+  A Finite-Element Model of the TI DLP Mirror

The 3D solid model for the single mirror below is based on public literature and educated guesses for the fabrication process and device dimensions.

Texas Instrument DLP

The following shows the mesh on one of the drive electrodes. It is used for electrostatic capacitance & charge simulations.

Texas Instrument DLP

The surface charge distribution below is calcuated by a boundary-element method (BEM). This will determine the electrostatic force which will rotate the mirror into contact with an underlying electrode at the same potential.

Texas Instrument DLP

The tilted mirror is shown in three different perspectives below. The color countors are the magnitude of the von Mises stress, and are highest in the regions of contact and in the torsional arms.

Texas Instrument DLP
Texas Instrument DLP
Texas Instrument DLP

Finally, the deflection versus a single drive electrode voltage is plotted, showing pull-in to contact and beyond allowing for slight bending of the contact springs.

Texas Instrument DLP

+  Mechanical Property Characterization

MEMS Polysilicon Beams

This 100X Nomarski photo of microelectromechanical (MEMS) clamped-clamped beams shows that the 800um and 1mm long are buckled because of excessive compressive stress. These beams are fabricated using polysilicon micromachining.

The airgap separating the capacitive electrodes formed by the beams and the substrate narrows with applied voltage, allowing the beam to deform and pull-in (contact). With oscillating voltages, the beams can mechanically resonate at several 10's of kilohertz and higher.

+  Electromechanical Analysis of a Micromirror

TiltingMirrorVideo

(Click to animate image above)

This 150X interferometric black and white image of an unactuated octagonal mirror shows spherical curvature. The AVI animation linked to the photo (Real Audio Player needed, 776k,avi) is a sequence of static images 0 to 100 volts in 5 volt increments. Note: Between a full-phase of intensity variations, each fringe measures a surface height difference of 225nm.

The multiple fringes can be deconvolved to give a precise and continuous elevation plot of the mirror surface. By using IDEA an FFT-based deconvolver, the interferometric data produces the following contour plot (101k,jpg).

This animation (1.8M,mpeg) shows the dual-axis gimbal action of the micromirror based on 3D FEM results from CoventorWare.