Study Of High-precision Time Interval Measurement In Pulsed Laser Ranging System

Under the condition of no cooperative target to realize high-precision pulsed laser ranging currently has become a hot issue at home and abroad, which is widely used in engineering, geodesy, and security monitoring fields. So it has very important research significance and application prospects.This paper aims to achieve high-precision time interval measurement of pulsed laser ranging system. A new method of high-precision time interval measurement based on sine curve was proposed and studied. This paper analyzed the time interval measurement principle error which was generated by the nonlinear of the sine curve and studied the eliminating error mechanism of using the principle of multi-point average method. A method of pseudo-random sampling to realize the uniform sampling technology was proposed and analyzed.The hardware circuit which combined with high speed A/D and FPGA was designed. The hardware system is consisting of the sine quantization clock circuit, sweeping signal generated circuit, high-speed AD acquisition circuit and FPGA configuration circuit. We completed the hardware circuit components selection, circuit design and debugging.This paper used Verilog HDL language to develop FPGA. The software system is consisting of the control pulse laser transmitter module, time interval measurement module, data computing and storage module. We completed the module programming and software debugging.This paper preprocessed the raw sampling data, including singular points eliminating, data smoothing processing, error compensation of large number and the least squares curve fitting and so on. And finally the high precision time interval was calculated.The experimental device was set up to carry out ranging experiments. It realized the ranging accuracy ±(3+2ppm),corresponding to the time precision is better than 20 ps. The experiments show that the method of high-precision time interval measurement based on sine curve is feasible, and it can be used for high precision pulsed laser ranging in surveying and mapping instrument.