Active surface thickness optimization and prototype testing of an aluminum deformable mirror for spaceborne electro-optical payloads

Deformable mirrors (DM) are critical components of active optics systems that are used to compensate for wavefront correction in spaceborne electro-optical (EO) payloads. In comparison to glass mirrors, a metal-based mirror is lighter in weight, has more compact design, is less expensive, and can be manufactured quickly. Furthermore, aluminum has higher yield strength than glass, which is advantageous in the event of mirror deformation. We present finite element (FE) optimization of an aluminum mirror’s active surface for the contradictory requirements of flexibility for mirror deformation and stiffness for mirror fabrication. The active surface thickness considered for optimization is 1 to 6 mm for varied mirror diameters ranging from 80 to 100 mm. Aspects related to mirror fabrication on single point diamond turning (SPDT) machine have been considered during the design stage. We compare correction accuracy targeting more than 95%, peak to peak actuator stroke, and root mean square error for various diameters and thicknesses. The optimized mirror was fabricated using SPDT and tested using an interferometer. Later, a DM prototype was built using commercially available piezoelectric actuators, and targeted aberrations/shapes were generated to demonstrate the accuracy of correction.