Research On Key Technology Of Double-path Polarization Point Diffraction Interferometer

Point diffraction interferometry has become an important method of wavefront measurement,for its high precision,high resolution and instantaneous measurement,which has been widely adopted in various fields,such as high power laser,astronomical optics,biomedicine and so forth.The traditional pinhole type common-point diffraction interferometer is hard to introduce the phase shift in the optical path due to its completely common optical path structure,which limits its development in dynamic interference.Although previous phase-shifting point diffraction interferometers have achieved dynamic detection,problems such as the difficulties in producing diffraction plate,and the special condition requirements still existed.In this paper,a two-channel polarization point diffraction interference detection scheme has been designed to achieve the dynamic detection before wavefront testing,by realizing the polarization phase-shifting through the phase grating and the polarization camera.The double-path polarization point diffraction interferometric testing scheme is proposed.Splitting and merging the optical path by phase grating to realize the polarizing modulation,and in the help of polarization camera we can realize the dynamic measurement.The principle of phase-shifting and interference is studied by Jones vector.Testing wavefront is modulated by phase-shifting algorithm.Key technology of double-path polarization point diffraction interferometer is studied.Double grating diffraction model is deduced based on the scalar diffraction theory.Distribute the energy ratio of diffracted light reasonably by optimizing the parametric quantity of phase grating.The cause of introducing astigmatism into the +1 order diffracted light is studied.The reference wavefront pre-correction method is proposed and correct the astigmatism in the +1 order diffracted light successfully.After correction,the PV value of +1 order diffracted light is 0.276? and the RMS value of +1 order diffracted light is 0.044? which improves the reference wavefront quality and reduces the light intensity loss caused by pinhole diffraction.A polarized pinhole plate with high integration is designed,which can realize pinhole filtering and wavefront polarization modulation at the same time.The PV value of the diffraction reference wavefront is 0.087? and the RMS is 0.013?,which meets the requirements of high precision measurement.The accuracy of the double-path polarization point diffraction interferometer is tested.Compared with the testing results of the SID-4 wavefront detector,the PV testing accuracy is better than ?/10,and the RMS testing accuracy is better than ?/70,which verifies the correctness and feasibility of the double-path polarization point diffraction interferometry and can realize the real time measurement of testing wavefront in high precision.The errors introduced by splitting grating and combining grating in interferometer system are studied.The phase delay error introduced by divergent beams passing through quarter wave plate is calculated and deduced.The errors are calibrated.The dynamic testing performance of double-path polarization point diffraction interferometer is studied by using laser wind radar.The testing system is designed and set up.The aberrations introduced by atmospheric turbulence and wind direction in the optical system of laser wind radar are successfully detected.The wavefront deviation is between 0.08? and 0.25?,which provided a reference for the future design of the laser wind radar system.Double-path polarization point diffraction interferometer can reflect the influence of air disturbance on system wavefront in real time which verifies excellent dynamic testing performance.