A new design of resonant scanning mirror actuated by electromagnetic induction is presented. It is a planar device that was manufactured from 0.5 mm thick phosphor bronze by batch photofabrication. The monolithic mechanical structure have a frame, tree torsion bars and two rotors. Folded torsion bars connect the frame to the rotors, and a straight torsion bar interconnects both rotors. One rotor is devoted to the armature (moving coil), and the other rotor carries the mirror. There is a hole in the armature where a branch of the actuating magnetic core (stator) passes through, carrying the magnetic flux generated by an excitation coil of the stator. The efficiency on converting electric power to mechanical motion was increased two orders of magnitude from a previously published inductive planar device (0.005 W/deg against 2.2 W/deg). A prototype measuring 69 x 49 mm<sup>2</sup> oscillating at 64.4 Hz presented deflection angle of 12°<sub>pp</sub>, and a quality factor Q of 200. A mathematical model was derived and a design procedure was developed. The results shown that this device has potential to replace conventional resonant scanners on high-aperture optical systems or high-power laser applications.
The prediction of the behavior of the induction actuated scanners is a problem that involves the modeling of different physical domains as structural and electromagnetic. The Finite Element Approach is a highly viable alternative to obtain reliable predictions for its behavior over other available methods as the analytic, or circuit equivalent methods. In this owrk a finite element model for the structural an electromagnetic domains of the induction actuated scanning mirror was presented. To validate these models two experiments were performed, a laser doppler vibrometry of the double-rotor scanner to identify its modes shapes and natural frequencies and a magnetic field mapping of the actuator to obtain the spatial characteristic of the AC and DC magnetic fields generated by the actuator in the device armature region. There is a good agreement between the FEA models and the experimental results.
This paper presents a new scanning mirror structure. Large area (mm-order) scanning mirrors have been studied and developed due to the many applications where mm-order light beam size is present like optical microscopes and instrumentation systems. In the proposed structure the actuation and reflection mechanisms were separated in order to provide a more flexible and accurate design that considers the specific needs of each one. The new structure consists of two square rotors linked to a fixed frame by two torsion bars, a third torsion bar connect both rotors. The electromagnetic induction actuated scanners were made using bulk silicon micromachining technology, thin film techniques and mechancial assembly. The maximum optical deflection angle was 8.0°pp at the first resonant frequency of 1316Hz with a quality factor of Q=200. The second resonant frequency was 2542Hz with optical angle of 6°pp and a quality factor of Q=422.
A novel micromachined scanner with electromagnetic induction actuation principle is presented. It was manufactured by Si-LIG technique, where its mechanical structure was made by bulk silicon micromachining of 200μm thick (100) silicon substrate, and its electric circuit was made by deep UV lithography and Au electroplating. The monolithic mechanical structure is a 12×24 mm<sup>2 </sup>rectangular frame connected by 4.5mm long torsion bars to a 4×10mm<sup>2</sup> rectangular rotor. On one face of the rotor is the electric circuit, a 70μm thick, single turn, electroplated Au coil with 3.3mΩ electrical resistance. The other face of the rotor was mirrored by a 1480Å thick Al film. An external magnetic circuit generated a constant 1150 Gauss magnetic field parallel to the coil plane and a 100 Gauss (peak value) field normal to the coil plane. Maximum deflection angle of 6.5°<sub>pp</sub> at the 1311Hz resonance frequency was measured, and the quality factor Q was 402. The results shown that electromagnetic induction actuation is adequate for meso-scale systems and capable of producing resonant scanners with performance compatible with applications like bar code readers.
Home made masks having thick (35-50 micrometers ) silicon membranes as blanks were used in deep X-ray lithography of SU8 - a negative tone photoresist. X-ray masks were fabricated by the following sequence of steps: (a) vacuum deposition of Ti and Au thin layers on a 220 micrometers thick (100) silicon wafer, (b) optical lithography of two different patterns in both negative (SU-8) or positive (AZ4620) photoresist (c) gold electroforming and (d) silicon substrate thinning with KOH etch to form the membrane. X-ray exposures was performed in the X-ray beam line of the LNLS synchrotron light source. The samples consisted of 125 micrometers thick layers of SU-8 supported on silicon and assorted substrates. The optimum dose for silicon substrates have been used in the remaining substrates, namely, metallic thin films (Cr, Cu, Au, Pt), printed circuit board (PCB), quartz, alumina ceramic and glass. The influence of mask defects, substrate type and X-ray dose values on the lithography of SU-8 is discussed. Criteria for defining upper and lower dose values for SU-8 X-ray deep lithography was proposed on the basis of characteristic defects. Advantages in using SU-8 rather than PMMA in the LIGA technology are commented.