Design Of FMCW Laser Ranging System Based On Optical Frequency Comb

Advanced equipment manufacturing concerns the national economy and people’s livelihood,and the large-size and high-precision ranging is indispensable in equipment manufacturing.The Frequency Modulated Continuous Wave(FMCW)laser ranging can realize the absolute distance measurement,and its ranging accuracy and maximum detectable distance can meet the qualification of manufacturing.In this paper,the nonlinearity of FMCW is studied and the main research contents are as follows:1、Based on formula derivation,the principle of FMCW ranging and the negative effect of FMCW nonlinearity to the ranging accuracy were analyzed.The femtosecond optical comb can calibrate the laser frequency because of its discrete and equidistant modes in frequency domain,so a FMCW laser ranging system with optical frequency comb for FMCW nonlinearity calibration was designed.By mixing the optical frequency comb and FMCW laser to extract the calibration peaks of equal frequency interval,a short distance ranging experiment was carried out,while the distance was solved by the frequency-phase fitting method.The FMCW nonlinearity error curve was also obtained.2、According to the principle of frequency-phase fitting FMCW method based on optical comb,the light source was selected and a double optical path measurement system was built.Meanwhile,A laser collecting and coupling system based on Cassegrain telescope and self-focusing lens was designed to solve the problem of receiving reflected light in remote measurement.The ranging experiments of 60 m and550 m were carried out indoors and outdoors respectively.The experimental data show that the standard deviation of 60 m was less than 40 μm and the error was less than 70μm.The standard deviation at 550 m was better than 300 μm and the error was less than1 mm.3、The characteristics of microresonator and the generation principle of Kerr comb were studied.The filtering characteristics,resonant wavelength,free spectral range,quality factor and mode volume of the microresonator were analyzed,and the generation process of Kerr comb based on nonlinear effects was described briefly.Based on the optical comb generated by a high-index doped silica glass microresonator,the FMCW nonlinearity calibration and ranging experiments were carried out.The standard deviation was less than 11 μm and the error was less than 20 μm at a distance about 2 m,which proved the good repeatability and accuracy of this distance measuring system.