A multi-probe surface encoder for mosaic XY grating

A surface encoder, which can measure the displacements in the XYZ directions simultaneously with one measurement point, has been proposed. The surface encoder consists of a scale XY grating, which is two-axis grating, and an optical sensor head, where a reference XY grating is set perpendicular to the scale XY grating. The size of the scale XY grating determines the measurement range of the surface encoder along the in-plane direction of the scale XY grating. This paper proposes a utilizing a mosaic scale XY grating, which is composed of multiple scale XY gratings, to enlarge the grating area. But the mosaic scale XY grating lias problems of the gaps which exist between each scale XY grating. This paper also proposes a multi-probe surface encoder to solve these issues. The multi-probe surface encoder has multiple probes to be projected onto the mosaic scale XY grating. The displacements can be obtained by the probe which is not on the gaps. The prototype of the proposed multi-probe surface encoder was developed and a basic experiment was carried out with the mosaic scale grating. The experimental results show that the proposed multi-probe surface encoder is effective for the mosaic scale XY grating.