How it Works

Core Building Blocks

The Interferometric Modulator (IMOD ) element is a simple MEMS (micro-electro-mechanical system) device that is composed of two conductive plates. One is a thin film stack on a glass substrate, the other is a reflective membrane suspended over the substrate. There is a gap between the two that is filled with air.

The IMOD element has two stable states. When no voltage is applied, the plates are separated, and light hitting the substrate is reflected as shown above. When a small voltage is applied, the plates are pulled together by electrostatic attraction and the light is absorbed, turning the element black. This is the fundamental building block from which Qualcomm® mirasol displays are made.

Display Components

IMOD elements are minuscule, typically 10-100 microns on a side (400-1,000 dots per inch). Therefore, many IMOD elements are ganged and driven together as a pixel, or subpixel in a color display. The color of the IMOD element is determined by the size of the gap between the plates. As shown, the blue IMOD element has the smallest gap and the red has the largest. To create a flat panel display, a large array of IMOD elements are fabricated in the desired format and packaged. Finally, driver chips are attached at the edge to complete the mirasol™ display.

Bistable

IMOD element memory is crucial to producing a high quality display. IMOD elements, which make up the IMOD pixels, possess electro-mechanical memory called hysteresis. The hysteresis effect shown in the diagram works somewhat like the pull top on an aluminum can. Once the reflective membrane has been pulled down, it requires less energy to hold it than was exerted in pulling it down. This bistability not only allows the mirasol™ display to replace the non-linearity of an active matrix device, it can also act as a real memory element. An explanation of the IMOD element operation is detailed next to the diagram.