High-bias membrane mirror

Abstract

The deformable mirror is the single most expensive component in atmospheric correction systems of 100 actuators or less. An innovative design for a membrane mirror is proposed as a cost effective alternative to conventional deforniable mirrors. The mirror features a high voltage (250v) bias on the mirror surface, which eliminates many of the disadvantages of past membrane mirror designs. The High Bias Membrane Mirror provides a rugged, reliable, inexpensive unit suitable for low power, low density wavefront correction systems. As such it is ideal for compensated imaging systems for surveillance and astronomy, which may require only partial compensation. .0 INTRODUCTIONWith the surging interest among the astronomical and surveillance communities to incorporate partial atmospheric compensation to improve imaging systems, an inexpensive, easily fielthble alternative to traditional deformable mirror (DM) technology is an immediate requirement. A deformable mirror is the single most expensive component in wavefront correction systems of 100 subapertures (actuators) or less. Furthermore, they are traditionally bulky, they normally require high actuator voltages, and the connections between the actuators and the surface are fragile. In certain cases, manufacturing problems can cause artifacts such as surface ripple.Adaptive Optics Associates (AOA) has developed an alternative to traditional DMs for low power, low density, low cost applications: the High Bias Membrane Mirror (HBMM). This mirror promises to be the choice of the future for lightweight, low voltage, rugged, reliable, simple DMs.AOA has made a number of design decisions regarding the mirror based on its extensive experience with deformable mirrors in system, laboratory, and field conditions. From our experience with a large conventional mirror, we are aware of both the need and the difficulty of repairing a conventional DM. The HBMM has no complex electromechanical actuators--the one obvious potential repair is replacing the membrane itself, an easy and inexpensive task.In addition, field experiments have sometimes required installing wavefront sensors on the body of the telescope to maximize field of view and minimize light loss from intermediary surfaces. Although we have considered putting the entire adaptive optics system on the telescope, it would be extremely difficult given the bulk of the current hardware. However, the HBMM provides a critical piece of hardware that could conceivably make such a scenario feasible.AOA has worked previously with other membrane deformable mirrors under the Optical Divergence Sensor (ODS) contract1. The prototype mirror for that system had several problems, including relatively high voltage drivers (±lOOv), low deflection, and very tight machining tolerances. Others have built similar membrane deformable mirrors in the past with similar drawbacks. We feel that the innovation described here will transform a technical curiosity into a reliable deformable mirror suitable for many applications.Unlike a typical membrane mirro...