| The giant laser device used in ICF experiment is the largest optical engineering ever constructed by human beings,which needs thousands of ultra-precision large-aperture optics,the diagonal dimensions of some large-aperture optics are close to or even more than 1 meter,in order to ensure that the wavefront characteristics of the optics can meet the requirements of ICF,it is necessary to measure and control the wavefront error accurately in the whole manufacturing process,which poses a new challenge to the traditional wavefront error detection method,the main work was carried out as follows:The absolute measurement of wavefront error can improve the measurement accuracy by deducting the systematic error of interferometer.However,the accurate deduction of systematic error of large aperture interferometer is an international difficult problem.Firstly,an n-position rotation absolute measurement method of wavefront error based on rotation average and oddeven function is proposed.The surface error of interferometer standard mirror is obtained by using the characteristics of odd-even function and rotation average approximation,the absolute measurement of the wavefront error of ?600mm large aperture optics is realized.Then,absolute measurement technique of wavefront error based on oblique incidence is developed.The surface error of the interferometer is effectively deducted by using the property of oddeven function and the iterative algorithm of surface shape recovery,the wavefront error data of the measured components in the tilted state was converted to the normal incidence state by using the BICUBIC interpolation algorithm,the absolute measurement of wavefront error of some meter-sized optics in ICF is realized.At the same time,this paper presents a rotating mechanism composed of lifting structure,rolling pulley and soft tooth synchronous belt to realize the rotation of large-diameter flat crystal,the stress,deformation and absolute measurement error of large-aperture flat crystal are minimized.It is verified that the absolute measurement method established in this paper can improve the measurement accuracy of wavefront error of typical optics in ICF by about 10%.The Oblique incidence measurement method can only extend the measuring aperture of the interferometer in one dimension.The Oblique incidence angle can not exceed 60,and the corresponding measuring aperture can not extend more than 2 times due to the limitation of reflectivity of the measured element and measurement error.The sub-aperture stitching measurement technology can realize the wavefront error measurement of the larger aperture optics by using the smaller aperture interferometer,but the positioning accuracy,angle change,and vibration of the measured element during the stitching measurement will affect the accuracy of the measurement.This paper focuses on the problem of heavy load,long stroke and high precision movement in the measurement of meter-sized Optics splicing,proposed and verified the precision splicing device based on air-floating mechanism,made sure that the measured element moves along the guide rail precisely and straightly,the angle deviation of the splicing device is not more than 5"and the positioning error is not more than 50?m.The maximum deformation of the meter-grating substrate and the large-diameter nd: Glass are 4nm and 1.2nm respectively,and the measurement of the wavefront error of the meter-sized optics is realized.Compared with direct measurement,the PV and RMS deviation of reflected wave surface error is 0.010? and 0.003?,the corresponding values of the transmitted wave surface errors are 0.016?and 0.001?,which all meet the measurement requirements.The wavefront error detection of thousands of ultra-precision large-aperture optics in ICF is a very heavy task,and the traditional manual operation can not avoid the disturbance of the environmental temperature field,flow field and the balance state of the tested elements,in order to reduce the influence of interference on the test results,it is necessary to carry out the secondary balance to the measuring environment and the tested components,which greatly reduces the production efficiency.In addition,the manual handling of large-caliber Optics weighing tens or even hundreds of kilograms is not only labor-intensive,but also poses a high safety risk.Based on the 24-inch laser plane interferometer,an automatic measuring system for measuring the wavefront error of meter-sized Optics is designed and developed with the main idea of controlling the whole process of stress and deformation,the automation of the whole process from temperature balance,transfer,attitude adjustment to wavefront error measurement is realized.The detection capability of a single device is up to 8 pieces per day,the Test of 8optical elements can be completed in 64 minutes if the balance time is eliminated,which greatly improves the work efficiency and reduces the Labor intensity of the staff.At present,the mainstream large-aperture interferometers have all realized the digital acquisition and digital analysis of interferometric images,but the data processing software in the system has only some general functions,it can not meet the evaluation requirements of the wavefront characteristics of large-aperture Optics in ICF.Based on the theory of numerical analysis,according to the special requirements of ICF,the data processing flow,data processing method,parameter representation method and special data analysis software are established,it lays a foundation for evaluating the wavefront characteristics of meter-sized Optics in ICF.Finally,the engineering application of precision measurement technology of wavefront error of meter-sized optics is researched,and the validity of the absolute measurement method is further verified,the optical nonuniformity of nd: Glass Material and the wavefront errors of nd: Glass Element,polarizer element and meter-level grating element were measured systematically,based on the measurement results,the wavefront characteristics of all kinds of components and the causes of wavefront errors are analyzed in detail.It provides a powerful support for further improving the manufacturing precision of meter-sized Optics in ICF. |
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