Digital Micromirror Device(DMD) is a chip in MOEMS technology that controls the smallest micromirrors as light switches and is used in DLP projectors (Digital Light Processing). The micromirrors are arranged in matrix form as a mirror array. They can be tilted, have a mirrored surface and have an edge length of only about 14 µm.
The number of micromirrors depends on the resolution that can be displayed and on the projection concept, which can use single-chip or three-chip technology. Thus, there can be several million micromirrors on a DMD chip, which can be tilted like a seesaw up to 5,000 times per second.
The mirrors are tilted electrostatically by about 10° in both directions and are triggered by the memory cell located under the mirror. Depending on the charge of the memory cell, the micromirror is held in one position or the other. The projected light brightness can be controlled by the switching times. The necessary control is done with pulse width modulation( PWM). If the mirror reflects the incident light for a longer time, the brightness is higher, in the opposite case darker. With pulse width control, it is quite possible to achieve `2^8` (256) differences in brightness. With dark control, the micromirror is tilted more and the reflected light beam is directed into an absorber where it is absorbed.
Since the focusing of the light beam with a special lens precisely hits the micromirrors, there is only a small amount of stray light that falls on the neighboring mirrors. This results in high contrast with contrast values of 2,500:1. Recent developments with a further reduction in stray light are expected to provide contrast values of 5,000:1.
DMD chips are also used for pinpoint light distribution in automotive headlights.