Research On Single Frequency Laser Frequency Calibration Technique For Swept Frequency Interferometry Ranging

Swept-frequency laser interferometry ranging system i s a high-precision ranging system that uses a frequency-modulated laser to emit a frequency-modulated laser light source to measure the absolute distance of the object to be measured.Scalar distance measurement of effective means.However,this system is sensitive to vibration.The distance measurement result will amplify the vibration of the measured object.The tiny vibration will also have a huge impact on the distance measurement.Therefore,it is necessary to add a vibration compensation system in the application.A vibration compensation system uses light emitted by an independent single-frequency laser,is coupled into a ranging signal through modulation,and solves the vibration information of the object to be measured,and compensates the original frequency sweep interferometric system.The vibration compensation system can effectively reduce the influence of vibration on the frequency sweeping interference measurement of the ketosterone,but the vibration compensation system itself will also be aff ected by some factors such as temperature,environmental changes,thereby affecting the vibration compensation accuracy,and ultimately affecting the distance measurement Accuracy.This article mainly focuses on the problem that the vibration compensation is not accurate due to the inaccuracy of single frequency laser frequency in this kind of vibration compensation method.The method of calibrating single frequency laser frequency while sweeping interferometric ranging is studied..Mainly include the following content.Firstly,the principle of distance measurement and vibration compensation of the swept laser interferometry system and the influence of the accuracy of single frequency laser frequency on the accuracy of vibration compensation are analyzed.According to the reality of the swept laser interferometry system,a spectroscopic analysis method based on heterodyne interference was selected,and the principle of spectral analysis method based on heterodyne interference was described.Second,the overall design of the spectral analysis method based on heterodyne interference.Including two modules: spectral analysis module,real-time wavelength calibration module.The spectrum analysis module is divided into an optical path portion and a circuit portio n,which are used to form a beat frequency and process the beat frequency signal respectively.The real-time wavelength calibration module is divided into a relative wavelength calibration part and an absolute wavelength calibration part.The absolute wavelength measurement is performed using a HCN chamber and the relative wavelength measurement is performed using a Mach-Zehnder interferometer.Third,the system is analyzed and optimized for the parameters in the design.A system model was established to analyze the system for different circuit parameters,especially filter and power detector parameters.The effects of different filter types and different filter parameters on the final measurement result were analyzed,and the optimal system parameters were selected.Fourth,system hardware build and test.Including the establishment of heterodyne interference optical path,Mach-Zehnder interferometer,band-pass filter circuit,power detector circuit and subsequent signal processing circuit,and test the system.The wavelength calibration accuracy of the system was determined to be 0.1 pm,the spectral resolution was 6 MHz(approximately 50 fm),and the dynamic range was 35 dB.Swept with a laser interferometer distance measurement system under various experim ental vibration environment,demonstrate the effectiveness of the system,the compensation of the swept laser ranging system error when the vibration frequency due to a single frequency laser inaccuracy introduced,effective It improves the ranging accurac y of the vibration environment.