Dynamic response of ferrofluidic deformable mirrors using elastomer membrane and overdrive techniques

TL;DR

This paper demonstrates significant improvements in the response time of ferrofluidic deformable mirrors through the use of elastomer membranes, overdrive control techniques, and improved electronics, achieving potential millisecond-level settling times.

Contribution

It introduces a novel elastomer membrane coating technique combined with overdrive control to drastically reduce the response time of ferrofluidic mirrors.

Findings

Response time reduced from 100ms to 25ms with overdrive.

Membrane addition halves the response time further.

Combined techniques suggest possible millisecond response times.

Abstract

Here are presented the experimental results obtained with a ferrofluidic deformable mirror controlled by electro-magnet actuators. Using a step input through a single actuator we obtain a steady-state settling time of 100ms; however, different combinations of overdrive inputs can be used to decrease it to 25ms. Also, a new technique which consists in laying down an elastomer membrane, coated with an aluminum film, on the ferrofluid is discussed. By adding the membrane on the ferrofluid, it further decreases the time response by a factor of 2. Furthermore, the thin aluminum layer improves the reflectivity of the mirror. Finally, using the membrane and the overdrive techniques combined, the time response is improved by a factor of 20. Numerical simulations show that ferrofluidic mirrors using membranes and improved electronics should reach settling times of the order of a millisecond. Presumably even lower settling times could be possible.