Technology Research And Testing Before The Point Diffraction Interferometer Wave Based

Point diffraction interferometer (PDI) is an effective means for wavefront measurement, which can satisfy high precision measurement, with no standard lens and common optical path structure. In order to realize optical wavefront transient measurement, the point diffraction interferometer wavefront testing method is studied, which need only one defocus interferogram to retrieve the phase.Firstly, the scheme based on PDI is designed to test the dynamic wavefront. The theory of the PDI is studied. Three types of collimator structures for PDI wavefront collection are analyzed, including the refractive collimator, the coaxial reflective collimator and the off-axis reflective collimator. The off-axis reflective collimator is adopted.Secondly, the contrast of PDI interferogram is studied by simulation and experiment. In the simulation, the intensity of the convergent beam after passing the diffraction pinhole is analyzed, as well as the fringe contrast of interferograms with different defocus values. A point-diffraction plate is designed and fabricated. The corresponding interferograms are taken. The experimental results indicate the point-diffraction plate with6um diameter pinhole and0.2%transmittance meets the test requirement.Thirdly, the four phase stitching method and the improved coordinate transformation method are studied to retrieve the phase distribution from circular carrier interferogram. The accuracy and dynamic range of carrier frequency for the two methods are analyzed. Accuracies of both the two methods are better than the1/40wavelength, meeting the test requirement.Fourthly, an experimental setup based on PDI is demonstrated for wavefront testing. Transmission wavefront of a standard lens is measured. The wavefront has a peak-to-valley (PV) of0.264λ and a standard deviation (RMS) of0.032λ whereλ is532nm. Wavefront of same lens is also measured by a SID4wavefront sensor and a ZYGO interferometer. The wavefront determined by the experimental setup agrees well with those determined by the SID4wavefront sensor, indicating the feasibility of the experimental setup.Finally, an experimental setup is built for the determination of the transmission wavefront of a near-infrared optical system. The wavefront has a PV of1.486λ and a RMS of0.192λ, whereλ is1313nm, showing the point diffraction interferometer can be used to measure the near infrared wavefront.