Phase-shift digital holography using multilayer ceramic capacitor actuators

In this paper, a four-step phase-shift digital holography (DH) system using multilayer ceramic capacitors (MLCCs) as actuators is proposed. This system is capable of implementing DH with low costs and small-form factors. As a material for actuators, MLCCs are more economical and easier to construct than conventional piezoelectric transducers. By applying a voltage to a single MLCC and measuring the displacement and standard deviation based on the shape change observed on the top surface of the MLCC with laser Doppler velocimetry, the applicability of the MLCC in terms of suitable driving characteristics for use as an actuator in the DH system was confirmed. As the accurate phase step actuation required to employ the MLCC actuator for DH cannot be performed, a four-step hologram extraction method was employed using the intensity information of the hologram obtained by continuously driving the MLCC actuator. Consequently, the proposed MLCC actuator was applied to a typical Michelson interferometer setup to measure a 1.8 µm step sample, and the quantitative phase information was obtained with a standard deviation of less than 1.3 nm.