The Research Of FMCW Spherical Coordinate Measurement System Based Trigger Re-sampling Technology

This thesis researches the technology of spherical coordinate measuring system based on frequency modulated continuous wave laser technology and forms an modal machine.As to the ranging unit in the spherical coordinate measuring system,this paper researches the method of frequency modulated continuous wave laser ranging,using resample technology with fiber device suppresses frequency modulated non-linear errors.By the researching of the resampling method,this thesis presents three improved methods.1.This article presents trigger resampling measuring method that aims to improve sampling data utilization ratio and acquisition accuracy.It uses two fiber M-Z interferometries in its optical structure.One is measuring interferometer and the other one is auxiliary interferometer.A threshold voltage comparator is behind the auxiliary interferometer.When the auxiliary signal is greater than the upper voltage and less than the lower voltage;the acquisition card will take samples of measuring signal and auxiliary signal at the same time.2.This paper discusses the influence of Doppler Error caused by low-speed vibration and auxiliary fiber's length variation to resampling range result.On account of the resampling optical structure,presenting a three-light path compensation method that adds two partially reflecting mirror to the measuring light path.Then it uses the difference between the signal of mirror 1 and measurement signal to remove Doppler error.Through the correspondence between length of measurement and length of auxiliary fiber,the fiber length error was compensated.3.Researching the different time delay between measurement signal and auxiliary signal sampling time effects on ranging result.Presenting a new ranging measurement based on tandem double interference structure.The former interferometer produces a sinusoidal carrier signal whose light frequency changes with time.The latter one puts ranging signal in amplitude of carrier signal,and eliminates two signal's sampling time difference through extracting amplitude symbols of equal frequency intervals for amplitude signals.As to the angle measurement unit in the spherical coordinate measuring system,this paper considers the vertical error of revolving change,compatibility error,mirror inclination error and its offset error,out-put laser tilt error and its offset error,and thecircle grating installation error and its impact on angle measurement result.By using auto-collimator and collimation telescope to calibrate those errors and angular accuracy.The error calibration results are as following.Vertical error is 0.753'',compatibility error is 0.113 mm,mirror tilt error is 117.03'',mirror offset error is-0.618 mm.The precision measurement error results are as below,horizontal angle measuring accuracy is 0.4'',vertical measuring accuracy is 0.8''.Researching the assembly and calibrating method of spherical coordinate measurement system and the correction method of out-put laser azimuth are both mentioned in this research.Spherical coordinate system's calibrating results: the error of the coordinate component on X axis is 61.3um,on Y axis is 75.7um,on Z axis is78.4um.