A Three-axis Displacement Sensor with Nanometric Resolution

Instead of plane mirrors in a conventional Michelson interferometer for measurement of Z-directional displacement, the three-axis displacement sensor described in this paper employs two sinusoidal XY-grid mirrors with identical pitches (10 μm) and amplitudes (60 nm) of X- and Y-directional sine waves as the stationary reference mirror and the moving scale mirror, respectively. The positive and negative first-order diffraction light beams from the two XY-grids superimposing with each other to generate interference signals, from which the displacements of the scale grid along the X-, Y-, and Z-axes can be simultaneously obtained. Experimental results have verified that the sensor has nanometric resolutions in all the three axes.