When we talk about 3D vision application solutions, first of all, we need to understand the classification of optical measurement and its principles.

Optical measurement is divided into two types of ranging methods, one is active and the other is passive. The active ranging method requires a specific, human-controlled light source and sound source to illuminate the object being measured. We obtain the three-dimensional information of the object based on the surface reflection characteristics, optical and acoustic characteristics of the object. The active ranging method is mainly divided into three types: (1) structured light method (2) triangulation ranging method (3) time of flight method; the passive ranging method is mainly binocular stereo vision measurement.

1. Active ranging method

(1) Structured light method: Project various patterns of line structures onto the object to be measured. 

Through the geometric relationship between the grating reflected by the object to be measured and the 

reference grating, the height difference and depth information between each measured point can be obtain

ed through analysis.

(2) Triangulation distance measurement method: Based on the principle of optical triangulation, we determine the three-dimensional coordinates of each point of the spatial object according to the geometric imaging relationship between the object, the light source and the detector.

(3) Time of Flight (ToF): A pulsed laser signal is irradiated onto the surface of an object. The reflected signal is transmitted back along almost the same path to the receiver. The time difference between the emission and reception of the pulsed laser signal can be used to measure the distance of each pixel on the measured surface.

2. Passive ranging method

Passive ranging: The radiation source does not need to be set up by people. It reconstructs the 

three-dimensional information of the scene through the two-dimensional image under natural light. Its 

characteristics are: low cost, flexible implementation method, and strong adaptability.