Electrostatic-pneumatic membrane mirror with positive or negative variable optical power

Abstract

A MEMS deformable mirror is described that uses a novel actuation scheme to increase the optical focus range. In this method electrostatic-pneumatic actuation is used to achieve a convex surface curvature of the mirror, while direct electrostatic actuation creates a concave surface. The fabricated device consists of two membranes made of the photoset epoxy SU-8. One membrane serves as the deformable mirror and the other one as the pneumatic actuator. The pneumatic membrane also provides a built-in valve for pressure equalization. The principle of operation, fabrication process and results are presented.

Range Extension of a Bimorph Varifocal Micromirror Through Actuation by a Peltier Element

“…Optothermal actuation via a laser was also reported [19]. A combination of electrostatic and pneumatic actuation was recently demonstrated to achieve convex and concave VFM surfaces [20]. An electrostatically-actuated VFM with simultaneous scanning capability has been reported by Sasaki et al [21], achieving a focal plane tuning range from -128 mm to +98 mm.…”

A Focus Control System Based on Varifocal Mirror for CO2 Fiber-Coupled Laser Surgery

“…Also it is possible to achieve large OPR even for mirrors with large diameter. In [14], a 4 mm pneumatic-electrostatic VM achieved an OPR of 21 m −1 , while in [15] a 3 mm hydraulic VM achieved more than 50 m −1 of OPR .…”

“…Finally, pneumatic and hydraulic VMs control the deflection of the mirror by using fluid to apply a pressure difference to the membrane. The pressure on the fluid can be controlled by embedding linear actuators on the device, using magnetic [13] or electrostatic actuation [14], or by using a microfluidic channel connected to a pump [15]. The main advantage of this method is that the mirror deformation is parabolic, which results in optimal focusing.…”