Ballistic Measurement System Based On Laser External Differential Interference Principle Design

Laser differential interferometry has been widely used in vibration,short-range displacement,and flow velocity measurements,but there are few studies on such long-field measurements as ballistic measurements,so this paper focuses on the needs of this application.The main work are as follows.1.For the characteristics of ballistic measurement,a well-structured laser external aberration measurement system is built in this paper,using an aspherical fiber collimator as the transceiver probe,analyzing the collimated beam cross-section energy distribution by CCD camera,combining the Gaussian beam characteristics,making plane wave approximation for its collimated beam in the far-field near-axis region,focusing on the beam energy characteristics in the spot energy concentration region,fitting its variation with distance The second-order function curve is fitted.Using the micro-bead glass primary reflective film as the surface of the subject,the relationship curve between the optical coupling efficiency of the probe signal and the distance of the subject is analyzed,and the results show that the continuous external aberration measurement within 1m depth of field is feasible,and provide a basis for the optimization of the optical path structure.2.For the problem of uneven distribution of time-frequency energy caused by mechanical errors and scattering interference in long depth-of-field measurement,instead of using interpolation and fitting,the ridge extraction error is corrected by STFT weighted postprocessing algorithm,which ensures smooth and continuous velocity curve of long travel object movement and realism.3.A laboratory validation environment is built to meet the measurement requirements of ballistic measurement.Verification experiments are conducted for long depth of field,abrupt velocity,and measurement accuracy,and the feasibility of the measurement system is demonstrated by comparison with third-party equipment.The comparison experiments show that the peak velocity error in the Hopkinson rod abrupt velocity measurement is<0.5%,and the ballistic test experiment solves the velocity profile with high overlap and relative error<0.25%.Ballistic test experiments measured the ballistic velocity of 513.18m/sThis study provides theoretical support for laser epi-interferometry in ballistic measurement applications and provides a basis for future laser velocimetry system structure optimization.