Research On Absolute Distance Measurements By Multi-heterodyne Interferometry Using An Electro-optic Triple Comb

With the development of industrial manufacturing,aerospace and metrology technology,the precision manufacture of large-scale high-quality equipment has become the trend in modern industry field.High-precision,large-scale measurement technology has become an indispensable technical means to help its progress.Optical frequency comb is the new darling of optical measurement with its unique multi-wavelength,high stability and traceability advantages.The absolute distance measurement using optical frequency comb is beneficial to overcome the range and accuracy limitations and traceability problems in traditional measurement process.In this paper,the electro-optical optical frequency comb is taken as the research object,and an absolute distance measurement method based on multi-heterodyne interferometry using triple optical frequency combs is proposed.After analyzing the principle of electro-optic modulation,the mathematical model of electro-optic optical frequency comb has been established.And an optical frequency comb generating device is designed based on the cascaded electro-optic intensity modulators and phase modulators.Through the device selection and design,the generation of electro-optic optical frequency combs has been realized,which can be used for the absolute distance measurement of multi-heterodyne interferometry.The theory of absolute distance measurement by multi-heterodyne interferometry using triple optical frequency combs has been analyzed and interpreted in detail.With the generated three electro-optic optical frequency combs of different repetition frequencies,the ranging experiment verification on the standard guide rail has been completed through the design and construction of the measurement system based on the measurement theory.The results show that the measurement standard deviation is better than 15μm and the relative accuracy is 2.0×10^-7 in the range of 75 m.In order to meet the instrumentation requirements of the ranging system in the industry field,the electro-optic optical frequency comb generation and absolute distance measurement system has been designed and realized for the modular encapsulation and integration.An absolute distance ranger has been completed based on multi-heterodyne interferometry using triple electro-optical optical frequency combs.Via the ranging system,the absolute ranging experiments of indoor and outdoor environment are carried out.The uncertainty analysis of the outdoor experimental results shows that the measuring system can be used for large-scale high-precision absolute distance measurement.The relative measurement accuracy can reach9.2×10^-7.