Temporal Variability in Magnetically Actuated Deformable Mirror Surface Figure Measured Via Interferometry

Abstract

For space-based applications requiring precise wavefront control, such as direct imaging of exoplanets through high-contrast imaging, a deformable mirror (DM) is essential for achieving the desired scientific objectives. The stability of the DM surface over time is critical to meeting stringent performance specifications, yet the behavior of the DM surface under varying aberration conditions remains insufficiently documented. Additionally, a comprehensive frequency-domain analysis has not been thoroughly explored in the literature. This study investigates the performance of a 97-actuator ALPAO DM under various aberration conditions, including powered-on and powered-off states. Using a 4D PhaseCam 6000 interferometer, the DM surface is measured over 70 minutes, and both the RMS trend and Zernike coefficient variability are analyzed. A frequency-domain study is conducted to characterize the dominant frequencies and their corresponding magnitudes. A strong correlation between the applied aberration levels and temporal variability is established. The results reveal the dominance of two low-frequency components across all configurations, and 90\% of the magnitudes of the top 10 frequencies with the highest magnitude are found to be below 33.78. This work provides insights into the behavior of DM surfaces in space-based wavefront control applications and highlights the importance of understanding frequency characteristics for optimizing performance.