In just one year, almost all mainstream domestic brand mobile phones have brought models equipped with screen fingerprint scheme. According to the latest data released by IHS, 18 mobile phone models have adopted screen fingerprint technology by the end of 2018. In 2018, the total shipment of screen fingerprint modules reached 30 million pieces. According to the latest touch panel Market tracker report of IHS Markit, the shipment of screen fingerprints is expected to increase sixfold to nearly 180 million pieces in 2019.
In our previous evaluation, we mentioned that even when the early screen fingerprint scheme is not mature enough and the unlocking speed and success rate are very general, we still advocate this technology more than 3D face recognition. The reason is that screen fingerprint technology can better integrate various forms of comprehensive screen, avoid “bangs” that can not be ignored, and ensure that the form of comprehensive screen mobile phone is not limited. Secondly, the unlocking process of screen fingerprint is more like the independent capacitance fingerprint module in the past. After all, the existing fingerprint identification scheme is very mature and the user experience is good enough. Similar operations are more convenient for users and can ensure the convenience of use in various scenarios.
Of course, the implementation of screen fingerprint is not as simple as the traditional independent fingerprint module. As long as the independent fingerprint module has sufficient layout space, the rest is placed on the front, back or side of the fuselage according to the product form, and will not be subject to other components. At present, most of the on-screen fingerprint identification schemes on the market use optical fingerprint – rely on the sensor at the bottom of the screen to receive the fingerprint reflection information, and then unlock it after successful identification.
In addition to the recognition ability of the sensor itself, this technology must also rely on the AMOLED screen at this stage. Only the thickness and pixel gap of the AMOLED screen can make the light of the screen shine on the pressed finger and then reflect back to the recognition sensor. LCD screen cannot be realized.
Another aspect that the LCD screen is difficult to match the fingerprint under the screen at present is that it does not have the inherent characteristic of AMOLED – pixel self illumination. On any off screen fingerprint mobile phone, we can see that off screen fingerprint identification provides off screen identification function. It is with the help of the AOD (off screen display) feature of AMOLED panel that the fingerprint area can still be lit separately in the off screen state. If the LCD panel realizes this function, it is necessary to keep the screen on at any time, which will inevitably affect the power consumption.
The common screen fingerprint schemes mainly include optical screen fingerprint technology and ultrasonic fingerprint identification technology. In optical screen fingerprint identification, many companies have already made attempts. Huiding technology has long demonstrated the case of using AMOLED screen to realize screen fingerprint identification. The demonstration models are Samsung Galaxy S7 edge and vivo xplay6. The light generated by the screen irradiates the finger texture, and then the light is reflected on the fingerprint identification sensor under the screen to generate the fingerprint image.
In order to ensure better recognition effect, in the early optical screen fingerprint scheme, almost all the light used to reflect the fingerprint is more stable green light. When you press it, you can see that the screen recognition area will show bright green light. At present, the blue light used by vivo models is actually the light color superimposed by blue and green, taking into account the external visual experience and fingerprint reflection effect.
Corresponding to the photoelectric screen fingerprint is the ultrasonic screen fingerprint identification scheme, that is, through the built-in ultrasonic module, the pressed fingerprint is identified with the help of the reflection wavelength of ultrasonic. However, due to the difficulty of implementation, it is still unable to be applied on a large scale. Previously, only Xiaomi 5S and LETV Le Max 2 adopted this scheme. It was not until the newly launched Samsung Galaxy S10 series that we saw the combination of ultrasonic fingerprint technology and comprehensive screen. Considering the pricing and market share of Samsung Galaxy S10, the screen photoelectric fingerprint technology is better at this stage.