Research On Method Of Quick Acquisition And Processing Of Optical Frequency Scanning Interferometry Absolute Distance Measurement Signal

The manufacture of high-end equipment such as airplanes,rockets,ships,and large-scale scientific devices is inseparable from large-scale space precision measurement technology.As the core and foundation of large-scale space precision measurement,absolute ranging technology has great research significance.Among the existing absolute ranging technologies,optical frequency scanning interferometry(FSI)ranging has the advantages of large measurement range,high precision,strong antiinterference ability,and no measurement ambiguity,and has been applied to large-scale digital manufacturing and assembly sites.The FSI ranging resolution is proportional to the laser optical frequency scanning bandwidth.The broadband frequency-modulated laser improves the ranging resolution,but amplifies the nonlinear effect of the optical frequency scanning,and also leads to a large amount of sampling data of the interference signal.Therefore,it is necessary to improve the acquisition and processing speed of FSI ranging signals to meet the high-efficiency measurement requirements of large-scale digital manufacturing.This paper studies the key technologies of fast acquisition and processing of FSI ranging signals,including:1.The nonlinear method of signal sampling synchronization correction optical frequency scanning is studied.Based on the principle of equal optical frequency sampling,the auxiliary interference signal is used as the sampling clock,the high-speed sampling clock preprocessing board is designed to synchronously shape the auxiliary interference frequency conversion signal,the FPGA frequency conversion signal frequency multiplication program is developed to increase the sampling rate,and the development of the equal optical frequency sampling module is completed,which realizes the synchronous correction of the nonlinearity of the optical frequency scanning when the ranging interference signal is collected,and greatly improves the data collection efficiency.2.A high-speed data acquisition and processing unit is developed to realize the front-end distance calculation of the data link.A high-speed data acquisition and processing unit is built,and a phase linear regression analysis algorithm of ranging signal is written,which effectively utilizes the phase information contained in all sampling points,reduces the influence of random phase measurement noise,and improves the accuracy of distance calculation.Using this high-speed data acquisition and processing unit to build a ranging system and compare the accuracy of commercial laser interferometers,the measurement error is better than 8μm at the equivalent distance of 11 m and 16 m,and the measurement repeatability is better than 6μm.3.The fast distance calculation method based on SFFT-ZFFT step-by-step spectral refinement is studied.The SFFT algorithm is used to determine the range spectrum refinement interval,and the range spectrum refinement is realized based on the ZFFT algorithm.This method utilizes the frequency domain sparse characteristics of optical frequency sampling signals of FSI to improve the calculation speed,and evenly disperses noise interference in the whole frequency domain,effectively improving the data processing efficiency of the anti-noise solution method for ranging signals.The final distance calculation experiment shows that the distance calculation speed of this method is more than 10 times higher than that of the CZT algorithm,the measurement error of the equivalent distance of 15 m is better than 10μm,and the measurement repeatability is better than 6μm.