Parabolic liquid mirrors: reference surfaces in interferometry

摘要

A parabolic liquid mirror can be made by rotating a bath of mercury. The mirror focal length f is related to the angular speed of rotation approximately ega and the gravity g by the formula: f $EQ g/2$DOT approximately ega$+2$/. Good quality mirrors having a diameter up to 3 meters have been built and, telescopes and lidar based on this technology are running. The greatest advantage of liquid mirrors is the cost. For a big mirror the cost is 1 or 2 orders of magnitude less than a conventional glass mirror and its cell. The idea developed here is that if a good parabolic mirror can be produced at low cost, this one can be useful in optical shop testing as reference mirror and can fill the lack of aspheric reference. The liquid mirror can be used to test null correctors, to make holographic references or to control any system developed to test parabolic mirrors.