Study On Frequency Modulated Continuous Wave Laser Ranging System And Its Signal Processing Algorithms

Short-time, large-scale and high-precision measurement has become an important trend in large size measurement. Frequency modulated continuous wave(FMCW) laser ranging is a new method of laser range finder, which can be used as non-contact measurement for non-cooperative target. The advantageous characteristics of wide range, high ranging accuracy and spatial resolution make FMCW laser ranging superior amongst other measuring methods, exhibiting a broad application prospect in large-size and high-precision industrial measurement. The research on FMCW laser ranging system and its signal processing has important significance in improving the precision, resolution and scale of range finders.The research status at home and abroad about the signal processing algorithms of frequency modulated continuous wave laser ranging system is summarized in this paper in the first place. Given the deficient study in the influence of modulation linearity as well as scan range on ranging accuracy, we aimed at diminishing the impact of nonlinear modulation on ranging precision via signal processing algorithms and breaking through the limitation of scan range to reduce the errors in frequency measurement.In this paper, a new method by means of sampling the signal at equal frequency interval and splicing sampled signal to improve the measuring resolution of FMCW laser ranging system is presented. We designed and built a dual optic interferometer of fiber FMCW laser ranging system, using the auxiliary interferometer for generating the clock pulses to sample the measured signals at equally spaced optical frequencies and then splicing the sampling signal. By using LabVIEW graphical programming software, we designed and implemented a signal processing system which can be utilized to detect signal error, sample and splice signals. It is experimentally and theoretically proved that the method of sampling the measured signals at equally spaced optical frequencies and then splicing sampled signal can break though the tuning range of the laser source limitation and reduce the effect of tuning nonlinearity of the laser source, consequently improving the measuring resolution.The results reveal that the signal processing algorithm we used in the FMCW laser ranging system can improve the precision and resolution of the system efficiently. In the measurement experiment on spatial resolution at distances of 8.7 and 14.2 m, 70 ?m range resolution is demonstrated with high stability, realizing highly accurate measurement in far distances.