Research On High Precision Calibration Method Of Reference Flat In The Plane Interferometer

Large aperture plane optical element have been widely used in major national projects such as aerospace,astronomical exploration and high-power laser systems,therefore,research on surface shape detection of large aperture plane optical element is particularly necessary and important.The most common use of interference technique is to detect the plane shape.The Fizeau interferometer is a typical plane shape interference detection instrument,and its accuracy of measurement depends largely on the surface accuracy of optical reference plane.The increase of the aperture of the optical plane can lead to the raise of its own gravity,which will cause the gravity deformation of the reference plane,resulting in a great error on the test result of the planar element to be measured.Therefore,the calibration of the high-precision surface shape of the large-caliber reference plane becomes an essential part of the detection process and an inevitable way to improve the detection level of large aperture optical system.On the basis of the traditional three plane mutual check method for surface calibration,we used three plane cross calibration method for surface fitting based on Zernike polynomial fitting,combined with theoretical analysis and simulation of phase shift interferometry,the calculated error of interference fringes in phase shifting is 2 mm.At the same time,in view of 300 mm reference plane in the different way of clamping support,the thickness of the plane,plane size weight under the condition of deformation parameters,we used the method of finite element analysis to simulate and analyse.A more reasonable model T support for large caliber reference plane at six way of clamping support was selected,and this support mode reference the gravity deformation of up to 20 nm.Then,the influence of the deformation of the reference surface on the calibration results of the three-plane cross-check surface of Zernike polynomials was analyzed,and the deformation after deformation was up to 10nm.On the basis of this,a method to compensate the deformation of reference surface gravity deformation component is proposed.Finally,experiments on some standard planes of 100mm diameter were carried out with Zygo interferometer,by using Zernike polynomial fitting of three plane surface shape for the absolute calibration method,fixed gravity deformation in the interference wave.The final calculated reference plane is consistent with the PV of the nominal surface shape.Through the theoretical analysis,simulation and experiment,combined with the Zernike polynomial,this dissertation verifies the method of the calibration of the triplane mutual calibration and reliability of the calibration method of gravity deformation compensation,which provides important support for the high precision machining and inspection of the large caliber plane.