Measurement of space membrane mirror shaping based on fringe projection

In consideration of the inconvenience of dynamic measurement and the measuring limitation for surface shapes of mirrors in exciting measuring method,a shape measurement method based on sinusoidal fringe projection was proposed,and a test platform was built.Analysis and deduction indicates that the measurement uncertainty of the method is less than 0.385 μm and that of the platform is less than 4.25 μm.A standard spherical mirror was measured on this test platform to verify the feasibility of the platform.Finally,surface figures and surface figure errors of a Ф300 mm electrostatic stretching membrane mirror were measured with the proposed method and surface shape control algorithm.Results show that the measured values of center sag are consistent with theoretical ones.Furthermore,the RMS and PV values of shape surface are 5.214 μm and 39.327 μm,which has reduced about 30.17% and 23.7%,respectively.The results display that the shape measurement platform based on sinusoidal fringe projection meets the need of membrane mirrors for shape measurement and the membrane mirror surface shape control algorithm can control the membrane mirror to obtain the required surface shape and improve the surface accuracy.