Research On High Precision Absolute Ranging Method Of Optical Frequency Comb

This paper uses optical frequency combs for high-precision absolute distance measurement to solve the needs of higher-precision absolute distance measurement tasks,about aerospace,large-scale surface inspection,road and bridge inspection and other engineering fields.A method is proposed that it can combine the time-of-flight ranging method and the pulse interferometric auto-correlation ranging method.It is built an absolute distance measurement system combining a traditional laser rangefinder and an optical frequency comb Michelson interferometer system to achieve high-precision absolute distance measurement.The main content includes the following aspects:The time domain and frequency domain characteristics of the optical frequency comb femtosecond pulse are explained;the time domain frequency domain model of the optical frequency comb is established;the difference between the femtosecond pulse before and after the laser mode locking is compared;the femtosecond pulse in the dispersive medium is analyzed Propagation characteristics;the influence of each order of dispersion on the propagation of pulsed light is explained;the principle of pulse autocorrelation and the principle of femtosecond pulse ranging are analyzed;the theoretical model of optical frequency comb femtosecond pulse ranging is constructed.An absolute distance measurement method using the time-of-flight method combined with the pulse interferometric autocorrelation method is proposed to solve the shortcomings as low resolution of the traditional time-of-flight method and the pulse interferometer absolute measurement length can only be discrete values.The time-of-flight module and the Michelson interferometer module are designed which used the time-of-flight method for the rapid and timeliness of rough distance measurement.The improvement of the interferometric measurement accuracy also be realized.An absolute distance measurement system combining traditional laser rangefinder and optical frequency comb interferometric distance measurement system is built.The distance to be measured is roughly measured by a laser rangefinder.Then interferometric measurement is used to measure the spatial position information of the femtosecond pulse interference signal by scanning the repetition frequency of the optical frequency comb laser light source.Finally the results of measured distance are obtained combing with the rough measurement result of the flight time and the interferometric measurement.The simulation measurement experiment and research are carried out on the meter-level to-be-measured scale,and a detailed error analysis of the measurement data is carried out.Experiments show that in meter-level measurement tasks,the limit error of the ranging result is ±1.3μm and the peak-to-peak value of the limit error is no more than 2.6μm,which verifies the feasibility of this ranging method to achieve micron-level precision absolute ranging at the meter level.