In the eyes of many people, they think that the white iPhone 4S is identical to the black iPhone 4S in appearance except for the color. But careful friends will find. The white iPhone 4S will have a small black box above the earpiece than the black one. What is this black box on earth? Why does the white one exist while the black one does not?

The official price of the black and white iPhonen 4S is the same, and the official introduction is the same except for the color, so the white iPhone will certainly have no more functions than the black one. In fact, this cut is also found on the black iPhone 4S, just because the color of this cut is the same as that of the black version of the iPhone 4S, so we can't find it during normal use. If you shine the LED light of your phone on the handset of the iPhone 4S in the sun, you can also find this small black box.

In fact, the black hole is a distance sensor. Usually when we make a call, the screen will automatically close as soon as our face is close to the screen. After the call, the phone will automatically light up when it leaves the face. This is the effect of the distance sensor. It can greatly help us save power. In addition, it can also avoid misoperation caused by touching the screen when answering the phone.

The principle of the distance sensor is actually very simple. As shown in the figure below, there will be an infrared LED lamp in the distance sensor, which can emit infrared light. When an object approaches, the infrared light emitted by the infrared LED lamp will be reflected by the object, and the reflected infrared light will be captured by the proximity sensor at the top of the figure, In this way, our mobile phone can judge whether it is close to our face.

Since infrared ray needs to penetrate the glass to sense whether any object is close to the phone, the distance sensor position of our phone cannot be painted white, which is why the white iPhone has a small black box.

In addition, since we need to add a layer of glass on the surface of the sensor, which can also reflect infrared light, it is generally necessary to separate the infrared LED lamp and the proximity sensor with something to avoid the infrared light reflected by the screen glass interfering with the judgment.