Design and modeling of a novel electromechanical optical micro-scanner

Abstract

This article presents a design principle of a novel small-sized compliant optical micro-scanner with two translational (X, Y) and a rotational (θz) degree of freedoms (3-DOFs). A novel normal-stress electromagnetic actuator system is proposed to provide 3-DOFs actuating forces with the working strokes of hundreds of microns for the optical micro-scanner within a very compact structural envelope. The electromagnetic actuator system can not only generate high actuating force density which is similar to solenoid, but also has linear force-current relations along three actuating axes by adopting magnetic configuration design strategy. The theoretical analysis model of the actuator system is derived by using equivalent magnetic circuit method and the actuating force is analyzed through energy store method. Permanent magnet flux leakage and magnetic saturation of stator core in excitation situation are taken into consideration to improve the modelling accuracy. Finite element analysis (FEA) software is utilized to investigate the critical characteristics of the micro-scanner. By FEA comparison, both the theoretical and FEA results show that the actuating force generated by the designed electromagnetic actuator system has a linear relationship with the excitation current. Compare with the normal optical micro-scanner actuated by voice coil motors (VCMs) or piezoelectric (PZT) actuators, the normal-stress based micro-scanner can not only offer movements with three degrees of freedom within a very compact structural envelope, but also achieve high actuating forces which are over 6 times higher than the same sized VCM-actuated micro-scanners. The workspace of this scanner is more than 800 × 800 μm2, which is more than 8 times larger than that of PZT-actuated scanner. The volume of this stage is 60 * 60 * 14 mm3, resulting in a high area-ratio of 1.2%. The cross-axis coupling motion is less than 24 μm at the full primary motion. The resonant frequencies of the two working axes are about 184 Hz.