A hybrid mechanical/electrostatic force actuator has been developed for use in deformable mirror applications. Some deformable mirrors, designed to correct errors in optical systems, use electrostatic forces between the flexible mirror surface and a backplane to control the shape of the mirror. Undesirable coupling of voltages used to generate electrostatic forces at various discrete zones on the mirror is a common problem.
The applied electrostatic force is a function of the voltage delta between the mirror and the backplane, and also the separation distance between the backplane and the mirror. Typical electrostatically figured mirrors control the voltage in individual zones to adjust mirror shape. Coupling can adversely affect the ability to control shape. In this hybrid actuator design, the zonal voltages are held constant and the separation of the backplane and the mirror is controlled using a precision piezoelectric actuator. This innovation solves the problem of zonal voltage coupling, and provides for better figure control of the mirror surface.