Microscanner

Microscanner und optical control systems

The main part of the microscanner is a microactuator of the ferromagnetic shape memory alloy Ni-Mn-Ga, which shows ferromagnetic properties as well as the conventional shape memory effect. A room temperature, the microactuator is deflected by a permanent magnet (state a). Upon electrical heating above the ‘Curie‘ temperature and the critical temperature of reverse phase transformation, the microactuator is set back (state b), because the magnetic attraction is lost and, simultaneously, the shape memory force F_SMA occurs in opposite direction (intrinsic antagonism). Consequently, periodic electrical heating induces an oscillatory motion of the microactuator, which is used to periodically deflect a collimated light beam.

Schematic of a microscanner consisting of a ferromagnetic shape memory microactuator (double-beam cantilever) and a micromirror at the front end

Microscanner demonstrators of this type allow extremely large deflections even for small beam dimensions (60° for a length of 3 mm) at steplessly variable frequency up to 200 Hz. Thereby, for instance, optical sensors can be realized for portable or mobile systems.

Demonstrator of a microscanner

Further information:

• D. Brugger, M. Kohl, U. Hollenbach, A. Kapp and C. Stiller, Ferromagnetic shape memory microscanner system for automotive applications, International Journal of Applied Electromagnetics and Mechanics 23 (2006) 107–112.

• M. Kohl, M. Gueltig, V. Pinneker, R. Yin, F. Wendler, and B. Krevet, Magnetic Shape Memory Microactuators, Micromachines 5, (2014), 1135-1160.