Actuating methods of quasistatic micromirrors for active focus variation

Abstract

For zoom and focus applications in the UV and IR spectral range mirrors with actively deformable surfaces are promising for reflective adaptive optics as an alternative to refractive optics. To realise an adjustable focus length interval from infinity to the centimetre range the needed surface deformation can be described by a hemisphere. For shorter focus lengths and optical on-axis applications the parabolic shape has to be used. The actuation principle of a quasistatic micromirror with actively deformable surface can be realised using electrostatic, ther-mo-mechanic, piezoelectric or electromagnetic effects. This paper compares electrostatic, thermo-mechanic and piezoelectric actuation methods for deformable micromirrors. Thereby models of curved thin plates and estimations on power consumption for low frequency or quasistatic operation are discussed. Due to the low power consumption and the low driving voltage, the piezoelectric effect is determined as most promisin g driving principle for devices used in mobile applications

Thickness dependence of piezo-bimorph adaptive mirror bending

“…a result derived by Conrad et al 18 Such a case may arise if the thick mirror substrate were replaced by a thin wafer.…”

“…Here, following Conrad et al, 18 we substitute thermal strain with piezoelectric strain, which, by design, occurs in a direction perpendicular to the applied voltage, in the long direction of the mirror. This strain is proportional to the coefficient of the piezoelectric tensor, d 31 , and the applied electric field, Ez: d 31 Ez.…”

Aluminum nitride thin film development using statistical methods

“…Other, in this work not presented models for the (00.4) diffraction peak height and for the full width at half maximum values of the (00.2) and (00. 4 (Fig. 14) regression coefficients normalized absolute value / % to film thickness normalized grain size interactions preferred AlN grain orientation.…”

“…The development of highly textured AlN thin films used as a piezoelectric active material in micro-opto-electromechanical systems (MOEMS), such as actively focusing micro mirrors [4] are of prior interest for this work. To achieve piezoelectric properties within polycrystalline AlN thin films the polar axis and therefore the textural alignment plays a dominant role.…”