Future space telescopes require primary mirrors that have larger apertures and less mass than the current ones. To reduce the mass as much as possible, ultra-thin aspheric glass mirrors are used for the optical surface and a rigid, lightweight frame with actuators for support. The accuracy of the optical surface is actively maintained by adjusting the actuators. On the other hand, the ultra-thin spherical glass mirrors can be utilized to shape aspheric ones based on same active optics technology. The method can avoid the difficulty of manufacture and measure for large aspheric surface mirrors. We have built a measurement system for shaping a parabolic surface using a 340mm diameter ultra-thin spherical mirror. According to an existing active support system the theoretical accuracy of parabolic surface figure is presented. The test results show that the method of shaping aspheric ones from spherical surfaces is fully feasible: the surface quality is λ/5 RMS, which is in accord with the simulation analysis. If the best fitting sphere and the array of actuators be suitably chosen, and the initial figure accuracy of ultra-thin spherical surfaces can be increased, the accuracy of shaping aspheric surface will be improved.

Date Published: 6 October 2010
PDF: 8 pages
Proc. SPIE 7655, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Advanced Optical Manufacturing Technologies, 76552N (6 October 2010); doi: 10.1117/12.867719

Published in SPIE Proceedings Vol. 7655:
5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Advanced Optical Manufacturing Technologies
Li Yang; Yoshiharu Namba; David D. Walker; Shengyi Li, Editor(s)