Research On High Precision K-B Mirror Surface Detection Technology

Advanced light sources such as the new generation synchrotron radiation source and X-ray free electron laser have become an indispensable research tool in many disciplines.Among them,the K-B mirror system is the key focusing optical element in the advanced light source,while the surface accuracy required better than 0.2 nm RMS,residual slope error within 0.1 μrad and roughness less than 0.1 nm RMS.At present,stitching interferometry technology based on angle information has gradually become the main development trend of K-B mirror detection technology.Stitching interferometry technology based on angle information can effectively expand the measurement range of the interferometer,so as to obtain more abundant surface detection information.It is an important detection technology in K-B mirror measurement technology.The stitching interferometry technology based on angle information mainly reduces the stitching error by introducing a high-precision measuring device or relying on the accuracy of the displacement turntable itself.There are few reports on the data processing methods of diagonal stitching.This paper mainly focuses on the research of K-B mirror surface detection technology,focusing on a universal stitching data processing method based on angle information,and providing a cross-validation between the micro-stitching interferometry and the CGH stitching interferometry technology.The specific research work is divided into three parts:1.To solve the mismatch of adjacent sub-aperture overlap areas,a sub-aperture overlap area matching algorithm based on Zernike polynomial is presented: Several sets of matching feature pairs are obtained by minimizing the Zernike polynomial of order3 or more in a particular overlapping area to determine the overlapping area location,which improves the point-to-point matching accuracy of the overlapping area.At the same time,to solve the problem of inaccurate calculation of the spatial angle of adjacent subaperture,a subaperture spatial position and posture solution algorithm based on dual quaternion is presented: the sub-aperture spatial angle adjustment process in classical stitching method is separated from the stitching operation by using the even quaternion sub-aperture spatial position adjustment method as an independent link in the stitching process,which reduces the stitching accumulation error caused by the error in solving the sub-aperture spatial angle.In the key technology of angular stitching,the stitching process is further subdivided into: overlapping area alignment,sub-aperture spatial posture adjustment and stitching.2.A self-residuals iteration algorithm is presented.Based on the common stitching algorithm,using the reversible property of the principle of consistency of sub-aperture overlap areas,known information or constraints are used to iterate repeatedly between the base sub-aperture and the overlap areas of adjacent sub-apertures to obtain more accurate adjustment parameters.The comparison experiment verifies that the selfresidual iteration algorithm can effectively improve the stitching accuracy on the basis of smooth stitching.3.To solve the problem of inaccurate subaperture adjustment aberration model based on CGH splicing interferometry technology,a subaperture adjustment aberration model based on 2-D Chebyshev polynomial is presented.Based on the rigid body rotation theorem and wave aberration theory,the expression of aberrations in overlapping areas caused by a certain amount of adjustment of adjacent sub-aperture is quantitatively analyzed.Combining with the second-order Chebyshev polynomial,the subaperture adjustment aberration model is deduced,and the stitching interference theory based on CGH is improved.Relevant simulation and experimental studies have been carried out.The accuracy analysis shows that the repeatability of the technology is better than 0.69 nm RMS,and the measurement accuracy deviation from CGH is better than 1.39 nm RMS.