Electromagnetically driven two‐axis optical beam steering MEMS mirror and its dependence of actuation on magnetic field

Abstract

SUMMARYThis paper describes the development of an electromagnetically driven two-axis MEMS mirror which steers an optical beam, and the dependence of the tilting angles on the magnet shape and size and the initial gap between planar coils and the magnet surface. A reflective Au mirror (1.8 × 1.8 mm 2 ) can be tilted bidirectionally with an electromagnetic force induced by the current of the planar coils and the magnetic field of a permanent magnet. A newly developed MEMS mirror device (10 × 10 × 0.2 mm 3 ) was set on a printed circuit board (15 × 15 × 1.0 mm 3 ), and the board was fixed on a holder in which a magnet was inset. The utilized magnets were cubic (6, 8, and 15 mm square and 5 mm thick), cylindrical (6 and 8 mm in diameter and 5 mm thick), and spherical (8 mm in diameter) to investigate efficient actuation. The initial gaps of the planar coils and magnet surface were 0, 500, 1000, and 2000 µm. The magnetic flux density and its gradient decreased with distance from the magnet surface. The tilting angles of the MEMS mirror increased with decreasing size of the square magnet and shorter distance, and were largest when using a magnet 6 mm square and a 500-µm gap, in which condition the maximum tilting angles in the X and Y directions were 2.95 and 3.68 deg/mA, respectively. In addition, we obtained 3D-OCT images of human finger tissue by using a Fourier domain fiber interferometer with a newly developed MEMS mirror.

MEMS Scanning Mirrors for Optical Coherence Tomography

“…Figure 16 shows a 3D OCT image of fingertip tissue where the fingerprint orientations are visible. Watanabe et al [56] have demonstrated an electromagnetic MEMS scanner for OCT imaging. The schematic diagram of a fabricated mirror scanner is shown in Figure 17.…”

“…Two x-scan coils are formed on the x-frame. All the coils have a Watanabe et al [56] have demonstrated an electromagnetic MEMS scanner for OCT imaging. The schematic diagram of a fabricated mirror scanner is shown in Figure 17.…”

“…Figure 17. Architecture of the MEMS electromagnetic scanner: (a) device schema and (b) the top view of the mirror actuator (Figures from[56]). …”