For most mid-to-high-end smartphones, the screen fingerprint function has become an essential selling point, but consumers have surely noticed that currently, phones using screen fingerprints are mostly equipped with AMOLED screens, which can be somewhat frustrating for those consumers who are not satisfied with AMOLED screens.
Of course, this is a helpless situation. According to feedback from the supply chain, due to the need for a backlight layer in LCD screens, and the overall thickness of the screen module, screen fingerprint technology based on optoelectronic technology cannot be applied to LCD screens. Therefore, the vast majority of screen fingerprint phones must be paired with AMOLED screens.
However, for some consumers, using PWM dimming on AMOLED screens at low brightness can cause discomfort to the eyes. Although some manufacturers have adopted DC-like dimming strategies to alleviate this issue, it is never a complete cure.Additionally, the color performance of AMOLED screens is generally not as good, so in certain display effect comparisons, they do not perform as well as LCD screens.
However, with continuous breakthroughs in the supply chain, the monopoly of AMOLED screens on screen fingerprints is expected to be broken.According to online news, the supply chain manufacturer Fushi Technology announced that it has successfully developed a screen fingerprint solution based on LCD panels, and using a neural network deep learning solution, the recognition speed and accuracy are now comparable to capacitive fingerprint recognition.
In theory, LCD screens have advantages in terms of production capacity and cost. If the LCD screen fingerprint unlocking solution can be successfully popularized, it will significantly help reduce mobile phone costs.However, the supply chain has not yet mass-produced this solution, and perhaps products equipped with this technology will not be available to us in the short term.
Xiaomi product manager Wang Teng stated that he has indeed heard that a solution for LCD screen fingerprints has appeared in the supply chain, but it is unlikely to be on the market within this year.In fact, it often takes a long time for a technology to go from emergence to maturity, just like it took three years for screen fingerprint technology to go from birth to commercial use.
Moreover, if only one supplier develops an LCD screen fingerprint solution, it is unlikely to be adopted by other manufacturers, as manufacturers would have no advantage in bargaining.If we want to use LCD screen fingerprint technology, we will have to wait until the supply chain is popularized and can produce in large quantities.
The Technological Route Controversy of Under-Screen Fingerprints
The current mainstream under-screen fingerprint solution in the industry is the optical under-screen fingerprint solution paired with OLED panels. The main principle is to combine a visible light camera with the display panel through a specific process, utilizing the transparency of the OLED panel to capture fingerprints in a “photographic” manner.The representative manufacturers here are Goodix and Silead.Including VIVO, Xiaomi, Huawei, and OPPO primarily adopt this under-screen fingerprint method.
Currently, the photoelectric fingerprint recognition under the screen is achieved by collecting fingerprint information through the OLED screen when it is lit and then reflecting it to the fingerprint recognition module, so the area where the fingerprint is recognized often experiences localized lighting. However, this is fatal damage to OLED screens, as it can easily cause burn-in.Moreover, the production capacity of OLED screens is monopolized by Samsung, and compared to the mainstream LCD screens in the current mobile phone market, under-screen fingerprints on OLED screens have inherent disadvantages, with high costs.
If we look at materials, the ultrasonic solution (represented by Qualcomm) is basically not affected by materials, and ultrasonic fingerprint recognition technology can, in principle, be used on various material panels, with better results than optical under-screen fingerprint recognition technology.However, it is generally believed that Qualcomm’s first two generations of fingerprint recognition chips are not mature enough, especially as they cannot meet the thickness requirements for penetrating LCD screens.Once ultrasonic fingerprints mature, terminal manufacturers will be able to choose LTPS or a-Si screens to implement under-screen fingerprints.
Another material is LCD screens (represented by Fushi), which, due to the existence of backlighting, cannot naturally allow light to pass through, which has been a field that fingerprint chip manufacturers have been seeking breakthroughs in over the past year or two.After all, LCD panels far exceed OLED panels in terms of production capacity and sales, and consumer electronic products widely using LCD panels are mostly popular bestsellers, which also hope to have under-screen fingerprint solutions as a selling point.Theoretically, the lifespan of OLED screens is 50,000 hours, but the corresponding lifespan of LCD screens is double that.
In 2018, LCD screen phones accounted for over 85% of the total smartphone shipments (based on a total of 1.4 billion phones, about 1.19 billion phones used LCD), while in the past, there were only under-screen fingerprint products for OLED phones.There has been no under-screen fingerprint solution compatible with LCD full screens on the market.Due to the lack of manufacturers launching under-screen fingerprints that support LCD panels, some people lament that:Under-screen fingerprints have never been destined to be with LCD panels, and LCD phones can only continue to use traditional capacitive fingerprint solutions.
As light cannot penetrate the backlight of the LCD panel, camera-based under-screen fingerprint solutions are thus insulated.Currently, other light-sensitive solutions, such as internal photoelectric diodes, do not yet possess performance and yield advantages, and still have a long way to go before mass production.According to industry insiders, manufacturers such as Dunjie Optoelectronics, Woge Broadcasting, and Shentianma are conducting research on LCD under-screen fingerprints.
What Are the Benefits of Using LCD Under-Screen Fingerprints?
On April 24, 2019, after nearly two years of research and development, Fushi Technology held a press conference in Shenzhen, successfully developing a screen fingerprint solution suitable for ordinary TFT-LCD display panels.
When mentioning Fushi Technology, many may find it somewhat unfamiliar, as it is a very new company.Last October, Fushi Technology held a 3D sensing press conference in Shenzhen, launching a payment-grade recognition 3D camera solution.Targeting the depth sensing field that traditional 2D facial sensing technology cannot achieve, Fushi Technology, with its strong capabilities and various industry advantages, provides complete solutions for customers, further enhancing the security and interactive user experience of facial sensing.Currently, Fushi has achieved deep cooperation with many smart lock, payment device, security device, and mobile phone manufacturers.
Fushi Technology founder Mo Lianghua
However, Fushi Technology is not just a company providing 3D sensing technology; strictly speaking, Fushi is an artificial intelligence technology provider.3D facial recognition involves many machine vision activities, and in addition to auditory speech, from fingerprints to vision and cognition, Fushi can provide a complete set of artificial intelligence biometric solutions.
Although it has not been long since its establishment, companies such as Huawei, Transsion, Meizu, nubia, TCL, Wentai, and Longqi are all customers of Fushi Technology. In 2018, Fushi Technology also experienced a significant round of financing.Founder Mo Lianghua also introduced the product progress of LCD under-screen fingerprints, the original intention of development, and the behind-the-scenes stories of continuous trial and error iterations.
Fushi Technology founder Mo Lianghua believes that although OLED under-screen fingerprints have many advantages, LCD also has many strengths because LCD screens are complex and can be modified in many ways.For example, sensors can be placed inside, and camera sensors can be embedded in the LCD screen.By directly placing the sensor on the LCD substrate, a full-screen fingerprint can be achieved.This method can realize true full-screen fingerprint recognition while also having cost advantages, avoiding the need for additional cameras.
There are also spatial advantages; as long as the fingerprint is integrated, it can be directly realized through optical means, and touch chips can also be saved.
Fushi Technology R&D head Lin Feng
Fushi Technology R&D head Lin Feng stated that in terms of cost, the hardware cost and the under-screen part can be adjusted according to the differences between OLED and LCD screens, with most of the changes in the backlight module and other materials.In the initial phase of new product launches, there will be a certain premium compared to traditional LCD screens.However, the overall price of the LCD under-screen module will be much cheaper than that of similar OLED under-screen modules.
How to Create an LCD Under-Screen Fingerprint Solution?
Lin Feng stated that when Fushi Technology began developing LCD under-screen fingerprints in 2017, due to the inherent principle defects of LCD screens, the industry generally believed that achieving LCD under-screen fingerprints was “difficult to accomplish.”After the technical team worked tirelessly day and night, experiencing over 20 failures and trying various solutions such as under-screen drilling and light supplementation, they finally achieved mass production of LCD under-screen fingerprint technology in 2019.Fushi Technology General Manager Mo Lianghua recalled:“After several failed attempts, we did not lose heart; we continued to research, boldly explore, and carefully verify, which ultimately led to today’s achievements.”
It is reported that while developing 3D sensing technology, Fushi applied many fingerprint recognition technologies and patents, especially the deep learning neural network algorithms used in 3D facial recognition, which were further applied to the research and development of LCD under-screen fingerprints.Fushi Technology R&D head Lin Feng believes that while researching 3D facial recognition solutions, the R&D team gained a lot of experience, which was successfully absorbed into the research and development of under-screen fingerprints, allowing product development to welcome multiple opportunities for technological breakthroughs after a period of stagnation, successfully transforming into foreseeable technological achievements.Lin Feng stated that the algorithm from 3D facial recognition applied to under-screen fingerprints has excellent robustness under conditions such as wet and dry fingers and strong light.
Through continuous modifications and attempts on the LCD backlight, adjustments and improvements to the fingerprint optical path solution, including the use of active high-transmission emission wide-band light receiving technology, LCD screen backlight film material combination experiments, neural network image reconstruction algorithms, etc., they successfully solved bottleneck issues such as display effects and fingerprint imaging effects.
Lin Feng emphasized that due to the use of deep learning neural network Deblur algorithms, combined with multi-point distortion image calibration fingerprint recognition algorithms, the current overall recognition rate can rival that of capacitive fingerprint metrics.
Around the Spring Festival of 2019, Fushi Technology successfully developed the first LCD panel + under-screen fingerprint solution that can clearly see fingerprint images. In the limited environments corresponding to LCD under-screen fingerprint collection, Fushi Technology adopted an algorithm-assisted approach, optimizing through the latest deep learning neural network algorithms, achieving rapid recognition of LCD under-screen fingerprints. Currently, it is known that its fingerprint recognition rate can rival traditional capacitive fingerprints, and the algorithm is continuously evolving.Lin Feng stated that he is very confident about achieving mass production in 2019.
It is understood that the LCD under-screen fingerprint solution has undergone nearly two years of time in Fushi Technology’s internal R&D team, accumulating over 100 patents and experiencing at least three significant product direction adjustments, ultimately determining that LCD under-screen fingerprints will be an important direction in 2019. (Chip Pa Ke, Lei Technology)
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