IPhonex face is unlocked, and the reason for turning off the lights at night can be identified:
Apple uses structured light to realize face recognition.
The whole structure of structured light consists of transmitting mechanism and receiving mechanism.
There is a 940nm VCSEL laser in the transmitting part, and many laser concentrators used in mobile phones are based on this principle. There is a DOE (Diffraction Optical Device) in front of the laser, whose main function is to form different speckle codes on the target. What Apple uses is to form a picture with coded information on the face.
The chip at the receiving end uses the infrared image sensor of ST 1.4M, because the image with laser coded information on human face is transmitted to ISP for processing, and then decoded according to the image and the code on DOE to generate 3D distance information, and a face image with depth information is generated, which is compared with the depth information stored in this machine, and can be unlocked when the accuracy reaches a certain percentage.
Because the image sensor always has light input and 940nm laser is always emitted, in fact, the visible light is shielded and only receives the emitted 940nm light, so the visible light is useless, so there is no problem of bad use or failure at night. This is a technical explanation of the Face ID of the iPhoneX and the original camera.
In short, the facial recognition light used by the iPhonex is invisible to the naked eye, so there is no problem that it cannot be unlocked in the dark.