| With the increasing demand for large-aperture optics,which find extensive use in frontier fields such as astronomy,aerospace,energy,and remote sensing,the development trend of interferometric systems is towards larger apertures.Larger aperture interferometric systems face more difficult problems in design,assembly,and testing.This paper studies the key technologies required for interferometers with a meter-scale aperture,based on the maximum large aperture interferometer on the market,which isФ800 mm.It investigates the wavelength tuning phase shift,system design,collimated wavefront testing,measurement and calibration of surface maps of large-aperture optical flat in the meter-scale aperture interferometer（Ф1000mm）.The research of optics,mechanics,electronics,and computer technology of the meter-scale aperture interferometer has been completed.The main research work is as follows:The optical system and supporting system of the meter-scale aperture interferometer are designed,and key technical issues such as the influence of the wavefront caused by the inhomogeneity of the meter-scale optical material refractive index are analyzed.The optical configurations of interferometer are compared,and the modular design is adopted to facilitate hierarchical assembly and measurement.The Fizeau interferometric system is designed withФ100 mm interferometer as the basic module,Ф100 mm—Ф1000 mm non-focal system as the beam expansion module,Ф1000 mm TF and RF as the interferometric cavity.The collimated wavefront of the meter-scale aperture interferometric system will be affected by the inhomogeneity of the refractive index of the meter-scale aperture optics.We analyzed the influence of the inhomogeneity of the refractive index in the radial direction of theФ1000 mm collimating lens and the transmission flat,considering the order of the inhomogeneity is 10-6magnitude at home and abroad.The simulation of the interferometric system is established,and the interferometric measurement results influenced by the wavefront error is analyzed within the cavity length of 1 m～3 m.Optimizing the surface map of theФ100 mm aperture beam expander and the non-working surface of TF is proposed to compensate the influence of the inhomogeneity.In order to solve the problem of testing the collimated wavefront in meter-scale aperture optical system,a scanning and reconstruction method with pentaprism array based on asymmetric sampling is proposed to measure the three-dimensional distribution of meter-scale aperture collimated wavefront.The slope in the X direction of the collimated wavefront is measured simultaneously by three parallel pentaprisms parallel to the scanning direction,and the slope in the Y direction of the collimated wavefront is measured simultaneously by three series pentaprisms perpendicular to the scanning direction.The measured slope is fitted by the derivative of the 4～11 terms of Zernike polynomial to obtain the three-dimensional distribution of the collimated wavefront represented by Zernike polynomial.The feasibility and accuracy of the reconstructed wavefront using the slope of the three lines are verified by simulations.The theoretical error of the method is analyzed and the error is calibrated in the experiment.The proposed method is carried out to measureФ1000 mm aperture collimated wavefront,and the results are compared with the testing results using interferometry.The numerical values and distribution form of the results obtained by the two methods are consistent.Under the long cavity length,the collimated wavefront of the meter-scale aperture interferometer is detected by interferometry.The assembly and adjustment of the meter-scale aperture interferometer system is completed.A hybrid self-calibration method is proposed to eliminate the reference surface error,as the reference surface error is non-negligible when testing meter-scale optical flat in sub-aperture stitching interferometry.The shift-rotation operations are leveraged to generate a couple of sub-apertures covering the surface under test,whereby a ring of sub-apertures and a central sub-aperture are acquired by rotations and a lateral shift,respectively.The shift-rotation method and the maximum likelihood method are proposed to obtain the rotationally asymmetric components of the test surface.The rotationally symmetric components of the test surface are acquired utilizing the measured data before and after the shift.Simulations are conducted and the errors of the proposed method are analyzed and discussed.Sub-aperture testing experiments of a 100-mm aperture flat are performed and compared with full-aperture absolute measurement results.The stitched errors with 0.018λPV and 0.0032λRMS are obtained.The successful verification of the stitching method lays the groundwork for testing meter-scale optical flat based onФ800 mm aperture interferometer.A 1000 mm aperture lightweight Si C mirror has been designed and manufactured which is suitable for the hybrid self-calibration method.The absolute surface maps of the Si C mirror is obtained using sub-aperture stitching interferometry with commercially availableФ800 mm aperture interferometer.The surface maps of the TF are then measured and obtained through the Si C mirror,realizing the error traceability and transmission.Measuring the reference surface of TF in theФ1000 mm aperture interferometer,with Si C mirror.Then,the absolute surface maps of TF（excluding power）are obtained by eliminating the surface maps of the Si C mirror,which engendering the error transmission fromФ800 mm aperture interferometer toФ1000mm aperture interferometer.The power term of TF is measured with three-flat method,and the testing of TF is completed.The surface maps of RF are measured with TF.Simultaneously,the measured surface maps on the Y-direction axis through three-flat method can be mutually verified with the full-aperture surface maps.After the surface measurement of TF and RF,the performance parameters of the meter-scale aperture interferometer are tested and the measurement uncertainty analysis of the meter-scale aperture interferometer is analyzed and discussed.The system accuracy is determined to be 0.092λ（58.22 nm）,the cavity accuracy is0.016λ（10.12 nm）,the repeatability is 0.00081λ（0.51 nm）,and the stability is 0.11λ（69.61nm）. |
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