A large size MEMS scanning mirror for speckle reduction application

Abstract

Based on microelectronic mechanical system (MEMS) processing, a large-size 2-D scanning mirror (6.5 mm in diameter) driven by electromagnetic force was designed and implemented in this paper. We fabricated the micromirror with a silicon wafer and selectively electroplated Ni film on the back of the mirror. The nickel film was magnetized in the magnetic field produced by external current coils, and created the force to drive the mirror's angular deflection. This electromagnetically actuated micromirror effectively eliminates the ohmic heat and power loss on the mirror plate, which always occurs in the other types of electromagnetic micromirrors with the coil on the mirror plate. The resonant frequency for the scanning mirror is 674 Hz along the slow axis, and 1870 Hz along the fast axis. Furthermore, the scanning angles could achieve ±4.5 • for the slow axis with 13.2 mW power consumption, and ±7.6 • for the fast axis with 43.3 mW power consumption. The application of the MEMS mirror to a laser display system effectively reduces the laser speckle. With 2-D scanning of the MEMS mirror, the speckle contrast can be reduced from 18.19% to 4.58%. We demonstrated that the image quality of a laser display system could be greatly improved by the MEMS mirror.

Optimization of MOEMS Projection Module Performance with Enhanced Piezoresistive Sensitivity

“… Schematic measurement setup: the 2-Dscanning mirror was driven independently by function generators [ 31 ]. …”

Large-Area and Ultrathin MEMS Mirror Using Silicon Micro Rim

“…The large-area mirror often overcomes the film deformation by employing a thick mirror membrane, and thus maintains the high flatness of the mirror during the actuation. For instance, a single-crystal-silicon (i.e., SCS) as thick as a few tens of micrometers is commonly used as a flat substrate for the movable membrane due to its low residual stress and low surface roughness [ 8 , 9 , 10 ]. However, the thick membrane significantly limits an actuation displacement without high enough driving powers due to its non-negligible mass, and thus hampers the MEMS actuator with further large-area mirrors.…”

Modeling and Optimization of a Novel ScAlN-Based MEMS Scanning Mirror with Large Static and Dynamic Two-Axis Tilting Angles

“…Generally, the large aperture size and mass of a MEMS scanning mirror limits the possibility of achieving a larger scanning angle and a higher operation frequency unless the actuation moment is high enough [ 9 ]. Up to now, to overcome the aforementioned limitations of PZT-, AlN- and ScAlN-based micromirrors, a MEMS scanning mirror with two-dimensional static and/or dynamic tilting angles of greater than ±15° in the centimeter range is desired and being pursued for laser projection applications [ 11 , 31 ]. In addition to improving the fabricate uniformity with low residual stress, raising the piezoelectric coefficient of ScAlN material and deploying multiple ScAlN layers, one of the most pressing areas of research needed to significantly promote MEMS mirror technology lies primarily in pushing novel advanced designs.…”