Micromirror

A micromirror is a small reflective surface used in microelectromechanical systems (MEMS). Typically tens to hundreds of micrometers across, the mirror is mounted on a hinge or torsion frame and is actuated to tilt or rotate. By changing its orientation, the micromirror redirects incident light with high speed and precision. In many devices, an array of micromirrors forms a programmable surface where each element acts as an individual pixel or channel.

Actuation methods for micromirrors include electrostatic, electrothermal, and piezoelectric approaches. Electrostatic actuators, such as capacitive comb drives or parallel-plate configurations, are common due to low static power consumption and fast switching. Electrothermal actuators can achieve larger angular deflections but use more power and may generate heat. Piezoelectric actuators offer high stiffness and precision in some designs. The reflective surface is usually coated with materials like aluminum or silver to maximize reflectivity over a broad spectral range, with protective or dielectric coatings to enhance durability and environmental resistance.

Applications for micromirrors span displays, sensing, and optical control. In display technology, arrays of micromirrors are central to digital light processing (DLP) systems, where mirrors switch rapidly to modulate light and form images. Beyond displays, micromirrors are used in optical switching networks, laser scanning systems, adaptive optics in astronomy, and certain microscopy modalities for fast light modulation and beam steering. They are also explored for compact projectors, holographic devices, and other precision illumination applications.

Manufacturing and reliability considerations include MEMS fabrication on silicon substrates, with surface or bulk micromachining to create movable mirrors and torsion supports, followed by metal coatings. Challenges encompass stiction during release, packaging that protects moving parts, repeatability of angular position, and wear over many cycles, all of which influence long-term reliability in commercial products.