Via-Less Two-Axis Electromagnetic Micro Scanner Based on Dual Radial Magnetic Fields

We propose a two-axis electromagnetic micro scanner with a two-phase current path satisfying three criteria (via less microfabrication, independent biaxial scan with minimization of crosstalk, and no current path on the mirror). In the design of a dual radial magnetic field, current paths are arranged to maximize the torque in the active current that actuates a mirror, while nullifying the torque in the passive current that is not intended to actuate the mirror but rather just to complete an electrical current loop. The use of W-shaped springs for the slow-axis scan considerably reduced the torsional spring constant by 2.7 times, whereas it increased the in-plane sliding spring constant by 2.4 times, compared to conventional I-shaped springs. This indicates that the W-shaped springs effectively increase scan angle and enhance the actuation stability. The scanner with a reflection mirror with 3 mm in diameter was fabricated, and in the raster scan gave a maximum scan angle of 50.6° (resonant) and 9.1° (quasi-static) in fast- and slow-axis scans, respectively, with a power consumption of 28.1 mW. The maximum crosstalk of the slow and fast axis from the other axis were measured as small as 0.45% and 0.43%, respectively.