Design Of 3D Camera System Based On Time-of-flight Principle

Compared to ordinary 2D image,3D image can give us a more realistic visual experience,which is more promising in future application.With the rapid development of all kinds of high technology and the support from relevant national policies,3D vision system is widely focused in various fields recently,such as VR technology,3D printing,machine vision,artificial intelligence and so on.So,it is critical to design a stereo imaging system that can precisely measure 3D scenes.Based on the application of 3D imaging,this paper analyzes the imaging principle of several 3D measurement systems,compares their advantages and disadvantages,selects the TOF method as the key research object,and designs a 3D imaging system.TOF measurement techniques include direct TOF measurements and indirect TOF measurements.On the basis of comparing and analyzing these 2 measuring theories,the indirect TOF measuring technique,or analog signal phase modulation demodulation is adopted in this paper.The main purpose of using phase modulation is to measure the phase delay between the transmitted modulation signal and the reflected signal by four samples.The phase difference produced by the analog modulated optical signal during the round-trip measurement system and the target scene.Then,distance can be calculated according to the modulation frequency and the speed of light.The TOF measurement imaging system uses the active light source to radiate the infrared modulation signal to the target scene.The receiver,a TOF sensor which can sense a particular wavelength signal,is used to synchronously demodulate the reflected signal containing the distance information.At the same time,considering the measurement accuracy and range of TOF method,this thesis analyzes the problems,improves the existing exposure algorithms,and prompts an automatic exposure algorithm to increase the ranging precision and measuring range.In order to prevent the target from over-exposure or under-exposure,the automatic exposure algorithm selects the region of interest according to the target scene,and automatically adjusts the exposure time of modulating light source,thereby improving the accuracy and the measuring range.Finally,this thesis uses TOF method and 3D ranging theory to design 3D TOF imaging system,and divide this system with 2 parts of hardware and software respectively.The hardware takes the TOF image sensor as the core,and consists of an acquisition module,a control module,a conversion module,an interface module and a display module.The main function of hardware is to collect the image signals,convert the optical signals into electrical signals,and transmit the image signals to application software through the ADC transformation.The host computer software is responsible for receiving and storing the image data,the realization of the 4 sampling ranging algorithm,image filtering,noise reduction,3D point cloud reconstruction,displaying gray image and 3D point cloud image,etc.