Electromagnetically Driven 2-axis Optical Beam Steering MEMS Mirror and Its Dependence of Actuation on Magnetic Field

Abstract

This paper describes development of electromagnetically-driven 2-axis MEMS mirror which steers an optical beam, and dependences of tilting angles on magnet shape, size and initial gap of planar coils - magnet surface. A reflective Au mirror (1.8×1.8mm²) can be tilted bi-directionally with electromagnetic force induced by current of planar coils and magnetic field of a permanent magnet. A developed MEMS mirror device (10×10×t0.2 mm³) was set on a printed circuit board (15×15×t1.0 mm³), and the board was fixed on a holder in which a magnet was inset. Utilized magnets were cubic ( 6, 8, 15mm and 5mm thick), cylindrical (φ6, φ8mm and 5mm thick) and spherical (diameter 8mm) for investigating efficient actuation. Initial gaps of planar coils and magnet surface were 0, 500, 1000 and 2000μm. Magnetic flux density and its gradient decreased with distance from magnet surface. Tilting angles of MEMS mirror increased with smaller square magnet and shorter distance, and were largest by using 6mm magnet and 500μm gap in which condition maximum tilting angle toward X and Y direction were 2.95 and 3.68 deg./mA, respectively. In addition, we have obtained 3D-OCT images of human finger tissue by using a Fourier domain fiber interferometer with a developed MEMS mirror.