Research Of Key Techniques In Scanning Laser 3D Imaging Based On Differential Optical Path Technology

Laser 3D imaging has been widely used in aviation, aerospace, environmental monitoring, geological mapping, digital city modeling and other fields for its advantages of simple principle, initiative non-contact detection and abundant information, etc. Current laser 3D imaging is usually detected by certain imaging modes based on the basis of laser ranging. Comparing the research status at home and abroad, low ranging accuracy, low imaging resolution, low imaging efficiency and unable to get large format of APD detector are the mainly problem existed in our country. To solve these problems, this thesis has designed a laser 3D imaging system through differential echo receiving optical path combined with MOEMS scanning imaging and explored something useful in the aspects of improving the ranging accuracy and imaging efficiency of the system, mainly completed two aspects in detail.1. Analyzed the existing laser ranging method and chose the pulse method that is suitable for the laser 3D imaging as the method of access distance information, the accuracy of the pulse method is not high because of the low accuracy of the echo time identifying, so in this thesis, our research group proposed a method of the pulse laser ranging based on differential optical path, this method receives echo through the dual channel and then have a differential treatment, from this way it can improve the system sensitivity and restrain background noise by transforming the traditional peak moment to zero point identification, thus improve the signal-to-noise ratio and the ranging accuracy. So we designed and built an actual distance measuring system based on the theory and simulation analysis, first we verified the relationship between optimal sensitivity and difference distance. Under the condition of optimum sensitivity, we compared the distance measurement results of traditional experiment method and the optical path difference method, the results showed that under the same background noise, the root-mean-square of ranging error based on the method of optical path difference decreased from 95 mm to 70 mm, reduced to 73.7%.2. MOEMS is the direction of the next generation of 3D laser imaging scanning technology development with its advantages of small size, high precision and fast speed, etc. this thesis has designed a scanning laser 3D imaging system with the hardwire of MOEMS and peripheral control circuit based on MOEMS scanning device through the study of the working mechanism of MOEMS. Also we researched and designed the scanning control algorithm, designed a mechanical structure and set up the experimental system. Then we did the experiment of 3D scanning imaging based on the system designed before. We obtained the clear image of the object by adjusting the step length of scanning and made a useful exploration to improve the efficiency of the laser 3D imaging system.