Surface encoders for a mosaic scale grating

The surface encoder we propose for simultaneously measuring XYZ-directional displacements consists of a XY-axis with a scale grating and an optical sensor head. The XY-axis scale grating size determines the surface encoder's measurement range in plane - in the X and Y directions. The mosaic XY-axis scale grating we use to expand the measurement range in plane consists of multiple XY-axis scale gratings arranged in plane. We present two optical configurations for the mosaic XY-axis scale grating. To confirm our configurations' effectiveness, we fabricated two prototypes that we tested in basic experiments using a mosaic single-axis scale grating.