Research On The Absolute Distance Measurement Of A Non-cooperative Target By Dual-comb

Dual-comb absolute distance measurement has been developing towards the direction of high precision and low complexity,and new technologies keep emerging in the laser source and the measurement method of dual-comb.The types of light sources include two mode-locked lasers completely locked by the external phaselocked loop,two free-running mode-locked lasers and single dual-comb laser.The ranging methods include dual-comb dispersion spectrum ranging and dual-comb time of flight ranging.The combination of single dual-comb laser and dual-comb time-offlight ranging system makes the system simpler and can achieve high ranging accuracy.In order to make dual-comb ranging used more widely,the absolute distance of noncooperative target is measured by dual-comb time of flight method for the first time in this paper.The main content of the paper is as follows:1.The development history and structural characteristics of single dual-comb laser and dual-comb ranging are expounded.The basic principle of optical comb,dual-comb time of flight ranging method,envelope extraction of dual-comb interferogram and dual-comb interference ranging are introduced emphatically.2.A dual-comb interference ranging device was built and used for the first time on non-cooperative targets.The distance measurement device includes a dualwavelength mode-locked laser,an optical filtering device,an optical amplification and transceiver device and an optical interference device.In this paper,the parameters related to the the system of the dual-wavelength laser are detected,and the stability of its repetition frequency difference is demonstrated.The filtering device limits the spectral width and avoids the aliasing effect.The optical amplifiers increase the power of the output target pulses,and the receiver is a large-diameter telescope,which improve the signal-to-noise ratio of the received signal.The advantages and disadvantages of spatial optical path interference and fiber-coupled interference are experimentally verified,and the data acquisition and processing procedures are written.3.The relationship between the center wavelength of the dual-comb and the accuracy of ranging is analyzed for the first time in this paper.The variation of the ranging accuracy at different center wavelengths of the dual-comb is simulated,and the correlation between them is proved by connecting optical filters with different center wavelengths in ranging system.It is proved that the center wavelength changes the carrier density of the dual-comb interferogram,and the sparse or dense fringe causes low ranging accuracy.4.Three steps are built by using four precision gauge blocks of different thicknesses,and the steps are used as a reference for verifying the accuracy of the ranging system.The gauge blocks are fixed on a displacement platform so that the target pulses can be scanned over the polished surface of the three steps,and then the steps of different heights are measured.In experiment 100 ranging data are measured for each step,and the residual value is within 10 ?m after averaging.The anodized aluminum plate with surface roughness RMS=1.6 ?m is used to verify the measurement effect to non-cooperative target of the ranging system.Kalman filter is added to the data processing to reduce the standard deviation of the ranging to 7.47 ?m,which improved the real-time performance of the ranging system.