Study On Ranging Algorithm For Pulse Laser And Its Realization On FPGA

The quantum leaps of technology serve as the catalyst for increasing demand of range measurement exactitude, while the emergency of a series of novel methods of range measurement makes the exactitude one of the most profound attributes. Laser pulse ranging, which is famous for exactitude, simplicity of operation, time-saving nature, anti-interference property, leads the way in extensive use among the fields like aerospace industry, navigation, medical imaging, engineering practice.However, the echo signal is impacted by environment seriously, as a result, the echo signal is always mix with noise burr and the amplitude and waveform is often distorted that making echo location more difficult. Laser pulse ranging is measurement of time between the laser pulse emission and echo.Clock counting mehtod is used in Laser pulse ranging, but that mehtod will have a clock cycle random error as a result of the echo moment and the clock is asynchronous. When the clock frequency is not allowed too high, the random error is obvious and the precision of laser pulse ranging is affected seriously.According to problem of echo with noise mixing in it, the thesis studies the threshold method to wipe off the noise. When there are multiple continuous sampling points exceeding the threshold, we consider it as the echo signal, otherwise we filter it out as noise burr. For the difficulty of positioning the Echo moment brought by the distortion of echo amplitude and waveform, this thesis takes the method of ARC timing to time the echo signal to improve the timing precision of the echo effectively. In order to reduce the random errors caused by the clock counting method without raising the counting clock frequency, this thesis focuses on the Time Digital Converter (TDC) algorithm. Currently TDC has digital method, simulation method and digital interpolation method. For the digital method in this thesis we study the method of cycle shift method. For digital interpolation method this thesis studies the pulse shrinking method, relay pulse delay method and Vernier method. We design and simulate the four algorithms respectively, meantime we analysis the index of precision and so on.The rewritable nature, ample resource, parallel processing property of Field Programmable Gate Array serve give flexibility and adaptability to the new generation electronic system. The ultimate part of the thesis presents the experimental result of the laser pulse ranging algorithm based on FPGA and gives analysis to the experiment result and influence factors to the precision. The experimental results show that the algorithm is meeting the design for the established index requirements.