Relationship between modulation frequency and range accuracy in the double polarization modulation range finding system

Abstract

Accurate measurement of absolute distance is crucial for developing the progressive military, aerospace, manufacturing large scientific instruments and other fields. Instead of the traditional phase discrimination scheme in general phase-shift distance measurement, the double polarization modulation range-finding system can simplify the simulation phase circuit, reduce the phase shift noise and improve the accuracy by using interference phase demodulation. The in-depth discussion of theoretical derivation and experimental verification are proposed based on the double polarization modulation range-finding system. The detailed theoretical analysis of optical structure is proposed, and the factors affecting the range accuracy are analyzed based on the theoretical formula of ranging result. Finally, the theoretical formula of range accuracy is obtained, and experimental validation is carried out. In this experiment, the wavelength of laser source is 735 nm, and the phase modulator is 4431 model from the Newport company. The ranging experiment is conducted in the modulation frequency ranges of 0.75-0.85 GHz, 2.7-2.8 GHz, 4.3-4.4 GHz, 6.1-6.2 GHz, and 7.8-7.9 GHz. Experimental results indicate that the measurement accuracy of phase-shift range-finding technology is improved with the increase of modulation frequency. Moreover, the accuracy is proportional to the parameter f/N, in which f is the modulation frequency uncertainty and N is an integer in our algorithm. With the appropriate modulation frequency, the range accuracy of the double polarization modulation range-finding system can reach up to 10-7.