processing and matching.

The sensor is responsible for identifying the fingerprint and collecting the rough fingerprint image.

According to the collection principle, it is mainly divided into optical type, capacitive type, ultrasonic type, and according to the acquisition mode, it is mainly divided into scraping type and pressing type.

Processing the collected fingerprint image still needs to be processed. Firstly, the fingerprint lines are made clearer by means of gray equalization, noise elimination and image enhancement, and then the fingerprint feature data is extracted by the algorithm.

10 fingerprints can generate about 4900 independently measurable features, such as core points, triangular points, number of lines, direction, curvature, position and so on.

Finally, the feature data formed by the fingerprint image is stored as a template.

After the fingerprint is collected and processed again, the fingerprint identification module matches the characteristic data of the new fingerprint with the existing template through the algorithm, and the matching degree is higher than the threshold through recognition.

3. What are the mobile phone fingerprint recognition technologies? The document gentleman mainly introduces the fingerprint identification technology of the sensor in the above acquisition process.

Capacitive fingerprint recognition technology is a mature traditional fingerprint identification technology, which has a high popularization rate in the field of smart phones. The principle of implementation is as follows:

There are N small capacitor plates with the same area on the capacitance sensor, and the finger can be regarded as a large capacitor plate. When the finger touches the capacitance sensor, N small capacitors are formed. Their capacitance value depends on the distance from the fingerprint to the small capacitor plate.

The "ridge" (j í) of the fingerprint is raised, close to the plate, and the capacitance is large; the "valley" of the fingerprint is concave, far away from the plate, and the capacitance is small.

In the process of discharge, due to the different capacitance, the crest discharge is slower and the valley discharge is faster. The undulating lines on the fingerprint are converted into electrical signals, which are accurately identified.

Capacitive fingerprint identification has two acquisition methods: scratch type and press type.

Scraping is similar to a panoramic camera, where the sensor "photographes" and then "splices" the fingerprint when the finger slides on the surface of the sensor.

The disadvantage is that the fingers must slide uniformly according to a specific direction and angle, resulting in unsatisfactory recognition rate and convenience, and the scratch fingerprint recognition module can no longer be seen on the mobile phone.

Press as the optimization scheme of the former, I believe we are all very familiar with it. As long as the finger is pressed on the sensor, the fingerprint can be quickly identified and easier to operate.

At first, mobile phones generally used the front fingerprint identification method of combining sensors with Home keys, but with the craze of large screen and full screen, there was no extra room for physical buttons on the front of the phone.

In order not to affect the screen ratio, the sensor is moved to the back of the phone, but this post-fingerprint identification method requires the user to press it blindly, which may not be accurate at once, which is not in line with the user's habit.

Many mobile phones combine sensors with power keys, resulting in side fingerprint identification, but it is easy to be mistakenly touched. Moreover, the larger the effective identification area of the fingerprint is, the thicker the mobile phone will be, and the fingerprint recognition rate and the lightness of the mobile phone can not be both.

In fact, for capacitive fingerprint identification technology, whether scratching or pressing, whether it is front, rear or side, there must be a physical sensor on the outer surface of the phone, which will affect the appearance of the phone to a certain extent.

In recent years, users' demand for mobile phones tends to be comprehensive large screen, thin body, beautiful appearance and so on, and the mobile phone screen is also in the transition from LCD screen to OLED screen.

The off-screen fingerprint identification scheme based on OLED screen arises at the historic moment. Placing the fingerprint sensor at the bottom of the screen also gives users a stronger sense of technology when they identify their fingerprints.

At present, there are two ways to realize off-screen fingerprint recognition: optical mode and ultrasonic mode.

Optical fingerprint identification technology is a common fingerprint identification technology in daily life, such as the punch-in machine used in attendance. Mainly based on the principle of light reflection:

The finger presses the screen, and the screen glows to illuminate the finger pressing area. When the light hits the "ridge" and "valley" of the fingerprint, it will produce different angles and degrees of reflected light, which will pass through the gap between the pixels on the screen and be received by the optical sensor under the screen to identify the fingerprint.

The advantages of optical fingerprint identification technology are: easy to operate, good penetration, mature technology and low cost.

But there are obvious disadvantages: unable to identify the dermis, low security, poor security, and specific areas of the screen need to shine for a long time, increase power consumption, which may affect the life of the screen.

Ultrasonic fingerprint identification technology is a new technology in recent years, similar to the principle of sonar.

The finger presses the screen, and the sensor under the screen emits ultrasonic waves to the finger pressing area. When the ultrasonic wave comes into contact with the "ridge" and "valley" of the fingerprint, the degree of absorption, penetration and reflection is different, which will produce echoes of different energy and be received by the sensor, so as to construct a 3D fingerprint image.

The advantages of ultrasonic fingerprint identification technology are: strong penetration, strong resistance to water stains and stains, high recognition rate, support for in vivo detection and high security.

The disadvantages are: high cost, relatively immature technology and low market share.

4. How did mobile phone fingerprint recognition technology develop? The MB 860, launched by Motorola in April 2011, is widely believed to be the first smartphone with fingerprint recognition, and users perform scratch fingerprint recognition on the sensor on the top of the phone.

Best known is Apple's iPhone 5S, released in September 2013, which supports pre-press fingerprint recognition, with a sensor built into a circular Home key and a stainless steel sensor ring.

It can be said that iPhone 5S led the trend of mobile fingerprint recognition. Since then, a variety of mobile phones that support fingerprint recognition have sprung up into the market.

……

In 2014, Huawei Mate 7: the first Android phone that supports post-fingerprint recognition.

In 2015, Nubia Z9 premium version: the first mobile phone to support side fingerprint recognition.

In 2018, the vivo X20 Plus UD: the first mass-produced phone that supports off-screen optical fingerprint recognition.

In 2019, Samsung S10: the first phone to support off-screen ultrasonic fingerprint recognition.

……

In March 2023, Nubia's first flagship Ultra model, the Z50 Ultra, was officially released, using off-screen optical fingerprint recognition and the fourth generation of off-screen camera technology to bring users a perfect and comprehensive screen experience!

According to statistics, Apple models that cancel fingerprint recognition have continued to sell well in recent years, affecting the overall penetration rate of fingerprint recognition, and the carrying rate of fingerprint recognition on domestic smartphones dropped to 79% in 2022.

Among them, the rear fingerprint gradually fades out of the market, while the side fingerprint seizes most of the middle and low-end LCD screen mobile phone market, with a carrying rate of 44% and an off-screen fingerprint recognition rate of 30%.

In fact, for the majority of users, no matter what kind of fingerprint identification technology, easy to use is the most important.

The current off-screen fingerprint identification technology not only continues the convenient operation of pre-identification, but also does not need to set sensor grooves in the fuselage like rear and side identification, but also enables mobile phones to achieve more extreme lightness and screen ratio.

At present, mobile phones equipped with ultrasonic 3D wide-area screen fingerprint identification module have appeared in the market, which can achieve more interactive functions based on double fingerprint recognition.

This also opens our way of thinking that fingerprint recognition is not just about unlocking mobile phones and mobile payments.

Each of us has ten fingers, which is equivalent to ten unique keys. how can we use these keys to open more and wider space on our mobile phones? This is a question worth thinking about.

5. Look forward to too many tags belonging to fingerprint recognition technology: "recognition rate", "recognition speed", "convenience", "security", "performance-to-price ratio".... The future trend of fingerprint identification technology must be a better solution that can balance these indicators.

In the near future, ultrasonic fingerprint recognition technology may become the mainstream.

In the more distant future, will fingerprint recognition technology evolve to extract more features under the skin of infiltrating fingers for recognition?

Mobile fingerprint recognition technology has brought us unlimited imagination, welcome to talk about your views in the comments area.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

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