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Ultrasonic fingerprint identification technology

2018-09-16 22:30 admin
Capacitive, optical and ultrasonic fingerprinting is the key to War Within Three Kingdoms. There are mainly three kinds of fingerprint recognition technologies used in smart phones: capacitive, optical and ultrasonic. At present, the most mature fingerprint handsets on the market are basically capacitive. But what happens to all three fingerprint recognition technologies, and who will be more dominant in the future? Let's have a look together.

Capacitive fingerprint module uses fingerprint sensor and conductive electrolyte to form an electric field. The fluctuation of fingerprint will lead to different changes in the pressure difference between the two, so that accurate fingerprint measurement can be achieved. This method has strong adaptability and no special requirements for the use of the environment. At the same time, the space occupied by silicon crystal and related sensing elements is within the acceptable range of mobile phone design, so the technology has been better promoted in the mobile phone.

Although the technology is very sophisticated, but in the heated concept of a full-screen mobile phone, capacitive seems a bit out of place. Fingerprint recognition can be integrated into a mobile phone in almost any of these forms: post and pre, as well as the side and so on.
Positive fingerprint recognition is a relatively popular solution. From the visual point of view, the positive position is more in line with the traditional interactive aesthetic, and more intuitive in operation, users do not have to pick up the phone can be unlocked through fingerprint identification. In the pursuit of extreme screen occupation, positive recognition is in a very awkward situation.

Back side fingerprint recognition is a more common location plan. AuthenTec has accumulated a large number of core patents in the frontal capacitive pressing fingerprint identification field, and stopped serving the outside world after being acquired by Apple, and the original Android models were mostly virtual keys, which is why the back fingerprint scheme has been widely adopted. But as far as the experience is concerned, users have to pick up the phone if they want to unlock it, which is more troublesome, and other functions are usually integrated on the fingerprint identification buttons. When users use these functions, the back position is not intuitive enough.

Although the side position does not occupy the front and rear panel space, but the thickness of the fingerprint module will have an impact on the screen width of the border, and the mobile phone is thinner and thinner, allowing the side of the fingerprint occupies less and less space, fingerprint identification scanning area shrinkage brings the most direct change is the fingerprint recognition rate is reduced. So it is less likely that the side position scheme will become the final form of fingerprint recognition.

Optical fingerprint recognition
Optical fingerprint identification is a kind of fingerprint identification technology which has been applied earlier. For example, many attendance machines and entrance guards used optical fingerprint identification technology.
Mainly using the principle of refraction and reflection of light, the finger on the optical lenses, the finger in the light of the built-in light source, light from the bottom to the prism, and through the prism, the light emitted by the fingerprint on the surface of the uneven lines of refraction angle and reflected back light will be different. It is projected onto CMOS or CCD with a prism to form a digital multi-gray fingerprint image with black ridges (ridges with certain width and direction in the fingerprint image) and white valleys (depressions between ridges) that can be processed by fingerprint algorithm. Then compare the databases to see if they are consistent.

At the World Mobile Conference (MWC2017) at the end of February this year, Huiding also used Samsung's Galaxy S7 Edge to demonstrate the optical fingerprint unlocking technology that can be unlocked by pressing the screen directly with the finger.

At present, many fingerprint chip companies are developing and distributing the optical fingerprint market, including Shanghai Shaoji, Xinsi, Huiding and so on. In the second half of last year, Xinsi invested in Shanghai Shaoji. Although many fingerprint chip markets are currently in the layout, but overall, there is still a long way from the market volume.
Guo Mingchi, a well-known Apple analyst, believes that the unit price of optical screen fingerprint identification is now about three to five times that of the mainstream capacitor type, and is expected to be produced in the second half of 2008. However, he also mentioned that the technology is now poor penetration, easily affected by light sources and screen colors, the problem of identification errors. It also indicates that the consumption level optical screen fingerprint identification will be mass-produced in the second half of next year.
Ultrasonic fingerprint identification

Ultrasound fingerprint identification and capacitive fingerprint detection need to be different from the surface of the fingerprint. Ultrasound has penetration. Ultrasound scanning finger with specific frequency emitted by fingerprint module can establish 3D fingerprint pattern by using the different reflection of the fingerprint to the ultrasonic. Therefore, the cleanliness of fingerprint surface need not be considered too much. In addition, due to the strong penetration of ultrasound, can penetrate metal, glass and other commonly used mobile phone materials, so the appearance of the mobile phone will not be too limited.

At the 2015 MWC exhibition, Qualcomm released Sense ID 3D ultrasonic fingerprint identification technology. At present, this technology has been used by many professional organizations and government departments. Millet 5S is carrying Qualcomm's ultrasonic fingerprint identification chip. At the World Mobile Congress in June, the vivo booth showed the use of an underwater ultrasound fingerprint sensor to unlock the phone and take photos underwater. So your phone can not only be waterproof, but also be used underwater, which is a special advantage of ultrasonic fingerprint identification technology.
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Ultrasonic fingerprint identification technology

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author:UCESONIC

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