The distance sensor is usually placed next to the earpiece to detect the distance between the front of the mobile phone and other objects. If the distance reaches a threshold, the screen is shut down automatically. The first saves power and the second prevents the touchscreen from being misoperated.
In most cases, a distance sensor is applied to two aspects of a mobile phone. On the one hand, when the mobile phone makes a call, the screen is automatically turned off when the phone makes a call close to the head. In addition, if you close the screen during a call, you can save power by shutting down the screen. On the other hand, when you take the phone away from your ear, it will be automatically lit up. On the other hand, you can avoid misoperations when the mobile phone is on the screen in your pocket or packet, and the proximity sensor detects an object at a short distance. The mobile phone is notified to automatically turn off the screen.
The distance sensor is next to the earpiece. If your mobile phone is covered with a sticker, you can see that the other opening on the sticker is for the distance sensor, except the earpiece and the front camera. When you cover the distance sensor with your finger alone, the screen will be black immediately!