High contrast at small separation – III. Impact on the dark hole of MEMS deformable mirror control electronics

Abstract

The creation of a dark hole (DH) region in the science image for exoplanet direct detection depends on deformable mirrors (DM), where the imperfect control of DM limits the achievable contrast. The mirror surface height resolution is set by the DM drive electronics, and the quantization errors in DM impact the contrast in the DH. Consequently, determining the optimal voltage value for the flattening map of DM is essential, as it involves balancing dynamic and accuracy considerations. We conduct a numerical study to examine the impact of these parameters on microelectromechanical DM within the high-contrast field of view of several DH with various characteristics and optical configurations. Our analysis includes an exploration of their influence on both small and moderate angular separations. We compare our numerical results with a formula available in the literature that aims to capture the dependence of contrast on DM quantization errors. We show that the formula accuracy to predict the contrast limit when the DM deflection curves follow the as-manufactured quadratic power-law is dependent on the DM flattening map voltage domain, regardless of DH size and angular separations. Further these results appear to be insensitive to factors such as actuator number, coronagraph type, setup architecture, and science objective (small or moderate angular separations). We provide guidelines for determining the optimal voltage for the DM flattening map, discuss the domain validity of the formula used to predict DM quantization errors on the contrast, and provide insights into balancing DM actuator density and mirror surface height resolution.