Research On Optical Surface Self-calibration Measurement Technology Based On Shift And Rotation Difference Reconstruction

With the rapid development of modern optical technology,optical systems with high-precision optical components have been widely used in the filed such as astronomical optics,space optics,inertial confinement fusion,deep ultraviolet and extreme ultraviolet projection exposure systems,thus challengeing the processing and measurement of high-precision optical components.On the one hand,the development of high-precision optical components is moving toward ultra-high-precision quality.For example,the extreme ultraviolet lithography objective lens requires a 0.1 nm root-mean-squares error.On the other hand,the shape of the components is more and more complicated.For example,the free-form optical system develops from infrared to visible light or even ultraviolet,and the accuracy requires 0.1?m or higher,and the surface sag can reach millimeters or even tens of millimeters.These optical components pose a very high challenge to the level of optical inspection.At present,commonly used optical testing methods mainly include interferometry and profile scanning method.The measurement accuracy of interferometry is mainly limited by the surface accuracy of the reference surface and the accuracy of the profile scanning method is mainly subject to the motion error of the scanning guide.Adoptting the self-calibrated method based on shift and rotation difference reconstruction and multi-sensor error separation method,this paper studies the error separation of reference surface in interferometry and straightness error separation in profile scanning method.The research work of this paper can be divided into the following aspects:(1)The merits and drawbacks of traditional translation shearing method and rotation-shift method are analyzed.The double shear-based shearing method and the rotation-shift are proposed,which can simultaneously realize the reconstruction of large shear and pixel-level resolution.In the aspect of reconstruction algorithm,the matrix method based on linear equations is used to express the relationship between the original surface and the measurement surface,which can realize the reconstruction without theoretical error.The virtual sub-aperture stitching solves the problem of excessive memory consumption of the matrix method.(2)For the absolute testing of the flat,the traditional three-flat method and the extension method are summarized and compared.Firstly,trotation-shift three flat method is proposed.The traditional three-flat method is added with a 90° rotation and the double shear translation of the measuring component,which solves the problem of loss of angular harmonic components in the traditional three-plate method and the extended method,and can reconstruct the surface without theoretical error.From the profile to the three-dimensional shape reconstruction,the reconstruction principle of themethod is explained,and then the matrix-based matrix solving method is proposed.(3)A multi-translation rotation method based on angle measurement is proposed,which can be applied to the absolute testing of optical elements with various shapes.For non-circular optical components,the three flat method and the extented method cannot be directly applied.For the absolute testing of such optical components,this paper proposes a multi-translation rotation method based on angle measurement,which only needs the relative translation and rotation of the reference surface and the measured surface,and measures the change of the pitch angle during the translation by the angle-measuring device.In order to extend the proposed method to the testing of large-scale optical components,the idea of sub-aperture stitching is introduced.By analyzing the second-order error accumulation effect and propagation law in traditional sub-aperture stitching method,angle monitoring is proposed to suppress the cumulative effect.(4)The concept of virtual multi-sensor is proposed.Combined with the splicing of the auxiliary profile,it can realize the reconstruction of profile to three-dimensional topography.This paper first introduces the research status and existing problems of traditional multi-sensor error separation methods.Learning from the view of the angle-based multi-translation rotation method proposed in absolute testing,this paper proposes a double shear scanning method to decouple the zero point error and the angle error.The influence of the angle error on the reconstruction result is analyzed.Based on the simulation results,an improved double shear scanning method is proposed to calibrate the systematic error in the angular error through the external reference flat.Based on the profile error separation method,an auxiliary line stitchinmg method which can realize three-dimensional surface reconstruction is proposed.