Yes, iPhonex’s face unlock is read by ST’s 1.4M infrared image sensor, so it can be recognized even if the lights are turned off at night.
The reasons are as follows:
The entire structure of structured light consists of two parts: a transmitting mechanism and a receiving mechanism.
1. The emission part has a 940nm VCSEL laser. The laser focusers used in many mobile phones now follow this principle. There is a DOE (diffractive optical device) in front of the laser, whose main purpose is to form a focus on the target. Different speckle coding, Apple uses it to form a picture with coding information on the human face.
2. The receiving chip uses ST's 1.4M infrared image sensor. This is because the image with laser-encoded information on the face is transmitted to the ISP for processing. According to this image and the DOE The code is decoded to generate 3D distance information and a face image with depth information is generated and compared with the face depth information stored on the machine. The accuracy can be unlocked when the accuracy reaches a certain percentage.
Because the image sensor always has light input and the 940nm laser is always emitting. In fact, the visible light is blocked. It only receives the emitted 940nm light. The visible light is useless, so there is no problem at night. The issue of use or failure. This technically explains the Face ID and TrueDepth camera of iPhoneX.
In short, the facial recognition light used by iPhonex is invisible to the naked eye, so there is no problem of being unable to unlock when the light is dark.
Extended information
VCSEL, whose full name is Vertical Cavity Surface Emitting Laser, is developed based on gallium arsenide semiconductor material and is different from LED (light-emitting laser). Diode) and LD (Laser Diode, laser diode) and other light sources, have the advantages of small size, circular output spot, single longitudinal mode output, small threshold current, low price, easy to integrate into large-area arrays, etc., and are widely used in optical communications , optical interconnection, optical storage and other fields.
In the production process, VCSEL has many advantages over edge-emitting lasers. Edge-emitting lasers need to be tested after production is completed. If an edge-fired laser fails to operate, either due to poor contact or poor quality material growth, processing time is wasted in the manufacturing process and material processing. However, VCSEL can test its quality and solve problems during any manufacturing process. Because the laser of VCSEL is emitted perpendicularly to the reaction area, as opposed to the edge-emitting laser which is emitted parallel to the reaction area, tens of thousands of VCSELs can be operated at the same time. A three-inch gallium arsenic chip was processed. In addition, even though the VCSEL manufacturing process requires more labor and finer materials, the production results are controllable and more predictable.
Image sensing technology is developed on the basis of photoelectric technology. It uses the light-to-electricity conversion function of optoelectronic devices to convert the light signal on the photosensitive surface into an electrical signal that is proportional to the light signal. A technology of signal "image", which converts optical images into one-dimensional time series signals, and its key device is the image sensor.
Existing image detection systems include solid-state optical image sensing systems, infrared imaging systems, ultrasound imaging systems, microwave imaging systems, etc., which have been widely used in video, measurement, monitoring, medical care, artificial intelligence, etc. field.
Reference: Baidu Encyclopedia: iPhone X