An active optics system has been built and tested on a prototype 1.8 m lightweight borosilicate glass mirror. Tests of the system have been conducted in two different modes: the system has been used to compensate measured optical surface distortions, and it has been used to correct thermal distortion predicted by computer modeling based on measured mirror temperatures. Both modes were consistently able to reduce rms figure errors on the mirror surface. Test results show that distortions corresponding to astigmatism, coma, spherical aberration, trefoil, and quatrefoil can be effectively countered.
"Active Optics Correction Of Thermal Distortion Of A 1.8 Meter Mirror," Optical Engineering 27(2), 272115 (1 February 1988). https://doi.org/10.1117/12.7976655