Screen is the end | Mobile fingerprint recognition technology big Secret

Siemens demonstrated a back-scraping fingerprinting handset in 1998. Although only a prototype was not in production, he proved to the world the possibility of fingerprinting on the handset. Twenty years later, we experienced fingerprinting Big change, and finally ushered in the screen fingerprint - Vivo released the vivo X20Plus screen fingerprint version, let us see a set of mature production screen fingerprint program.

After the introduction of screen fingerprints, many of my friends are lamenting its magic, but rarely know how it works. So the current school of fever, we talk about the development of mobile phone fingerprinting technology to see it in the end is how to identify Of course, there are some technical difficulties.Of course, there is one of the most important question: the screen fingerprint will be rolling face recognition comeback?

We have seen fingerprinting locations these years

Fingerprint authentication is divided into two steps: the first is to extract the fingerprint features to be validated, the second is to extract the fingerprints, Then compare the fingerprint similarity with the template fingerprint in the fingerprint template library, and unlock the similarity when the similarity is reached.

The simple process, after design but can show a variety of programs.United position, the traditional fingerprint identification location there are three, with just recently released screen fingerprint there are four:

Back fingerprints

Fingerprint recognition can be said to be the mainstream of the identification program Andrews, the reason is that the fingerprint technology is limited, and Andrews rely mainly on the interaction of the front panel chin on the three diamond keys in the At that time, a more ingenious way to interact was to be developed.

In terms of experience, the user may have to pick up the phone if he / she wants to unlock it, and generally there are other functions integrated in the fingerprint identification button, and the user's position on the back may not be intuitive enough when using these functions.

Side fingerprints

Side fingerprint is actually a good location solution, will not affect the traditional way of interaction, and do not need to open holes in the panel affect the visual perception.But the side fingerprints also brings many problems: the thickness of the fingerprint module on the screen The width of the border has an impact, and more and more thinner in the mobile phone nowadays, the space occupied by the side fingerprint is getting smaller and smaller. The most direct change caused by the reduction of the fingerprint recognition scanning area is the decrease of the fingerprint recognition rate.

Positive fingerprint

Fingerprint became the most popular recognition scheme after the new interaction mode was widely recognized.Front fingerprints are more intuitive to use than the first two, and do not need to pick up the mobile phone to use on the desktop, and can help interaction. And from the appearance, the front fingerprint has also become one of the means to make up the blank panel, with the upper handset coordination is even more coordinated.

Screen fingerprint

Full screen era, the forehead further narrowing the forehead to the forehead to narrow the front fingerprint, fingerprint under the screen has become the best alternative to the traditional location of the program.However, the current screen fingerprinting is still in its infancy, you need to specify In order to achieve recognition.

and Fingerprint recognition morphology, but not only the location difference so simple.

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In addition to location fingerprinting there is a lot of stress

Most people's impression, in addition to the location of fingerprints, seemingly no difference, but in fact, the market has seen the fingerprints vary widely, such as the most direct point is that the press can not be pressed.

Fingerprint module requires power to work.In general, press-type fingerprint recognition only screen on the screen after the power to the module, the benefits of doing so can be a certain degree of standby power. Not press-type module has been energized , The benefit of doing so is that you can achieve faster identification at any time, unlocking as soon as you touch it.

Pressurized fingerprint is more typical of the iPhone, the initial use of the press material force button, but later can not be pressed, but under the home button pressure sensor added, subject to certain pressure on the identification module energized, and thus To unlock.

In addition to the press can not be pressed, fingerprint identification surface cover is also quite exquisite.We see the traditional fingerprint identification is roughly divided into four cover options: Coating, glass, ceramic, sapphire Cost, said the lowest coating, the highest sapphire, but the four programs, but not just the difference in cost.

For example, I used the first domestic positive fingerprint recognition phone is the Meizu MX4 Pro, which should also be the first domestically produced press-type fingerprint recognition mobile phone, which is used from the top of the sapphire roof plan. Sapphire Cover does show a strong ability to wear, but the actual experience, the recognition rate and recognition speed are to be improved because the Meizu MX4 Pro uses a capacitive fingerprint scheme, the sapphire cover will bring the signal Of the attenuation and signal to noise ratio problems. Compared with the normal Touch IC, the sensitivity needs to be improved about 60 times.

Of course, relatively speaking, only the coating of the module is naturally the highest recognition accuracy, capacitive touch fingerprint recognition driver IC only need to enhance the sensitivity of ordinary Touch IC about 3 times.Meizu in its first high-end machine Pro 5 is the type of program used, compared to the MX4 Pro in the recognition rate and recognition speed can be said to have a qualitative improvement.But the problem is that this plan is not enough scratch tolerance.

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by Under Glass solution leads to the fingerprint packaging process

Later, we also see the new Under Glass solution, the typical models are ZUK Edge and Huawei P10. The technical principle is from IFI (Invisible Fingerprint Sensor) integrated fingerprint identification and touch technologies' Traditional capacitive fingerprint recognition technology, handset manufacturers do not need to open the hole in the phone front panel or rear shell fingerprint sensor module, but the fingerprint sensor hidden under the TP panel, the glass panel can also support the sapphire panel.

IFS technology does not require metal rings to communicate with the fingers to transmit signals, does not require touch switches, and does not require bonding material on the front of the chip for good identification, but this technique requires notching slots in the glass panel since smartphones The thickness of the front 2.5D glass panel exceeds 0.7mm, and according to the principle of capacitive fingerprinting, the recognition accuracy will be greatly reduced if the thickness of the cover glass above the chip exceeds 0.3mm. Glass panel thickness is maintained at 0.2 ~ 0.3mm, to allow effective signal transmission.

In addition, the chip package is also some stress.First, most of the fingerprinting using wire bonding packaging process, but this process requires plastic cover the metal lead hidden in order to form a flat surface and cover fit, resulting in chip The thickness of the increase will affect the recognition accuracy to some extent.

In order to make more identification chip contact with the cover to reduce signal loss, trench technology has also been applied later, in short, is the surface of the chip 'dug', used to wire the fingerprint chip connected with the outside world, not Occupy the surface space iPhone 5s is mainly used on the trench + wire bonding process.

TSV is a relatively better packaging solution.This solution allows the chip to effectively detect a substantial increase in area, the thickness of the chip and the module thickness can be reduced.This solution can produce ultra-thin fingerprint identification module, and even can So that the thickness of the cover glass does not exceed, so for the Under Glass program more appropriate, TSV fingerprint identification module into the cover glass possible.

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The above is about vivoX20Plus screen fingerprint version of the product evaluation reports, vivoX20Plus screen fingerprint version of the appearance, screen, camera, battery life, performance and other follow-up content, please continue to focus on the report on vivoX20Plus screen fingerprint version of the report.

Capacitive wilting Ultrasound and optics are the future

Capacitive

We just mentioned the capacitive fingerprint recognition. The principle is the use of silicon wafer and the conductive subcutaneous electrolyte to form an electric field, the ups and downs of the fingerprint will lead to different pressure difference between the two changes, in order to achieve accurate fingerprinting At present, this kind of scheme is the most mature, except for a few very few ultrasonic fingerprints, we basically see the fingerprints of the mobile phone adopt the capacitive scheme.

The reason why capacitive maturity, not only lies in the fingerprint recognition of this program has excellent recognition rate and recognition speed, but also because this program also has a subsidiary program to enhance security in the Meizu PRO 6 Plus, we see the top Of the living fingerprinting scheme.Capacitive capacitive recognition is easy to crack by fake fingerprints because it only detects the fingerprint lines.However, the biometric fingerprinting scheme integrates the capacitive fingerprint sensor and the optical detection sensor into a silicon sensor, , Finger skin color and heart rate signals to verify the user's real identity.

But after all, capacitance is still difficult to become the ultimate identification program, in addition to capacitive fingerprints in the wet hand to unlock the poor performance, the biggest reason is the penetration is not strong.We have just mentioned, under the Under Glass program, Capacitive solutions still need to slot, which is clearly not suitable for full screen needs.

Ultrasound

Ultrasound (radio frequency) fingerprint identification scheme is a good solution, but for now there is no mature product for its confidence in the development of full screen, the typical failure case is millet 5S. The principle is through ultrasound Of the launch and reception to obtain the dermis fingerprint image.From the theoretical point of view, ultrasonic fingerprint recognition because it will only have human dermal skin reflex, so basically eliminate the artificial fingerprints, but also wet fingers up to 99% Recognition rate.

Qualcomm has partnered with vivo to showcase its second-generation ultrasound screen-based fingerprint solution at MWC 2017. It is reported that the solution can scan, input and match fingerprints through an OLED display up to 1200 microns thick. For the glass and Metal Qualcomm's Fingerprint Sensor is the first commercially available solution that enables scanning through glass panels as thick as 800 microns and aluminum casings up to 650 microns in thickness, enabling the last 400 microns of glass or metal penetration Significantly improved.

Moreover, the second-generation solution can show underwater fingerprint matching and device wake-up, which can bring better mobile authentication experience by detecting heartbeat and blood flow, greatly improving the security.But the second generation of ultrasonic fingerprint sensor is still limited With OLED screen, but for the higher thickness of the LCD screen still can not do anything.

Optical

Currently the only product on the market vivo X20Plus screen fingerprint version of the screen fingerprint using photoelectric reflection technology, to put it bluntly is the optical fingerprint. The principle is through the light source adapted to fit the OLED screen emits light, reaching the fingers reflect different light lines , Which can be recognized by the sensor under the screen.At present, this kind of optical fingerprint can only be realized on the OLED screen. The gap between the RGB pixels of the OLED can pass through the related process and the light can pass through to reach the sensor.

From the experience point of view, this identification method is currently not as good as the recognition speed of traditional capacitive fingerprint recognition, the other physical examination is similar, but there are many limitations, such as the sensor can only specify the location, the film requires the use of special high-transparency film Wait.

There is more to optical fingerprint than this, and in the future we may see a more evolutionary optical fingerprint.

It is reported that in the OLED and MicroLED display screen with fingerprints added to the sensor layer of the sensor, the formation of 'interactive pixel', that is, add a fingerprint recognition pixel next to each of the traditional RGB pixel, then no longer need fingerprinting Identify the concept of chips, because the display screen has become a large fingerprint recognition chip.

Moreover, in order to distinguish with the RGB visible light in the mobile phone display, and reduce the interference of ambient light, the optical fingerprint recognition may adopt the light source of near infrared light. The core of the whole product besides the algorithm, the most important change on the hardware side, More near-infrared light sources, optics, image sensors, etc. That is, such screen fingerprints can be identified without the need for the naked eye to see the highlights.

Write in the end

Screen Fingerprint Face Recognition compared to which is the future? See here, I believe many of my friends have such a problem. Technically speaking, the two tit for tat, face recognition iPhone 3D 3D structure of the fingerprint identification vivo Screen fingerprints, the two are similar in recognition speed, the use of experience also have their own outcome.

But from the use of scenarios, the biggest difference between the two is that do not need to touch. Face recognition for non-contact type recognition, you can achieve no action to unlock, for example, can be used to lock the application of seamless; Unlike smart home, mobile phones Clasp in hand, there will be fingerprinting contacts, but also for payment, contact identification more secure.

Which one is better, one debate tells you -

"Square: facial recognition is the future" "

""Opposition: screen fingerprint must be king "

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