Development of a two-dimensional nano-displacement measuring system utilizing a combined optical and x-ray interferometer

We have developed a two-dimensional nano-displacement measuring system utilizing a combined optical and x-ray interferometer (COXI). The system consists of optical interferometers for two-dimensional displacements and an x-ray interferometer. The x-ray interferometer was used to calibrate the non-linearity of the optical interferometers. The x-ray interferometer can subdivide the optical interference signal with 0.2 nm linear scales. The measured non-linearity of the heterodyne optical interferometer was less than 2 nm. The calibrated optical interferometers were used to measure two dimensional nanoscale displacements, and the accuracy of the optical interferometers was reduced to sub-nanometer after the compensation. To demonstrate the application of the system, we have measured the non-linearity of capacitive sensors using the calibrated optical interferometers.