Nanometer measurement of the planar motion of a magnetic levitation stage based on optical heterodyne interferometry

Nanoscale micromotion stage is a key instrument for the reasarch of nanotechnology that provides one-dimensional, two-dimensional, or three-dimensional nanoscale movement. In this paper, a magnetic levitation stage that can provide large range micromotion with nanometer positioning accuracy is proposed, and a height measurement and calibration of the stage using a triplex heterodyne interferometer is presented. This measurement system is mainly consists of three parts: two-frequency He-Ne laser, three heterodyne interferometers and three phase meters, respectively. Each heterodyne interferometer is used to measure the displacement of the magnetic levitation stage in the vertical direction. Then, the triplex heterodyne interferometer can realize the nanometer measurement of three degrees of freedom motion for the stage, that is, translation in the z-axis and rotations around the x- and y-axes. Furthermore, the three heterodyne interferometers have a common planar reflecting mirror, thus, the advantage of this measurement method is that the heterodyne interference can always produce within the travel range wherever the stage travels, this ensure the stage can always have the same height as that of desired position, and this measurement can give fine height consistency.