Throw in some curves and things get interesting, especially when you can control the curve with a touch of your finger, as with this variable surface convex mirror. The video below starts off with ...

The Hi-Speed DM37 deformable mirror from Alpao (Biviers, France) has a clear aperture of 7.5 mm but a large stroke of more than ±35 μm for astigmatism and focus wavefront correction ...