Theoretical and experimental research on temperature-induced surface distortion of deformable mirror.

In a well-manufactured deformable mirror (DM), the temperature-induced distortion (TID) has been reported exist on the surface shape of the DM, when the working environment temperature is not equal to that of the manufacturing environment. The DM could not effectively correct this actuator-corresponding TID and the correction ability of the DM would be limited. In this paper, the the TID's essential mechanism is analyzed systematically based on the thermal stress characteristics. An efficient method based on an auxiliary temperature compensation module (TCM) and a hybrid closed-loop control algorithm are presented accordingly. A finite element model is built to evaluate the TID characteristics and the compensation capability of the TCM. In the simulation, by using the TCM, the the DM's improved surface shape does not contain the dynamic high-frequency distortion caused by the actuators tilt. In the experiment, which uses a designed TCM and a hybrid closed-loop control algorithm, a DM's TID is effectively depressed and a well-compensated DM surface shape is finally achieved.