It is a very troublesome thing to look at the mobile phone screen in the sun light. You often have to block the sun light to see the content of the screen clearly. The reason why the screen content cannot be seen clearly in the sunlight is that the screen reflects light. When the light reflected by the screen is stronger than the light emitted by the display screen in strong light, it will be difficult for us to see the screen content clearly. In the face of the problem that you cannot see the screen clearly outdoors, the simplest way is to increase the brightness of the screen. However, there is a power consumption problem simply by increasing the screen brightness. At present, the screen is already a major power consumer in mobile phone accessories. If you increase the brightness of the screen, it will only result in shorter flight duration.

In order to solve this problem of mobile phones without affecting the endurance, Nokia has adopted a technology called ClearBlack happy screen display. At present, this technology has been applied to Lumia 920, Lumia 800 and other mobile phones. The picture on the left shows the Nokia C6-01 with ClearBlack, and the picture on the right shows the C6-01 prototype without this technology. We can see that the screen content on the left can still be seen, while the phone screen on the right is white and cannot see the content clearly.

Nokia said that this technology can make the screen remain as indoor in the hot sun. The principle of this technology is similar to that of polarized sunglasses, but the polarizer layer in the display screen is a little more complex than that of sunglasses. On a sunny day, if you look directly at the water surface without polarized eyes, you will not be able to see anything below the water surface due to the reflection of the water surface. The same is true of the mobile phone screen. What kind of technology is this? Let's take a look.

Nokia has previously introduced this technology on its official blog. In the figure below, we can see three layers, including the linear polarization layer, quarter wave retardation film and reflection layer. When the light enters the polarizer, the following occurs:

• Light reaches the linear polarization layer, which allows light to be polarized vertically.
• The light then reaches the circular polarization retardation film. This layer can change the direction of light again, making the light right circular polarization.
• The light then reaches the screen and is reflected off the screen, rotating to the far left.
• Then the light passes through the delay film again and becomes horizontally polarized.
• Finally, the ray reaches the linear polarization layer. Since the ray is horizontally polarized at this point, this layer can completely block the ray.

So why does the polarizer not block the light of the display screen when it comes? Because the light on the screen only passes through the second half of the journey, the light from the screen can finally reach people's eyes.