**4. Measurement Setup**

By using a Polytec MSA 400 Laser-Doppler-Vibrometer (LDV) with OFV 5000 Controller, the frequency-response-functions (FRF) of the MOEMS are recorded. A chirp signal with an amplitude of ±1 V is applied to the top electrode of one actuator. The opposite actuator is driven with a 180◦ phase shifted signal with the same frequency and amplitude. So, the actuators work in antiphase mode. The amplitude of deflection is measured at the mirror plate edge. By measuring the resonance frequency, the stiffness of the MOEMS can be identified indirectly. This allows to compare static performance values for similar mechanical parameters of the MOEMS.

For measuring higher tilt angles, a high-deflection setup was introduced in [8,9]. Mechanical tilt angles up to approximately 15◦ can be measured. A laser beam is projected onto the mirror at a 45◦ angle. The mirror reflects it on an adjustable screen with a metric scale, which is also attached at a 45◦ angle to the mirror. The components like the laser mount and screen are fixed on a ring, adapted to the prober station (see Figure 5).

**Figure 5.** Schematic of the experimental setup [9].

The transversal piezoelectric coefficient defines the piezoelectric crystal deformation in result of an electric field. If samples with different piezoelectric material thicknesses and piezoelectric coefficients are used, the electric voltage as parameter for actuation is not sufficient to interpret the system performance. Therefore, the results are additionally documented in relation to the electric field in MV/m.
