Research On Precise Ranging Technologies Based On Electro-optic Frequency Combs

The high-speed developments of science and industry have put forward higher requirements for large-scale precision ranging technologies.On the other hand,the invention of optical frequency comb(OFC)provide infinite possibilities to laser measurement technologies,and the ranging technologies based on OFC have been studied extensively as well.The precision potential and good traceability of OFC ranging make it an ideal choice for the new generation of precision ranging technology.In this doctoral thesis,we focus on the research of the OFC ranging technologies,and choice the electro-optic frequency comb(EO-comb)with simple construction and strong stability as the light source.The synthetic wavelength ranging method based on triple EO-comb and the spectral interference ranging method based on signal EO-comb are theoretically&experimentally discussed in this thesis.Besides,the long-distance ranging and non-cooperative targets ranging experiments have been carried out to compare the application potential of the two schemes.The triple EO-comb synthetic wavelength method range based on multiple heterodyne interference principle.A series of synthetic wavelength chains are formed by the plentiful modes of signal comb pair.The long synthetic wavelength is employed for rough measurement,which can ensure a large non-ambiguous range(NAR);the short synthetic wavelength is employed for fine measurement,which can ensure the ranging accuracy.In the 70 m absolute ranging experiment,we obtain the ranging consistency of 10-7·L compared with an incremental laser interferometer.The spectral interference method range based on the spectral modulation characteristics of multi-wavelength laser interference,a broad-spectrum EO-comb after dispersion compensation and nonlinear spectrum expansion act as the light source,and the measured distance can be obtained by solving the envelope frequency of the interference spectrum.The experimental results demonstrate an agreement within±13 ?m over 70 m distance.The instrumental design and long-distance ranging experiment were carried out.Due to the turbulence of airflow,the ranging accuracy of the synthetic wavelength ranging and the spectral interference ranging decrease obviously.Since the short NAR,spectral interference ranging has lost the validity of long-distance measurement.While the synthetic wavelength method can keep the validity in the whole range by means of its well balance of precision and NAR.Besides,the synthetic wavelength methods even can be used for monitoring the change of optical path as long as there are sufficient update rate and measurement time.In the non-cooperative target ranging experiment,a plane mirror,a ground glass diffuser,and the ridge and valley of an iron horizontal-milling specimen were employed as targets individually in the contrast experiment.An experiment was implemented to observe the powers,cross sectional profiles and polarization states of the returned lights from different specimens,and verifies the relationship between the return power and angle at the ridge and valley of the horizontal-milling specimen.Due to the influence of the roughness of non-cooperative targets,the power and the spot shape of return light deteriorate obviously with the surface texture,which lead to a significant impact on the range and accuracy of synthetic wavelength method.However,due to the high robustness of spectral interference method,the measurement can still be completed in weak light.Hence,the roughness of surface has negligible effect on measurement range,and the ranging accuracy is also determined by the resolution of spectral interference method.The research shows that the EO-comb has a good potential of ranging application.The triple EO-comb synthetic wavelength method has the capacity to balance the non-ambiguous range and resolution,which can cope with the large-scale and high-precision ranging assignments;While the spectral interference method has the ability of ranging through week returned light,which can adapt to the demand of precise ranging of rough surfaces.