Development of active optics for thin meniscus mirrors in 1-meter-class telescopes

Abstract

This paper presents the ongoing project of implementing an active optics system in an 1-meter telescope to build a lightweight, cost-effective system with high imaging quality. A systematic design methodology for meniscus mirrors based on thin plate theory and finite element analysis enables target-oriented engineering of a support system that takes the application-dependent optical mirror requirements into account. The actuators for the lateral and axial system are based on stepper motors and designed in a modular manner, adjustable for a wide range of nominal force values. The axial actuators integrate an optical force measurement to achieve a compact design. Laser triangulation sensors placed in the mirror cell measure the lateral mirror position in 3 degrees of freedom with respect to its cell, providing position data that is used in a feedback control to compensate for finite stiffness of the support structure and thermal disturbances. Tests of the lateral system’s performance show maximum displacements of 1.4 μm in both lateral directions, keeping the according wavefront RMS error below 5 nm.