Research On The Key Technology Of Optical Frequency Scanning Interferometry Absolute Ranging System

Recently,the manufacturing technology in major equipment such as aerospace equipment,large ship,electromechanical device and large research equipment is developing in the direction of large scale and high precision.Spatial coordinate measuring technology has attracted widespread attention,because it is an important support technique in major equipment manufacturing.The absolute ranging technology as the core and basis in the above technology is of important research significance.Laser ranging technology has always been a hotspot in domestic and international studies because of its good directional,monochromatic,coherent and high precision.As a new type of laser absolute distance measurement technology,optical frequency scanning interferometry(OFSI)ranging technology makes up for the incremental distance measurement and insufficiency in traditional interference.OFSI possesses the advantages of large scale and high precision at the same time.This paper has studied the key technology in improving precision of OFSI.The main research contents are as follows:1.Based on the analysis of the basic principle of OFSI ranging technology,this paper compared the characteristics of phase measurement method and beat frequency measurement method.In the paper,the range resolution of the system is derived by the Fourier transform.To increase frequency resolution,the frequency spectrum of the interference signals is refined by the linear frequency modulation z transform(CZT).The measurement precision of the beat frequency is improved.The factors influencing the accuracy of OFSI such as frequency modulation nonlinearty,aberration drift due to environmental factors and optical dispersion are analyzed emphatically.2.To eliminate the spectrum broadening impact of interference signal by nonlinear frequency modulation,the optical frequency sampling method is proposed in this paper,resampling the interference signal by using auxiliary interference signal as a trigger sampling clock signal.3.To eliminate the target drift error on final measurement precision,the method for compensating the drift error is used by optical frequency scanning with triangular wave,according to that the sign of drift error is consistent with direction of frequency scanning.A comparison experiment was designed to verify the feasibility of this method.And the repeatability of measurements is greatly improved.4.Using the heterodyne phase measurement technology and the phase compensation principle of the optical fiber PZT,this paper designed a long fiber locking system based on PID control,improving the stability of long fiber length in reference interferometer.