MEMS scanners for display, imaging, and spectroscopy and their dynamic characterization

Abstract

Moving micro-mechanical structures combined with laser light sources and micro-optics enable a number of powerful applications in display, imaging, and spectroscopy. Examples of systems developed in our laboratory are: rotational scanners developed for micro-projectors, dynamic diffraction gratings with large out-of-plane motion developed for Fourier Transform spectrometers, and 2 degree-of-freedom MEMS stages that carry micro-lens arrays for laser beam steering and imaging applications. Precise control of motion is critical in all those applications. We developed a number of optical characterization tools for point-based and full-field dynamic characterization of micro and nano mechanical structures. In this paper, we first briefly discuss the applications and then describe the details of the optical characterization tools. First setup is a stroboscopic interferometry for dynamic deformation analysis. Second setup is a simple technique for simultaneous in-plane and out-of-plane measurement with nanometric precision. The setup is constructed using one photo detector and a Mirau-type interference objective. For out-of-plane measurements, interference fringes are used to compute the the deflection amount. For in-plane measurements, knife edge technique is used to modulate the reflected beam intensity using a sharp edge in the object. Third setup is a simple optical angle sensor for rotational mirrors, which uses only one bi-cell photo detector. The setup is able to measure amplitude, phase, and quality factor of torsional devices.