The ambient light sensor under Goodix technology helps Xiaomi 12Pro increase the screen ratio. TMD3719 is the first ambient light sensor, which can be applied under the screen design. There are 6 kinds of ambient light and color-sensitive channels, while AMS is equipped with UV/IR barrier filters for RGBL (color gamut) and transparent channels, respectively. The sensor is also It can eliminate the radiant energy of the display screen mixed in the ambient light, so as to measure the color temperature and brightness of the current environment of the device with high precision.

With the explosion of full screen, the ultra-high screen ratio has become a promotional bargaining chip for consumer electronics manufacturers, and improving the screen ratio has become an inseparable development goal among manufacturers. However, at present, the high-ratio screens on the market are mainly bangs screens, water drop screens, hole screens, etc., and there are only a few integrated screens in the true sense. Why are there only a few truly integrated screens? Actually, it has to do with the location of the ambient light sensor. In order to achieve an integrated screen in the true sense, major manufacturers are actively developing screen technology, trying to put sensors under the screen, reducing bangs, increasing the screen ratio, and bringing greater visual impact to consumers.

What is the problem to be solved by turning the photosensitive element towards the underside of the screen?

First, changes in light transmittance and optical properties lead to changes in screen materials. With the improvement of consumers' aesthetic level, curved screen and folding screen mobile phones are becoming more and more popular in the market. The screen has gradually transitioned from a traditional hard screen to a flexible screen. The material required for the BD65492MUV-E2 to make the screen has also changed from hard glass to soft and ductile plastic material. Due to the varying transmittance and optical properties of different materials, solutions for ambient light sensors need to redefine manufacturers.

Second, the interference of the screen's own light source to the ambient light sensor. The photosensitive element itself is a photosensitive device. Placed under the screen, the light source itself can seriously affect the sensitivity and accuracy of the ambient light sensor. Even if this problem is solved, the problem of transmitting external light through the screen light source to the ambient light sensor is also solved. It should be known that the transmittance of the same light source through different color pixels is different. If these two problems cannot be solved well, the measurement value of the ambient light sensor will deviate from the reality. Through this method, not only the power consumption of the device cannot be reduced, but also the user experience is affected.

Apple wants to apply ambient light sensor on the screen and say goodbye to bangs

Realizing the true full screen of bangs has always been the focus of everyone's attention, and it is also a problem that major manufacturers need to overcome. As the top three Apples with the largest annual shipments, Apple is also constantly exploring ways to reduce or eliminate bangs.

According to foreign media reports, Apple's patent application submitted last year mentioned that Apple is developing an ambient light sensor that can be used on the screen, mainly to solve the interference of the screen itself of the ambient light sensor. The principle of the patent right is that when testing the brightness of the ambient light sensor, the brightness of the pixel array light source above the sensor can be controlled to eliminate the influence of ambient light and achieve better adjustment of screen brightness and color temperature, thereby reducing the difference between screen applications and general applications. gap between. The patent helps Apple reduce the size of the notch on the iPhone. However, judging from the iPhone 13 series models released this year, although the area of the "bangs" on the top of the phone has been reduced by 20%, this patented technology has not been used.

Ambient light sensor under Goodix technology helps Xiaomi 12Pro increase the screen ratio

Huiding Technology has been deeply involved in the optical field for many years, and currently has dozens of optical screen products. Among them, on August 10 this year, Xiaomi MIX4 adopted Huiding Technology's ultra-thin screen fingerprint solution. According to the official disclosure of Huiding Technology, the recently released 12Pro mobile phone is equipped with Huiding Technology's first under-screen ambient light sensor, which is used to adjust the screen color and bring a more comfortable visual experience.

It is reported that the Xiaomi Mi 12 Pro uses the GLS6155 ambient light sensor under the screen. High-precision color temperature, luminance measurement and proximity sensing functions are highly integrated into the sensor. Using a high 10KHz sampling rate and a built-in hardware light leakage processing module, it can capture black frames on the screen in a very short time, reduce the impact of screen light leakage on the sampling accuracy of the sensor, and achieve high-precision color temperature ambient light intensity measurement.

At the same time, Goodix Technology also provides a unique leakage reduction algorithm for this sensor. Combining it with software and hardware can improve the measurement accuracy of the ambient light sensor under the screen, and make the display color soft and bright, which is more suitable for the current environment, thereby reducing eye fatigue.

However, the placement of the ambient light sensor directly affects the proximity sensing function. When the LED or VCSEL is placed under the screen, it will not work in the bright screen state, and the proximity sensing function can only be enabled in the closed screen state. Placing an LED or VCSEL in the gap at the top of the screen will not affect proximity sensing.

The invention is especially suitable for terminal applications with high screen ratio, and can be adaptively adjusted according to the color temperature and brightness of ambient light, thereby prolonging the life of the equipment.

Ambient light sensor under AMSOLED screen

AMS is a leader in optics. A number of ambient light sensors suitable for dark glass work have come out. In 2020, it will combine ambient light detection, near detection, light source flicker detection and other technologies to introduce the ambient light sensor TMD3719 into the ambient light sensor.

TMD3719 is the first ambient light sensor, which can be applied under the screen design. There are 6 kinds of ambient light and color-sensitive channels, while AMS is equipped with UV/IR barrier filters for RGBL (color gamut) and transparent channels, respectively. The sensor is also It can eliminate the radiant energy of the display screen mixed in the ambient light, so as to measure the color temperature and brightness of the current environment of the device with high precision. Obtain the real scene information of ambient light and realize the best screen adjustment function.

At the same time, three IRVCSELs are integrated with an advanced VCSEL driver. Sensor sensitivity, noise, and power consumption can be optimized by adjusting the operating time and power of the IRVCSEL. Among them, VCSEL is mainly used for the proximity sensing function of target distance. The use of three-way VCSEL scattering can effectively prevent screen display distortion.

The light flicker detection function is mainly reflected in the imaging effect of the front camera. Using the light source flickering function, combined with the detection algorithm, can effectively improve the feedback speed of the detection results and eliminate the interference of light on the front camera when shooting.

Epilogue

The explosion of full-screen applications has driven the development of technology under the screen. The maturity of under-screen ambient light sensor technology helps achieve higher screen ratios. I believe there will be more 100% full screen devices in the not too distant future.