Research On Dynamic Wavefront Measurement Based On Point-diffraction Interferometry

In point-diffraction interferometer(PDI),a pinhole is utilized to generate a diffracted ideal spherical wavefront to act as the reference wavefront in interferometer.By this method,not only the precise measurement results can be obtained,but also the cost of measurements can be reduced,which can be considered as an advantage comparing with the conventional interferometer.However,it is difficult to obtain the phase-shifting,especially the simultaneous phase-shifting,in PDIs.Therefore,it is challenging to apply PDIs into dynamic measurements.A quasi-common-path PDI using PLP,i.e.,PLP-PDI is proposed.In PLP-PDI,a PLP is utilized in PDI to act as the point-diffraction plate,generating a diffracted ideal spherical wavefront.A loop light path of interference system is utilized in PLP-PDI,which makes the orthogonally polarized reference and test beams can be simultaneously obtained a quasi-common-path PDI can be realized.The simultaneous phase-shifting can be obtained with phase grating and phase retardation array to reduce the influence of environmental vibration and other factors on interference measurements.The design idea and processing method of PLP are detailedly analysed.The parameters and selection principles of each optical elements are introduced.The position and angle relationship of these optical elements are calculated,and how we set up the experimental instruments is described.We measured the wavefront in experiments,then compared them with the results obtained by SID4,it shows that the PV value of the difference of the two results is 0.014?,proving the high precision of PLP-PDI.And the results of consecutive measurements proved the stability of PLP-PDI.The possible errors in PLP-PDI are analysed and described.Some methods like mathematical modeling and simulations are used to verify that the errors will not impact on the measurement results,so PLP-PDI can be applied into high-precision dynamic wavefront measurements.