Study On Receiving And Positioning System In Non-cooperative Frequency Modulated Continuous Wave Measurement

The real-time and high-precision field measurement of non-cooperative target has become an important development trend of industrial large-size measurement.Compared with other traditional ranging methods,frequency modulation continuous wave(FMCW)has high accuracy,large ranging range and no cooperative target measurement and has become a research focus of laser measurement.The echo receiving system is an important component in the optical system and the receiving characteristic of the echo receiving system also affects the accuracy of the system.In order to realize the real-time control of the measuring system,Camera positioning system is necessary for this instrument.In this paper,the two parts are studied,and the echo signal receiving system based on Cassegrain telescope and the camera positioning system based on monocular vision are proposed and designed.In this paper,the echo signal receiving system of laser measuring instrument is studied,and the receiving system based on Cassegrain telescope and multimode fiber is modeled by optical design software.Through analyzing and optimizing the aberration and light receiving efficiency,the parameters of the Cassegrain telescope in the system is determined.Then the Gaussian scattering model of the backscatter of the determinand is established,and the receiving optical path is set up completely.The received power of the system under different conditions is analyzed quantitatively and the rule between receiving efficiency,focusing position,the distance and surface of the object is investigated.The research results show that,for the sample block of the same processing method,the system receives power is negatively correlated with the target distance and its roughness,while the system focus distance is positively correlated with the target distance and its roughness.For designing the camera positioning system,this paper presents a new method which combines monocular camera and without the cooperative target ranging to locate the laser spot and the location of the target point.The structure of the camera positioning system is determined firstly.The internal parameters of the camera are obtained by the traditional camera calibration method and the angle of the turntable is calculated by geometrical projection principle with the ranging information and the pose information of the turntable.Then C++ and OpenCV library are used to design software which complete the camera image acquisition,data processing and control of the turntable,and MFC class library is also used for human-computer interaction interface.At last,the method of equipment alignment based on laser spot recognition is put forward and the experimental device of camera positioning system is constructed.The experiments on different positioning distance which using the checkerboard calibration plate verify the correctness of the algorithm,and the error of positioning system is analyzed.