Actuation for carbon fiber reinforced polymer active optical mirrors

Adaptive or active elements can alter their shape to remove aberrations or shift focal points. Carbon fiber reinforced polymer (CFRP) material improves upon current active mirror materials, such as Zerodur, in several ways: low stiffness-to-weight ratio, very low hysteresis, and greater dynamic range of correction. In this paper, we present recent developments in CFRP mirror actuation, i.e., changing the mirror´s shape in an accurate and repeatable fashion. Actuation methods are studied both theoretically, using finite element analysis, and experimentally, using interferometric testing. We present results using two annular rings to push against the mirror´s back, producing a wavefront with less than 20 waves of total error. Applications for this work include active telescope secondaries, phase diversity, and adaptive zoom systems.