Electronic control of a digital micromirror device for projection displays

Digital micromirror devices (DMDs), developed as spatial light modulators for video projection systems, have evolved to the hidden hinge concept. The DMD consists of a pair of torsion hinges that support a yoke assembly on which a mirror-supporting post and mirror are attached. Underlying electrodes supply the electromotive forces to rotate the mirrors about the axis of the torsion hinges. To tilt the mirror to a desired position, true and complementary data are applied to the two electrodes. The resultant electrostatic force tips the mirror toward the desired position. An additive bias voltage is applied to the mirror. The additional torque applied to the hinges by the bias EMF tilts the mirror to its mechanical stop. It is important to note that the mirror will remain electromechanically latched in this position, regardless of the electrode data, as long as the bias voltage is maintained. The time required for the mirror to transit from the “on” position to the “off” position is 20 μs. This response allows the use of binary pulse-width modulation (PWM) to digitally control “on” versus “off” time. The observer of the display naturally integrates the binary optical stream to perceive continuous tones