LINE-ADDRESSABLE TORSIONAL MICROMIRRORS FOR LIGHT-MODULATOR ARRAYS

This paper describes novel surface-micromachined torsional micromirrors for spatial light modulation. Typically, the aluminized polysilicon micromirrors have a surface of 30 by 30 mum2 and are suspended by 15 mum long and 0.4 mum wide beams. When a voltage higher than the switch voltage (around 30 V) is applied on the address electrode, the electrically grounded mirror rotates by an angle of up to 7.6-degrees and hits the landing electrode. The latter is also electrically grounded to avoid charge sticking effects. For the mirror to return to its initial position, the address voltage is reduced below the release voltage (around 20 V). Hence, the electromechanical system is bistable; by choosing proper voltages, single mirrors can be addressed individually in a two-dimensional array employing a hold line and an address line. An operating 32 by 32 mirror array is presented as a prototype structure for an application in a printing or projection display device.