Research On Nonlinear Correction Method On Laser Frequency Sweep Interference

In aerospace,military,civilian and many other fields,with the precision machining and forging of large workpieces and the improvement of three-dimensional geological morphological measurement requirements,laser sweeping interferometry absolute distance measurement technology stands out,it has the advantages of high measurement accuracy,high efficiency,no contact,no blind spots,etc.,and has become a research hotspot in this field in recent years.Laser frequency modulation continuous wave(FMCW)technology relies on the linear modulation of lasers,but in engineering applications,it is difficult for lasers to be fully linearized due to various factors,which will bring greater error and complexity to the ranging system.In this thesis,aiming at the basic principle of FMCW absolute distance measurement,the extended phase frequency sampling method is proposed on the basis of frequency sampling,and by expanding the corrected signal and combining the frequency sampling method,the target optical path can be measured in the case of the optical path of the auxiliary interferometer by 1/2,which brings new ideas for the range expansion under the condition of satisfying the Nyquist sampling law.In this thesis,the selection of key devices is completed,and a laser sweep interference ranging system is built.The phase spread frequency sampling method can effectively correct the frequency modulation nonlinearity of the laser,and the problem of interferometric signal frequency domain widening can be solved.The results of the experiment were calibrated with the help of a high-precision Hexagon coordinate measuring machine: the repeatability of the ranging system was verified,with a measurement uncertainty of 1.6 μm,and in free space ranging experiments,the standard deviation of the measurement was 14.5 μm.The margin of error is between 30 μm.In summary,the extended-phase frequency sampling method has a good correction effect on the frequency modulation nonlinearity of the laser,and the stability of the system is high,with good repeatability and high ranging accuracy.