Design Of Digital Phase Shift Ranging System For Far Target

High-precision far-target laser range finder is one of the basic measuring instruments which is necessary during the stage of building,construction and maintenance of large engineering structures(such as bridges,tunnels,high-rise buildings,etc.).At present,this kind of instruments are mainly based on the principle of pulse laser ranging,which has complex structure and high cost.To this end,a simple and cheap digital phase shift laser ranging system is designed in this paper.In this paper,the basic principle of single-frequency digital phase shift ranging is adopted,key technologies such as weak laser signal detection and unambiguous distance measurement is solved,and a high precision remote target digital phase shift ranging instrument circuit system based on 32-bit embedded controller and FPGA is designed.The main research content is as follows:1.A high-precision far-target ranging scheme based on the principle of digital single-frequency phase shift ranging is proposed.In this scheme,high-frequency sinusoidal signals modulated by different pulse widths are transmitted,and the phase information is extracted after echo signals are converted,amplified,frequency-reduced and filtered at the receiving end,then high-precision distance values and fuzzy distance values are obtained.The results of high-precision distance measurement and fuzzy distance measurement were analyzed by MATLAB simulation,and the feasibility of the scheme was verified.2.A digital phase shift rangefinder circuit system with 32-bit embedded controller and FPGA as the core is designed,which mainly including: laser transmitting and receiving circuit,mixing circuit,AD sampling circuit,FPGA configuration circuit and power circuit.Circuit schematic diagram and PCB designs,component parameter selections,circuit board productions and debugging are finished.The developed circuit board meets the design specifications is showed by the debugging results.3.Quartus Ⅱ software and Verilog HDL language were used to complete the programming and debugging of FPGA software,including laser emission module,data acquisition module,FFT phase detection module,data storage and bus read-write module.4.An optical mechanical system of a total station distance measuring head is used.The developed circuit board is assembled on the distance measuring head,and the overall function of each circuit function module is experimentally tested and analyzed.The design requirements of a target measuring range greater than 500 m as well as the ranging accuracy reaching ±(3mm+2ppm×D)(D means measuring distance)are met.