Research On Gravity And Stress Decoupling Technology In Large-caliber Space Sic Mirror Detection

The large aperture optical element,that be used in space,requires that the ground test accuracy is consistent with the optical accuracy of space use.During processing,under the combined action of the gravitational field,the temperature field,the clamping stress and so on,the large aperture optical elements are prone to random changes in the shape of the surface.This kind of change,that is coupled with the machining error,is very difficult to separate from the actual error.In the different measuring methods and measuring process,the difference of the pose and position of the mirror will affect the uncertainty of the measurement results.It is an important foundation to ensure the quality of the large aperture mirror in space by improving the reliability of the measurement,and obtaining the true error of the mirror surface by decoupling analysis the measuring error that caused by multi factors,resolving the consistency of the mirror state under the coupling of various factors.In this paper,the Sic(silicon carbide)aspheric primary mirror of lm diameter is taken as the object of study,and the mechanical model is established by finite element analysis.The effects of gravity and supporting stress on the primary mirror deformation are analyzed.Zero compensation test principle of the vertical and horizontal placement of two measurement programs for surface detection.By using the finite element method and the mechanical model,the supporting scheme of 6-point floating support of the optical axis is simulated and analyzed,and the supporting structure of 6-point floating support is tested and verified experimentally.By using the method of multi-angle rotation,the mathematical model of gravity error separation is established by Zernike polynomial surface error analysis,and the method of separation of gravity error by wavefront reconstruction is designed.The support structure and the gravity rotation measurement can be seen that the six-point floating support structure effectively avoids the influence of the supporting stress on the surface shape of the reflecting primary mirror,and can ensure that,in the measurement process,The angle of the primary mirror can be used to obtain the correct measurement result,which can effectively reduce the support stress and the influence of gravity on the primary mirror reflection process.At the same time,a lm-diameter Sic reflection primary mirror error test optical path is built up.The two methods of the optical axis vertical placement and the optical axis horizontal placement are used to detect the mirror shape of the primary mirror,and the detection results of the two methods are compared Analysis,after the comparative analysis,the final selection of the primary mirror to position the mirror to detect the reflection of the primary mirror shape,is conducive to reduce and weaken the support stress and gravity on the reflection of the primary mirror detection accuracy.