I found myself playing with the honey bottle at the breakfast table the other day (as you do). Inverting this caused an air bubble to form and rise through the body of the viscous liquid.
I then thought that if I were to rotate the honey bottle about a horizontal axis at the right rate, I could maintain the bubble at a fixed vertical position within it -each different bubble/liquid combination would have a characteristic spin rate required to hold the bubble steady.
Today’s invention is to set up such a rotating system, with optically suitable fluids, and then to spin the whole thing also about a vertical axis. The large bubble lens would thus be held steady and could have its curvature finely controlled by the rate of vertical axis rotation.
This would allow light, gathered by mirrors, to be fed into the system and focussed by this continuously focussable lens. It should be possible to compensate (perhaps computationally) for the complicated 3D interactions between the two axial fluid motions.