Using the Modeshapes of a Vibrating PVDF Film as a Deformable Mirror Surface

One of the challenges of all telescope imaging is the adverse effects of atmospheric turbulence in the optical path. These effects can be mitigated by the use of Adaptive Optics (AO) and Digital Image Processing (DIP). However, it is always desirable to correct as much as possible with AO prior to attempt any further corrections with DIP as more of the original signal can be retained by optical means. The central element of a modern adaptive optics system is its deformable mirror which can be considered as a micro-mechanical device. The surface curvature is made to vary by means of an array of actuators of different technologies and a bank of sophisticated control circuitry. The basic idea is to reproduce the opposite aberration on the mirror surface as a combination of fundamental deformations described by a set of polynomials called Zernike polynomials. The plots of these Zernike polynomials bear great resemblance to the modeshapes of a circular membrane under tension. In this paper, we are presenting encouraging test results of a vibrating PVDF (Polyvinylidene fluoride) film at its natural frequencies. The possibility of using inexpensive PVDF deformable mirrors has the prospect of increasing the speed as well as the affordability of adaptive optics systems while reducing their complexity. An emerging field of application for lightweight and low cost AO systems is the next generation of micro UAVs (Unmanned Aerial Vehicles).