3D sensing technology analysis

9-11 Apple officially released the iPhone 11 and 11 Pro series of new mobile phones, claiming to further improve the performance based on the original technology, and added new color matching, but as a technology control, we still have to take a look at this new product Some technical hotspots related to us in China.

The technology related to our profession refers to 3D sensing. The new generation iPhone does not use screen fingerprints and other technologies like previous rumors or many domestic mobile phones. Instead, it uses the previously-acclaimed Face ID function. Users only You need to point the front-facing camera at your face to easily perform face unlocking, payment and other operations. Face ID mainly uses 3D structured light technology. Apple has used this technology for the third consecutive year, which shows that it is indeed safe and reliable, and it is better than the fingerprint unlocking experience.

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In fact, in recent years, 3D structured light technology has not only been applied to smartphones such as the iPhone, it has played an important role in the fields of 3D face payment, new retail, 3D spatial scanning, intelligent logistics systems, and intelligent security. Hundreds of industries have a very broad market prospect. Why is 3D structured light technology so important? First of all, let's take a look at several ways to implement 3D.

Different from the traditional 2D application scenarios of machine vision, the main implementation methods of 3D vision include three methods: binocular vision, 3D structured light, and TOF (light time of flight).

The principle of the binocular ranging method is close to the human eye. Under the condition of natural light, two cameras are used to capture the image, and the depth information is calculated by the triangular ranging principle. Binocular vision is a very common, important and cutting-edge research direction in domestic universities. There are also some landing projects in different industries and application scenarios. However, because of the high computing power required, the binocular measurement method has poor real-time performance. The lighting object texture has a relatively large impact, so it is not suitable for miniaturized application scenarios, and has not been commercialized on a large scale. If you want to do related research in this area, you can choose the MV-VS220 binocular vision system made by Wisdom.

The TOF time flight law uses special sensors to capture the flight time of near-infrared light from emission to reception, and judges and calculates the distance information of the object. Although TOF technology has good real-time performance and simple algorithm, it has the problems of immature sensor technology, low image resolution, high cost, and high power consumption. At present, it is more used in object ranging and other fields.

Therefore, the 3D structured light technology in the civil field has high measurement accuracy, can reach 1mm (millimeter level), has many advantages such as relatively low power consumption, and is more suitable for close face recognition. Scenarios such as payment have great potential, so they have attracted much attention from the industry. The technical principle is that the laser speckle image is projected on the surface of the object, and then the infrared camera receives the speckle information reflected from the surface of the object, and hands it to the ASIC processing chip, and calculates the position and depth information of the object based on the change of the optical signal caused by the object.