SPIE Proceedings [SPIE Eighth International Symposium on Advanced Optical Manufacturing and Testing Technology (AOMATT2016) - Suzhou, China (Tuesday 26 April 2016)] 8th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Advanced Optical Manufacturing Technologies - Annular-force-based variable curvature mirror combined with multi-point actuation array to improve the surface figure accuracy: a prototype design