A novel high-speed piezoelectric deformable varifocal mirror for optical applications

We describe the characteristics of a microelectromechanical deformable optical component: a parabolic focusing mirror having a focal length that is controlled by piezoelectric actuation of thin-film PZT. Devices of two different sizes were tested and have resonant frequencies in the low MHz range, nominal focal lengths between 1500 and 2000 /spl mu/m and numerical apertures of approximately 0.10 and 0.05. Tuning ranges of several hundred microns have been demonstrated. Finite element modeling is described and compared to measured results. The equations required for device scaling are provided to show some of the tradeoffs that can be made between aperture size, mechanical bandwidth and focal length tuning range.