Micromirrors

Micromirrors are tiny, high-precision reflective elements used in microelectromechanical systems (MEMS). Each mirror is typically on the order of tens of micrometers across and is mounted on a hinge on a silicon chip. Arrays containing thousands to millions of such mirrors form the core of digital light processing (DLP) devices and other optical scanning systems.

Most micromirrors are mounted on a torsional hinge and coated with a highly reflective metal, such as aluminum. They are individually addressable by underlying electrode structures, which apply voltages to tilt the mirror. Electrostatic actuation is the predominant mechanism in commercial devices, though other actuation methods have been explored in research settings. The mirrors are designed for rapid, repeated movement and are packaged to protect them from contaminants while allowing optical access.

In operation, each mirror can be driven between two stable positions. In DLP-based systems, the mirrors reflect light toward a screen when in the on state and redirect light away in the off state, enabling high-resolution, grayscale imaging. Grayscale is typically achieved through temporal dithering or modulation rather than analog analog tilt levels. Color is produced by modulating illumination, often with a color wheel, RGB LEDs or lasers.

Applications extend beyond projection displays to optical switching networks, beam steering for fiber-optic communications, and scanning systems used in LIDAR, astronomy, and microscopy. Advantages of micromirror arrays include fast switching speeds, high brightness and contrast, high fill factor, and compact, solid-state construction. Limitations can include finite tilt angles, mechanical wear over time, nonuniformity across the array, and, in color-wheel-based systems, perceptual artifacts such as the rainbow effect. Development and deployment are closely tied to MEMS fabrication and precision drive electronics.