Performance test and analysis of 913-element deformable mirrors

In order to correct high order aberration for an adaptive optics (AO) system and make it operate normally at cryogenic temperature, a 913-element discrete actuators continuous facesheet deformable mirror (DM) was developed. A Veeco interferometer in Ø300mm diameter was used to examine partial static performance of the deformable mirror:the influence function of an individual actuator, flattening test and the correction capability of the deformable mirror about Zernike aberrations fitting. The surface of DM from 20℃ to -10℃ was measured by a 4-D dynamic interferometer. The testing results show that the max correction ability of the deformable mirror actuated by an individual actuator is ±3.5μm. The distance between the neighbor actuators is 9.8μm and the coupling between the neighbor actuators is 9.3%. The surface of the deformable mirror after flattening is really smooth, of which the PV is 66.0nm and the RMS is 5.0nm. The fitting capability of the Zernike polynomials of the 913-element deformable mirror satisfies the demand of the adaptive optics. The thermally induced surface deformation didn't influence the performance of DM at low temperature. According to these tests, the 913-element deformable mirror satisfies the actual demands of the adaptive optics system.