DEWOBBLED – minimizing optical path modulation

4th August 2011

Fraunhofer

ES Admin

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Laser sources are widely used in the industry for labeling and material-machining applications. To meet the fast growing demands concerning precision and processing speed, optical scanner systems are applied for the modulation or deflection of light. Compared to mechanical translation stages optical scanner systems provide clear benefits regarding positioning accuracy and repeatability as well as very high dynamics.

Conventional galvanometer-based optical scanners typically feature large optical apertures. However, the macroscopic design limits the precision of motion, particularly at high velocity. Requirements for bearings on moving parts are exceptionally high. A characteristic measure for the quality of motion is the dynamic mirror tilt perpendicular to the axis of rotation. Mirror tilt leads to a tumbling motion and a deformation of the projected figure (see drawing). This property is often referred to as cross-axes wobble. Cross-axes wobble of conventional resonant galvanometer scanners is typically in the order of 200 µrad.

The Fraunhofer IPMS develops customized silicon based resonant and quasi-static micro-electro-mechanical systems (MEMS) for deflection and modulation of light. Those devices offer highest velocity with superior precision. Scientists now have demonstrated that typical resonant designs provide a cross-axes wobble of less than 35 µrad. Thereby the device oscillates at 23 kHz with a mechanical amplitude of ± 9°.

Dr. André Dreyhaupt, scientist at the microscanner product development group, stated: »The optical MEMS structures of the Fraunhofer IPMS perfectly fit for challenging applications with high demands on velocity and precision of motion at the same time.«